ASNT NDT Handbook Volume 4 Infrared and Thermal Testing

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NONDESTRUCTIVE TESTING Third Edition

HANDBOOK

Volume 4

Radiographic
Testing

Technical Editors
Richard H. Bossi
Frank A. Iddings
George C. Wheeler
Editor
Patrick O. Moore

® American Society for Nondestructive Testing

FOUNDED 1941

Copyright © 2002
AMERICAN SOCIETY FOR NONDESTRUCTIVE TESTING, INC.
All rights reserved.

No part of this book may be reproduced, stored in a retrieval system or transmitted, in any form or by any means —
electronic, mechanical, photocopying, recording or otherwise — without the prior written permission of the publisher.
Nothing contained in this book is to be construed as a grant of any right of manufacture, sale or use in connection with
any method, process, apparatus, product or composition, whether or not covered by letters patent or registered
trademark, nor as a defense against liability for the infringement of letters patent or registered trademark.

The American Society for Nondestructive Testing, its employees, and the contributors to this volume assume no
responsibility for the safety of persons using the information in this book.

Copyright © 2002 by the American Society for Nondestructive Testing, Incorporated. All rights reserved. ASNT is not
responsible for the authenticity or accuracy of information herein, and published opinions and statements do not
necessarily reflect the opinion of ASNT. Products or services that are advertised or mentioned do not carry the
endorsement or recommendation of ASNT.

ACCPSM, IRRSPSM, Level III Study GuideSM, Materials EvaluationSM, NDT HandbookSM, Nondestructive Testing HandbookSM,
The NDT TechnicianSM and www.asnt.orgSM are service marks of the American Society for Nondestructive Testing.
ASNT®, Research in Nondestructive Evaluation® and RNDE® are registered trademarks of the American Society for
Nondestructive Testing.

ASNT exists to create a safer world by promoting the profession and technologies of nondestructive testing.

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1711 Arlingate Lane
PO Box 28518
Columbus, OH 43228-0518
(614) 274-6003; fax (614) 274-6899
www.asnt.org

Errata

Errata if available for this printing may be obtained from ASNT’s Web site, www.asnt.org, or as hard copy by mail from ASNT,
free on request addressed to the NDT Handbook Editor at the address above.

Library of Congress Cataloging-in-Publication Data

Radiographic Testing / technical editors, Richard H. Bossi, Frank A. Iddings,

George C. Wheeler; . -- 3rd ed.

p. cm. — (Nondestructive testing handbook ; v. 4)

Includes bibliographic references and index.

ISBN 1-57117-046-6

1. Radiography, industrial. I. Bossi, R. H. II. Iddings, F.A. III. Wheeler, G.C.

IV. Moore, Patrick O. V. American Society for Nondestructive Testing.

IV. Series: Nondestructive testing handbook (3rd ed.) ; v. 4.

TA417.25 .R32 2002 2002012672

620.1’1272--dc21

Published by the American Society for Nondestructive Testing
PRINTED IN THE UNITED STATES OF AMERICA

NOTE:

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printed version of this publication. For Library of Congress Cataloging-in-
Publication data pertaining to the CD-ROM edition, please click this link.

ii Radiographic Testing

President’s Foreword

The twenty-first century has now arrived ASNT career briefly in 1974. His start in
and we are aware that technology will the NDT profession came as a
continue to accelerate at blinding speed. radiographer in the Boston ship yards. His
As these changes occur, adaptation and name was Philip Johnson. He was the
implementation by the end user must architect and founder of this society. He
keep pace with proven innovations. As was the visionary who saw the need to
managers and engineers we have been draw upon our collective differences and
quick to defend the status quo and have unite for a common cause.
been slow to change when change is
needed. Currently we are seeing a Johnson served as the organization’s
significant lag in the usage of such Secretary from 1941 to 1965. He also
innovations as digital radiography. The assumed the dual role of editor for many
new challenge for practitioners and of those years. In addition Johnson served
regulatory bodies will be the acceptance as our Executive Director from 1965
and integration of this already proven through 1974. Phil provided the
technology. continuity and focus that must sustain
any organization in those formative years.
The vitality and future of the American As you read through this book remember
Society for Nondestructive Testing depend that it was Johnson that made possible
on the creation, improvement and the process of cooperative collaboration.
sharing of information so that safety and
reliability stay at the forefront of product Stephen P. Black
development. ASNT President, 2001-2002

This volume represents the efforts of
many dedicated professionals who have
embraced change and given freely of their
time with the mission of making a
difference in their chosen profession.
ASNT commends each and every
contributor for their efforts in bridging
today’s technology with tomorrow’s
possibilities.

There were more than 100 individual
contributors and reviewers, representing
both volunteers and staff in an essential
ongoing partnership. Each has given a
piece of themselves that can never be
repaid.

A special thanks is due to technical
editors Richard Bossi, Frank Iddings and
George Wheeler for their commitment to
this project. This job requires an in-depth
understanding of the component parts of
the technology. The job is long and
tedious and must be driven from the heart
and the mind.

I must also thank the ASNT staff and
NDT Handbook Editor Patrick Moore for
their guidance and continued pursuit of
excellence. Year in and year out they have
made the necessary sacrifices to ensure
quality and value.

Finally, reflective tribute must go to an
individual who crossed paths with my

Radiographic Testing iii

Foreword

Aims of a Handbook industry. This handbook provides a
collection of perspectives on its subject to
The volume you are holding in your hand broaden its value and convenience to the
is the fourth in the third edition of the nondestructive testing community.
Nondestructive Testing Handbook. Now is a
good time to reflect on the purposes and The present volume is a worthy
nature of a handbook. addition to the third edition. The editors,
technical editors and many contributors
Handbooks exist in many disciplines of and reviewers worked together to bring
science and technology, and certain the project to completion. For their
features set them apart from other scholarship and dedication I thank
reference works. A handbook should them all.
ideally give the basic knowledge necessary
for an understanding of the technology, Gary L. Workman
including both scientific principles and Handbook Development Director
means of application.

The typical reader may be assumed to
have completed three years of college
toward a degree in mechanical
engineering or materials science and
hence has the background of an
elementary physics or mechanics course.
Additionally this volume provides a
positive reinforcement for the use of
computer based media that enhances its
educational value and enlightens all levels
of education and training.

Note that any handbook offers a view
of its subject at a certain period in time.
Even before it is published, it can begin to
get obsolete. The authors and editors do
their best to be current but the
technology will continue to change even
as the book goes to press.

Standards, specifications,
recommended practices and inspection
procedures may be discussed in a
handbook for instructional purposes, but
at a level of generalization that is
illustrative rather than comprehensive.
Standards writing bodies take great pains
to ensure that their documents are
definitive in wording and technical
accuracy. People writing contracts or
procedures should consult the actual
standards when appropriate.

Those who design qualifying
examinations or study for them draw on
handbooks as a quick and convenient way
of approximating the body of knowledge.
Committees and individuals who write or
anticipate questions are selective in what
they draw from any source. The parts of a
handbook that give scientific background,
for instance, may have little bearing on a
practical examination except to provide
the physical foundation to assist handling
of more challenging tasks. Other parts of
a handbook are specific to a certain

iv Radiographic Testing

Preface

Radiographic testing has been a may rely on other chapters for details on
preeminent method of nondestructive a particular concept. The reader is
testing since the discovery of X-rays in encouraged to refer to the index to find
1895. Film radiography in particular has information on items of interest in
been the backbone of industrial multiple chapters. Because of the current
applications of penetrating radiation. It is rate of change in technology, it is not
fundamentally a very elegant analog possible to have a handbook that is
process that provides an internal completely up to date. This handbook
evaluation of solid objects. Although film contains the fundamental, as well as the
radiography remains the most widely most recent material available at the time
used method of radiographic testing, of its writing. Where possible, tables and
many other penetrating radiation figures are used to serve as a quick and
techniques for nondestructive testing ready means of finding essential technical
have been developed. In recent years the information. The references for each
advancements in speed and capability of chapter should be helpful for the reader
digital data processing have increased the seeking additional material. Readers are
application of digital methods for also encouraged to use the internet and
penetrating radiation inspections. The ASNT’s Web site to find supplemental
transition from analog to digital material on equipment and topics that are
technology will continue into the future. subject to change with technological
advancement.
This volume of the Nondestructive
Testing Handbook, third edition, combines It has been the pleasure of the
essential information on the traditional technical editors to work with the authors
penetrating radiation testing techniques and ASNT’s Nondestructive Testing
and incoming techniques using digital Handbook staff to provide this third
technology. Building on material in the edition of the radiography handbook. We
first edition (1959) and the second edition wish to thank all the contributors,
(1985), the many contributors of this including those named in the current
volume have assembled the basic body of volume, those who provided material to
knowledge for radiographic testing. Much the contributors and may not have been
of the information in the second edition named, and those whose contributions to
radiography volume has been maintained earlier editions have been carried over to
and enhanced, while some dated or rarely this edition. We hope this edition proves
used material has been dropped. The first useful as both a quick reference for
and second editions thus remain useful technical details and a source of
references — not only for historical fundamental information for
purposes but for material that could not comprehensive understanding.
longer be included in the present edition.
Richard H. Bossi
Considerable new information has Frank A. Iddings
been added, particularly in the area of George C. Wheeler
digital imaging, data processing and
digital image reconstruction. Other
material has been updated with recent
information in such areas as radiation
sources, standards, interpretation and
applications. Techniques such as
backscatter imaging and computed
tomography were not covered in earlier
editions but have their own chapter in
this edition.

The team of contributors has tried to
prepare as useful a text as possible. In
many cases, items are discussed in
multiple chapters to keep the continuity
of the discussion in that particular
chapter. This also provides multiple
contexts for understanding concepts and
techniques. In other cases the handbook

Radiographic Testing v

Editor’s Preface

Radiographic testing was the dominant Acknowledgments
method of nondestructive testing during
the first two decades of the American Handbook Development
Society for Nondestructive Testing (ASNT), Committee
founded in 1941. When this handbook
was first envisioned in the 1940s, it was Gary L. Workman, University of Alabama,
projected to be a single volume devoted Huntsville
entirely to radiography.
Michael W. Allgaier, GPU Nuclear
In 1959, when the first edition of the Albert S. Birks, AKZO Nobel Chemicals
Nondestructive Testing Handbook finally Richard H. Bossi, The Boeing Company
appeared, a fourth of it was devoted to Lisa Brasche, Iowa State University
radiographic testing. In the twenty-first William C. Chedister, Circle Systems
century, the first edition still sells scores James L. Doyle, Northwest Research
of copies every year.
Associates, Inc.
A quarter century was to pass before Nat Y. Faransso, Halliburton Company
that presentation of radiographic testing François Gagnon, Vibra-K Consultants
was replaced. The second edition gave a Robert E. Green, Jr., Johns Hopkins
complete volume to the method when, in
1985, ASNT published Radiography and University
Radiation Testing. Much of the volume in Matthew J. Golis, Advanced Quality
the present third edition is based directly
on that second edition. Concepts
Gerard K. Hacker, Teledyne Brown
The process of outlining this third
edition volume and recruiting volunteers Engineering
for it began in 1996. Richard Bossi and Harb S. Hayre, Ceie Specs
George Wheeler deserve the gratitude of Frank A. Iddings
ASNT for the planning that launched the Charles N. Jackson, Jr.
project. In 2001 Frank Iddings, who had John K. Keve, DynCorp Tri-Cities Services
already edited several chapters, was Lloyd P. Lemle, Jr., BP Oil Company
appointed as the third technical editor. Xavier P.V. Maldague, University Laval
Paul M. McIntire, ASNT
Seven ASNT past Presidents Mani Mina, Iowa State University
participated in the writing and review of Ron K. Miller, Physical Acoustics
this volume, demonstrating ASNT’s
strength as a truly technical society. Corporation
Scott D. Miller, Saudi Aramco
This series is not a collection of articles Patrick O. Moore, ASNT
but a work of collective authorship by Stanley Ness
ASNT, so authors are called contributors. Louis G. Pagliaro, Technical Associates of
Volunteers whose contributions to the
second edition have been updated for this Charlotte
edition are listed if they were able to Emmanuel P. Papadakis, Quality Systems
participate and to approve the product.
Concepts
In the list below, people listed as Stanislav I. Rokhlin, Ohio State University
contributors were also reviewers but are Frank J. Sattler
listed only once, as contributors. Fred Seppi, Williams International
Amos G. Sherwin, Sherwin Incorporated
It has been an honor to work with Kermit S. Skeie
ASNT’s volunteers, whose technical Roderic K. Stanley, Quality Tubing
expertise is matched by their generosity in Holger H. Streckert, General Atomics
sharing it. Stuart A. Tison, Millipore Corporation
Noel A. Tracy, Universal Technology
I would like to thank staff members
Hollis Humphries and Joy Grimm for Corporation
their contributions to the art, layout and Satish S. Udpa, Michigan State University
text of the book and also thank Sotirios J. Vahaviolos, Physical Acoustics
Publications Manager Paul McIntire for
years of encouragement. Corporation
Mark F.A. Warchol, Aluminum Company
Patrick O. Moore
NDT Handbook Editor of America
Glenn A. Washer, Federal Highway

Administration
George C. Wheeler

vi Radiographic Testing

Contributors Reviewers

Richard D. Albert, Digiray Corporation Arthur E. Allum, Blacksburg, South
Richard C. Barry, Lockheed Martin Carolina

Missiles and Space Vijay Alreja, VJ Technologies
Garry L. Balestracci, Balestracci Unlimited John K. Aman
John P. Barton Ringo C. Beaumont
George L. Becker Boyd D. Howard, Westinghouse Savannah
Harold Berger, Industrial Quality,
River Company
Incorporated Mark Branecki, NRay Services
Bruce E. Bolliger, Agilent Technologies Jack S. Brenizer, Pennsylvania State
Richard H. Bossi, The Boeing Company,
University
Seattle Joseph F. Bush, Jr., NDT Training
Lisa Brasche, Iowa State University Richard E. Cameron, General Electric
Roy L. Buckrop
Clifford Bueno, General Electric Company Nuclear Energy
William D. Burnett W. Dennis Cabe, Duke Energy Company
Paul Burstein, Skiametics Incorporated Eugene J. Chemma, Bethlehem Steel
Herbert Chapman
Francis M. Charbonnier Corporation
Kenneth W. Dolan, Lawrence Livermore Thomas N. Claytor, Los Alamos National

National Laboratory Laboratory
C. Robert Emigh Robert L. Crane, Air Force Research
Toshiyasu Fukui
Donald J. Hagemaier Laboratory
Jerry J. Haskins, Lawrence Livermore Claude D. Davis, Unified Testing Services
John Deboo, The Boeing Company
National Laboratory Donny Dicharry, Source Production and
Charles J. Hellier III, Hellier and
Equipment
Associates Paul Dick
Eiichi Hirosawa Louis J. Elliott, Lockheed Martin Tactical
Frank A. Iddings
Timothy E. Kinsella, Carpenter Defense Systems
Hugh W. Evans, Amersham Corporation
Technology Corporation Jonathan C. Fortkamp, ABB Automation
Gary G. Korkala, Security Defense Systems
Andreas F. Kotowski, Rapiscan Security Incorporated
William D. Friedman, Lockheed Martin
Products Steven G. Galbraith, INEEL, Idaho Falls
Lawrence R. Lawson Bryan C. Goode, Faxitron X-Ray
Harry E. Martz, Lawrence Livermore
Corporation
National Laboratory Thorsten Graeve, Rad-Icon Imaging
William E.J. McKinney
Masahisa Naoe Corporation
James M. Nelson, The Boeing Company, Joseph N. Gray, Iowa State University
Nand Gupta, Omega International
Seattle
Stig Oresjo, Agilent Technologies Technologies
William B. Rivkin David P. Harvey, Oremet-Wah Chang
Stanislav I. Rokhlin, Ohio State University Manfred P. Hentschel, Federal Institute for
Edward H. Ruescher
Frank J. Sattler Materials Research and Testing, Berlin,
Daniel J. Schneberk, Lawrence Livermore Germany
Michael R. Holloway, Eastman Kodak
National Laboratory Company
Samuel G. Snow James W. Houf, American Society for
George R. Strabel, Howmet Research Nondestructive Testing
Bruce G. Isaacson, ISA
Corporation Chester W. Jackson, Westinghouse
Holger H. Streckert, General Atomics James H. Johnson, Varian Industrial
Marvin W. Trimm, Westinghouse Products
Thomas S. Jones, Howmet Research
Savannah River Company Corporation
George C. Wheeler Jim F. Kelly, Rivest Testing USA/IUOE
Gerald C. Wicks Bradley S. Kienlen, Entergy Operations
William P. Winfree, National Aeronautics Richard Kochakian, Agfa Corporation
Jeffrey Kollgaard, The Boeing Company
and Space Administration James R. Korenkiewicz, Samsung
Aerospace, Pratt and Whitney
Joseph L. Mackin, International Pipe
Inspectors Association
K. Dieter Markert
Nick Martinsen, Varian Industrial
Products
Robert W. McClung

Radiographic Testing vii

Thomas E. McConomy, Special Metals Additional Acknowledgments
Corporation
For Chapter 8, “Radiographic
Claude H. McDaniel Interpretation,” the contributors and
Robert M. McGee, Ford Motor Company editors gratefully acknowledge the
Richard D. McGuire, National Board of contributions by Newport News
Shipbuilding and Drydock Company (R.R.
Boiler and Pressure Vessel Inspectors Hardison, L.S. Morris, D.L. Isenhour and
William D. Meade, The Boeing Company R.D. Wallace) and by the National
John Munro III Institute of Standards and Technology
Antonio G. Pascua, The Boeing Company, (G. Yonemura). Appreciation is also
expressed to Eastman Kodak Company,
Canoga Park Electric Power Research Institute, ASTM
J.A. Patsey, US Steel Tubular Products International and the Southwest Research
Patrick Pauwels, Agfa-Gevaert, Mortsel Institute for permission to use
Thea Philliou, Thermo Eberline illustrations.
David H. Phillips, Hytec, Incorporated
Robert F. Plumstead, Lucius Pitkin The applications presented in
Chapter 13, “Image Data Analysis,” are
Incorporated the result of many collaborative efforts.
William C. Plumstead, Sr., PQT Services Thanks to Ford Nondestructive Evaluation
Rita Pontefract, Yxlon International, Laboratory (R. McGee and staff); to
VJ Technologies (V. Alreja,
Akron S. Nagabhushana and V. Butani); to
Joergen Rheinlaender, InnospeXion ApS, Chrysler Kokomo Casting (R. Nicholson,
D. Guthrie and W. Kendricks); to
Hvalsø, Denmark Caterpillar, Incorporated (C. Andersen and
Wade J. Richards, McClellan Air Force G. Happoldt); to the Boeing Company
(W. Meade and M. Negley); and to
Base Lawrence Livermore National Laboratory
Scott D. Ritzheimer, Allegheny Ludlum (D. Chinn and others).

