Appendix 14 Gamma Radiation Measurements on Bikini Island, 1974 External gamma exposure rate measurements were made by N. A. Greenhouse and V. A. Nelson in the village area on Bikini Island during December 1974. The measurements were made with a Reuter-Stokes environmental radiation monitor, model RSS-111, which uses a pressurized ion chamber as a detector. The response of this instrument is relatively independent of gamma-ray energy (+5%) for incident photons from about 0.2 to 4 MeV. (The largest contributor to the gamma background at Bikini is 137cs with a gamma energy of 0.667 MeV.) The results, which include cosmic-ray background (%4 LR/hr; +35 mR/yr), are given in the table below. Measurements made through the interior of Bikini Island along the "center baseline" road indicated gamma exposure rates from 3 to 6 times as high as the village averages. A detailed survey of the interior is planned for early 1975. Location Gamma exposure rate 1 m above floor or ground, uR/hr Annual gamma exposure, mR Inside Inside Back yard Back yard House #4 7.8 13.2 68 116 House #20 8.0 7.7 70 67 House #28 9.3 15.5 81 136 House #40 9.3 15.5 81 136 75 114 Average ~ 154 -