HOO LL oe “ SEE oe + GELeae {3 2 John C. Sugher, U. D., Mirector vay 1b, 195) “iviaion of Biology and Medicine Corvion HN, "mring, MNealth Physicist Biophysics Branch, Division of Biology and Wedicine DATA OW SOTL SAMPLFS COLLFCTPD ON THE ISLANDS OF THE PACIFIC FOLLOW ING "HE FIRST DETONATION AND ALSO mE DOSE RATE READINGS AT TE SAME LOCALITIES, Attached (Arex I) are data on soil samles collected on the islands of the Pacific following the first cetonation and also the dose rate readings at the same localities. ‘ne method of evaluating stch data is to try to establish relationships between different mits if pos sible. One useful relationship would be the conversion of disinte- creations per minute per cram of soil to miliiroentgens per hour of gamma radiation at a three-foot height or vice versa. Larson's work with soils around ‘PG during we spring 1953 tests indicated the following relationship: aqg.ft. beta counts of soil (after absorption and geometry ‘oreed nes —— 1 or/hr cama at 3 feet. ‘te found that essentially all of fhe activity was in the firat one inch of top soil, | Po DATE f Deere & —-m es --* BY AUTHORITY OF DOEsEPC 0160S ee ee CLASSIFICATICN CaANCELLED In collecting soil on the Pacific Islands good care was taken to collect one square foot of surface (in fact, templets were mace for this ourpose). It was impossible, however, to scoop up the soil to a uniform depth so the rule followed was to collect to one inch or greater. If the fallout activity in the Pacific Islands also was contained in the first one inoh, the additional soil below this contributed mass but little activity to the sample, By taking the disintegrations per minute per gram (after a thorough mixing) and multiplying by the total nusber of crama for each sasple one should arrive at the activity per square foot, The plot of beta disintegrations per ninute per gram of soil versus ar/hr of gamma at 3 feet is show on the attached graph. lation is not too geod. ily drawn on the graph, The corre- For references, several curves are arbitrar‘the data strongly suggest that less than tndsae ft. 1a equivalent to l ar/hr. For lower levels of activity |data are more of the order of 2 pel 39. ft.—— 1 or/br and for fWvelbs.afactivity lesa than 3q ten edadmeet if ; codeve to su ely scatte 5