Fission-Product-Rate Measurements and Yields

Measurements of the reaction rates for gamma-active fission product and yields from fission of 235U, 238U, 239Pu, and 237Np irradiated in the Coupled Fast Reactivity Measurements Facility and engineering mockup critical assembly neutron fields are reported. The fission products 95Zr, 103Ru, and 140Ba were measured by gamma-ray spectroscopy at four independently calibrated laboratories. It is concluded that each laboratory is capable of measuring absolute reaction rates to an accuracy of less than ±2%. Fission yields of six gamma-active nuclides are reported. The primary objective of this work is to demonstrate the capability of measuring fission rates within fast-reactor environments to accuracies approaching 2.5%. It is shown that foil-activation techniques are capable of this accuracy under ideal conditions. Even greater accuracy is possible for relative measurements which utilize the identical gamma-ray detector and nuclear decay data used to measure the fission yield. The fission yields measured in this study are compared to other measurements, and we find that the ENDF/B, Version IV, yields are, in general, consistent to within ±2% of our results for 235U, 238U, and 239Pu.