Nuclear charge distribution for the 131 and 133 mass chains from the thermal-neutron induced fission of ²³³U

Abstract

The fractional cumulative chain yields at 131Sb and 133Sb and the fractional independent chain yields at 131mTe, 131gTe, 133mTe, 133gTe, 131I and 133I were measured for the thermal-neutron fission of 233U. The measured values are 0.52±0.03, 0.08±0.04, 0.334±0.020, 0.135±0.020, 0.55±0.02, o.21±0.02, 0.014±0.003 and 0.155±0.010, respectively. These values were combined with the yields reported by other authors (3, 5, 6) to compare the 131, 132 and 133 fractional cumulative chain yields from thermal-neutron fission of 233U and 235U. The comparison revealed that the displacements of the experimentally determined yields from a Gaussian curve are similar for the thermal-neutron fission of 233U and 235U. The direction of the observed displacements from a Gaussian curve is attributed to an odd-even effect. No strong evidence for a 50-proton or 82-neutron shell effect was observed. The ratio of the yields between the metastable and ground state tellurium isomers was found to be the same for both the 131 and 133 chains or 233U fission. The value of this ratio, however, was found to be slightly greater than the published value for 235U fission (21). A half-life of 31.3±0.5 hr was obtained for 131mTe. This value is in agreement with the literature value of 1.2 days (8) but has a smaller standard deviation.--Summary.