Adopting the International System of
Units for Radiation Measurements in
the United States

Proceedings of a Workshop

Ourania Kosti, Rapporteur

Nuclear and Radiation Studies Board

Division on Earth and Life Studies

THE NATIONAL ACADEMIES PRESS
Washington, DC
www.nap.edu

THE NATIONAL ACADEMIES PRESS 500 Fifth Street, NW Washington, DC 20001

This activity was supported by Contract No. 200-2011-38807 TO# 50 with the Department of Health and Human Services’ Centers for Disease Control and Prevention. Any opinions, findings, conclusions, or recommendations expressed in this publication do not necessarily reflect the views of any organization or agency that provided support for the project.

International Standard Book Number-13:978-0-309-45388-2
International Standard Book Number-10:0-309-45388-7
Digital Object Identifier:10.17226/24645

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Suggested citation: National Academies of Sciences, Engineering, and Medicine. 2017. Adopting the International System of Units for Radiation Measurements in the United States: Proceedings of a Workshop. Washington, DC: The National Academies Press. doi: 10.17226/24645.

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WORKSHOP PLANNING COMMITTEE¹

STEVEN L. SIMON, Chair, National Cancer Institute, Bethesda, Maryland

DANIEL J. BLUMENTHAL, U.S. Department of Energy, Washington, DC

E. VINCENT HOLAHAN, JR., U.S. Nuclear Regulatory Commission, Rockville, Maryland

MARK L. MAIELLO, New York City Department of Health and Mental Hygiene, Queens

RUTH E. McBURNEY, Conference of Radiation Control Program Directors, Inc., Frankfort, Kentucky

JESSICA WIEDER, U.S. Environmental Protection Agency, Washington, DC

Staff

OURANIA KOSTI, Study Director

TONI GREENLEAF, Administrative/Financial Associate

DARLENE GROS, Senior Program Assistant

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¹ The National Academies of Sciences, Engineering, and Medicine’s workshop planning committees are solely responsible for organizing the workshop, identifying topics, and choosing speakers. The responsibility for the published Proceedings of a Workshop rests with the workshop rapporteur and the institution.

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NUCLEAR AND RADIATION STUDIES BOARD

ROBERT C. DYNES, Chair, University of California, San Diego

JAMES A. BRINK, Vice Chair, Massachusetts General Hospital, Boston

GEORGE E. APOSTOLAKIS, Massachusetts Institute of Technology (emeritus), Cambridge

DAVID J. BRENNER, Columbia University, New York

MARGARET S. Y. CHU, M.S. Chu & Associates, LLC, Albuquerque, New Mexico

TISSA H. ILLANGASEKARE, Colorado School of Mines, Golden

CAROL M. JANTZEN, Savannah River National Laboratory, Aiken, South Carolina

MARTHA S. LINET, National Institutes of Health, Bethesda, Maryland

NANCY JO NICHOLAS, Los Alamos National Laboratory, Los Alamos, New Mexico

HENRY D. ROYAL, Washington University School of Medicine, St. Louis, Missouri

DANIEL O. STRAM, University of Southern California, Los Angeles

WILLIAM H. TOBEY, Belfer Center for Science and International Affairs, Cambridge, Massachusetts

SERGEY V. YUDINTSEV, Russian Academy of Sciences, Moscow

Staff

KEVIN D. CROWLEY, Director

JENNIFER HEIMBERG, Senior Program Officer

OURANIA KOSTI, Senior Program Officer

TONI GREENLEAF, Administrative and Financial Associate

LAURA D. LLANOS, Administrative and Financial Associate

DARLENE GROS, Senior Program Assistant

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Reviewers

This Proceedings of a Workshop was reviewed in draft form by individuals chosen for their diverse perspectives and technical expertise. The purpose of this independent review is to provide candid and critical comments that will assist the institution in making its published Proceedings of a Workshop as sound as possible and to ensure that the Proceedings of a Workshop 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 process. We wish to thank the following individuals for their review of this Proceedings of a Workshop:

Although the reviewers listed above have provided many constructive comments and suggestions, they did not see the final draft of the Proceedings of a Workshop before its release. The review of this Proceedings of a Workshop was overseen by Barbara L. Hamrick, University of California, Irvine, Medical Center. She was responsible for making certain that an independent examination of this Proceedings of a Workshop was carried

out in accordance with institutional procedures and that all review comments were carefully considered. Responsibility for the final content of this Proceedings of a Workshop rests entirely with the rapporteur and the institution.