Steel Company Sources of illustrations are
Morteza Safai, FMC FoodTech acknowledged in a section at the end of
Robert L. Schulte, Digtome Corporation this book.
Russell G. Schonberg, Schonberg Research

Corporation
Noel D. Smith, NDS Products
Joel Henebry, Test and Measurement

Organization
Jana Knezovich, Agilent Technologies
Habeeb H. Saleh, WJE Associates
Fred J. Schlieper, Teradyne
Peter Soltani, Direct Radiography

Corporation
Dennis S. Smith, McDonnell Douglas

Aerospace
Richard C. Stark
Brian Sterling, Timco
Richard Z. Struk, Shellcast Foundries,

Montreal, Canada
Barry N. Taylor, National Institute of

Standards and Technology
Jay D. Thompson, Lockheed Martin

Missiles and Space
Michael L. Turnbow, Tennessee Valley

Authority
Ray Tsukimura, Aerotest Operations
Jerry A. Tucker, Industrial Nuclear
Thomas B. Turner, BWX Technologies
John J. Veno
Mark F.A. Warchol, Alcoa, Incorporated
Randall D. Wasberg, Amcast Automotive
Glenn A. Washer, Federal Highway

Administration
Amy Waters, Varian Industrial Products
Gene A. Westenbarger, Ohio University
Dwight S. Wilson, The Boeing Company,

Long Beach
Charles B. Winfield, Tru-Tec Services,

Incorporated
Sik-Lam Wong, Maxwell Physics

International
Daniel A. Wysnewski, Agfa Corporation

viii Radiographic Testing

CONTENTS

Chapter 1. Introduction to Chapter 6. Radiation Safety . . . . . . . 113
Radiographic Testing . . . . . . . . . . 1
Part 1. Management of Radiation
Part 1. Nondestructive Testing . . . . 2 Safety . . . . . . . . . . . . . . . 114
Part 2. Management of
Part 2. Dose Definitions and
Radiographic Testing . . . . 12 Exposure Levels . . . . . . . 119
Part 3. History of Radiographic
Part 3. Radiation Protection
Testing . . . . . . . . . . . . . . . 21 Measurements . . . . . . . . 121
Part 4. Units of Measure for
Part 4. Basic Exposure Control . . 127
Radiographic Testing . . . . 29 Part 5. Shielding . . . . . . . . . . . . . 130
Part 6. Neutron Radiographic
Chapter 2. Radiation and Particle
Physics . . . . . . . . . . . . . . . . . . . . 37 Safety . . . . . . . . . . . . . . . 134

Part 1. Elementary Particles . . . . . 38 Chapter 7. Principles of Film
Part 2. Properties of Radioactive Radiography . . . . . . . . . . . . . . 139

Materials . . . . . . . . . . . . . 42 Part 1. Film Exposure . . . . . . . . . 140
Part 3. Electromagnetic Part 2. Absorption and

Radiation . . . . . . . . . . . . . 48 Scattering . . . . . . . . . . . . 152
Part 3. Radiographic Screen . . . . 159
Chapter 3. Electronic Radiation Part 4. Industrial X-Ray Films . . 163
Sources . . . . . . . . . . . . . . . . . . . 55 Part 5. Radiographic Image

Part 1. Physical Principles . . . . . . 56 Quality and Detail
Part 2. Basic Generator Visibility . . . . . . . . . . . . 170
Part 6. Film Handling and
Construction . . . . . . . . . . 59 Storage . . . . . . . . . . . . . . 177
Part 3. Megavolt Radiography . . . 67 Part 7. Film Digitization . . . . . . . 180

Chapter 4. Isotope Radiation Sources Chapter 8. Radiographic
for Gamma Radiography . . . . . . 73 Interpretation . . . . . . . . . . . . . 185

Part 1. Selection of Part 1. Fundamentals of
Radiographic Sources . . . . 74 Radiographic
Interpretation . . . . . . . . 186
Part 2. Source Handling
Equipment . . . . . . . . . . . . 79 Part 2. Viewing in Radiographic
Testing . . . . . . . . . . . . . . 189
Chapter 5. Radiation Measurement . . 89
Part 1. Principles of Radiation Part 3. Densitometers . . . . . . . . 194
Measurement . . . . . . . . . . 90 Part 4. Radiographic
Part 2. Ionization Chambers and
Proportional Counters . . . 91 Interpretation
Part 3. Geiger-Müller Counters . . 96 Reporting . . . . . . . . . . . . 199
Part 4. Scintillation Detectors . . . 100 Part 5. Radiographic Artifacts . . . 202
Part 5. Luminescent Part 6. Discontinuity
Dosimetry . . . . . . . . . . . 102 Indications . . . . . . . . . . 207
Part 6. Neutron Detection . . . . . 104
Part 7. Semiconductors . . . . . . . 106 Chapter 9. Radiographic Film
Part 8. Film Badges . . . . . . . . . . . 108 Development . . . . . . . . . . . . . . 219

Part 1. Radiographic Latent
Image . . . . . . . . . . . . . . 220

Part 2. Chemistry of Film
Radiography . . . . . . . . . 230

Part 3. Darkroom . . . . . . . . . . . . 237
Part 4. Processing Technique . . . 241
Part 5. Silver Recovery . . . . . . . . 247

Rdiographic Testing ix

Chapter 10. Radioscopy . . . . . . . . . . 253 Chapter 15. Special Radiographic
Techniques . . . . . . . . . . . . . . . 403
Part 1. Fundamentals of
Radioscopic Imaging . . . 254 Part 1. Microfocus Radiographic
Testing . . . . . . . . . . . . . . 404
Part 2. Light Conversion . . . . . . 256
Part 3. Image Quality . . . . . . . . . 261 Part 2. Flash Radiography . . . . . 409
Part 4. Imaging Systems . . . . . . . 265 Part 3. Reversed Geometry
Part 5. Cameras . . . . . . . . . . . . . 269
Part 6. Viewing and Recording . . 275 Radiography with
Part 7. System Considerations . . 277 Scanning Source . . . . . . 414
Part 4. Stereo Radiography . . . . . 419
Chapter 11. Digital Radiographic Part 5. X-Ray Diffraction and
Imaging . . . . . . . . . . . . . . . . . . 283 X-Ray Fluorescence . . . . 427

Part 1. Overview of Digital Chapter 16. Neutron
Imaging . . . . . . . . . . . . . 284 Radiography . . . . . . . . . . . . . . 437

Part 2. Principles of Digital Part 1. Applications of Neutron
X-Ray Detectors . . . . . . . 286 Radiography . . . . . . . . . 438

Part 3. Image Contrast and Part 2. Static Radiography with
Signal Statistics . . . . . . . 289 Thermal Neutrons . . . . . 440

Part 4. X-Ray Detector Part 3. Special Techniques of
Technology . . . . . . . . . . 296 Neutron Radiography . . 446

Chapter 12. Computed Chapter 17. Radiographic Testing of
Tomography . . . . . . . . . . . . . . 303 Metal Castings . . . . . . . . . . . . . 453

Part 1. Introduction to Computed Part 1. Introduction to
Tomography . . . . . . . . . 304 Radiographic Testing
of Metal Castings . . . . . . 454
Part 2. Laminography . . . . . . . . 306
Part 3. Principles of Computed Part 2. General Radiographic
Techniques for Metal
Tomography . . . . . . . . . 310 Castings . . . . . . . . . . . . . 455
Part 4. Resolution and
Part 3. Radiographic Indications
Contrast . . . . . . . . . . . . 316 for Metal Castings . . . . . 461
Part 5. Computed Tomographic
Part 4. Radiographic Testing and
Systems . . . . . . . . . . . . . 318 Process Scheduling . . . . . 465
Part 6. Applications of Computed
Part 5. Problems in Radiographic
Tomography . . . . . . . . . 323 Testing of Metal
Part 7. Reference Standards Castings . . . . . . . . . . . . . 467

for Computed Chapter 18. Radiographic Testing
Tomography . . . . . . . . . 328 of Welds . . . . . . . . . . . . . . . . . 473

Chapter 13. Image Data Analysis . . . 345 Part 1. Introduction to
Radiographic Testing
Part 1. Fundamental Properties of Welds . . . . . . . . . . . . 474
of Digital Images and
Processing Schemes . . . . 346 Part 2. Weld Design . . . . . . . . . . 475
Part 3. Discontinuities in
Part 2. Image Analysis
Techniques and Welds . . . . . . . . . . . . . . . 478
Radiographic Tests . . . . . 353 Part 4. Technique

Part 3. Automated Testing Development . . . . . . . . . 482
Techniques . . . . . . . . . . 354 Part 5. Standards and Specifications

Chapter 14. Backscatter Imaging . . . 379 for Radiographic Testing
of Welds . . . . . . . . . . . . 489
Part 1. Physical Principles . . . . . 380 Part 6. Radiography of Weld
Part 2. Backscatter Imaging Discontinuities . . . . . . . 491
Part 7. In-Process Radioscopy of
Techniques . . . . . . . . . . 388 Arc Welding . . . . . . . . . . 502
Part 3. Reconstruction and Image Part 8. False Indications in
Radiographs of
Processing Techniques . . 392 Aluminum Alloy
Part 4. Applications of Welds . . . . . . . . . . . . . . . 507

Backscatter Imaging . . . . 394

x Radiographic Testing

Chapter 19. Radiographic Testing in
Utility, Petroleum and Chemical
Industries . . . . . . . . . . . . . . . . . 513

Part 1. Overview . . . . . . . . . . . . 514
Part 2. Pipe and Tubing

Applications . . . . . . . . . 515
Part 3. Vessel and Component

Applications . . . . . . . . . 526
Part 4. Nuclear Fuel

Applications . . . . . . . . . 530
Part 5. Other Uses for

Radiographic Testing . . . 537

Chapter 20. Aerospace Applications
of Radiographic Testing . . . . . 543

Part 1. Film Radiography of
Aviation Components . . 544

Part 2. Radiographic Testing
of Space Flight
Components . . . . . . . . . 550

Part 3. Techniques for Advanced
Materials . . . . . . . . . . . . 559

Chapter 21. Other Applications of
Radiographic Testing . . . . . . . . 569

Part 1. Radiation Gaging of
Density or Thickness . . . 570

Part 2. Radioscopy of
Electronics . . . . . . . . . . . 578

Part 3. Radiographic Testing of
Consumer Goods . . . . . . 584

Part 4. Radiographic Testing in
Security Systems . . . . . . 588

Part 5. Infrastructure
Applications of
Radiographic Testing . . . 591

Part 6. Radiographic Testing in
Conservation of Historic
Buildings and Museum
Objects . . . . . . . . . . . . . 594

Chapter 22. Attenuation
Coefficients . . . . . . . . . . . . . . . 609

Part 1. Introduction to
Attenuation
Coefficients . . . . . . . . . . 610

Part 2. Attenuation Coefficient
Tables . . . . . . . . . . . . . . 612

Chapter 23. Radiographic Testing
Glossary . . . . . . . . . . . . . . . . . . 653

Index . . . . . . . . . . . . . . . . . . . . . . . . 675

Figure Sources . . . . . . . . . . . . . . . . . . 691

Radiographic Testing xi

Copyright © 2002
AMERICAN SOCIETY FOR NONDESTRUCTIVE TESTING, INC.
All rights reserved.

No part of this book may be reproduced, stored in a retrieval system or transmitted, in any form or by any means —
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Nothing contained in this book is to be construed as a grant of any right of manufacture, sale or use in connection with
any method, process, apparatus, product or composition, whether or not covered by letters patent or registered
trademark, nor as a defense against liability for the infringement of letters patent or registered trademark.

The American Society for Nondestructive Testing, its employees, and the contributors to this volume assume no
responsibility for the safety of persons using the information in this book.

Copyright © 2002 by the American Society for Nondestructive Testing, Incorporated. All rights reserved. ASNT is not
responsible for the authenticity or accuracy of information herein, and published opinions and statements do not
necessarily reflect the opinion of ASNT. Products or services that are advertised or mentioned do not carry the
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Library of Congress Cataloging-in-Publication Data

Radiographic Testing [computer file] / technical editors, Richard H. Bossi, Frank
A. Iddings, George C. Wheeler; . -- 3rd ed.
1 computer optical disc; 4 3/4 in. — (Nondestructive testing handbook; v. 4)
System requirements for Windows: 486 or Pentium PC; 8 MB RAM (16 MB

RAM for windows NT); Windows 95/98 or windows NT 4.0 with Service Pack 3
or later; Adobe Acrobat Reader 5.0 (included); CD-ROM drive.

System requirements for Macintosh: Apple Power Macintosh; 4.5 MB RAM;
System 7.1.2 or later; 8 MB free hard disk space; Adobe Acrobat Reader 5.0
(included); CD-ROM drive.

Title from disc label.
Audience: Quality control engineers and inspectors
Summary:
ISBN 1-57117-098-7

NOTE:

Information presented on this page is specific for the CD-ROM version of this
publication. For Library of Congress Cataloging-in-Publication data pertaining to
the printed edition, please click this link.

