Lattice Physics Analysis of Measured Rod-by-Rod FP Inventory Distributions of Burnt BWR 9×9 UO2 Assemblies

Abstract

Fuel rod gamma-ray spectrometry was performed for five-cycle irradiated BWR 9 × 9-9 and 9 × 9-7 fuel assemblies, and relative rod-by-rod FP inventory distributions of 137Cs, 134Cs, 106Ru, 95Zr and 154Eu were obtained for lower and upper axial nodes of the assemblies. The inventories of these nuclides represent burnups, burnups multiplied by a thermal neutron flux, a buildup of Pu, and a fission rate at the end of a fuel discharge cycle. The measured distributions were compared with those calculated by a general purpose neutronics code system SRAC and a continuous energy Monte Carlo burnup calculation code MVP-BURN with infinite assembly models. The calculations adopted nuclear data libraries JENDL-3.2, −3.3, and ENDF/B-VI.8. The calculated results generally well reproduce the measured distributions, and the root mean square errors (RMSs) of the calculated results against the measurements are 1 to 2% for the inventory distributions of 137Cs, 2 to 4% for 134Cs, 2 to 5% for 106Ru, 3 to 4% for 95Zr, and 4 to ...