EXPOSURE RATE REDUCTION ON BIKINI ISLAND DUE TO CONCRETE DWELLINGS INTRODUCTION During the May 1972 AEC sponsored resurvey of Bikini Atoll measurements were made to determine the reduction of exposure rates at dwelling sites due to the shielding effect of the concrete structures being erected for occupancy by the returning Bikini people. Exposure rates were measured at several points around and within each dwelling using a Baird Atomic NE-148 Scintillation Monitor 904-148, sodium iodide system calibrated with respect to 13765, The dwellings are constructed of wood and concrete. The floors are concrete slab, not extending beyond the walls of the houses. The concrete slab walls are pierced by windows and, on the longer sides, by entrance ways. The roofing is constructed of wood framing and aluminum sheet. Local sources of sand and coral aggregate suitable for use in making conerete were identified by AEC prior to construction as having the minimum radioactive material content of those available on the atoll. The architectural drawings of the dwellings that were developed by the Office of Trust Territory, Department of Interior, in consultation -with the Bikini people, were reviewed by the AEC staff. Recommendations were made that would reduce radiation levels and thus keep exposures as low as feasible,