MULTIMEDIA CONTENTS

Chapter 4. Isotope Radiation Sources Chapter 13. Image Data Analysis . . . 345
for Gamma Radiography . . . . . . 73 Movie. Exfoliation corrosion,
thin to thick . . . . . . . . . 374
Movie. Isotopic source . . . . . . . . . 74 Movie. General corrosion,
Movie. Collimators . . . . . . . . . . . 82 thin to thick . . . . . . . . . 374
Movie. Cracks around fasteners . 374
Chapter 6. Radiation Safety . . . . . . . 113 Movie. Cracks around fasteners,
Movie. Radiation injury . . . . . . . 114 in layers from top . . . . . 374
Movie. Survey meters . . . . . . . . . 117
Movie. Check equipment . . . . . . 121 Chapter 14. Backscatter Imaging . . . 379
Movie. Personnel Monitoring Movie. Backscatter scan of
Devices . . . . . . . . . . . . . 124 undamaged area . . . . . . 397
Movie. Warning tape and signs . 128 Movie. Moving source and
sensor into place . . . . . . 397
Chapter 7. Principles of Film Movie. Pillowing and corrosion . 397
Radiography . . . . . . . . . . . . . . 139
Chapter 20. Aerospace Applications
Movie. Conventional of Radiographic Testing . . . . . 543
radiography gives
shadow image . . . . . . . . 140 Movie. Automated inspection
of rocket motor . . . . . . . 551
Chapter 10. Radioscopy . . . . . . . . . . 253
Movie. Automated wheel Chapter 21. Other Applications of
inspection . . . . . . . . . . . 279 Radiographic Testing . . . . . . . . 569

Chapter 12. Computed Movie. Inspection of printed
Tomography . . . . . . . . . . . . . . 303 circuit boards . . . . . . . . . 583

Movie. Second generation Movie. Radiographic
(rotate and translate) . . . 319 inspection of light bulb . 587

Movie. Third generation Movie. Cargo scanning . . . . . . . 589
(rotate only) . . . . . . . . . 319 Movie. Image acquisition and

Movie. Electronic device evaluation . . . . . . . . . . . 589
on turntable . . . . . . . . . 327 Movie. Images at 3 MV

Movie. Images of electronic and 6 MV . . . . . . . . . . . 589
device . . . . . . . . . . . . . . 327 Movie. Contraband in water

Movie. Tomographic data tank . . . . . . . . . . . . . . . . 589
image of electronic
device . . . . . . . . . . . . . . 327

Movie. Image slices of device,
top to bottom . . . . . . . . 327

Movie. Slices show
delaminations in
composite fastener
hole . . . . . . . . . . . . . . . . 327

Movie. Transverse image of
delaminations in
fastener hole . . . . . . . . . 327

Rdiographic Testing

1

CHAPTER

Introduction to
Radiographic Testing

Harold Berger, Industrial Quality, Incorporated,
Gaithersburg, Maryland (Part 3)
Holger H. Streckert, General Atomics, San Diego,
California (Part 4)
Marvin W. Trimm, Westinghouse Savannah River
Company, Aiken, South Carolina (Parts 1 and 2)

PART 1. Nondestructive Testing1

Nondestructive testing (NDT) has been sampling. Sampling (that is, less than
defined as comprising those test methods 100 percent testing to draw inferences
used to examine or inspect a part or about the unsampled lots) is
material or system without impairing its nondestructive testing if the tested sample
future usefulness.1 The term is generally is returned to service. If the steel is tested
applied to nonmedical investigations of to verify the alloy in some bolts that can
material integrity. then be returned to service, then the test
is nondestructive. In contrast, even if
Strictly speaking, this definition of spectroscopy used in the chemical testing
nondestructive testing includes of many fluids is inherently
noninvasive medical diagnostics. X-rays, nondestructive, the testing is destructive if
ultrasound and endoscopes are used by the samples are poured down the drain
both medical and industrial after testing.
nondestructive testing. Medical
nondestructive testing, however, has come Nondestructive testing is not confined
to be treated by a body of learning so to crack detection. Other discontinuities
separate from industrial nondestructive include porosity, wall thinning from
testing that today most physicians do not corrosion and many sorts of disbonds.
use the word nondestructive. Nondestructive material characterization
is a growing field concerned with material
Nondestructive testing is used to properties including material
investigate specifically the material identification and microstructural
integrity of the test object. A number of characteristics — such as resin curing, case
other technologies — for instance, radio hardening and stress — that have a direct
astronomy, voltage and amperage influence on the service life of the test
measurement and rheometry (flow object.
measurement) — are nondestructive but
are not used specifically to evaluate Nondestructive testing has also been
material properties. Radar and sonar are defined by listing or classifying the
classified as nondestructive testing when various techniques.1-3 This sense of
used to inspect dams, for instance, but nondestructive testing is practical in that it
not when they are used to chart a river typically highlights methods in use by
bottom. industry.

Nondestructive testing asks “Is there Purposes of
something wrong with this material?” In Nondestructive Testing
contrast, performance and proof tests ask
“Does this component work?” It is not Since the 1920s, the art of testing without
considered nondestructive testing when destroying the test object has developed
an inspector checks a circuit by running from a laboratory curiosity to an
electric current through it. Hydrostatic indispensable tool of fabrication,
pressure testing is another form of proof construction and manufacturing
testing, one that may destroy the test processes. No longer is visual testing of
object. materials, parts and complete products
the principal means of determining
Another gray area that invites various adequate quality. Nondestructive tests in
interpretations in defining nondestructive great variety are in worldwide use to
testing is future usefulness. Some material detect variations in structure, minute
investigations involve taking a sample of changes in surface finish, the presence of
the inspected part for testing that is cracks or other physical discontinuities, to
inherently destructive. A noncritical part measure the thickness of materials and
of a pressure vessel may be scraped or coatings and to determine other
shaved to get a sample for electron characteristics of industrial products.
microscopy, for example. Although future Scientists and engineers of many
usefulness of the vessel is not impaired by countries have contributed greatly to
the loss of material, the procedure is nondestructive test development and
inherently destructive and the shaving applications.
itself — in one sense the true test object —
has been removed from service The various nondestructive testing
permanently. methods are covered in detail in the

The idea of future usefulness is relevant
to the quality control practice of

2 Radiographic Testing

literature but it is always wise to consider fluctuates and reverses at low or high
objectives before details. How is frequencies. Frequency of stress reversals
nondestructive testing useful? Why do increases with the speeds of modern
thousands of industrial concerns buy the machines and thus parts tend to fatigue
testing equipment, pay the subsequent and fail more rapidly.
operating costs of the testing and even
reshape manufacturing processes to fit the Another cause of increased stress on
needs and findings of nondestructive modern products is a reduction in the
testing? safety factor. An engineer designs with
certain known loads in mind. On the
Modern nondestructive tests are used supposition that materials and
by manufacturers (1) to ensure product workmanship are never perfect, a safety
integrity and, in turn, reliability; (2) to factor of 2, 3, 5 or 10 is applied. However,
avoid failures, prevent accidents and save because of other considerations, a lower
human life (see Figs. 1 and 2); (3) to make factor is often used that depends on the
a profit for the user; (4) to ensure importance of lighter weight or reduced
customer satisfaction and maintain the cost or risk to consumer.
manufacturer’s reputation; (5) to aid in
better product design; (6) to control New demands on machinery have also
manufacturing processes; (7) to lower stimulated the development and use of
manufacturing costs; (8) to maintain new materials whose operating
uniform quality level; and (9) to ensure characteristics and performance are not
operational readiness. completely known. These new materials
create greater and potentially dangerous
These reasons for widespread and problems. As an example, an aircraft part
profitable nondestructive testing are was built from an alloy whose work
sufficient in themselves but parallel hardening, notch resistance and fatigue
developments have contributed to its life were not well known. After relatively
growth and acceptance. short periods of service some of these
aircraft suffered disastrous failures.
Increased Demand on Machines Sufficient and proper nondestructive tests
could have saved many lives.
In the interest of greater speed and
reduced cost for materials, the design As technology improves and as service
engineer is often under pressure to reduce requirements increase, machines are
weight. This can sometimes be done by subjected to greater variations and to
substituting aluminum alloys, magnesium wider extremes of all kinds of stress,
alloys or composite materials for steel or creating an increasing demand for
iron but such light parts may not be the stronger or more damage tolerant
same size or design as those they replace. materials.
The tendency is also to reduce the size.
These pressures on the designer have Engineering Demands for Sounder
subjected parts of all sorts to increased Materials
stress levels. Even such commonplace
objects as sewing machines, sauce pans Another justification for nondestructive
and luggage are also lighter and more tests is the designer’s demand for sounder
heavily loaded than ever before. The stress
to be supported is seldom static. It often FIGURE 2. Boilers operate with high internal steam pressure.
Material discontinuites can lead to sudden, violent failure
FIGURE 1. Fatigue cracks caused damage to aircraft fuselage, with possible injury to people and property.
causing death of flight attendant and injury to passengers
(April 1988).

Introduction to Radiographic Testing 3

materials. As size and weight decrease and of several others. Loss of such production
the factor of safety is lowered, more is one of the greatest losses resulting from
emphasis is placed on better raw material part failure.
control and higher quality of materials,
manufacturing processes and Applications of
workmanship. Nondestructive Testing

An interesting fact is that a producer of Nondestructive testing is a branch of the
raw material or of a finished product materials sciences that is concerned with
sometimes does not improve quality or all aspects of the uniformity, quality and
performance until that improvement is serviceability of materials and structures.
demanded by the customer. The pressure The science of nondestructive testing
of the customer is transferred to incorporates all the technology for
implementation of improved design or detection and measurement of significant
manufacturing. Nondestructive testing is properties, including discontinuities, in
frequently called on to deliver this new items ranging from research specimens to
quality level. finished hardware and products in service.
By definition, nondestructive testing
Public Demands for Greater Safety methods are means for examining
materials and structures without
The demands and expectations of the disruption or impairment of serviceability.
public for greater safety are apparent Nondestructive testing makes it possible
everywhere. Review the record of the for internal properties or hidden
courts in granting high awards to injured discontinuities to be revealed or inferred
persons. Consider the outcry for greater by appropriate methods.
automobile safety, as evidenced by the
required automotive safety belts and the Nondestructive testing is becoming
demand for air bags, blowout proof tires increasingly vital in the effective conduct
and antilock braking systems. The of research, development, design and
publicly supported activities of the manufacturing programs. Only with
National Safety Council, Underwriters appropriate nondestructive testing
Laboratories, the Occupational Safety and methods can the benefits of advanced
Health Administration and the Federal materials science be fully realized. The
Aviation Administration in the United information required for appreciating the
States, as well as the work of similar broad scope of nondestructive testing is
agencies abroad, are only a few of the available in many publications and
ways in which this demand for safety is reports.
expressed. It has been expressed directly
by passengers who cancel reservations Classification of Methods
following a serious aircraft accident. This
demand for personal safety has been In a report, the National Materials
another strong force in the development Advisory Board (NMAB) Ad Hoc
of nondestructive tests. Committee on Nondestructive Evaluation
adopted a system that classified
Rising Costs of Failure techniques into six major method
categories: visual, penetrating radiation,
Aside from awards to the injured or to magnetic-electrical, mechanical vibration,
estates of the deceased and aside from thermal and chemical/electrochemical.3 A
costs to the public (because of evacuation modified version is presented in Table 1.1
occasioned by chemical leaks), consider
briefly other factors in the rising costs of Each method can be completely
mechanical failure. These costs are characterized in terms of five principal
increasing for many reasons. Some factors: (1) energy source or medium used
important ones are (1) greater costs of to probe object (such as X-rays, ultrasonic
materials and labor; (2) greater costs of waves or thermal radiation); (2) nature of
complex parts; (3) greater costs because of the signals, image or signature resulting
the complexity of assemblies; (4) greater from interaction with the object
probability that failure of one part will (attenuation of X-rays or reflection of
cause failure of others because of ultrasound, for example); (3) means of
overloads; (5) trend to lower factors of detecting or sensing resultant signals
safety; (6) probability that the failure of (photoemulsion, piezoelectric crystal or
one part will damage other parts of high inductance coil); (4) method of indicating
value; and (7) part failure in an integrated or recording signals (meter deflection,
automatic production machine, shutting oscilloscope trace or radiograph); and
down an entire high speed production (5) basis for interpreting the results (direct
line. When production was carried out on or indirect indication, qualitative or
many separate machines, the broken one quantitative and pertinent dependencies).
could be bypassed until repaired. Today,
one machine is tied into the production

4 Radiographic Testing

The objective of each method is to Classification Relative to Test
provide information about the following Object
material parameters: (1) discontinuities
and separations (cracks, voids, inclusions Nondestructive testing techniques may be
delaminations and others); (2) structure or classified according to how they detect
malstructure (crystalline structure, grain indications relative to the surface of a test
size, segregation, misalignment and object. Surface methods include liquid
others); (3) dimensions and metrology penetrant testing, visual testing, grid and
(thickness, diameter, gap size, moiré testing. Surface/near-surface
discontinuity size and others); (4) physical methods include tap, potential drop,
and mechanical properties (reflectivity, holography and shearography, magnetic
conductivity, elastic modulus, sonic particle and electromagnetic testing.
velocity and others); (5) composition and When surface or surface/near-surface
chemical analysis (alloy identification, methods are applied during intermediate
impurities, elemental distributions and manufacturing processes, they provide
others); (6) stress and dynamic response preliminary assurance that volumetric
(residual stress, crack growth, wear, methods performed on the completed
vibration and others); (7) signature object or component will reveal few
analysis (image content, frequency rejectable discontinuities. Volumetric
spectrum, field configuration and others); methods include radiography, ultrasonic
and (8) abnormal sources of heat. testing, acoustic emission testing and less
widely used methods such as
Terms used in this block are further acoustoultrasonic testing and magnetic
defined in Table 2 with respect to specific resonance imaging. Through-boundary
objectives and specific attributes to be techniques described include leak testing,
measured, detected and defined. some infrared thermographic techniques,
airborne ultrasonic testing and certain
The limitations of a method include techniques of acoustic emission testing.
conditions required by that method: Other less easily classified methods are
conditions to be met for method material identification, vibration analysis
application (access, physical contact, and strain gaging.
preparation and others) and requirements
to adapt the probe or probe medium to No one nondestructive testing method
the object examined. Other factors limit is all revealing. That is not to say that one
the detection or characterization of method or technique of a method is
discontinuities, properties and other rarely adequate for a specific object or
attributes and limit interpretation of component. However, in most cases it
signals or images generated. takes a series of test methods to do a
complete nondestructive test of an object

TABLE 1. Nondestructive testing method categories. Objectives
Categories

Basic Categories

Mechanical and optical color; cracks; dimensions; film thickness; gaging; reflectivity; strain distribution and magnitude; surface
Penetrating radiation finish; surface flaws; through-cracks
Electromagnetic and electronic cracks; density and chemistry variations; elemental distribution; foreign objects; inclusions; microporosity;
misalignment; missing parts; segregation; service degradation; shrinkage; thickness; voids
Sonic and ultrasonic alloy content; anisotropy; cavities; cold work; local strain, hardness; composition; contamination;
corrosion; cracks; crack depth; crystal structure; electrical conductivities; flakes; heat
Thermal and infrared treatment; hot tears; inclusions; ion concentrations; laps; lattice strain; layer thickness; moisture content;
Chemical and analytical polarization; seams; segregation; shrinkage; state of cure; tensile strength; thickness; disbonds
crack initiaion and propagation; cracks, voids; damping factor; degree of cure; degree of impregnation;
degree of sintering; delaminations; density; dimensions; elastic moduli; grain size; inclusions;
mechanical degradation; misalignment; porosity; radiation degradation; structure of composites; surface
stress; tensile, shear and compressive strength; disbonds; wear
anisotropy, bonding; composition; emissivity; heat contours; plating thickness; porosity; reflectivity; stress;
thermal conductivity; thickness; voids; cracks; delaminations; heat treatment; state of cure; moisture;
corrosion
alloy identification; composition; cracks; elemental analysis and distribution; grain size; inclusions;
macrostructure; porosity; segregation; surface anomalies

Auxiliary Categories dimensional variations; dynamic performance; anomaly characterization and definition; anomaly
Image generation distribution; anomaly propagation; magnetic field configurations
data selection, processing and display; anomaly mapping, correlation and identification; image
Signal image analysis enhancement; separation of multiple variables; signature analysis

Introduction to Radiographic Testing 5

or component. For example, if surface situations, if internal discontinuities were
cracks must be detected and eliminated to be detected, then ultrasonic testing or
and the object or component is made of radiography would be the selection. The
ferromagnetic material, then magnetic exact technique in either case would
particle testing would be the obvious depend on the thickness and nature of
choice. If that same material is aluminum the material and the types of
or titanium, then the choice would be discontinuities that must be detected.
liquid penetrant or electromagnetic
testing. However, for either of these

TABLE 2. Objectives of nondestructive testing methods.

