Fractionation effect of hot particles from the nineteenth Chinese nuclear test explosion

Gamma-ray spectrometric studies were conducted on the radionuclide fractionation appearing in individual hot particles (highly radioactive fallout particles) from the nineteenth Chinese nuclear test explosion on September 26, 1976, which was reported as being in the range of magnitude 20 - 200 kilotons in the atmosphere. The activities of the fourteen nuclides, 95Zr, 97Zr, 99Mo, 103Ru, 131I, 132I, 133I, 140Ba, 141Ce, 143Ce, 144Ce, 147Nd, 137U and 239Np were determined, and the initial atom numbers of these nuclides contained in each sample were estimated. The fractionation factor defined with respect to 95Zr was calculated in order to express the degree of fractionation. Some pairs of radionuclides were selected for estimation of their respective initial atom number ratios, among which the one of 239Np to 237U was estimated at about 35. The relatively higher concentration of 239Np to 237U in the nineteenth Chinese nuclear test indicates that the thermonuclear reaction did not play a significant role in this test. (author)