Title Analysis of the U-238 Livermore Pulsed Sphere Experiments Benchmark Evaluations
Author T. Goričanec , A. Trkov, R. Capote Noy
Date Nov 2017
Institute International Atomic Energy Agency, Vienna, Austria
Vienna International Centre, P.O. Box 100, A-1400 Vienna, Austria
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Work on the analysis of the 238U Livermore Pulsed Sphere experiments relevant for the validation of the CIELO evaluation is presented. The aim of the work described in this report was to validate the new ENDF/B-VIII.0 nuclear data library by comparing calculations to the benchmark experiments. The pulsed sphere experiments were performed at the Lawrence Livermore National Laboratory (LLNL). Different references describing the experimental configuration were reviewed. The evaluated experiments with their characteristics are listed. Calculations were performed using Stephanie C. Frankle reference benchmark model received from Denise Neudecker (LANL). The calculated neutron spectra with a reference model were compared with the experimental values for different experimental configurations and various deviations were observed. Due to the inconsistent results of different detectors the possible reasons for discrepancies (e.g. flight path length, detector angle, etc.) were evaluated. It was concluded that the uncertainty in the flight path length and detector angle have negligible effect on the detected neutron spectra, however the effect of not explicitly modelling experimental geometry can not be neglected. To evaluate the bias due to the not explicitly modelled experimental geometry a detailed computational model with Monte Carlo neutron transport code MCNP was made. In addition, it was found out that the neutron source included in the MCNP model does not take into account the additional neutron peak at 2.8 MeV and the calculated results are considered to be less reliable below 4 MeV.