JEF-2 delayed neutron yields for 39 fissioning systems

There is a need for a more complete and accurate knowledge of absolute delayed neutron yields (vd). One method to derive vd for a given fissioning system involves a summation calculation using cumulative fission yields (Cu) and the delayed neutron branching ratios (Pn) of all precursors, In this work, we have used for these data the recently revised European JEF-2.2 evaluation (Joint Evaluated File-version 2.2). We have limited the number of precursors to 158, comprising 100 measured Pn data and 58 calculated values. We show that the contribution to the vd calculation of the unmeasured Pn values is almost negligible, However, it seems that the new nuclear mass data may improve the prediction of Pn values. According to our results, the relative uncertainty due to the Cu yields is three times higher than that due to the Pn values. We also present a systematic way to derive vd for exotic fissioning systems