Variations in radionuclide concentrations and size distribution of radioactive particles from the Chinese nuclear weapon test of October 16, 1980

Debris from Chinese twenty-sixth nuclear explosion test (October 16, 1980) was collected by a high volume air sampler equipped with five-stage cascade impactors at the ground level in Fukuoka, Japan. The variations of radionuclide concentrations were measured for a period of about ten months following the test. The fallout seemed to be injected into the lower stratosphere as well as the troposphere because the effect persisted for about eight months until June 1981. The¹⁴¹Ce/⁹⁵Zr and¹⁴¹Ce/¹⁴⁴Ce of the particles smaller than 1.1 μm were relatively constant in spite of different collection periods. However, in the particle range larger than 1.1 μm, depletion of¹⁴¹Ce atom was observed and it was greater in the larger particles, but it reached gradually a constant value as time passed. This variation pattern was explained by the time difference between particle formation and detonation and the height of the fireball when the particles were formed.