Radiochemical and Physical Characteristics of Single Fallout Particles

Highly radioactive single fallout particles from the third Chinese nuclear explosion in May 1966 were identified by means of autoradiography and G. M. counting of rain and air-borne dust samples, collected at Fayetteville, Arkansas, and Osaka, Japan. Several characteristic features including color, diameter, and gross-beta activity of these particles were measured and a correlation between the particle diameter and its beta activity was found. Gamma-ray measurements revealed that the single particles were enriched in refractory, and were depleted in volatile, radionuclides. From the radiochemical measurements, the concentrations of several nuclides in these single particles were determined and the corresponding fractionation factors were calculated.