Fallout Dosages at Washington, D.C.

Abstract

It has been assumed that the fission product conglomerate emits one gamma ray per beta particle throughout its lifetime. The fallout velocities are not accurately known, and in some cases the detonation and response times have been approximated. For these reasons, the dosages reported in this paper can be accurate in order of magnitude only. With these reservations, an infinity dose of 0.2 roentgen or less due to all explosions between January 1951 and May 1955 is reported for Washington, D.C. Therefore, it is probable that the total fallout from all weapons tests that have so far been conducted will produce only a fraction of the lifetime dosage due to natural radioactivity and cosmic radiation (6). Most of the dosage comes from the Nevada tests, and only a small part from the Pacific thermonuclear tests (7). Fission products contained in that part of the cloud of a thermonuclear explosion which extends above the level of precipitation is found to contribute only very slightly to the dosage at great distances. No analysis was carried out for air activity data taken at other locations, but their qualitative similarity to those taken in Washington suggests that infinity doses in most other locations in the northern hemisphere will not be greatly different. Present results are in essential agreement with two other measurements that have been reported. Eisenbud and Harley (8) have measured fallout deposited on gummed papers (9) at various locations in the United States and have found an average dose of 0.001 roentgen per year. Stewart, Crooks, and Fisher (10) have measured the activity of air, rainwater, and ground deposits in England and report an infinity dose of 0.055 roentgen. This somewhat lower figure may result from their greater distance from Nevada, which appears to be the source of most of the fallout in the United States. The authors wish to thank Dr. H. Friedman and Dr. L. B. Lockhart for their continued support and for many helpful discussions.