Mass Distribution in the Reactor-Neutron-Induced Fission of Thorium-232

Abstract

The mass distribution in the reactor-neutron-induced fission of 232Th has been studied using radiochemical techniques and direct gamma-ray measurements. Absolute fission yields of the standard nuclides 99Mo and 132Te were obtained from 232Th sources irradiated in a fission counter. The yields of 36 mass chains, including three that have been measured for the first time, were determined both from measurements relative to 235U(nth,f) yields and from 232Th data alone.The peak-to-valley ratio of the mass-yield curve is found to be ∼100. The light and heavy mass peaks are centered at masses 91 and 140, respectively. The results suggest the presence of a small third peak in the valley of the mass distribution. “Best” yield values are proposed taking into account our values and those from recent compilations.