Proton-recoil neutron spectroscopy at the Pool Critical Assembly

Fast neutron spectrum measurements have been made in the Pool Critical Assembly (PCA) associated Light Water Reactor (LWR) Dosimetry Pressure Vessel Benchmark (PVB) fields. These measurements cover the neutron energy range between approximately 60 keV and approximately 2 MeV. Hydrogen and methane filled proton-recoil detectors were used to obtain the proton-recoil spectra from which the neutron spectra were derived. Measurements were taken at the midplane elevation on the surface, at 1/4 thickness of the steel, at 1/2 thickness of the steel and in the void box positions of the PVB. The neutron spectra showed considerable variation at the various positions with the energy distribution shifting toward lower energy between the face and void box of the PVB. In a similar manner considerable spectral structure developed in the spectra. These measurements were performed to provide neutron spectra. These measurements were performed to provide neutron spectral definition which is required to appropriately perform and interpret neutron dosimetry measurements related to fast neutron damage in light-water pressure vessel steels. These measurements also provide data for comparison with calculated spectra