Delayed neutron emission measurements from fast fission of U-235 and Np-237

摘要

Experiments have been designed and conducted to measure the periods and yields of delayed neutrons from fast fission of (sup 235)U and (sup 237)Np. These measurements were performed in a pool type reactor using a fast flux in-core irradiation device. The energy dependent neutron flux spectrum within the irradiation device was characterized using a foil activation technique and the SAND-II unfolding code. Five delayed neutron groups were measured. The total yield (sum of the five group yields) for (sup 235)U was found to be 0.0141 (+-) 0. 0009. The total yield for (sup 237)Np was found to be 0.0102 (+-) 0. 0008. The total delayed neutron yield data were found to be in good agreement with previous measurements. The individual group yields reported here are preliminary and are being further refined.