Speaker
Description
The scarcity of independent yields for Pu-239 at fast neutron energies hinders the ability to properly generate a predictive model and requires additional measurements for proper simulations. Obtaining independent yields can be difficult, as the measurement of short-lived fission products places a time constraint on detection methods available. The use of a monoenergetic neutron beam and rapid -detection following cyclic irradiations can serve to quantify these short-lived fission products and extract independent yields. In a joint-collaboration between LANL, LLNL and TUNL, quasi-monoenergetic neutrons produced from 2H(d,n)3He and 3He(d,n)4He reactions were used to irradiate a ~200 mg Pu-239 sample at 4.6, 9.0 and 14.8 MeV incident neutron energies, respectively. The target was irradiated using a series of irradiation time/count time cycles, in combination with a dual fission ionization chamber. The use of a dual-fission chamber allowed for normalization of FPY measurements independent of the nuclide’s cross section and neutron flux. The cyclic activation technique was accomplished using a 10- meter belt-driven rabbit system, that transferred the sample from the irradiation position to a counting position between two shielded HPGe detectors. This presentation will highlight the short-lived fission products yields that were determined from this series of measurements.