Objectives Attributes Measured or Detected

Discontinuites and separations

Surface anomalies roughness; scratches; gouges; crazing; pitting; inclusions and imbedded foreign material

Surface connected anomalies cracks; porosity; pinholes; laps; seams; folds; inclusions

Internal anomalies cracks; separations; hot tears; cold shuts; shrinkage; voids; lack of fusion; pores; cavities; delaminations;
disbonds; poor bonds; inclusions; segregations

Structure molecular structure; crystalline structure and/or strain; lattice structure; strain; dislocation; vacancy;
Microstructure deformation
grain structure, size, orientation and phase; sinter and porosity; impregnation; filler and/or reinforcement
Matrix structure distribution; anisotropy; heterogeneity; segregation
leaks (lack of seal or through-holes); poor fit; poor contact; loose parts; loose particles; foreign objects
Small structural anomalies assembly errors; misalignment; poor spacing or ordering; deformation; malformation; missing parts
Gross structural anomalies

Dimensions and metrology linear measurement; separation; gap size; discontinuity size, depth, location and orientation
unevenness; nonuniformity; eccentricity; shape and contour; size and mass variations
Displacement; position film, coating, layer, plating, wall and sheet thickness; density or thickness variations
Dimensional variations
Thickness; density

Physical and mechanical properties

Electrical properties resistivity; conductivity; dielectric constant and dissipation factor

Magnetic properties polarization; permeability; ferromagnetism; cohesive force

Thermal properties conductivity; thermal time constant and thermoelectric potential; diffusivity; effusivity; specific heat

Mechanical properties compressive, shear and tensile strength (and moduli); Poisson’s ratio; sonic velocity; hardness; temper and
embrittlement

Surface properties color; reflectivity; refraction index; emissivity

Chemical composition and analysis

Elemental analysis detection; identification, distribution and/or profile

Impurity concentrations contamination; depletion; doping and diffusants

Metallurgical content variation; alloy identification, verification and sorting

Physiochemical state moisture content; degree of cure; ion concentrations and corrosion; reaction products

Stress and dynamic response

Stress; strain; fatigue heat treatment, annealing and cold work effects; residual stress and strain; fatigue damage and life (residual)

Mechanical damage wear; spalling; erosion; friction effects

Chemical damage corrosion; stress corrosion; phase transformation

Other damage radiation damage and high frequency voltage breakdown

Dynamic performance crack initiation and propagation; plastic deformation; creep; excessive motion; vibration; damping; timing of
events; any anomalous behavior

Signature analysis potential; strength; field distribution and pattern
Electromagnetic field isotherms; heat contours; temperatures; heat flow; temperature distribution; heat leaks; hot spots; contrast
Thermal field noise; vibration characteristics; frequency amplitude; harmonic spectrum and/or analysis; sonic and/or
Acoustic signature ultrasonic emissions
distribution and diffusion of isotopes and tracers
Radioactive signature image enhancement and quantization; pattern recognition; densitometry; signal classification, separation;
Signal or image analysis and correlation; discontinuity identification, definition (size and shape) and distribution analysis;
discontinuity mapping and display

6 Radiographic Testing

Value of Nondestructive nondestructive testing at the end of a
Testing manufacturing process. This approach will
ultimately increase production costs.
The contribution of nondestructive When used properly, nondestructive
testing to profits has been acknowledged testing saves money for the manufacturer.
in the medical field and computer and Rather than costing the manufacturer
aerospace industries. However, in money, nondestructive testing should add
industries such as heavy metals, though profits to the manufacturing process.
nondestructive testing may be reluctantly
accepted its contribution to profits may Overview of
not be obvious to management. Nondestructive Testing
Nondestructive testing is sometimes Methods
thought of only as a cost item. One
possible reason is industry downsizing. To optimize the use of nondestructive
When a company cuts costs, two testing, it is necessary first to understand
vulnerable areas are quality and safety. the principles and applications of all the
When bidding contract work, companies methods. This book features radiographic
add profit margin to all cost items, testing (Fig. 3) — only one of the
including nondestructive testing, so a nondestructive testing methods. Several
profit should be made on the other methods and the applications
nondestructive testing. However, when associated with them are briefly described
production is going poorly and it is next.
anticipated that a job might lose money,
it seems like the first corner that Visual Testing
production personnel will try to cut is
nondestructive testing. This is Principles. Visual testing (Fig. 4) is the
accomplished by subtle pressure on observation of a test object, either directly
nondestructive testing technicians to with the eyes or indirectly using optical
accept a product that does not quite meet instruments, by an inspector to evaluate
a code or standard requirement. The the presence of surface anomalies and the
attitude toward nondestructive testing is object’s conformance to specification.
gradually improving as management Visual testing should be the first
comes to appreciate its value. nondestructive testing method applied to
an item. The test procedure is to clean the
Nondestructive testing should be used surface, provide adequate illumination
as a control mechanism to ensure that and observe. A prerequisite necessary for
manufacturing processes are within design competent visual testing of an item is
performance requirements. It should knowledge of the manufacturing processes
never be used in an attempt to obtain by which it was made, its service history,
quality in a product by using potential failure modes and related
industry experience.
FIGURE 3. Representative setup for radiographic test.
Applications. Visual testing provides a
Radiation source means of detecting and examining a
variety of surface discontinuities. It is also

FIGURE 4. Visual test using borescope to
view interior of cylinder.

Specimen

Void

Image plane Discontinuity images

Introduction to Radiographic Testing 7

the most widely used method for surface discontinuities, seams, cracks, laps,
detecting and examining for surface porosity and leak paths.
discontinuities associated with various
structural failure mechanisms. Even when Magnetic Particle Testing
other nondestructive tests are performed,
visual tests often provide a useful Principles. Magnetic particle testing is a
supplement. For example, when the eddy method of locating surface and slightly
current testing of process tubing is subsurface discontinuities in
performed, visual testing is often ferromagnetic materials. It depends on the
performed to verify and more closely fact that when the material or part under
examine the surface condition. This test is magnetized, discontinuities that lie
verification process can impact the in a direction generally transverse to the
evaluation process associated with other direction of the magnetic field will cause a
nondestructive test methods being used. leakage field to be formed at and above
The following discontinuities may be the surface of the part. The presence of
detected by a simple visual test: surface this leakage field and therefore the
discontinuities, cracks, misalignment, presence of the discontinuity is detected
warping, corrosion, wear and physical by the use of finely divided ferromagnetic
damage. particles applied over the surface, with
some of the particles being gathered and
Liquid Penetrant Testing held to form an outline of the
discontinuity. This generally indicates its
Principles. Liquid penetrant testing (Fig. 5) location, size, shape and extent. Magnetic
reveals discontinuities open to the particles are applied over a surface as dry
surfaces of solid and nonporous materials. particles or as wet particles in a liquid
Indications of a wide spectrum of carrier such as water or oil.
discontinuity sizes can be found regardless
of the configuration of the workpiece and Applications. The principal industrial uses
regardless of discontinuity orientations. of magnetic particle testing are for final,
Liquid penetrants seep into various types receiving and in-process testing; for
of minute surface openings by capillary quality control; for maintenance and
action. The cavities of interest can be very overhaul in the transportation industries;
small, often invisible to the unaided eye. for plant and machinery maintenance;
The ability of a given liquid to flow over a and for testing of large components. Some
surface and enter surface cavities depends of the typically detected discontinuities
principally on the following: cleanliness are surface discontinuities, seams, cracks
of the surface, surface tension of the and laps.
liquid, configuration of the cavity, contact
angle of the liquid, ability of the liquid to Eddy Current Testing
wet the surface, cleanliness of the cavity
and size of surface opening of the cavity. Principles. Based on electromagnetic
induction, eddy current testing (Fig. 6) is
Applications. The principal industrial uses used to identify or differentiate among a
of liquid penetrant testing are final
testing, receiving testing, in-process FIGURE 6. Representative setup for eddy current test.
testing and quality control, maintenance
and overhaul in the transportation Primary electromagnetic field
industries, in plant and machinery
maintenance and in testing of large Coil in eddy current probe
components. The following are some of
the typically detected discontinuities:

FIGURE 5. Liquid penetrant indication of Direction of
cracking. primary current

Induced field

Conducting specimen Direction of eddy
currents
Eddy current strength
decreases with
increasing depth

8 Radiographic Testing

wide variety of physical, structural and Applications. An important industrial use
metallurgical conditions in electrically of eddy current testing is on heat
conductive ferromagnetic and exchanger tubing. For example, eddy
nonferromagnetic metals and metal parts. current testing is often specified for thin
The method is based on indirect wall tubing in pressurized water reactors,
measurement and on correlation between steam generators, turbine condensers and
the instrument reading and the structural air conditioning heat exchangers. Eddy
characteristics and serviceability of the current testing is also used often in
parts being examined. aircraft maintenance. The following are
some of the typical material
With a basic system, the part is placed characteristics that can be evaluated by
within or adjacent to an electric coil in eddy current testing: cracks, inclusions,
which high frequency alternating current dents and holes; grain size and hardness;
is flowing. This excitation current coating and material thickness;
establishes an electromagnetic field dimensions and geometry; composition,
around the coil. This primary field causes conductivity or permeability; and alloy
eddy current to flow in the part because composition.
of electromagnetic induction. Inversely,
the eddy currents affected by all Ultrasonic Testing
characteristics (conductivity, permeability,
thickness, discontinuities and geometry) Principles. Ultrasonic testing (Fig. 7) is a
of the part create a secondary magnetic nondestructive method in which beams of
field that opposes the primary field. The sound waves at a frequency too high to
results of this interaction affect the coil hear are introduced into materials for the
voltage and can be displayed in a variety detection of surface and subsurface
of methods. discontinuities in the material. These
acoustic waves travel through the material
Eddy currents flow in closed loops in with some attendant loss of energy
the part or air. Their two most important (attenuation) and are reflected at
characteristics, amplitude and phase, are interfaces. The reflected beam is displayed
influenced by the arrangement and (or reduces the display of transmitted
characteristics of the instrumentation and sound) and is then analyzed to define the
test piece. For example, during the test of presence and locations of discontinuities
a tube the eddy currents flow or discontinuities.
symmetrically in the tube when
discontinuities are not present. However, Applications. Ultrasonic testing of metals
when a crack is present, then the eddy is widely used, principally for the
current flow is impeded and changed in detection of discontinuities. This method
direction, causing significant changes in can be used to detect internal
the associated electromagnetic field.

FIGURE 7. Representative setups for ultrasonic testing: (a) longitudinal wave technique; (b) shear wave
technique.
(a) (b)

Crack

Crack Entry surface
Crack
Time
Bolt ab
Skip distance
Back surface
Introduction to Radiographic Testing 9
Transducer

Crack

discontinuities in most engineering The source of acoustic emission energy
metals and alloys. Bonds produced by is the elastic stress field in the material.
welding, brazing, soldering and adhesive Without stress, there is no emission.
bonding can also be ultrasonically Therefore, an acoustic emission test
examined. Inline techniques have been (Fig. 8) is usually carried out during a
developed for monitoring and classifying controlled loading of the structure. This
materials as acceptable, salvageable or can be a proof load before service; a
scrap and for process control. Other controlled variation of load while the
applications include testing of piping and structure is in service; a fatigue, pressure
pressure vessels, nuclear systems, motor or creep test; or a complex loading
vehicles, machinery, structures, railroad program. Often, a structure is going to be
rolling stock and bridges and thickness loaded hydrostatically anyway during
measurement. service and acoustic emission testing is
used because it gives valuable additional
Leak Testing information about the expected
performance of the structure under load.
Principles. Leak testing is concerned with Other times, acoustic emission testing is
the flow of liquids or gases from selected for reasons of economy or safety
pressurized or into evacuated components and a special loading procedure is
or systems intended to hold fluids. The arranged to meet the needs of the acoustic
principles of leak testing involve the emission test.
physics of fluid (liquids or gases) flowing
through a barrier where a pressure Applications. Acoustic emission is a
differential or capillary action exists. natural phenomenon occurring in the
Leaking fluids (liquid or gas) can widest range of materials, structures and
propagate from inside a component or processes. The largest scale events
assembly to the outside, or vice versa, as a observed with acoustic emission testing
result of a pressure differential between are seismic and the smallest are small
the two regions or as a result of dislocations in stressed metals.
permeation through a barrier. The
importance of leak testing depends on the The equipment used is highly sensitive
size of the leak and on the medium being to any kind of movement in its operating
leaked. Leak testing encompasses frequency (typically 20 to 1200 kHz). The
procedures that fall into these basic equipment can detect not only crack
functions: leak location, leakage growth and material deformation but also
measurement and leakage monitoring.
FIGURE 8. Acoustic emission testing setup in which eight
Applications. Like other forms of sensors permit computer to calculate location of crack
nondestructive testing, leak testing has a propagation.
great impact on the safety and
performance of a product. Reliable leak Acoustic
testing decreases costs by reducing event
number of reworked products, warranty
repairs and liability claims. The most Preamplifier
common reasons for performing a leak
test are to prevent the loss of costly Computer
materials or energy; to prevent
contamination of the environment; to Test
ensure component or system reliability; object
and to prevent the potential for an
explosion or fire.

Acoustic Emission Testing

Principles. Acoustic emissions are stress
waves produced by sudden movement in
stressed materials. The classic source of
acoustic emission is discontinuity related
deformation processes such as crack
growth and plastic deformation. Sudden
movement at the source produces a stress
wave that radiates out into the structure
and excites a sensitive piezoelectric sensor.
As the stress in the material is raised,
emissions are generated. The signals from
one or more sensors are amplified and
measured to produce data for display and
interpretation.

10 Radiographic Testing

such process as solidification, friction, through the connection produces an
impact, flow and phase transformations. increase in surface temperature of the
Therefore, acoustic emission testing is also connection.
used for in-process weld monitoring,
detecting tool touch and tool wear during Applications. There are two basic
automatic machining, detecting wear and categories of infrared and thermal test
loss of lubrication in rotating equipment, applications: electrical and mechanical.
detecting loose parts and loose particles, The specific applications within these two
detecting and monitoring leaks, categories are numerous. Electrical
cavitation, flow, preservice proof testing, applications include transmission and
in-service weld monitoring and leak distribution lines, transformers,
testing. disconnects, switches, fuses, relays,
breakers, motor windings, capacitor
Infrared and Thermal Testing banks, cable trays, bus taps and other
components and subsystems. Mechanical
Principles. Conduction and convection applications include insulation (in boilers,
are the primary mechanisms of heat furnaces, kilns, piping, ducts, vessels,
transfer in an object or system. However, refrigerated trucks and systems, tank cars
electromagnetic radiation is emitted from and elsewhere), friction in rotating
a heated body when electrons in that equipment (bearings, couplings, gears,
body change to a lower energy state. gearboxes, conveyor belts, pumps,
Thermal testing involves the compressors and other components) and
measurement or mapping of surface fluid flow (steam lines; heat exchangers;
temperatures when heat flows from, to or tank fluid levels; exothermic reactions;
through a test object. Temperature heating, ventilation and air conditioning
differentials on a surface, or changes in systems; leaks above and below ground;
surface temperature with time, are related cooling and heating; tube blockages;
to heat flow patterns and can be used to systems; environmental assessment of
detect anomalies or to determine the heat thermal discharge; boiler or furnace air
transfer characteristics of an object. For leakage; condenser; turbine air leakage;
example, during the operation of an pumps; compressors; and other system
electrical breaker, a hot spot detected at applications).
an electrical termination may be caused
by a loose or corroded connection (see Other Methods
Fig. 9). The resistance to electrical flow
There are many other methods of
FIGURE 9. Infrared thermography of nondestructive testing, including optical
automatic transfer switches of emergency methods such as holography,
diesel generator. Hot spots appear bright in shearography and moiré imaging; material
thermogram. identification methods such as chemical
spot testing, spark testing and
spectroscopy; strain gaging; and acoustic
methods such as vibration analysis and
tapping.

Introduction to Radiographic Testing 11

PART 2. Management of Radiographic Testing

Radiography may be considered the most Management of
effective nondestructive testing method Radiographic Testing
merely because of its universal use and Programs
acceptance in industry. Radiography can
be used to test most types of solid Management of a radiographic testing
material. Exceptions include materials of program will require consideration of
very high or very low density. Neutron many items before a program can produce
radiography, however, can often be used the desired results. Six basic questions
in such cases. There is wide latitude both must be answered before a true direction
of material thickness that can be tested can be charted. They are as follows.
and in the techniques that can be used.
Usually conditions that result in a two 1. Are regulatory requirements in place
percent or greater difference in that mandate program characteristics?
through-section thickness can usually be
detected. 2. What is the magnitude of the program
that will provide desired results?
Radiography has three main
advantages: (1) detection of internal 3. What provisions must be made for
discontinuities, (2) detection of significant personnel safety and for compliance
variations in composition and with environmental regulations?
(3) permanent record of test data.
4. What is the performance date for a
Compared to other nondestructive test program to be fully implemented?
methods, radiography can be expensive.
Large capital costs and space allocations 5. Is there a cost benefit of radiographic
may be required for radiographic testing?
activities. Cost may be reduced if
equipment of smaller size or lower energy 6. What are the available resources in
requirement can be used. The magnitude personnel and money?
of potential test activities, however, must
be considered before limits are placed on Once these questions are answered, then a
the test facility. recommendation can be made to
determine the best path forward. Three
There are three major limiting factors primary paths are (1) service companies,
that must be considered before (2) consultants and (3) in-house programs.
radiography becomes the method of
choice. Though these are primary paths, some
programs may on a routine or on
1. Discontinuity detection depends on as-needed bases require support personnel
radiation beam orientation. In general, from a combination of two or more of
radiography can detect only features these sources. Before a final decision is
that have a thickness change in a made, advantages and disadvantages of
direction parallel to the radiation each path must be considered. Therefore,
beam. the following are details that must be
considered.
2. Radiography typically involves the
transmission of radiation through the Service Companies
part or component, in which case
both sides of the part must be 1. Who will identify the components
accessible. within the facility to be examined?

