Analysis of neutronics parameters measured in Phase-II experiments of the JAERI/US collaborative program on fusion blanket neutronics. Part I: Source characteristics and reaction rate distributions

Abstract

Fusion blanket neutronics parameters measured in the Phase II assembly have been analyzed at both JAERI and the US. Both parties have analyzed the experiments independently by using different nuclear data and calculational methods based on 3-D Monte Carlo and 2-D Sn codes. This part includes the results of the analysis on the source characteristics in the assembly and the reaction rate distributions in the test zone consisting of Li2O with and without a beryllium multiplier. The source characterization has been made by measuring the neutron spectrum and various reaction rates. These reactions include 58Ni(n,2n), 58Ni(n,p), 27Al(n,α), 93Nb(n,2n), 197Au(n,2n), and 197Au(n,γ). The ratios of calculated to measured values are compared among both countries and the different nuclear data used. Considerable discrepancies have been observed for the 58Ni(n,2n), 58Ni(n,p) and 93Nb(n,2n) reactions depending on which nuclear data was used, while good agreement is seen for the reactions 197Au(n,2n) and 27Al(n,α). The distributions of these reaction rates in the test zone have also been analyzed to examine the prediction accuracy of neutronics parameters in a breeder zone. Using the recently measured cross sections at the FNS resulted in a significant reduction in the discrepancies for most reaction rates.