ON THE EFFECT OF ENDF/B-VI BERYLLIUM DATA ON THE NEUTRONICS OF ITER BLANKETS

Abstract

The present study examines the effect of different beryllium data (from ENDF/B-V, from a revised Los Alamos evaluation ENDF/B-VLa, and from ENDF/B-VI) on the neutronic characteristics of the solid breeder blanket for ITER. It is found that the total tritium breeding ratio of this blanket calculated with ENDF/B-V (1.26) is significantly higher, by about 7%, than that from ENDF/B-VI (1.18) and ENDF/B-VLa (1.19). The fast neutron flux above 10 MeV at the superconducting magnet, relevant for the correct determination of the charged particle production and damage rates, is higher by up to 27% when using beryllium data from ENDF/B-VI. These differences, which are critical for assessing properly tritium breeding and shielding design requirements, are due to two main reasons. First, the (n,2n) beryllium cross section is 6% higher in ENDF/B-V (and ENDF/B-VLa) than in ENDF/B-VI (i.e. 0.513 versus 0.485 barns at 14 MeV). Second, the energy distribution of the secondary neutrons from the beryllium (n,2n) reaction is harder in ENDF/B-VI than in ENDF/B-V, and ENDF/B-VLa as well.