Status of the Dosimetry for the Radiation Effects Research Foundation (DS86)

Committee on Dosimetry for the Radiation Effects Research Foundation

Board on Radiation Effects Research

Division on Earth and Life Studies

National Research Council

NATIONAL ACADEMY PRESS
Washington, D.C.



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Status of the Dosimetry for the Radiation Effects Research Foundation (DS86) Status of the Dosimetry for the Radiation Effects Research Foundation (DS86) Committee on Dosimetry for the Radiation Effects Research Foundation Board on Radiation Effects Research Division on Earth and Life Studies National Research Council NATIONAL ACADEMY PRESS Washington, D.C.

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Status of the Dosimetry for the Radiation Effects Research Foundation (DS86) NATIONAL ACADEMY PRESS 2101 Constitution Avenue, NW Washington, DC 20418 NOTICE: The project that is the subject of this report was approved by the Governing Board of the National Research Council, whose members are drawn from the councils of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine. The members of the committee responsible for the report were chosen for their special competences and with regard for appropriate balance. This report was prepared under Department of Energy Cooperative Agreement DE-FC03– 97SF21318 between the National Academy of Sciences and the Department of Energy. International Standard Book Number: 0-309-07559-9 Library of Congress Control Number: 2001012345 Additional copies are available from: National Academy Press 2101 Constitution Ave., NW Box 285 Washington, DC 20055 800–624–6242 202–334–3313 (in the Washington Metropolitan area) http://www.nop.edu Copyright 2001 by the National Academy of Sciences. All rights reserved. Printed in the United States of America

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Status of the Dosimetry for the Radiation Effects Research Foundation (DS86) THE NATIONAL ACADEMIES Advisers to the Nation on Science, Engineering, and Medicine National Academy of Sciences National Academy of Engineering Institute of Medicine National Research Council The National Academy of Sciences is a private, nonprofit, self-perpetuating society of distinguished scholars engaged in scientific and engineering research, dedicated to the furtherance of science and technology and to their use for the general welfare. Upon the authority of the charter granted to it by the Congress in 1863, the Academy has a mandate that requires it to advise the federal government on scientific and technical matters. Dr. Bruce M.Alberts is president of the National Academy of Sciences. The National Academy of Engineering was established in 1964, under the charter of the National Academy of Sciences, as a parallel organization of outstanding engineers. It is autonomous in its administration and in the selection of its members, sharing with the National Academy of Sciences the responsibility for advising the federal government. The National Academy of Engineering also sponsors engineering programs aimed at meeting national needs, encourages education and research, and recognizes the superior achievements of engineers. Dr. William A.Wulf is president of the National Academy of Engineering. The Institute of Medicine was established in 1970 by the National Academy of Sciences to secure the services of eminent members of appropriate professions in the examination of policy matters pertaining to the health of the public. The Institute acts under the responsibility given to the National Academy of Sciences by its congressional charter to be an adviser to the federal government and, upon its own initiative, to identify issues of medical care, research, and education. Dr. Kenneth I.Shine is president of the Institute of Medicine. The National Research Council was organized by the National Academy of Sciences in 1916 to associate the broad community of science and technology with the Academy’s purposes of furthering knowledge and advising the federal government. Functioning in accordance with general policies determined by the Academy, the Council has become the principal operating agency of both the National Academy of Sciences and the National Academy of Engineering in providing services to the government, the public, and the scientific and engineering communities. The Council is administered jointly by both the Academies and the Institute of Medicine. Dr. Bruce M.Alberts and Dr. William A.Wulf are chairman and vice chairman, respectively, of the National Research Council.

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Status of the Dosimetry for the Radiation Effects Research Foundation (DS86) COMMITTEE ON DOSIMETRY FOR THE RADIATION EFFECTS RESEARCH FOUNDATION (RERF) WARREN K.SINCLAIR, Chair, National Council on Radiation Protection and Measurements (ret.), Escondido, CA HAROLD AGNEW, General Atomics (ret.), Los Alamos National Laboratory(ret.), Solana Beach, CA HAROLD L.BECK, Environmental Measurements Laboratory (ret.), New York, NY ROBERT F.CHRISTY, California Institute of Technology, Pasadena, CA SUE B.CLARK, Washington State University, Pullman, WA NAOMI H.HARLEY, NYU School of Medicine, New York, NY ALBRECHT M.KELLERER, University of Munich KENNETH J.KOPECKY, Fred Hutchinson Cancer Center, Seattle, WA WAYNE M.LOWDER, Environmental Measurements Laboratory (ret.), Valhalla, NY ALVIN M.WEINBERG, Oak Ridge Associated Universities, Oak Ridge, TN ROBERT W.YOUNG, INSIGHT, Winter Springs, FL MARCO ZAIDER, Memorial Sloan-Kettering Cancer Center, New York, NY Special Scientists TAKASHI MARUYAMA, Head of Division of Planning, Radiation Effects Association, Tokyo, Japan HARRY M.CULLINGS, Research Scientist, Radiation Effects Research Foundation, Hiroshima, Japan National Research Council Staff EVAN B.DOUPLE, Study Director BENJAMIN HAMLIN, Project Assistant DORIS E.TAYLOR, Staff Assistant Editor NORMAN GROSSBLATT

