Soest myer pe spon TER om NE ENSRUIN L Brien” approNye e+ Cae ky _ () SHORETSE ONY = « DRAFT TFM:em 2/24/67 PLAN FOR MEASUREMENT OF EXTERNAL NUCLEAR RADIATION LEVELS AT BIKINI ATOLL, MARCH 1967 Purpose. The purpose of this plan is to describe procedures to be used (te-obtaining-date-thet-wittprovide-e-besta] for determining external radiation levels that exist on various islands of Bikini Atoll. Discussion. . In order to establish the levels of radiation that may be found at Bikini Atoll, it may be worthwhile to review briefly the data collected during the most recent sampling mission conducted in 1964 by the University of Washington, under contract with the Division of Biology and Medicine, and to present for comparison the reported levels for Rongelap Atoll at the time of repatriation. The attached Table presents these data. The average level of external radiation on Rongelap Island (0.03 mr/hr) at the time the inhabitants were returned was only slightly higher than the average value used for natural background radiation for the U. S. population of about 100 to 200 mr/yr. or about 0.02 mr/hr. The average level on Bikini Island in 1964 was about 0.04 mr/hr with Enyu Island at a somewhat lower level of 0.01 mr/hr. These two islands contain the major land masses within the atoll and as such represent the most likely areas of habitation. Though these values are low, it is important to determine with confidence the range of external radiation levels that exist on Bikini Atoll. Such external radiation exposures, above background, must be added to that from internal emitters in order to arrive.at the total dose any permanent resi- ' FAORRO Me eri OM - dent may receive from past tests. Considering the uncertainties inherent sree alos |PO2F ;