3. Radiation safety is always necessary to 2. Will the contract be for time and
a successful operation. materials or have a specific scope of
work?
In addition, radiographic images (in
the form of film or digital images) may 3. If a time and materials contract is
need to be stored for years to comply with awarded, who will monitor the time
quality assurance or regulatory and materials charged?
requirements.
4. If a scope of work is required, who is
technically qualified to develop and
approve it?

5. What products or documents (test
reports, trending, recommendations,
root cause analysis and others) will be
provided once the tests are completed?

12 Radiographic Testing

6. Who will evaluate and accept the 2. What are the regulatory requirements
product (test reports, trending, (codes and standards) associated with
recommendations, root cause analysis program development and
and others) within your company? implementation?

7. Do the service company workers 3. Who will develop a cost benefit
possess qualifications and analysis for the program?
certifications required by contract and
by applicable regulations? Will other 4. How much time and resources are
contractors be required to take care of available to establish the program?
related matters such as radiation
safety? 5. What are the qualification
requirements (education, training,
8. Do the service company workers experience and others) for personnel?
require site specific training (confined
space entry, electrical safety, hazardous 5. Do program personnel require
materials and others) or clearance to additional training (radiological safety,
enter and work in the facility? confined space entry or others) or
qualifications?
9. If quantitative tests are performed, do
program requirements mandate 6. Are subject matter experts required to
equipment calibration? provide technical guidance during
personnel development?
10. Does the service company retain any
liability for test results? 7. Are procedures required to perform
work in the facility?
Consultants
8. If procedures are required, who will
1. Will the contract be for time and develop, review and approve them?
materials or have a specific scope of
work? 9. Who will determine the technical
specifications for test equipment?
2. If a scope of work is required, who is
technically qualified to develop and Test Procedures for
approve it? Radiographic Testing

3. Who will identify the required The conduct of facility operations
qualifications of the consultant? (in-house or contracted) should be
performed in accordance with specific
4. Is the purpose of the consultant to instructions from an expert. This is
develop or update a program or is it to typically accomplished using written
oversee and evaluate the performance instructions in the form of a technical
of an existing program? procedure. In many cases codes and
specifications will require the use of a
5 Will the consultant have oversight technical procedure to perform required
responsibility for tests performed? tests.

6. What products (trending, The procedure process can take many
recommendations, root cause analysis forms, including general instructions that
and others) are provided once the tests address only major aspects of test
are completed? techniques. Or a procedure may be
written as a step-by-step process requiring
7. Who will evaluate the consultant’s a supervisor’s initial or signature after
performance (test reports, trending, each step. The following is a typical
recommendations, root cause analysis format for an industrial procedure.
and other functions) within your
company? 1. The purpose identifies the intent of the
procedure.
8. Does the consultant possess
qualifications and certifications 2. The scope establishes the latitude of
required by contract and by applicable items, tests and techniques covered
regulations? and not covered by the procedure.

9. Does the consultant require site 3. References are specific documents from
specific training (confined space entry, which criteria are extracted or
electrical safety, hazardous materials documents satisfied by
and others) or clearance to enter and implementation of the procedure.
work in the facility?
4. Definitions are needed for terms and
10. Does the consultant retain any abbreviations that are not common
liability for test results? knowledge to people who will read the
procedure.
In-House Programs
5. Statements about personnel requirements
1. Who will determine the scope of the address specific requirements to
program? Will the radiation source be perform tasks in accordance with the
isotopes or X-ray machines? Will the procedure — issues such as personnel
images be recorded on film or on qualification, certification, access
digital media? clearance and others.

Introduction to Radiographic Testing 13

6. Equipment characteristics, calibration 6. The source intensity (total quantity of
requirements and model numbers of penetrating rays) will directly affect
qualified equipment must be specified. the exposure time. Increased exposure
time may affect safety requirements.
7. Safety issues must be addressed because
of the nature of penetrating radiation. Selection of Imaging

8. The test procedure provides a sequential Typically an image is the end product of a
process to be used to conduct test radiographic examination. The image may
activities. be the captured output of a radioscopic or
electronic imaging system. Its format may
9. Acceptance criteria establish component be a hard copy (film or paper), a computer
characteristics that will identify the image file or a video monitor displaying
items suitable for service. an image in real time.

10. Reports (records) provide the means to 1. The first consideration is the ability to
document specific test techniques, detect discontinuities of interest.
equipment used, personnel performing
activity, date performed, test results, 2. Examination environment.
compliance with environmental 3. Image handling requirements include
regulations and safety procedures.
provisions for processing, evaluation
11. Attachments may include (if required) and transmitting of images.
items such as report forms, instrument
calibration forms, qualified equipment Interpretation
matrix, schedules and others
Interpretation may be complex. The
Once the procedure is completed, interpreter must have a knowledge of the
typically an expert in the subject matter following: (1) the radiographic process
performs a technical evaluation. If the (radiation source, exposure technique,
procedure is deemed adequate (meeting image storage system and other means
identified requirements), the expert will used to obtain the image); (2) the item
approve it for use. Some codes and being examined (its configuration,
standards also require the procedure to be material characteristics, fabrication
qualified — that is, demonstrated to the process, potential discontinuities and
satisfaction of a representative of a other aspects); and (3) the acceptance
regulatory body or jurisdictional criteria.
authority.
Standards and
Test Specifications for Specifications for
Radiographic Testing Radiographic Testing

A radiographic specification must Standards have undergone a process of
anticipate a number of issues that arise peer review in industry and can be
during testing. invoked with the force of law by contract
or by government regulation. In contrast,
Source Selection a specification represents an employer’s
instructions to employees and is specific
The radiation source requirements (energy to a contract or work place. Specifications
level, intensity and physical size) to detect may form the basis of standards through a
the target discontinuities must be review process. Standards and
determined. specifications exist in three basic areas:
equipment, processes and personnel.
1. The selected means of imaging may
dictate source energy and intensity 1. Standards for equipment include
levels. calibrated electronic radiation sources
and isotope sources. Standardized
2. The radiation source may need to be reference objects such as image quality
mobile for use in various locations. indicators (penetrameters), calibrated
density strips and radiation survey
3. The energy level (ability to penetrate) meters would also fit into this
of the radiation sources affects category.
radiographic contrast. Radiographic
contrast is an element of image
sensitivity.

4. The physical size of the radiation
emitting surface affects the geometric
unsharpness of the radiographic
image.

5. High energy levels may increase safety
issues because of increased shielding
requirements.

14 Radiographic Testing

2. ASTM International and other 2. ANSI/ASNT CP-189, Standard for
organizations publish standards for Qualification and Certification of
test techniques. Some other standards Nondestructive Testing Personnel
are for quality assurance procedures resembles SNT-TC-1A but also
and are not specific to a test method establishes specific attributes for the
or even to testing in general. Tables 3 qualification and certification of
and 4 list some of the standards used nondestructive testing personnel.
in radiographic testing. A source for However, CP-189 is a consensus
nondestructive testing standards is the standard as defined by the American
Annual Book of ASTM Standards.5 National Standards Institute (ANSI). It
is recognized as the American standard
3. Qualification and certification of test for nondestructive testing. It is not
personnel are discussed below, with considered a recommended practice; it is
specific reference to recommendations a national standard.6
of ASNT Recommended Practice No.
SNT-TC-1A.4 3. The ASNT Central Certification Program
(ACCP), unlike SNT-TC-1A and
Personnel Qualification CP-189, is a third party certification
and Certification process. Currently it has identified
qualification and certification
One of the most critical aspects of the test attributes for Level II and Level III
process is the qualification of test nondestructive testing personnel. The
personnel. Nondestructive testing is American Society for Nondestructive
sometimes referred to as a special process. Testing certifies that the individual has
The term simply means that it is very the skills and knowledge for many
difficult to determine the adequacy of a nondestructive testing method
test by merely observing the process or applications. It does not remove the
the documentation generated at its responsibility for the final
conclusion. The quality of the test is determination of personnel
largely dependent on the skills and qualifications from the employer. The
knowledge of the inspector. employer evaluates an individual’s
skills and knowledge for application of
The American Society for company procedures using designated
Nondestructive Testing (ASNT) has been a techniques and identified equipment
world leader in the qualification and for specific tests.7
certification of nondestructive testing
personnel for many years. By 1999, the Selections from
American Society for Nondestructive ASNT Recommended Practice
Testing had instituted three major No. SNT-TC-1A
programs in place for the qualification
and certification of nondestructive testing To give an overview of the contents of
personnel. these documents, the following items are
specified in the 1996 edition of
1. ASNT Recommended Practice SNT-TC-1A. (For the purpose of this
No. SNT-TC-1A provides guidelines for discussion the quantities cited are those
personnel qualification and that address radiographic testing only.)
certification in nondestructive testing.
This recommended practice identifies Scope. This recommended practice has
the specific attributes that should be been prepared to establish guidelines for
considered when qualifying the qualification and certification of
nondestructive testing personnel. It nondestructive testing personnel whose
requires the employer to develop and specific jobs require appropriate
implement a written practice knowledge of the technical principles
(procedure) that details the specific underlying the nondestructive test they
process and any limitation in the perform, witness, monitor or evaluate.
qualification and certification of This document provides guidelines for the
nondestructive testing personnel.4 establishment of a qualification and
certification program.

Written Practice. The employer shall
establish a written practice for the control
and administration of nondestructive
testing personnel training, examination
and certification. The employer’s written
practice should describe the responsibility
of each level of certification for
determining the acceptability of materials
or components in accordance with
applicable codes, standards, specifications
and procedures.

Introduction to Radiographic Testing 15

Table 3. Some radiographic standards published by ASTM International.

C 638-92 (1997), Standard Descriptive Nonmenclature of Constituents of Aggregates for Radiation-Shielding Concrete
E 94-00, Standard Guide for Radiographic Examination
E 155-00, Standard Reference Radiographs for Inspection of Aluminum and Magnesium Castings
E 170-99e1, Standard Terminology Relating to Radiation Measurements and Dosimetry
E 186-98, Standard Reference Radiographs for Heavy-Walled (2 to 4 1/2-in. [51 to 114-mm]) Steel Castings
E 192-95 (1999), Standard Reference Radiographs for Investment Steel Castings of Aerospace Applications
E 242-95 (2000), Standard Reference Radiographs for Appearances of Radiographic Images as Certain Parameters Are Changed
E 272-99, Standard Reference Radiographs for High-Strength Copper-Base and Nickel-Copper Alloy Castings
E 280-98, Standard Reference Radiographs for Heavy-Walled (4 1/2 to 12-in. [(114 to 305-mm]) Steel Castings
E 310-99, Standard Reference Radiographs for Tin Bronze Castings
E 390-95, Standard Reference Radiographs for Steel Fusion Welds
E 431-96, Standard Guide to Interpretation of Radiographs of Semiconductors and Related Devices
E 446-98, Standard Reference Radiographs for Steel Castings Up to 2 in. (51 mm) in Thickness
E 505-96, Standard Reference Radiographs for Inspection of Aluminum and Magnesium Die Castings
E 592-99, Standard Guide to Obtainable ASTM Equivalent Penetrameter Sensitivity for Radiography of Steel Plates 1/4 to 2 in. (6 to 51 mm) Thick

with X Rays and 1 to 6 in. (25 to 152 mm) Thick with Cobalt-60
E 666-97, Standard Practice for Calculating Absorbed Dose from Gamma or X Radiation
E 689-95 (1999), Standard Reference Radiographs for Ductile Iron Castings
E 746-02, Standard Test Method for Determining Relative Image Quality Response of Industrial Radiographic Film
E 747-97, Standard Practice for Design, Manufacture and Material Grouping Classification of Wire Image Quality Indicators (IQI) Used for Radiology
E 748-95, Standard Practices for Thermal Neutron Radiography of Materials
E 801 (2001), Standard Practice for Controlling Quality of Radiological Examination of Electronic Devices
E 802-95 (1999), Standard Reference Radiographs for Gray Iron Castings Up to 4 1/2 in. [114 mm]) in Thickness
E 803, Standard Test Method for Determining the L/D Ratio of Neutron Radiography Beams
E 975-00, Standard Practice for X-Ray Determination of Retained Austenite in Steel with Near Random Crystallographic Orientation
E 999-99, Standard Guide for Controlling the Quality of Industrial Radiographic Film Processing
E 1000-98, Standard Guide for Radioscopy
E 1025-98, Standard Practice for Design, Manufacture, and Material Grouping Classification of Hole-Type Image Quality Indicators (IQI) Used for Radiology
E 1030-00, Standard Test Method for Radiographic Examination of Metallic Castings
E 1032-95, Standard Test Method for Radiographic Examination of Weldments
E 1114-92 (1997), Standard Test Method for Determining the Focal Size of Iridium-192 Industrial Radiographic Sources
E 1161-95, Standard Test Method for Radiologic Examination of Semiconductors and Electronic Components
E 1165-92 (2002), Standard Test Method for Measurement of Focal Spots of Industrial X-Ray Tubes by Pinhole Imaging
E 1254-98, Standard Guide for Storage of Radiographs and Unexposed Industrial Radiographic Films
E 1255-96, Standard Practice for Radioscopy
E 1320-00, Standard Reference Radiographs for Titanium Castings
E 1390-90 (2000), Standard Guide for Illuminators Used for Viewing Industrial Radiographs
E 1411-95, Standard Practice for Qualification of Radioscopic Systems
E 1441-00, Standard Guide for Computed Tomography (CT) Imaging
E 1453-93 (1996), Standard Guide for Storage of Media That Contains [sic] Analog or Digital Radioscopic Data
E 1475-97, Standard Guide for Data Fields for Computerized Transfer of Digital Radiological Test Data
E 1496-97, Standard Test Method for Neutron Radiographic Dimensional Measurements
E 1570-00, Standard Practice for Computed Tomographic (CT) Examination
E 1647-98a, Standard Practice for Determining Contrast Sensitivity in Radioscopy
E 1648-95 (2001), Standard Reference Radiographs for Examination of Aluminum Fusion Welds
E 1672-95 (2001), Standard Guide for Computed Tomography (CT) System Selection
E 1734-98, Standard Practice for Radioscopic Examination of Castings
E 1735, Standard Test Method for Determining Relative Image Quality of Industrial Radiographic Film Exposed to X-Radiation from 4 to 25 MV
E 1742-00, Standard Practice for Radiographic Examination
E 1814-96, Standard Practice for Computed Tomographic (CT) Examination of Castings
E 1815-96 (2001), Standard Test Method for Classification of Film Systems for Industrial Radiography
E 1894-97, Standard Guide for Selecting Dosimetry Systems for Application in Pulsed X-Ray Sources
E 1931-97, Standard Guide for X-Ray Compton Scatter Tomography
E 1936-97, Standard Reference Radiograph for Evaluating the Performance of Radiographic Digitization Systems
E 1955-98, Standard Radiographic Examination for Soundness of Welds in Steel by Comparison to Graded ASTM E 390 Reference Radiographs
E 2002-98, Standard Practice for Determining Total Image Unsharpness in Radiology
E 2033-99, Standard Practice for Computed Radiology (Photostimulable Luminescence Method)
E 2116-00, Standard Practice for Dosimetry for a Self-Contained Dry-Storage Gamma-Ray Irradiator
F 629-97, Standard Practice for Radiography of Cast Metallic Surgical Implants
F 947-85 (1996), Standard Test Method for Determining Low-Level X-Radiation Sensitivity of Photographic Films
F 1035-91 (1997), Standard Practice for Use of Rubber-Cord Pie Disk to Demonstrate the Discernment Capability of a Tire X-Ray Imaging System

16 Radiographic Testing

TABLE 4. Some standards and practices for radiographic testing and for radiation safety.

