STUDY OF POST-NEUTRON MASS AND CHARGE YIELDS FOR 232U(nth,f) and 238Pu(nth,f)I. Ph. USTHB BP 32, El Alia, Alger, Algérie J. Crançon, G. Lhospice GEN/G, DRF/SPh/PhAN, 85X, 38041 Grenoble Cedex, France The post-neutron mass yields for 232U(nth,f) and 238Pu(nth,f) have been studied, for the first time, through γ-ray spectroscopy. A rabbit system was used to irradiate the encapsuled fissile material. Because of small quantities (<0.1 μg) of 'fission targets', an extreme care was taken as to the purity of the environment and the handling material as to the contamination from 235U. In the case of 232U(nth,f), the yields of 36 fission products in 27 mass chains were determined. They represent ≈ 60% and ≈ 77% of the surface of the light and heavy mass peaks with <AL> = 92.1 ± 0.1 and <AH> = 137.9 ± 0.1 leading to <νγ> = 2.8 ± 0.3. The mean proton odd-even effect δp from 6 mass chains = (24.6 ± 3.0)%. For 238Pu(nth,f), the yields of 51 fission products in 36 mass chains were obtained. They represent ≈ 62.5% and ≈ 82% of the surface of the light and heavy mass peaks with <AL> = 93.1 ± 0.1 and <AH> = 137.2 ± 0.1 -leading to <νγ> = 2.5 ± 0.2. The mean δp from 9 mass chains = (14 ± 3)%. These data will be compared with those for the other fissioning system. |