Delayed neutron yields for 39 fissile systems

Accurate knowledge of absolute delayed neutron yields (νd) needs to be improved. A method to derive the antiνd is to do a summation calculation using cumulative fission yields (CU) and delayed neutron branching (Pn) for all precursors. For the 'CU' we have taken the data from the JEF-2 file for 3 fissile systems. We have also done the calculations with the 'CU' distributed by Wahl for U233T, U235T and F, U238F, PU239T, PU241T. In JEF-2 we have 'Pn' data for 156 precursors, almost 100 coming from experimental results and the others from a calculation by Klapdor. The results are compared with the last evaluations for the systems already measured. The relative uncertainty is three times higher for the 'CU' than for the Pn