RADIONUCLIDE FRACTIONATION IN FALLOUT PARTICLES FROM AN AIR BURST

Radionuclide fractionation in individual hot particles (highly radioactive fallout particles) from the third Chinese nuclear explosion on 9 May, 1966 has been investigated by gamma-ray supectrometry. Activities of ten radionuclides, 95Zr, 97Zr, 99Mo, 140Ba, 141Ce, 143Ce, 144Ce, 147Nd, 237U and 239Np, were measured and the initial atom numbers of these nuclides contained in each sample were estimated. In order to express the degree of fractionation, the fractionarion factors defined with resupect to 95Zr were calculated for each sample. The experimental results obtained were discussed concerning the following items. (1) Relation between the initial atom number and the particle volume. (2) Relation between fractionation factors. (3) Fractionation in relation to the decay chains. (4) Estimation of the time-interval between detonation and formation of particles. (5) Fractionation in relation to the chemical composition of the matrix materials. © 1968 Health Physics Society.