Table 3. “Ae Estimated mean exposure rates (uR/hr) used for the dose calculations. Village island “iltuse interior Beach Loven Other islanis 4 4 1 3.5 50 l Eneu 2 Bikini 24° 42? 5 3.5 42 3 Bikini 24% 42? 5 3.5 42 4 Bikini 34° 42° 5 3.5 42 5 Bikini 53¢ 41° 5 3.5 42 6 Bikini 53¢ 41° 5 3.8 42 “Includes area 1 in Fig. 4. O includes areas 3 and 4 in Fig. 4. “includes area 2 in Fig. 4. Includes area 3 in Fig. 4. “Includes area 4 less area 3 in Fig. 4. ).2 ~R/hr due to naturally occurring radionuclides in the sea water. Cases 3 and 4 wemonstrate the effect of remedial action on reducing the gamma exposure rates. Since the people spend a considerable fraction of their time in the immediate vicinity of their homes, it appears that it may be feasible to take certain remedial actions to reduce the exposure rates in this area. For instance, placing S cm of clean coral gravel around the houses out to a distance of 10 m, a common practice in the Marshall Islands, will reduce the exposure rates by a factor of 2. Removing and re- placing with clean soil the top 20 cm of soil out to a distance of 10 m from the houses will reduce the exposure rates by a factor of 8. In addition, the shielding provided by “he houses themselves will reduce the exposure rates by a factor of 2. Mixing or over- turning of the topsoil will most likely not be effective since the soil has already been thoroughly disturbed by the agricultural rehabilitation activities. Based upon the data of Bennett and Beck,” it appears that it may be reasonable to assume, for dose prediction purposes, that the gamma exposure rates on the islands are due to 1375 and 606 activities with respective contributions of 80% and 20%. This assumption will be reexamined by means of the gamma spectral analyses of the soil samples collected during this survey. Using this assumption and the information presented in Tables 2 and 3, we calculated the integral first-year and 30-year whole-body external gamma-ray doses for each age group for each living pattern presented in Table 1. results were then combined by "folding in" the present population distribution. effect of radioactive decay was included in the calculation; however, The The the additional reduction in exposure rates due to possible weathering or agricultural crop production processes was not included.