Issuing Organization Representative Standards and Related Documents

American National Standards Institute ANSI N43.9-1991, Gamma Radiography — Specifications for Design and Test of Apparatus
(revision and redesignation of ANSI N432-1980)

ANSI PH2.8-1975, Sensitometry of Industrial X-Ray Films for Energies up to 3 Million Electron

Volts, Method for.

See also ASME and ASNT.

American Society of Mechanical Engineers ANSI/ASME B31.1, Power Piping
ANSI/ASME B31.3, Process Piping
American Society for Nondestructive Testing ASME Boiler and Pressure Vessel Code: Section I — Power Boilers
American Society for Testing and Materials ASME Boiler and Pressure Vessel Code: Section III — Components
ASME Boiler and Pressure Vessel Code: Section V — Power Boilers
ASME Boiler and Pressure Vessel Code: Section VIII — Pressure Vessels
ASME Boiler and Pressure Vessel Code: Section XI — Inservice Inspection of Nuclear Vessels
ASME PTC 19-1, Performance Test Codes, Supplement on Instruction and Apparatus

ASNT Recommended Practice No. SNT-TC-1A
ANSI/ASNT CP-189, ASNT Standard for Qualification and Certification of Nondestructive Testing

Personnel
See Table 3

American Petroleum Institute API 510, Pressure Vessel Inspection Code: Maintenance Inspection, Rating, Repair and Alteration

API 570, Piping Inspection Code: Inspection, Repair, Alteration, and Rerating of In-Service Piping

Systems

API 650, Welded Steel Tanks for Oil Storage

API 1104, Welding, Pipelines and Related Facilities

American Water Works Association AWWA D100-96, Welded Steel Tanks for Water Storage

American Welding Society AWS D1.1, Structural Welding Code — Steel

AWS D1.5, Bridge Welding Code

Canadian General Standards Board CAN/CGSB-48-GP-2M, Spot Radiography of Welded Butt Joints in Ferrous Materials

CAN/CGSB-48.3-92, Radiographic Testing of Steel Castings

CAN/CGSB-48.5-95, Manual on Industrial Radiography

CAN/CGSB-48.9712-95, Non-Destructive Testing — Qualification and Certification of Personnel

Deutsche Institut für Normung DIN 6814, Terms and Definitions in the Field of Radiological Techniques

DIN 6832-2, Radiographic Cassettes; Test for Light-Proofness and Test for Contact between

Radiographic Film and Intensifying Screen

DIN 25 430, Safety Marking in Radiation Protection

DIN 54 115, Non-Destructive Testing; Radiation Protection Rules for the Technical Application of

Sealed Radioactive Sources

DIN EN 444, Non-Destructive Testing; General Principles for the Radiographic Examination of

Metallic Materials Using X-Rays and Gamma-Rays

DIN EN 12 681, Founding — Radiographic Inspection

DIN EN 14 096, Non-Destructive Testing - Qualification of Radiographic Film Digitisation Systems

European Committee for Standardization CEN 584, Non Destructive Testing — Industrial Radiographic Film

EN 12 679, Non-Destructive Testing — Determination of the Size of Industrial Radiographic

Sources — Radiographic Method

International Organization for Standardization ISO 2504, Radiography of Welds and Viewing Conditions for Films — Utilization of

Recommended Patterns of Image Quality Indicators (I.Q.I.)

ISO 7004, Photography — Industrial Radiographic Film — Determination of ISO Speed and

Average Gradient When Exposed to X- and Gamma-Radiation

ISO 3999, Apparatus for Gamma Radiography

ISO 9712, Nondestructive Testing — Qualification and Certification of Personnel

ISO 9915, Aluminium Alloy Castings — Radiography Testing

ISO 11 699, Non-Destructive Testing — Industrial Radiographic Films

Japanese Standards Association K 7091, Testing Method for Radiography of Carbon Fibre Reinforced Plastic Panels Edition 1

K 7521, Dimensions for Photographic Film in Sheets and Rolls for Medical, Industrial and Dental

Radiography

Z 4560, Industrial Gamma-Ray Apparatus for Radiography

Korean Standards Association A 4907, Film Marker of Radiography

A 4921, Industrial X-Ray Apparatus for Radiography

M 3910, Dimensions for Photographic Film in Sheets and Rolls for Medical, Industrial and Dental

Radiography

National Council on Radiation Protection NCRP 61, Radiation Safety Training Criteria for Industrial Radiography

Occupational Safety and Health Administration 29 CFR 1910, Occupational Safety and Health Standards [Code of Federal Regulations:
Title 29, Labor]

Society of Automotive Engineers SAE AMS 2635C, Radiographic Inspection

SAE ARP 1611A, Quality Inspection Procedure, Composites, Tracer Fluoroscopy and Radiography

SAE AS 1613A, Image Quality Indicator, Radiographic

SAE AS 7114/4, NADCAP Requirements for Nondestructive Testing Facility Radiography

Introduction to Radiographic Testing 17

Education, Training, Experience (12 in.) on a standard jaeger test chart.
Requirements for Initial Qualification. This test should be administered annually.
Candidates for certification in
nondestructive testing should have Written Examination for NDT Levels I
sufficient education, training and and II. The minimum number of
experience to ensure qualification in questions that should be administered in
those nondestructive testing methods for the written examination for radiographic
which they are being considered for test personnel is as follows: 40 questions
certification. Table 5 lists the in the general examination and 20
recommended training and experience questions in the specific examination. The
factors to be considered by the employer number of questions is the same for Level
in establishing written practices for initial I and Level II personnel.
qualification of Level I and II individuals
for radiographic testing. Practical Examination for NDT Level I
and II. The candidate should demonstrate
Training Programs. Personnel being ability to operate the necessary
considered for initial certification should nondestructive test equipment, record
complete sufficient organized training to and analyze the resultant information to
become thoroughly familiar with the the degree required. At least one selected
principles and practices of the specified specimen should be tested and the results
nondestructive test method related to the of the nondestructive test analyzed by the
level of certification desired and candidate.
applicable to the processes to be used and
the products to be tested. Certification. Certification of all levels of
nondestructive testing personnel is the
Examinations. For Level I and II responsibility of the employer.
personnel, a composite grade should be Certification of nondestructive testing
determined by a simple averaging of the personnel shall be based on
results of the general, specific and demonstration of satisfactory qualification
practical examinations described below. in accordance with sections on education,
Examinations administered for training, experience and examinations, as
qualification should result in a passing modified by the employer’s written
composite grade of at least 80 percent, practice. Personnel certification records
with no individual examination having a shall be maintained on file by the
passing grade less than 70 percent. The employer.
examination for near vision acuity should
ensure natural or corrected near distance Recertification. All levels of
acuity in at least one eye such that nondestructive testing personnel shall be
applicant can read a minimum of jaeger recertified periodically in accordance with
size 2 or equivalent type and size letter at the following: evidence of continuing
a distance of not less than 305 mm satisfactory performance; reexamination
in those portions of examination deemed
TABLE 5. Recommended training and experience for necessary by the employer’s NDT Level III.
Recommended maximum recertification
radiographic testing personnel according to intervals are three years for Level I and
ASNT Recommended Practice No. SNT-TC-1A.4 Level II and five years for Level III.

Level I Level II These recommendations from
SNT-TC-1A are cited only to provide a
Radiographic Testing 39 h 40 h flavor of the specific items that must be
High school graduatea 29 h 35 h considered in the development of an
Two years of collegeb in-house nondestructive testing program.
Work experiencec 3 mo 9 mo However, if an outside agency is
contracted for radiographic test services,
Neutron Radiographic Testing 28 h 40 h then the contractor must have a
High school graduatea 20 h 40 h qualification and certification program to
Two years of collegeb 24 mo satisfy most codes and standards.
Work experiencec 6 mo
Central Certification
a. Or equivalent.
b. Completion with a passing grade of at least two years of engineering or Another standard that may be a source for
compliance is contained in the
science study in a university, college or technical school. requirements of the International
c. Work time experience per level. Note: for Level II certification, the Organization for Standardization (ISO).
The work of preparing international
experience shall consist of time as Level I or equivalent. If a person is standards is normally carried out through
being qualified directly to Level II with no time at Level I, the required technical committees of the International
experience shall consist of the sum of the times required for Level I and Organization for Standardization, a
Level II and the required training shall consist of the sum of the hours worldwide federation of national
required for Level I and Level II. standards bodies. Each ISO member body
interested in a subject for which a
technical committee has been established

18 Radiographic Testing

has the right to be represented on that 6. Be aware of any potentially explosive
committee. International organizations, atmospheres. Determine whether it is
governmental and nongovernmental, in safe to take your equipment into the
liaison with the International area.
Organization for Standardization, also
take part in the work. 7. Do not enter any roped off or no entry
areas without permission and
Technical Committee ISO/TC 135, approval.
Non-Destructive Testing Subcommittee
SC 7, Personnel Qualification, prepared 8. When working on or around moving
international standard ISO 9712, or electrical equipment, remove pens,
Nondestructive Testing – Qualification and watches, rings or objects in your
Certification of Personnel.8 In its statement pockets that may touch (or fall into)
of scope, ISO 9712 states that it energized equipment.
“establishes a system for the qualification
and certification, by a certification body, 9. Know interplant communication and
of personnel to perform industrial evacuation systems.
nondestructive testing (NDT) using any of
the following methods: (a) eddy current 10. Never let unqualified personnel
testing; (b) liquid penetrant testing; operate equipment independently
(c) magnetic particle testing; (d) from qualified supervision.
radiographic testing; (e) ultrasonic
testing” and that the “system described in 11. Keep a safe distance between you and
this International Standard may also any energized equipment. In the
apply to visual testing (VT), leak testing United States, these distances can be
(LT), neutron radiography (NR), acoustic found in documents from the
emission (AE) and other nondestructive Occupational Safety and Health
test methods where independent Administration, the National Fire
certification programs exist.” The Prevention Association (National
applicability of ISO 9712 to radiographic Electric Code),9 the Institute of
testing therefore depends on activity of Electrical and Electronics Engineers
the national certifying body. (National Electrical Safety Code)10 and
other organizations.
Safety in Radiographic
Testing 12. Be aware of the personnel
responsibilities before entering a
To manage a radiographic testing confined space. All such areas must be
program, as with any test program, the tested satisfactorily for gas and oxygen
first obligation is to ensure safe working levels before entry and periodically
conditions. The following are components thereafter. If odors are noticed, or
of a safety program that may be required unusual sensations such as earaches,
or at least deserve serious consideration. dizziness or difficulty in breathing are
experienced, leave the area
1. Identify the safety and operational immediately.
rules and codes applicable to the areas,
equipment and processes being 13. Notice that the safety considerations
examined before work is to begin. listed above are applicable to many
test methods. Because ionizing
2. Provide proper safety equipment radiation can hurt people, additional
(protective barriers, hard hat, safety precautions are needed for
harnesses, steel toed shoes, hearing radiographic testing and are discussed
protection and others). in a separate chapter.

3. Provide necessary training in radiation Most facilities in the United States are
safety. required by law to follow the
requirements in the applicable standard.
4. Before the test, perform a thorough Two Occupational Safety and Health
visual survey to determine all the Standards in the United States that should
hazards and identify necessary be reviewed are Occupational Safety and
safeguards to protect test personnel Health Standards for general industry11 and
and equipment. the Occupational Safety and Health
Standards for the Construction Industry.12
5. Notify operative personnel to identify
the location and specific equipment Personnel safety is always the first
that will be examined. In addition, a consideration for every job.
determination must be made if signs
or locks restrict access by personnel. Ensuring Reliability of Test
Be aware of equipment that may be Results
operated remotely or may started by
time delay. When a test is performed, there are four
possible outcomes: (1) a discontinuity can
be found when a discontinuity is present;
(2) a discontinuity can be missed even
when a discontinuity is present; (3) a
discontinuity can be found when none is

Introduction to Radiographic Testing 19

present; and (4) no discontinuity is found
when none is present. A reliable testing
process and a qualified inspector should
find all discontinuities of concern with no
discontinuities missed (no errors as in
case 2, above) and no false callouts
(case 3, above).

To achieve this goal, the probability of
finding a discontinuity must be high and
the inspector must be both proficient in
the testing process and motivated to
perform a maximum efficiency. A reckless
inspector may accept parts that contain
discontinuities, with the resultant
consequences of possible inservice part
failure. A conservative inspector may
reject parts that contain discontinuities
but the inspector also may reject parts
that do not contain discontinuities, with
the resultant consequences of unnecessary
scrap and repair. Neither inspector is
doing a good job.

Summary

As noted in this discussion, many factors
must be considered before a program of
radiographic testing can begin at a facility.
To manage a nondestructive testing
program many options must be
considered. The final decision for a path
forward must be based on requirement
documents (codes, standards or
specifications) and what is best for your
company. If a person in a position of
responsibility lacks the expertise for this
critical decision, the industry has many
talented individuals willing to assist. The
American Society for Nondestructive
Testing is a place to begin the decision
making process.

20 Radiographic Testing

PART 3. History of Radiographic Testing13

Röntgen and compressibility of liquids. As a
director of the Physical Institute at
Wilhelm Conrad Röntgen (Fig. 10) made Würzburg, Röntgen had freedom to
his momentous discovery of X-rays on pursue scientific ideas that were of
Friday, 8 November 1895, in his interest to him. In 1895, he began
laboratory at the University of Würzburg collecting the equipment needed to
in Germany. The importance of this new investigate luminescence effects. He
kind of ray was recognized immediately studied early work by people before him
The see-through property of X-rays created — Faraday, Geissler, Hittorf and Crookes,
a sensation, not only in the scientific for example — as well as the more current
community but also in the popular press. work of fellow German scientist Philipp
By early January 1896, newspapers around Lenard. These scientists and others had
the world carried news of these new rays studied luminescence in gases and solids
and their ability to pass through flesh and using a partially evacuated tube, popularly
other materials. The newspaper accounts known as a crookes tube.14 This was
correctly predicted the tremendous impact typically a pear shaped glass tube,
that X-rays were to have on medical containing two electrodes. When a high
diagnosis. Röntgen and other early X-ray voltage was put between the electrodes,
workers showed X-ray images of things: the positively charged ions from the gas
Röntgen took X-ray images of his bombarded the negative electrode,
shotgun, a compass and weights in a box. causing the release of electrons, then
Much experimental work ensued in an called cathode rays. The electrons caused
almost playful atmosphere, as researchers luminescence in the partial gas filling, in
radiographed hundreds of different kinds the glass walls of the tube or in other
of objects. Industrial applications of a sort materials placed in their path.
were found almost immediately, in the
sense that artillery shell casings were FIGURE 10. Wilhelm Conrad Röntgen.
among the objects so examined. It was
decades before nonmedical uses of X-rays
became important.

Clearly, the practical uses for X-rays
have gone well beyond the early concepts.
Immediate medical uses foreseen included
setting of broken bones and location of
foreign objects — bullets, pins, coins and
others. Medical applications have now
expanded to include diagnosis of diseases
such as tuberculosis, malfunctions such as
blockages of the circulatory system and
the detection of many abnormalities such
as tumors and calcium loss in bones.
X-rays are now used for medical therapy,
to identify and analyze materials, to
inspect industrial materials and, a use all
airplane travelers recognize, to inspect
baggage and packages. The methods
include fluoroscopy and film radiography
— the two methods Röntgen used — and
more modem techniques such as
electronic radioscopy, tomography,
backscatter imaging, radiation gaging,
diffraction, fluorescence and others.