Preface

Most countries in the world use the SI (Système International, also known as the metric system) units for radiation measurements in commercial and technical activities. The United States, in contrast, uses a mix of SI and conventional¹ units for radiation measurements, despite 30-year-old national and international recommendations to exclusively use SI.

SI units for radiation measurements are the gray (unit for absorbed dose, Gy), becquerel (unit for activity, Bq), and sievert (unit for dose equivalent and effective dose, Sv). Conventional units are the rad, curie, and rem. The size of the SI and conventional units differs, and in some cases conversions are not arithmetically convenient: 1 rad = 0.01 Gy; 1 Ci = 3.7 × 10¹⁰ Bq; 1 rem = 0.01 Sv. Radiation professionals in the United States are faced with the need to understand both systems and make conversions between the two.

Several post–Fukushima Daiichi Nuclear Power Plant accident² reports noted that the use of conventional units in the United States and the need to convert to/from SI hindered the exchange and interpretation of information during the accident response. The experience from the Fukushima nuclear accident led the Centers for Disease Control and Prevention to ask the Nuclear and Radiation Studies Board of the National Academies of Sciences, Engineering, and Medicine (the National Academies) to host this workshop, Adopting the International System of Units for Radiation

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¹ Also referred to as “traditional.”

² The Fukushima Nuclear Plant accident was initiated by the March 11, 2011, Great East Japan Earthquake and Tsunami.

Measurements in the United States. Its objective was to obtain perspectives from the radiation protection and user communities on potential communication improvements associated with adopting SI units for radiation measurements in the United States.

The workshop was held September 29-30, 2016, at the National Academies in Washington, DC. It was organized by a committee of six experts³ and featured a range of presentations⁴ on the topics listed in the statement of task (see Box P.1). The workshop was undertaken with the premise that adoption of the SI units for radiation measurements would improve the effectiveness of responding to national and international radiation emergencies and communicating with the public and among radiation experts.

This Proceedings of a Workshop, prepared by Dr. Ourania Kosti, who is a National Academies staff member, serves as a record of the workshop. It does not provide findings or recommendations or represent a consensus of workshop participants. Dr. Kosti is responsible for the overall quality and accuracy of this proceedings.

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³ See p. v for the planning committee membership and Appendix C for short biographical information.

⁴ See Appendix A for the workshop agenda and Appendix B for short biographical information on the workshop speakers.

This proceedings is organized into five chapters:

• Chapter 1 introduces the issue of adoption of SI units for radiation measurements in the United States.
• Chapter 2 summarizes current (as of September 2016) practices in use of units for radiation measurements in the United States.
• Chapter 3 summarizes the issues with continuing use of conventional units for radiation measurements and benefits and challenges of exclusive use of SI.
• Chapter 4 discusses lessons learned from international experience in adopting the SI units for radiation measurements.
• Chapter 5 describes options on possible next steps forward toward the exclusive use of SI units for radiation measurements in the United States.

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Contents

ACRONYMS AND ABBREVIATIONS

OVERARCHING WORKSHOP THEMES

1 INTRODUCTION AND CONTEXT

U.S. Policies for Adopting SI Units for All Measurements

National and International Recommendations for Adopting SI Units for Radiation Measurements

Summary

2 PRACTICES IN USE OF UNITS FOR RADIATION MEASUREMENTS

Federal Agencies

State and Local Governments

Nuclear Power Industry

Medicine

Scientific Publications

Summary

3 EXCLUSIVE USE OF SI UNITS FOR RADIATION MEASUREMENTS

Issues with Continuing Use of Conventional Units

Benefits of Exclusive Use of SI Units for Radiation Measurements

Challenges to Exclusive Use of SI Units for Radiation Measurements

Obstacles to Exclusive Use of SI Units for Radiation Measurements

Summary

4 LESSONS LEARNED FROM INTERNATIONAL EXPERIENCES

Canada

United Kingdom

European Union

Summary

5 POSSIBLE STEPS TOWARD THE EXCLUSIVE USE OF SI UNITS FOR RADIATION MEASUREMENTS

No Action Needed

Develop a Plan for Adoption of SI Units for Radiation Measurements

Summary

REFERENCES

APPENDIXES

A Workshop Agenda

B Speaker Biographies

C Planning Committee Member Biographies

Acronyms and Abbreviations