SURVEY INFORMATION Tabulations for the islands of Rikini Atoll on the following pages will indicate: 1. the background gamma exposure rates as measured with a Baird Atomic NE-148A scintillator calibrated against 137c¢> 2, a summary of the radiological waste removal and disposal results of sample analyses and when appropriate, projection of the background decay as a function of time. CONCENTRATION-EXPOSURE RATE RELATIONSHIP In order to estimate the expected reduction in exposure rate for the various islands as a function of time, it was necessary to develop weighting factors for each of the gamma emitting radionuclides identified in the analysis of soil samples. For purposes of this report, it was assumed that the various radionuclides were uniformly distributed by depth throughout the soil and that the only change in relative concentrations is due to the differential decay rates. This is obviously an oversimplification but would tend to give conservative results. The data of Crocker, Connors, and Wong (4) were used to indicate the relative effect of each nuclide on the exposure rate. Since 102Mpy was not among the nuclides included in their tabulation, data from their table were normalized by effective energy and number of nhotons per disintegration and plotted. The exposure rate factor for )°*™Rh effective energy 0.62 Me’ was taken from this curve and corrected for 2.96 gamma per disintegration.* The final tabulation of the composite exposure rate reduction was then calculated using the decay factor, initial concentration and exposure rate weighting factor. *Decay scheme taken from Table of the Isotopes - Ledever, Hollander, and Perlman.