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 study was supported by contract DTRA01-01-C-0012 between the National Academy of Sciences and the Defense Threat Reduction Agency. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the views of the organizations or agencies that provided support for the project.

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COVER PHOTO. Soldiers watching atomic-bomb detonation at Yucca Flat, Nevada. This photo is Shot DOG in which a 21.5-kiloton device was dropped from a B-50 bomber in the BUSTER-JANGLE series of tests on November 1, 1951. This photo was also published in the November 12, 1951, issue of Life Magazine.