410727 R » we John C,. Sugher, ye Jey Vay L, 195h DLreotor ™Mvisdion of Biology and Nedicine Certon MN. “mrming, ‘lealth Physicist Biophysics 3ranch, Division of 31ology and Medicine PATA OW SOIL SAMPLFS COLLFSTFD ON THE ISLANDS OF THE PACIFIC FOLLOW ISG "HE FIRST “ETONATION AND ALSO TUE DOSE RATE READINGS AT THE SAME LOCALITIES, oe k A ESL se Reed fase fave Attached (Annex I) are data on soil samles collected on the islands of the Pacific following the first ietonation 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 disintecrations per cinute per cram of soil to millircentgens per hour of gamma radiation at a three-foot height or vice versa. Larson's work with soils around HPC during ue Spring 1953 tests indicated the following relationsarip: sfoastte beta counts of 7 3oil (after absorption and geometry sorredtions at 3 feet. — 1 ar/hr gama ‘e found that essentially all of _ activity was in the first one inch of top soll. Pot DATE afl BY AUTHGRIFY Or “LOE/ Pc CLASSIFICATIC(: Col VCULLLED In collecting soil on the Paeific Islands good care was taken to collect one square foot of surface ‘in fact, templets were mace for this urpose). It was impossible, iowever, to scoop up the soil to a uniform dept so the rnle followed was to collect to one inch or greater. If the fallowt activity in the Pacific Islands also was contained in the first one inch, the additional soil below this contributed masse but little activity to the sample, By taking the disintegrations per minute per gram (after a thorough mixing) and multiplying by the total number of grams for each sample one should arrive at the activity per square foot. The plot of beta disintegrations per xinute per gram of soil versus ar/hr of gamma at 3 feet is showm on the attached graph. ‘The corre lation is not too good. For references, several curves are arbitrarlly drawn on the graph. ‘he data strongly suggest that less than isdate ft. 18 equivalent to l ar/hr. For lower levels of activity idata are sore of the order of 2 ye/sq. ft. ———> 1 ar/hr and for f X¥vels.af activity less than’q pe/sq.ft.——> laor/hr. If SURNAME p __ Dunning: Mack. DATE > lL Prem «beta S/L/Su