Cross Section Assessment by Measurement of Time Dependent Neutron Spectra from Lithium Assemblies

概要

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Time dependent neutron spectra from lithium assemblies were measured to assess the neutron cross sections of 7Li in ENDF/B-IV, which is important nuclide for the D-T fusion reactor blanket material. Pulsed neutrons produced by D-D or D-T reaction were used to measure leakage neutron spectra from cubical lithium assemblies as a function of time by the use of NE213 liquid scintillator. Calculations of time dependent neutron spectra were carried out by the Monte Carlo code SIMON, which was prepared for this study. The group constants used in these calculations were processed from ENDF/B-1V data. The calculated and the measured neutron spectra were compared for the following three; a stationary spectrum, spectra at each time interval and decay curves for specified energy groups. Discrepancies between the measured and the calculated neutron spectra were found in these comparisons. In order to assure the cause of these discrepancies, some calculations were carried out with recently measured cross sections of inelastic scattering which excite 0.478 and 4.63 MeV level of <SUP>7</SUP>Li. It was concluded that some of the neutron cross section data of <SUP>7</SUP>Li in ENDF/B-IV should be ameliorated.