wo minimize external exposur2. 2 survey or Bikini Atoll was tropcsed. Tians zie ‘see acknowledgement) ana the sup- “<nitiai called for aerial surveys <=o tort of the =ERDA Researcn Vessei, Liktanur, ierermine external zamma -eveis cn ail islands in the atoil aleng with zround surveys using scintillatisn counters from June 15 througn June 24, 1975. The casic plans for the i975 Bikini survey are outlined below. and thermoiuminescent dosimeters (TLD). imphasis was to te placed on 3ikini and Eneu Islands, residence islands. SURVEY PROGRAM OF BIKINI SOIL AND GAMMA EXPOSURE RATE zhe prime In addition, there vas to te a rather large scale effort Survey of Gamma-Exposure Rate The program for the measurement of to sample the soil and vegetation to Zamma-ray exposure rates conducted on evaluate the potential csse via the the ground was designed to examine in terrestrial pathway. detail the geographical variability of Ir was feit thac this was an especially inportanc zoal 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 Znewetrak Methods and Measurements Atol.+ For a number of reasons, A Baird-Atomic scintillation detec the scale of the pvrogram had to be reduced from tor, which consists of a 2.5-cm-diam that originally planned. x 3.9-cem-long NaI crystal with a Manpower and support were reduced, and the aerial ratemeter readout was used. survey was temporally deferred, instrument was calibrated with a leaving The 13765 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, our experience at gamma measurements on Bikini and Eneu Enewetak showed that this was not a Islands. food chain pathways was iess extensive serious limitation because of the 137 than we had hoped, we maintained a background on the atoll. smaller scale program designed to help a Reuter-Stokes high pressure toniza- assess the potential dose via inges- tion chamber. tion pathways. the radiation-induced ionization within Although the sampling of the The 1975 Bikini survey was conducted with the help of 20 peo- -3j- dominance of Cs in the radiation We also used The current produced by the chamber is measured bv a sensitive