This document is a supplementary operating guide to document HW-44064, ``Process Specifications for Critical Mass Control -- Purex Plant.`` It is primarily intended that this document illustrate the actual operational means of conforming to the limits of critical mass control as presented in HW-44064.

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The detonation of shot one at Bikini Atoll on March 1, 1954, produced a fallout of radioactive ash upon Rongelap Atoll, Marshall Islands. The distribution of the radioactive ash on the islands and in the plants and animals of the area has been studied and evaluated. During the first expedition to Rongelap Atoll on March 26, 1954, biological samples were collected and measurements made of the radiation contamination. On three additional expeditions extensive collections of material were made for this study, the last on January 25-30, 1955. The decline in radioactivity was measured in 1499 samples of fish, invertebrates, land plants, algae, birds, plankton, soil, and water from the Rongelap area. During this study particular emphasis was placed upon evaluation of the radioactivity in food used by the natives. Coconut milk collected on March 26, 1954, contained 1.03 microcuries per kilogram of wet tissue while the coconut meat had 1.16 mu c/kg. By January 25-30, 1955, the level in coconut milk had declined to 0.041 mu c/kg and the meat to 0.036 mu c/ kg. Fish muscle on March 26, 1954, averaged 2.74 mu c/kg and fish liver 204.0 mu c/kg. The decline to January 25-30 was 0.10 mu c/kg …