Lattice physics analysis of measured rod-by-rod FP inventory distributions of burnt BWR 9x9 UO(2) assemblies

• Published in: Journal of nuclear science and technology Vol. 46; no. 7; pp. 653 - 664
• Main Authors: Yamamoto, Tom, Sasagawa, Masaru, Kanayama, Yuichiro
• Format: Journal Article
• Language: English
• Published: 01.07.2009
• ISSN: 0022-3131

Fuel rod gamma-ray spectrometry was performed for five-cycle irradiated BWR 9 x 9-9 and 9 x 9-7 fuel assemblies, and relative rod-by-rod FP inventory distributions of (137)Cs, (134)Cs, (106)Ru, (95)Zr and (154)Eu 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 (137)Cs, 2 to 4% for (134)Cs, 2 to 5% for 106Ru, 3 to 4% for (95)Zr, and 4 to 5% for (154)Eu, which include measurement and analysis errors. Small differences in the calculated distributions between SRAC and MVP-BURN were observed for (134)Cs, (106)Ru, and (154)Eu for some of the corner rods, Gd(2)0(3)-UO(2) rods, and other rods in the 9 x 9-7 fuel assembly.