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.