Revised Delayed Photoneutron Data for Use in CANDU-Reactor Analysis

Abstract

A new set of delayed-photoneutron parameters for four fissionable nuclides (235U, 238U, 39Pu and 241P is proposed for use in CANDU-reactor analysis. The new delayed photoneutron yields are all smaller than earlier values. This is especially the case for 239Pu The new photoneutron yields are very nearly consistent with the calculations Walker and Okazaki made in 1969 as well as the experimental measurements reported in 1973 by Baumann et al. The new photoneutron data are based on a reanalysis of an earlier experiment made by French in AECL's ZED-2 reactor. Since the direct delayed-neutron yield exceeds the delayed-photoneutron yield, the new total delayed neutron yields per fission representing the combination of the direct delayed-neutron and delayed photoneutron sources are only slightly less than the old yields, despite the significant relative reduction of the photoneutron components when viewed in isolation.