minimize external exposure, ple (see acknowledgment) and the sup- a survey of Bikini Atoll was proposed. Initial port of the ERDA Research Vessel, plans. called for aerial surveys to Liktanur, from June 16 through June 24, determine external gamma levels on all 1975. islands in the atoll along with ground surveys using scintillation counters The basic plans for the 1975 Bikini survey are outlined below. and thermoluminescent dosimeters (TLD). SURVEY PROGRAM OF BIKINI SOIL AND GAMMA EXPOSURE RATE Emphasis was to be placed on Bikini and Eneu Islands, the prime residence islands. In addition, there was to be a rather large scale effort Survey of Gamma-Exposure Rate The program for the measurement of to sample the soil and vegetation to gamma-ray exposure rates conducted on evaluate the potential dose via the the ground was designed to examine in terrestrial pathway. detail the geographical variability of It was felt that this was an especially important goal the exposure rates on Bikini and Eneu in view of the significance of the Islands, contribution of the food chain to the measured during previous visits. and verify exposure-rates total dose estimated at Enewetak Methods and Measurements Atol1.+ For a number of reasons, the scale A Baird-Atomic scintillation detec- of the program had to be reduced from tor, which consists of a 2.5-cm-diam that originally planned. x 3.9-cm-long NaI crystal with a Manpower and Support were reduced, and the aerial ratemeter readout was used. Survey was temporally deferred, leaving instrument was calibrated with a 137¢6 the entire program of measuring the point source in the primary calibra- external dose levels on Bikini and tion range of the National Environmen- Eneu Islands to be accomplished by tal Research Center, Las Vegas, Nevada. ground crews.” While the response of this instrument The emphasis of this reduced effort was toward the external is energy-dependent, The our experience at gamma measurements on Bikini and Eneu Enewetak showed that this was not a Islands. serious limitation because of the Although the sampling of the food chain pathways was less extensive dominance of 13764 in the radiation than we had hoped, we maintained a background on the atoll. smaller scale program designed to help a Reuter-Stokes high pressure ioniza- assess the potential dose via inges- tion chamber. tion pathways. the radiation-induced ionization within The 1975 Bikini survey was conducted with the help of 20 peo- 5009953 — ~ We also used The current produced by the chamber is measured by a sensitive