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Status of the Dosimetry for the Radiation Effects Research Foundation (DS86) BOARD ON RADIATION EFFECTS RESEARCH R.J.MICHAEL FRY,* Chairman, Oak Ridge National Laboratory, Oak Ridge, TN S.JAMES ADELSTEIN, Harvard Medical School, Boston, MA VALERIE BERAL, University of Oxford, United Kingdom SARAH S.DONALDSON, Stanford University Medical Center, Stanford, CA EDWARD R.EPP, Professor Emeritus, Harvard University, Boston, MA HELEN H.EVANS, Case Western Reserve University, Cleveland, OH WILLIAM F.MORGAN, The University of Maryland, Baltimore, MD FRANKLYN G.PRENDERGAST, Mayo Clinic Cancer Center, Rochester, MN DANIEL O.STRAM, University of Southern California, Los Angeles, CA National Research Council Staff EVAN B.DOUPLE, Director, Board on Radiation Effects Research RICK JOSTES, Senior Program Officer ISAF AL-NABULSI, Program Officer CATHERINE S.BERKLEY, Administrative Associate BRIDGET R.EDMONDS, Project Assistant BENJAMIN HAMLIN, Project Assistant DORIS E.TAYLOR, Staff Assistant *   Retired from Oak Ridge National Laboratory (effective 12/00)

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Status of the Dosimetry for the Radiation Effects Research Foundation (DS86) Preface The dosimetry of the atomic-bomb survivors of Hiroshima and Nagasaki has been a subject of great importance for several decades to the individual survivors, whose estimated dose depends on it, and second to all the peoples of the world, because estimates of risk of possible late effects (especially cancer) of an exposure to ionizing radiation are based mainly on the studies of the survivors. The continuing studies of the A-bomb survivors are the most complete and sophisticated evaluations of health effects in an irradiated population that are available to us. Knowledge of the dosimetry has increased because new techniques of calculation of radiation transport and new techniques of measurement continue to be developed and applied. These can improve our knowledge of the dosimetric circumstances of exposure to the A-bombs. In 1986, the senior committees of the United States (F.Seitz, Chair) and Japan (E.Tajima, Chair) approved the adoption of a new dosimetry system, DS86, for use by the Radiation Effects Research Foundation (RERF) in reconstructing the doses to the survivors. At the time, DS86 was believed to be the best available; it replaced the previous tentative system (T65D) completely, and it has shown itself to be superior to any previous system. It is also the first system to have direct experimental confirmation of the main component of the dose to the organs of exposed people—gamma rays. Nevertheless, questions have arisen about some features of DS86, in particular, whether it adequately describes the neutrons released by the Hiroshima bomb. Measurements of thermal-neutron activation in some materials have suggested more fast neutrons at greater distances from the hypocenter than calculated in DS86. This unresolved discrepancy has tended to cast suspicion on the validity of DS86 dose estimates for dose specifications for the survivors and as a basis of estimation of risk of expected effects in other exposed persons. For these reasons, the Committee on Dosimetry for RERF, which was set up by the National Research Council (NRC) more than a decade ago at the request of the US Department of Energy, has written this report to describe the present status of DS86 and to recommend studies needed for a possible further-improved dosime-

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Status of the Dosimetry for the Radiation Effects Research Foundation (DS86) try system. After studying the problems over a period of years, the committee convened a public forum to discuss extant difficulties with DS86 in Irvine, CA in 1996, at which a number of Japanese colleagues were present. During the meeting, a number of actions that could improve DS86 were discussed and were used as the basis of the committee’s subsequent letter report, which included a number of recommendations. Some of the recommendations already have been partially implemented; others are being pursued vigorously by the US and Japanese scientists who have continued to study the problem in their laboratories on the advice of this committee and the Japanese senior dosimetry committee. Formal scientific working groups have been set up recently in the United States and in Japan to undertake and complete these studies and two members of the Committee on Dosimetry for the RERF, R.Christy and R.Young, have agreed to step down from the committee to serve on the new working groups and to assist in the implementation of this report’s recommendations. Concerns within the radiation protection and risk assessment communities, the findings of the NRC committee, the commitment of the US Department of Energy and the Japanese Ministry of Health, Labour and Welfare to complete medical follow-up studies of the A-bomb survivors, and recent technical developments have all come together to set the stage for the current reassessment effort. It is now the hope of both Japanese and US scientists that an improvement to DS86 can soon be described in the form of a revised dosimetry system and approved for adoption. It is not expected that a revised system will differ greatly from DS86. In the meantime, the current report, which has been prepared by the committee members, will describe the present status of DS86, some of the apparent discrepancies that are now being investigated, some of the approaches recommended to solve the problems, and some results already achieved. WARREN K.SINCLAIR, Chairman Committee on Dosimetry for the RERF

