MEASUREMENT OF THE YIELDS OF 135I AND 140Ba IN THE FISSION OF 233U, 235U, 239Pu, AND 241Pu

Abstract

Fission yields of 135I and 140Ba have been measured relative to the yields from 235U for samples of different fissile materials irradiated in the NRU reactor in a flux of 2.7 × 1014 neutrons/cm2 sec for 24 hours. The relative 135I contents of the samples were determined from the reactivity effect of the daughter 135Xe in the Chalk River Pool Test Reactor using a pile oscillator. The relative concentrations of 140Ba were determined by gamma-ray counting of the daughter 140La. The fractional yields, normalized to 0.0625 for both fission products in 235U fission, are:[Formula: see text]In the fission of 233U and 239Pu the cumulative yields to 135I and 140Ba are approximately 20% and 7% less than the mass-spectrometrically-measured cumulative yields to 135Cs and 140Ce respectively. The differences are attributed to direct formation of 135Xe and 140La.