Preliminary Work

Röntgen was a respected scientist before
the X-ray discovery, having published
work on specific heat, optical phenomena

Introduction to Radiographic Testing 21

Discovery the general public. One of his mailed set
of reprints and photographs went to his
Röntgen was an institute director, with friend Ernst Warburg in Berlin. Warburg
graduate students and assistants available displayed the material as a poster exhibit
as needed. However, as was his usual at the 50th anniversary meeting of the
custom, Röntgen did many experimental Berlin Physical Society in 1896. Many saw
studies himself. His laboratory was only the exhibit in one corner of the hall.
one floor down from his living quarters in
the Physical Institute, so it was easily Another of his private communications
available to him as he desired. All was in went to a second college friend, Professor
readiness on the afternoon of Friday, Franz Exner in Vienna. Exner showed the
8 November 1895. Röntgen had his pictures to several fellow scientists. One of
covered tube and a darkened laboratory them, Professor Ernst Lecher visiting from
when he energized the cathode ray tube Prague, was so fascinated by the pictures
and noticed luminescence from a barium that he asked Exner if he could borrow
platinocyanide screen on a table about them overnight. Lecher shared the
2 m (7 ft) away. The luminescence was pictures with his father, Z. Lecher, editor
definitely associated with the tube, of the Vienna Presse newspaper. Lecher’s
turning on only when the tube was January 1896 article in the Vienna Presse
energized. Röntgen knew the effect could newspaper extolled the potential of these
not be cathode rays, because they new X-rays, correctly pointing out the
penetrate only a short distance in air. He benefits for medical diagnosis. The news
was intrigued; he investigated. quickly spread around the world,
appearing in many newspapers within the
He quickly learned about the following week. Röntgen received more
penetrating power of these new rays; they than 1000 pieces of mail in the first week
penetrated paper, wood, metal and flesh. following the press announcement.
The rays made shadow pictures on Within days, scientists everywhere, using
fluorescent screens and on film. crookes tubes, were repeating Röntgen’s
Nevertheless, he was skeptical about his observations and confirming his results.
discovery. As he became totally consumed
in a seven week intensive study he Once the news was out, there were
commented to his friend, Theodor Boveri, many offers of honors, lectures and visits.
“I have discovered something interesting However, Röntgen turned down most
but I do not know whether or not my such overtures. One he could not refuse
observations are correct.” At the same was a royal invitation. Röntgen gave a
time, as a scientist, he was excited. He demonstration of X-rays before Kaiser
knew he must report his findings and Wilhelm II and his court in January 1896.
obtain feedback from fellow scientists. As a result of this summons to the court,
Because the new rays darkened a Röntgen was awarded the Royal Order of
photographic plate, he could take pictures Merit, an award that permits one to use
and share them with others. One of these the title von, as an indication of nobility.
early pictures in December 1895 was a Röntgen never made the formal
15 min exposure showing the bones in application for the noble rank and refused
the hand of his wife, Bertha. Other early to use the term von in his name.
pictures taken with the new rays included
weights in a box, a compass, a piece of Another summons he could not turn
metal and a shotgun. He recognized that down was a call from his own university.
he must publish his results so that they In January 1896, he lectured on his
could be shared with others in the discovery before the Physical Medical
scientific community. His first technical Society in Würzburg and gave the first
paper on X-rays, “On a New Kind of Rays: public demonstration before an
A Preliminary Communication,” was overflowing audience. The image of
published in the annals of the Würzburg Röntgen’s lecture was captured in a 1961
Physical Medical Society in December painting (Fig. 11). During the lecture
1895.15 The reprints were ready by the Röntgen radiographed the hand of his
new year. As he mailed reprints and fellow university professor and well
photographs to colleagues, Röntgen said known anatomist, Albert von Kolliker.
to Bertha, “Now the devil will be to pay,” Kolliker was so enthused by the discovery
clearly a premonition of the coming that he announced that the new rays
drastic change in his life. should be called roentgen rays, as they are
still in Europe and within the medical
Fame community. The lecture and
demonstration were greeted with
Röntgen was apprehensive as he sent enthusiastic applause. It was to be
reprints and pictures to colleagues in Röntgen’s only formal public lecture on
January 1896, but he probably had no X-rays.
idea of what was in store for him. There
was tremendous interest in his new rays, The commercial community took note
both from the scientific community and of Röntgen’s discovery.14,16 An American
industrial group was said to offer Röntgen
a fortune for rights to his discovery.

22 Radiographic Testing

Röntgen was similarly approached by Crookes was always rejecting
many industrial groups, including a photographic plates because they were
documented overture by Max Levy of a fogged, most likely from X-ray exposure.
German company. However, Röntgen Philipp Lenard, who had helped Röntgen
remained true to his scientific calling, obtain one of his thin window tubes, had
saying that discoveries and inventions noticed that an electric charge some
belong to humanity and that they should distance away from his lenard tube was
not in any way be hampered by patents, discharged but he did not investigate
licenses or contracts, nor should they be fully.17
controlled by any one group.
One well documented early notice of
Edison, the renowned American X-rays occurred in the physics laboratory
inventor, was quoted as saying about of Arthur W. Goodspeed at the University
Röntgen’s attitude, “After they have of Pennsylvania.18 He was visited in
discovered something wonderful, February 1890, by photographer William
someone else must look at it from the Jennings to do some photography with
commercial point of view. One must see spark discharges. After the young men
how to use it and how to profit from it finished with the spark equipment,
financially.” Edison was among the first of Goodspeed showed Jennings his crookes
many Americans to investigate X-rays. He tube equipment in operation. Jennings
quickly designed and built X-ray tubes had several unexposed, covered
and a fluorescent screen fluoroscope, photographic plates on the table during
making use of the Edison discovery that a the crookes tube demonstration; he had
calcium tungstate phosphor screen gave placed several coins for his carfare on top
very bright X-ray images. Edison of the stack of plates. On returning to his
exhibited an X-ray fluoroscope at the laboratory, he processed the plates and
National Electrical Exposition at the found a curious image of several round
Grand Central Palace in New York in May objects. He dated and filed the plate, only
1896. The Exposition gave the general to bring it back at Goodspeed’s request
public a rare opportunity to see X-ray after the news of the X-ray discovery.
pictures. They could document that they had made
an X-radiograph five years before
Obviously, with crookes tubes in use in Röntgen’s discovery. Goodspeed and
laboratories around the world, it is clear Jennings merely brought the radiograph
that many people before Röntgen had to public attention, never claiming any
produced X-rays. Once the discovery was credit for discovering X-rays.
announced, many scientists recognized
that X-rays had been responsible for Röntgen himself published two
strange effects they had noticed (but not additional scientific papers about X-rays.
followed up) from earlier experiments. “On a New Kind of Rays, Continued,”15
was published by the same Würzburg
FIGURE 11. Röntgen demonstrates X-rays in 1896. publication in March 1896 and was
followed by “Further Observations on the
Properties of X-Rays,”19 published in
March 1897 by the Prussian Academy of
Sciences. His three scientific papers
presented thorough results about X-rays.

His investigations showed the
penetrating power of the new rays as
related to the density of the absorber and
the effect on fluorescent materials and
photographic film. Röntgen took pinhole
pictures to confirm that the source of the
X-ray emission was the point where the
cathode rays struck the glass wall or a
metal target. He recognized the
nonuniform distribution of the X-ray
emission from the target and found the
fundamentals of the inverse square law
for decreasing X-ray intensity with
increasing distance from the target. He
tried without success to deflect the X-ray
beam with a magnet or an electric field.
His attempts to demonstrate reflection
and diffraction were likewise without
success. His experiments did produce
evidence that the new rays caused
electrical conductivity in air and that
heavy metal targets such as platinum
produced more intense X-ray beams than

Introduction to Radiographic Testing 23

glass or aluminum targets. His three recognition that gas in the body can help
papers on X-rays gave the basic outline organs, an early concept of a
information about X-rays to the world.20 contrast medium.

Early Medical Applications Introduction of Additional
Radiation Sources
The medical use of X-rays began
immediately. It was straightforward to In 1898 Marie Sklodowska Curie (Fig. 12)
recognize the usefulness of X-rays to find and Pierre Curie published research
foreign objects in the body and to help showing the discovery of two new
set broken bones. There are many radioactive elements, polonium and
documented instances of such radium, laying the foundation for gamma
applications as early as January and radiography.
February 1896. The first recorded X-ray
picture in the Americas was taken by The early X-ray tubes were partially
Arthur W. Wright of Yale University, in evacuated glass bulbs. Metal targets and
January 1896. This was quickly followed curved cathodes were quickly added to
by X-ray work at other universities. increase X-ray output. Nevertheless, it was
a challenge to operate these early gas
Men recognized for early work in what tubes consistently The gas pressure
has become medical radiology include changed because of outgassing of the
Francis H. Williams, a doctor at the walls and other heating effects. One of
Boston City Hospital, and William J. the first X-ray related patents was for a
Morton, a New York City physician.21 technique of controlling the tube gas
Williams used X-rays to study anatomy, pressure (issued March 1896 to Siemens).
both diseased and normal. He used Among the early uses of radioscopy,
fluoroscopy and film radiography to study fluoroscopes similar to those at today’s
the thorax, for determining the outline of airports were used during World War I to
the heart, for diagnosis of tuberculosis inspect packages for contraband
and other medical studies. Williams had (Fig. 13).22
the advantage of working with two
Massachusetts Institute of Technology It was in this background that William
scientists, Charles Norton and Ralph D. Coolidge (Fig. 14) of General Electric
Lawrence, whose work advanced early introduced the hard vacuum, hot cathode
X-ray technology. Morton’s wide ranging X-ray tube, truly a significant advance in
pioneering X-ray work included the X-ray technology.23 This new X-ray tube
concept brought much improved
FIGURE 12. Marie Sklodowska Curie (1928). reproducibility and ease of operation to
X-ray technology and prepared the way
for high energy X-ray use. The patent for
this landmark X-ray development was
issued in 1916.24

FIGURE 13. Radioscopic system for detection of contraband
(circa 1910).

24 Radiographic Testing

X-Rays for Nondestructive Knipping26,27 and from the pioneering
Testing work of the father and son Bragg team.
28,29 X-ray diffraction is a widely used
X-Ray Diffraction method to identify and analyze
materials.25 Some idea of the impact that
Röntgen’s early X-ray work included X-ray diffraction has had on science is
unsuccessful attempts to show diffraction given by noting that twenty Nobel
effects by directing the rays through a fine physics prizes have been awarded for
slit. This effect was successfully shown achievements in crystallography.30
later following the 1909 work of Walter
and Pohl.25 It was Max von Laue who first Radiography
thought of using the regular order of a
crystal to diffract X-rays. Experimental Early advances in X-ray nondestructive
confirmation of this now important and testing were being made in many
widespread use of X-rays came from countries around the world.
Laue’s work with Friedrich and Documentation of early X-ray work in the
United Kingdom and in Germany
FIGURE 14. William Coolidge, inventor of X-ray tube: describes work going back to the time of
(a) posing with 1 MeV tube; (b) X-ray tube. World War I. The early work in the United
Kingdom, particularly the armament
(a) related X-ray nondestructive testing work
of V.E. Pullin, is well described by
Halmshaw.31 An excellent description of
early work in Germany shows many
examples of radiographic nondestructive
testing, including field test systems dating
from the 1920s.32 A recent summary of
X-ray history is given in the X-ray
centennial issue of Insight, including
articles about X-ray development in the
United Kingdom and in Germany.33

Early work in the United States is
documented in patents.34,35 Despite these
early efforts and many demonstrations of
X-rays for material examination,24
radiographic nondestructive testing did
not become important commercially until
World War II. In the United States,
workers in nondestructive testing cite the
early work of Horace Lester (Fig. 15) at the

FIGURE 15. Horace Lester.

(b)

Introduction to Radiographic Testing 25

Watertown Arsenal (Fig. 16) as laying the Horace Lester attended this 1929 X-ray
groundwork for our present use of lecture and contributed to the discussion
radiography.36,37 Lester’s work was included with the published article.
significant because it clearly demonstrated Lester’s comment discussed the increasing
that X-rays could be used to locate use of steel forgings and welded structures
internal discontinuities in castings, welds instead of castings because engineers
and other metal forms and that these believed that “these substitutes for
discontinuities could lead to premature castings are free from hidden defects and
failure. Lester’s contributions were also therefore more reliable.” He went on to
important because of his preeminent point that his work at Watertown Arsenal
position in the metallurgical field.38,39 showed that the assumption of soundness
However, there was significant work done for forgings and welds was not true.
in the United States in radiographic Wheeler Davey also attended the lecture
nondestructive testing even before Lester’s and contributed to the discussion. Davey’s
landmark research. An excellent review of comment may strike a responsive chord
early X-ray nondestructive testing work is even today: “the authors bring out the
given in the 1929 Fink and Archer paper fact, previously emphasized by Lester, that
for ASM International, when it was called there are few cases where it is good
the American Society for Steel Treating.40 economic sense to use radiography for
The paper cites 108 references, with 46 of 100 per cent inspection.”
these dating during the period 1915-1921.
Prominent among the early citations is It was in this environment of
the work of Wheeler R. Davey, who did unfavorable economics for widespread use
research on radiographic nondestructive of nondestructive testing that the
testing at the General Electric Research American Society for Nondestructive
Laboratory (1914 to 1926) and later at Testing began.
Penn State University. The Alcoa team of
Fink and Archer described X-ray exposure American Society for
techniques for aluminum and steel, Nondestructive Testing
including the use of fluorescent and lead
screens. This 1929 paper is given credit for The society was started officially by a
the first public description for the use of charter from the state of Massachusetts
lead intensifying screens.41 dated August 1941. Prominent among the
nine signers of the original charter are the
FIGURE 16. Laboratory of Horace Lester at Watertown first two names, Philip D. Johnson and
Arsenal, Watertown, Massachusetts. Carlton G. Lutts. Lutts served as the first
president of the American Industrial
Radium and X-Ray Society during its
initial year of operation, 1941-1942. The
new society’s first conference was held at
Massachusetts Institute of Technology in
October, 1941, highlighted by a
presentation (later called the Mehl Honor
Lecture) by Charles W. Briggs.

Formed as it was in late 1941, the
society was in place as the United States
entered World War II in December 1941.
The war effort required increasing
emphasis on product reliability and
nondestructive testing. The fledgling
society was there to provide a needed
forum for the exchange of nondestructive
testing information. The new society
journal, first called Industrial Radiography
and issued in the summer of 1942, played
a key role in spreading knowledge about
nondestructive testing.

Ralph Turner, ASNT national president
during 1971-1972 and an ASNT historian,
reflected on the early years of the Society:
“The Society has not done badly. Perhaps
the most fortunate event was its
inadvertent birth just before World
War Il.”42 Clearly the war years gave a
needed push to help the new society
survive and grow during the crucial
formative years.

26 Radiographic Testing

An early recognition was that States Capitol (September 1985) and the
nondestructive testing included methods Statue of Liberty (October 1985).
other than radiography. Liquid penetrants
and magnetic particles were in wide use The journal has also provided an
and other methods such as ultrasonic opportunity for commercial development
testing were becoming important. With of X-ray technology. Early advertisers in
Volume 5 in the summer of 1946, the the journal included equipment suppliers
journal name and mission were expanded such as General Electric, Keleket, North
to Industrial Radiography & Non-Destructive American Philips, Picker and
Testing. In the fall of 1947 the name of Westinghouse, film suppliers such as
the society was changed to the Society for Agfa-Ansco, DuPont and Eastman Kodak;
Non-Destructive Testing. The hyphen in and tube/accessory suppliers such as
the name disappeared in 1952. The Bar-Ray Products, Machlett, Pako and Ray
journal expanded publication to Proof Corporation. Only a few of these
bimonthly (instead of quarterly) in 1953 early X-ray companies continue to supply
and became a monthly journal in 1964, at the X-ray nondestructive testing market
the same time changing the journal name in the 21st century; others, Keleket and
to Materials Evaluation.43 By 1967 many Machlett, for example, have disappeared
other countries had nondestructive testing completely.
societies and there had been five
International Conferences on Many of the society honors and awards
Nondestructive Testing (now called World have had a radiation connection. The
Conferences), so it seemed appropriate to Coolidge Award, named for William D.
change the society name again; it became Coolidge, the inventor of the hard
the American Society for Nondestructive vacuum X-ray tube (Fig. 14), was
Testing (ASNT). presented from 1953 to 1964 for
outstanding contributions “to the
ASNT can be proud of its role in advancement of nondestructive testing
advancing the state-of-the-art of using X-rays.” The Lester Honor Lecture,
nondestructive testing and X-ray named for the X-ray pioneer Horace
technology. The national conferences, the Lester (Fig. 15), has been presented since
section meetings for local information 1943. The Mehl Honor Lecture, named for
exchange, the topical conferences, the Robert Mehl, an early contributor to
society’s international participation, the gamma radiography,44 has been presented
Nondestructive Testing Handbook series and since 1941. Although the honor lectures
educational and personnel activities all are named for men known for their work
provided opportunities for exchange of in radiation, the topics of the lectures
nondestructive testing information. The cover the entire field of nondestructive
early issues of the journal were heavily testing.
weighted toward X-ray technology,
reflecting the original name of the society. Throughout the society history there
Early contributors to the journal included has been a clear division of effort in
many respected engineers and scientists. advancing nondestructive testing between
Early issues contained articles by Arthur the American Society for Nondestructive
Barkow, Charles Barrett and George Clark Testing and the American Society for
(all of whom made early contributions to Testing and Materials Committee E-7 on
the advancement of X-ray diffraction), Nondestructive Testing, organized in
James Bly and Gerold Tenney (whose 1938.45 The American Society for Testing
work included developments in high and Materials activity produces consensus
energy radiography), Donald O’Connor standards for nondestructive testing
(whose group at the Naval Ordnance methods and applications. The American
Laboratory, with colleagues Edward Society for Nondestructive Testing efforts
Criscuolo and Daniel Polansky, provide a forum for information
contributed much to the early X-ray exchange, education and personnel
nondestructive testing standards), Leslie certification. The role of the two
Ball (an early user of X-ray technology in organizations was recognized early, as
the aircraft field), Donald Kerst, the indicated in a 1942 letter from Horace
developer of the betatron, film research Lester, Chairman of American Society for
workers Herman Seeman and George Testing and Materials E-7.
Corney and many others whose names
and works were well known. There are many individuals who
remain active in both the American
Along the way there have been many Society for Testing and Materials
noteworthy radiographic applications. Committee E-7 and the American Society
Materials Evaluation readers may recall the for Nondestructive Testing, thereby
following: the Vatican Pieta (June 1964), providing a strong link between the two
the world’s largest radiograph (November nondestructive testing organizations.
1964), the Liberty Bell (February 1976), a
lighthouse (March 1980), the United

Introduction to Radiographic Testing 27

Advances in Radiographic
Technology

The period from 1935 to 1960 saw
improvements in technology and
techniques for radiation safety,46 gamma
radiography,47-49 portable X-ray
machines,49,50 high voltage
radiography51-53 and nucleonic gaging.54
Radiographic testing found new
applications, in metals,55 shipbuilding56
and particularly in the aviation
industries.57-59

Although radiographic testing is still
performed essentially in the same
through-transmission, direct shadowing
way that Röntgen used 100 years ago, the
twenty-first century has much better
X-ray sources, detectors and
understanding of image quality factors
like scatter and unsharpness. In addition,
of course, the industry today has a large
arsenal of techniques — for example,
electronic radioscopy, computed
tomography, backscatter imaging,
laminography, dual energy,
microradiography, flash techniques and
in-motion radiography. The commercial
X-ray market for equipment, accessories
and supplies is still primarily weighted
toward medical fields but other X-ray
applications contribute to what is
estimated to be a $12 billion annual
market. In addition to the medical and
traditional nondestructive testing
applications, industry uses X-ray
diffraction and other analytical methods
such as fluorescence, radiation methods
for material modification, X-ray
lithography, radiation gaging and the ever
expanding use of X-rays for security.