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Status of the Dosimetry for the Radiation Effects Research Foundation (DS86) Acknowledgments The committee members and the National Research Council are especially appreciative for the valuable input provided by numerous members of the Japanese and US Dosimetry Working Groups. Many of these scientists attended meetings in Japan and the United States and presented their data for consideration by the members of this committee. Their work is also represented in the references discussed and listed in this report. In addition, several scientists from Japan and the US hosted Wayne Lowder, Takashi Maruyama, and Harry Cullings, who visited their laboratories to review data related to the committee’s work. We wish to thank those scientists who were willing to share their data with the committee and who provided data for the committee’s analysis. A special thanks is extended to scientists Harry Cullings and Takashi Maruyama, whose dedicated survey and analysis of the measurement data was critical to the work of this committee. The committee members are especially appreciative of the administrative assistance, logistical arrangements, and assistance with the manuscript preparation provided by Doris E.Taylor, Cathie Berkley, Benjamin Hamlin and Eric Truett. This report has been reviewed in draft form by persons chosen for their diverse perspectives and technical expertise, in accordance with procedures approved by the National Research Council’s Report Review Committee. The purpose of this independent review is to provide candid and critical comments that will assist the institution in making the published report as sound as possible and to ensure that the report meets institutional standards for objectivity, evidence, and responsiveness to the study charge. The review comments and draft manuscript remain confidential to protect the integrity of the deliberative process. We wish to thank the following persons for their participation in the review of this report: David Auton, Defense Nuclear Agency (retired) Randall S.Caswell, National Institute of Science and Technology (retired) Edward Epp, Harvard University (retired)

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Status of the Dosimetry for the Radiation Effects Research Foundation (DS86) Daniel O.Stram, University of Southern California, Los Angeles Paul Goldhagen, Department of Energy, Environmental Measurements Laboratory, New York George Kerr, Oak Ridge National Laboratory (retired) Atsuyuki Suzuki, Quantum School of Engineering, University of Tokyo, Tokyo, Japan Francis X.Masse, Massachusetts Institute of Technology, Cambridge Although the reviewers listed above have provided many constructive comments and suggestions, they were not asked to endorse the conclusions or recommendations nor did they see the final draft of the report before its release. The review of this report was overseen by David G.Hoel, Medical University of South Carolina and John Dowling, Harvard University. Appointed by the National Research Council, they were responsible for making certain that an independent examination of this report was carried out in accordance with institutional procedures and that all review comments were carefully considered. Responsibility for the final content of this report rests entirely with the authoring committee and the institution.

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Status of the Dosimetry for the Radiation Effects Research Foundation (DS86) Contents     EXECUTIVE SUMMARY   1 1   INTRODUCTION   7     DS86,   7     Gamma Rays,   8     Neutron Measurements and Discrepancy,   8     The National Research Council Committee on Dosimetry for the RERF,   11     United States-Japan Interactions,   12 2   GAMMA-RAY MEASUREMENTS   14     Thermoluminescent Measurements in Brick and Tile,   14     Comparison of TL Gamma-Ray Measurements Between Hiroshima and Nagasaki,   24 3   THERMAL-NEUTRON AND FAST-NEUTRON MEASUREMENTS   31     Fast-neutron Activation Measurements,   32     Thermal-neutron Activation Measurements,   32     Fast-neutron Activation Measurements of 63Ni,   33     Summary of Available Neutron Activation Measurements,   34     Comparison of Activation Measurements with DS86-Based Calculations,   36     Measurement Issues,   50     Uncertainty in Calculated Activation,   55     Summary, Conclusions, and Recommendations,   57 4   RADIATION TRANSPORT CALCULATIONS   60     The Nagasaki Discrepancy,   64     The Hiroshima Bomb and Possible Other Source Terms,   68     Alternative Disassembly Hypothesis,   70     Status of Efforts to Improve DS86,   73

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Status of the Dosimetry for the Radiation Effects Research Foundation (DS86) 5   BIOLOGICAL DOSIMETRY AT RERF   74 6   UNCERTAINTY IN DS86   79     Systematic Uncertainty,   80     Random Errors Resulting from Method,   82     Random Errors Resulting from Input Data,   83 7   IMPLICATIONS FOR RISK ASSESSMENT   87     Concerns about DS86,   87     The Neutron/Gamma-Ray Dose Ratio,   89     Effect of the Neutron Contribution as Inferred from RBE,   90     Comparison of Neutron Effects in Hiroshima and Nagasaki,   92     Implications of the Neutron Discrepancy,   93 8   CONCLUSIONS AND RECOMMENDATIONS   95     APPENDIXES     A   The RERF Dosimetry Measurements Database and Data Collection for the Dosimetry Reassessment   99 B   An Uncertainty Analysis of Neutron Activation Measurements in Hiroshima and Nagasaki   123 C   Cosmic-ray Neutron Contribution to Sample Activation   169 D   Letter from Committee on Dosimetry to DOE   174     GLOSSARY   177     REFERENCES   184     BIOSKETCHES   194