NEUTRON ENERGY SPECTRUM DETERMINATION IN THE PURDUE FAST BREEDER BLANKET FACILITY (PROTON, RECOIL, ELECTRIC, CORRECTION)
Abstract
The main objectives of this research were to measure neutron spectra in the second blanket loading of the Purdue Fast Breeder Blanket Facility (FBBF) and to achieve consistency between integral neutron reaction rate measurements and neutron energy spectra. To this end, composite neutron spectra were formed that contained calculated as well as measured neutron spectra. The calculated components contained a free parameter that was adjusted in order to reproduce the measured integral reaction rate trajectories through the radial blankets. The measured portions of the composite neutron spectra were obtained by means of the recoil-proton technique, using hydrogen- and methane-filled cylindrical proportional detectors. The measured recoil-proton distribution was corrected for distortions of the detector electric field with an improved method. The method of correction for electric field distortions developed in this research allows more accurate measured neutron spectra to be obtained. The calculated neutron spectra were obtained by means of the two-dimensional diffusion code 2DB and 50-group cross sections prepared from the cross section library LIB-IV by using the code 1DX. Consistency was achieved between the composite neutron spectra and all integral reaction rates considered in this work. Comparisons between the consistent, composite neutron spectra and calculated spectra show that the magnitude of the total flux falls off with blanket radius much more quickly for the calculated spectra. Agreement is closer at the inner blanket than at other blanket locations. In addition, the largest discrepancies occur at the higher energies, with the calculations predicting softer neutron spectra.
Degree
Ph.D.
Subject Area
Nuclear physics
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