Looking toward the future, only one
thing is clear — the technology will
continue to advance. Obvious directions
are the increasing use of computerized
instrumentation, automated testing and
greater use of nondestructive test
techniques in process control
applications. Regardless of the new
directions that nondestructive testing and
X-ray technology may take in the coming
century the American Society for
Nondestructive Testing’s roles of
education, information exchange and
personnel certification will continue.

Thanks to the superb investigative
talents of Wilhelm Conrad Röntgen, our
generation enjoys many benefits from
Röntgen’s rays. The new edition of the
Nondestructive Testing Handbook is a good
time to remember past achievements.

28 Radiographic Testing

PART 4. Units of Measure for Radiographic
Testing

Origin and Use of SI Multipliers
System
In science and engineering, very large or
In 1960 the General Conference on very small numbers with units are
Weights and Measures established the expressed by using the SI multipliers,
International System of Units. Le Systéme prefixes of 103 intervals (Table 9). The
International d’Unités (SI) was designed so multiplier becomes a property of the SI
that a single set of measurement units unit. For example, a millimeter (mm) is
could be used by all branches of science, 0.001 meter (m). The volume unit cubic
engineering and the general public. centimeter (cm3) is (0.01 m)3 or 10–6 m3.
Without SI, this Nondestructive Testing Unit submultiples such as the centimeter,
Handbook volume could have contained a decimeter, dekameter (or decameter) and
confusing mix of obsolete hectometer are often avoided in scientific
centimeter-gram-second (CGS) units, and technical uses of SI because of their
imperial units and the units preferred by variance from the 103 interval. However,
certain localities or scientific specialties. dm3 and cm3 are commonly used. Note
that 1 cm3 is not equal to 0.01 m3.
SI is the modern version of the metric Nevertheless, in equations, submultiples
system and ends the division between such as centimeter (cm) or decimeter (dm)
metric units used by scientists and metric are often avoided because they disturb the
units used by engineers and the public.
Scientists have given up their units based TABLE 7. SI derived units with special names.a
on centimeter and gram and engineers
made a fundamental change in Quantity Units Symbol Relation
abandoning the kilogram-force in favor of
the newton. Electrical engineers have to Other
retained their ampere, volt and ohm but SI Unitsb
changed all units related to magnetism.
Capacitance farad F C·V–1
Table 6 lists the seven SI base units. Catalytic activity katal kat s–1·mol
Table 7 lists derived units with special Conductance siemens S A·V–1
names. Table 8 gives examples of Energy joule J N·m
conversions to SI units. In SI, the unit of Frequency (periodic) hertz Hz 1·s–1
time is the second (s) but hour (h) is Force newton N kg·m·s–2
recognized for use with SI. Inductance henry H Wb·A–1
Illuminance lux lx lm·m–2
For more information, the reader is Luminous flux lumen lm cd·sr
referred to the information available Electric charge coulomb C A·s
through national standards organizations Electric potentialc volt V W·A–1
and specialized information compiled by Electric resistance ohm V·A–1
technical organizations.60-63 Magnetic flux weber Ω V·s
Magnetic flux density tesla Wb Wb·m–2
TABLE 6. SI base units. Plane angle radian T 1
Power watt rad J·s–1
Quantity Unit Symbol Pressure (stress) pascal W N·m–2
Radiation absorbed dose gray Pa J·kg–1
Length meter m Radiation dose equivalent sievert Gy J·kg–1
Mass kilogram kg Radioactivity becquerel Sv 1·s–1
Time second s Solid angle steradian Bq 1
Electric current ampere A Tempersature, celsius degree celsius sr K
Temperature kelvin K Timea hour °C 3600 s
Amount of substance mole mol Volumea liter h dm3
Luminous intensity candela cd L

a. Hour and liter are not SI units but are accepted for use with the SI.
b. Number one (1) expresses dimensionless relationship.
c. Electromotive force.

Introduction to Radiographic Testing 29

convenient 103 or 10–3 intervals that TABLE 9. SI prefixes and multipliers.
make equations easy to manipulate.
Prefix Symbol Multiplier
In SI, the distinction between upper
and lower case letters is meaningful and yotta Y 1024
should be observed. For example, the zetta Z 1021
meanings of the prefix m (milli) and the exa E 1018
prefix M (mega) differ by nine orders of peta P 1015
magnitude. tera T 1012
giga G 109
SI Units for Radiography mega M 106
kilo k 103
The original discoveries of radioactivity hectoa h 102
helped establish units of measurement deka (or deca)a da 10
based on observation rather than precise decia d 10–1
physical phenomena. Later, scientists who centia c 10–2
worked with radioactive substances (or milli m 10–3
who managed to manufacture radioactive micro 10–6
beams) again made circumstantial nano µ 10–9
observations that were then used for pico n 10–12
measurement purposes. This practical femto p 10–15
approach was acceptable at the time, but atto f 10–18
a broader understanding of physics and zepto a 10–21
the modern practice of using only one yocto z 10–24
unit for a quantity has led to the y
modification of many of the original units
(see Tables 10 to 12). In the SI system, a. Avoid these prefixes (except in dm3 and cm3) for
radiation units have been given science and engineering.
established physical foundations and new
names where necessary.

TABLE 8. Examples of conversions to SI units.

Quantity Measurement in Non-SI Unit Multiply by To Get Measurement in SI Unit

Angle minute (min) 2.908 882 × 10–4 radian (rad)
radian (rad)
Area degree (deg) 1.745 329 × 10–2 square millimeter (mm2)
Distance nanometer (nm)
square inch (in.2) 645 millimeter (mm)
Energy kilojoule (kJ)
angstrom (Å) 0.1 joule (J)
Power watt (W)
Specific heat inch (in.) 25.4 kilojoule per kilogram per kelvin (kJ·kg–1·K–1)

Force (torque, couple) British thermal unit (BTU) 1.055 joule (J)
Pressure kilopascal (kPa)
Frequency (cycle) calorie (cal), thermochemical 4.184 hertz (Hz)
Illuminance lux (lx)
British thermal unit per hour (BTU·h–1) 0.293 lux (lx)
Luminance candela per square meter (cd·m–2)
British thermal unit per pound 4.19 candela per square meter (cd·m–2)
Radioactivity candela per square meter (cd·m–2)
Ionizing radiation exposure degree fahrenheit (BTU·lbm–1·°F–1) 1.36 candela per square meter (cd·m–2)
Mass foot-pound (ft-lbf) 6.89 candela per square meter (cd·m–2)
Temperature (difference) pound force per square inch (lbf·in.–2) 60–1 candela per square meter (cd·m–2)
Temperature (scale) cycle per minute gigabecquerel (GBq)
Temperature (scale) millicoulomb per kilogram (mC·kg–1)
footcandle (ftc) 10.76 kilogram (kg)
kelvin (K) or degree celsius (°C)
phot (ph) 10 000 degree celsius (°C)
kelvin (K)
candela per square foot (cd·ft–2) 10.76

candela per square inch (cd·in.–2) 1 550

footlambert (ftl) 3.426

lambert 3 183 (= 10 000/π)

nit (nt) 1

stilb (sb) 10 000

curie (Ci) 37

roentgen (R) 0.258

pound (lbm) 0.454
degree fahrenheit (°F) 0.556

degree fahrenheit (°F) (°F – 32)/1.8

degree fahrenheit (°F) (°F – 32)/1.8) + 273.15

30 Radiographic Testing

Physical Quantities Mesures) permitted the units given in
Table 11 (curie, roentgen, rad and rem) to
Three physical quantities in particular are continue to be used with the SI until
widely used as measurement units — the 1998.61-63 However, these units must not
electronvolt (eV), the speed of light (c) be introduced where they are not
and the unified atomic mass unit (u). presently used. The National Institute of
Their precise values, however, are Standards and Technology strongly
obtained experimentally. discourages the continued use of curie,
roentgen, rad and rem.61-63 The American
Electronvolt. The electronvolt is the National Standards Institute, the
kinetic energy acquired by an electron in American Society for Testing and
passing through a potential difference of Materials, the Institute of Electrical and
1 V in vacuum; 1 eV = 1.602 176 462 × Electronics Engineers, the International
10–19 J with a combined standard Organization Standardization (ISO) and
uncertainty of 6.3 × 10–27 J.63,64 The and the American Society for
electronvolt is accepted for use with SI. Nondestructive Testing all support the
replacement of older English units with SI
Speed of Electromagnetic Radiation. The units.
quantity c represents the speed of light,
that is, the speed of electromagnetic Becquerel Replaces Curie. The original
waves in vacuum; 1 c = 299 792 458 m·s–1 unit for radioactivity was the curie (Ci),
exactly (670 616 629 mi·h–1). The speed of simply the radiation of one gram of
light is a physical quantity but can be radium. Eventually all equivalent
used as a unit of measure. radiation from any source was measured
with this same unit. It is now known that
Unified Atomic Mass Unit. The unified a curie is equivalent to 3.7 × 1010
atomic mass unit (u) is 12–1 of the mass of disintegrations per second. In SI, the unit
the atom of the nuclide carbon-12; 1 u = for radioactivity is the becquerel (Bq),
1.660 538 7310–27 kg with a combined which is one disintegration per second.
standard uncertainty of ±1.3 × Because billions of disintegrations are
10–34 kg.63,64 required in a useful source, the multiplier
prefix giga (109) is used and the unit is
Radiation Measurement normally seen as gigabecquerel (GBq).

Because of existing practice in certain Coulomb per Kilogram Replaces
fields and countries, the International Roentgen. The unit for quantity of
Committee for Weights and Measures electric charge is the coulomb (C), where
(CIPM, Comité Internationale des Poids et

TABLE 10. Physical quantities used as units. Values of physical quantities are experimentally obtained and
may only be approximated in SI. Conversions are provided here for descriptive purposes.

Physical Quantity Symbol Multiply by SI Unit SI Symbol

Electronvolt a eV 1.6 × 10–19 joule J
Speed of electromagnetic waves in vacuum 2.997 924 58 × 108 meter per second m·s–1
Unified atomic mass unit a,b c 1.66 x 10–27 kilogram kg
u

a. Approved for use with SI.
b. Mass of unified atomic mass unit is 12–1 of the mass of the atom of the nuclide carbon-12.

TABLE 11. Conversion to SI radiographic units.

Traditional Unit Symbol Multiply by Resulting SI Unit SI Symbol

Curie Ci 3.7 × 1010 becquerel Bq
Rad rad a 37 gigabecquerel GBq
Rem rem 10–2 gray Gy
Roentgen R 10 milligray mGy
10–2 sievert Sv
10 millisievert mSv
coulomb per kilogram C·kg–1
2.58 × 10–4 microcoulomb per kilogram µC·kg–1
258

a. The abbreviation rd may be used for radiation absorbed dose where there is possibility of confusion with radian
(rad), the SI unit for plane angle.

Introduction to Radiographic Testing 31

1 C = 1 A × 1 s. The original roentgen (R) roentgen converts to millisieverts on a
was the quantity of radiation that would
ionize 1 cm3 of air to 1 electrostatic unit one-to-ten basis.
of electric charge, of either sign. It is now
known that a roentgen is equivalent to Exposure charts were often made by
258 microcoulombs per kilogram of air
(258 µC·kg–1 of air). This corresponds to using curie minutes at a source-to-film
1.61 × 1015 ion pairs per 1 kg of air, which
has then absorbed 8.8 mJ (0.88 rad, where distance in inches squared. This was
rad is the obsolete unit for radiation written Ci·min·in.–2. Exposure charts
absorbed dose, not the SI symbol for
radian). made in SI use gigabecquerel minutes for

Gray Replaces Rad. The roentgen (R) was a source-to-film distance in centimeters
an intensity unit but was not squared, where 1 Ci·min·in.–2 =
representative of the dose absorbed by 50 GBq·min·cm–2. Table 12 lists some of
material in a radiation field. The radiation
absorbed dose (rad) was first created to these compound units.
measure this quantity and was based on
the erg, the energy unit from the old TABLE 12. Compound radiographic units.
centimeter-gram-second (CGS) system. In
the SI system, the unit for radiation dose Traditional Multiply Resulting
is the gray (Gy). The gray is useful because Unit by SI Unit
it applies to doses absorbed by matter at a
particular location. It is expressed in R·Ci–1·h–1 at 1 m 0.27 mSv·GBq–1·h–1 at 1 m
energy units per mass of matter or in Ci·min·in.–2 50 GBq·min.·cm–2
joules per kilogram (J·kg–1). The mass is R·min–1 a Gy·min–1
that of the absorbing body. R·min–1 b 0.01 Sv·min–1
R 0.01 C·kg–1
Sievert Replaces Rem. The SI system’s unit 2.58 × 10–4
for the dose absorbed by the human body
(formerly rem for roentgen equivalent man; a. Absorbed dose.
also known as ambient dose equivalent, b. Dose absorbed by human body.
directional dose equivalent, dose equivalent,
equivalent dose and personal dose equivalent)
is similar to the gray but includes quality
factors dependent on the type of
radiation. This absorbed dose has been
given the name sievert (Sv) but its
dimensions are the same as the gray, that
is, 1 Sv = 1 J·kg–1.

Compound Units

Exposure to ionizing radiation could be
measured in roentgens with an ionization
chamber that, when placed 1 m (39 in.)
from the radiation source, provided
necessary information — one roentgen
per curie per hour at one meter (R·Ci–1·h–1
at 1 m), for example. The numbers,
however, had limited physical meaning
and could not be used for different
applications such as high voltage X-ray
machines.

The roentgen per hour (R·h–1) was used
to designate the exposure to an ionizing
radiation of the stated value. Because the
radiation received from 1 R·h–1 was
considered about equal to 1 rem, the
relationship is approximated as 1 R·h–1 =
0.01 Gy·h–1 = 10 mGy·h–1.

A previously popular unit, roentgen per
curie per hour at one meter (R·Ci–1·h–1 at
1 m), is expressed in SI units as
millisievert per gigabecquerel per hour at
one meter (mSv·GBq–1·h–1 at 1 m), such
that 1 mSv·GBq–1·h–1 at 1 m =
3.7 R·Ci–1·h–1 at 1 m. In this relationship,

32 Radiographic Testing

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34 Radiographic Testing