Neutron and Gamma-Ray Physics in Fast Reactor Blankets

The main results of several years of research on neutron and gamma-ray physics in the Purdue Fast Breeder Blanket Facility (FBBF) are summarized. Presented are neutron capture rates in ²³⁸U, ²³²Th, gold, tungsten, and manganese, and fission rates in ²³⁵U and ²³⁹Pu. Neutron spectra are determined from proton recoil energies over the range from 2 keV to 2 MeV. The energy deposition of the gamma-ray field is measured with thermoluminescent detectors. Since the FBBF is a source-driven facility, all results are obtained on an absolute basis and are compared with corresponding calculations. Most of the results are presented as calculated/experimental trajectories except for the neutron spectra. The absolute and complete experimental results will be presented in separate papers. The comprehensive and coherent interpretation of deviations between calculated and experimental results is explored. Three major deviations are identified; they concern the “bulk” of the neutron population, the low-energy wing of the spectrum, and the space dependency of resonance absorption.