Analysis of core physics experiments on irradiated BWR MOX fuel in the REBUS program

Abstract

Critical experiments were performed in the REBUS program on a core loaded with a test bundle including 16 irradiated BWR-type MOX rods of average burnup of 61 GWd/t. The experimental data were analyzed using diffusion, transport, and continuous-energy Monte Carlo calculation codes coupled with nuclear data libraries based on JENDL-3.2 or JENDL-3.3. Biases in effective multiplication factors of the critical cores were 71.0%Dk for the diffusion calculations (JENDL-3.2), 70.3%Dk for the transport calculations (JENDL-3.3), and 0.2%Dk for the Monte Carlo calculations (JENDL-3.2). The measured core fission rate and co-activation rate distributions were generally well reproduced using the three types of calculations. The burnup reactivity determined using the measured water level reactivity coefficients was 72.41 + 0.08%Dk/kk', which also agreed with the results of the three type of calculations within the measurement and calculation errors. The most probable isotopic inventories in the irradiated MOX rods was tentatively obtained by using the ratios of the calculation to chemical assay data on a pellet sample, and the burnup reactivity was reanalyzed to split the calculation error into those due to the inventory and reactivity calculations. This approach showed that the inventory calculation error compensated the reactivity calculation error.

Analysis of Measured Isotopic Compositions of High-Burnup BWR MOX Fuel

“…Neutronics analysis of the data have been reported by the organizations participating in the programs. 1,[3][4][5][6][7][8][9][10] Alander et al 6) and Yamamoto et al, 7) who analyzed the measured isotopic compositions of the high-burnup BWR MOX fuel in the REBUS program, observed that the burnup calculations based on an infinite assembly model overestimated fissile isotopes of U and Pu. They attributed it to harder neutron energy spectra in the assembly calculations than those under actual irradiation conditions, where the MOX assembly was burnt surrounded by UO 2 assemblies.…”

Analysis of measured isotopic compositions of high-burnup PWR MOX and UO2fuels in the MALIBU program

“…In this study, the measurement data of the institutes A, B, and A were referred for the MOX, UO 2 -M, and UO 2 -L samples, respectively. This is because (1) the present authors have many experiences to analyze the isotopic composition data of the institute A [3,[9][10][11] for samples taken from MOX and UO 2 fuel assemblies and confirmed the characteristics of the measured data, (2) the institute B adopted a similar measurement technique to the institute A such as mass spectrometry, and (3) the data of the institute C often showed different trends from those of the other institutes.…”

Neutronics analysis of full MOX BWR core simulation experiments – FUBILA: Part 2

“…The axial configuration of the core structures and the fuel rods are shown in Refs. [4] and [10]. [9].…”

“…In order to extend database for the above validation study (ii), the Japan Nuclear Energy Safety Organization (JNES) has implemented a core physics experimental program FUBILA [2][3][4][5][6][7][8][9][10][11][12]. 1 It aimed at obtaining the core physics characteristics of full MOX BWR cores, which consisted of high Pu-content BWR MOX assemblies for achieving high burnup of fuel.…”