Radiochemical analysis of individual fall-out particles

Abstract

Quantitative measurements were made of the radioactivity of individual fall-out particles from a nuclear detonation at the Eniwetok Proving Grounds. These measurements were possible since individual particles which represented approximately 10 10 or more fissions were obtained. Although several types of particles were observed, the data were generally resolved as being derived from two major particle classes depending upon whether the coral had undergone an obvious physical alteration such as melting. A number of individual particles were radiochemically analysed for the nuclides 99Mo, 140Ba 140La, 89Sr and 239Np. The data obtained, together with γ-spectral and decay measurements, indicate that fractionation of radionuclides was prominent in the fall-out particles. Measured R values for 140Ba and 89Sr based on 99Mo were over an order of magnitude lower in the altered particles than in the more normal appearing or unaltered particles. The fissions/gramme values of altered particles averaged 100 times that of unaltered particles. γ-Decay curves of the two classes of particles taken from H + 50 to H + 10,000 hr showed marked dissimilarities.