Systematic sensitivity analysis of Ag release from TRISO particle during AGR-1 irradiation test and high temperature annealing safety test

Abstract

This paper describes the results of a systematic sensitivity analysis for silver diffusional release from Tristructural Isotropic (TRISO) fuel particles in the AGR-1 base irradiation test and high temperature safety test database. The BISON code was used to model the diffusional release of silver through the coated particle for a wide range of the irradiation and the high temperature conditions conducted in the AGR-1 tests. The current BISON results agree well with other computations and measurements. We then conducted the systematic sensitivity analysis to identify the impact of Ag diffusion coefficient in the TRISO layer materials on the prediction of Ag release. Sobol indices were computed to indicate the contribution of each input, and the scatter plots were analyzed to investigate the correlations between diffusivity parameters and predicted Ag release. Informed by the Sobol sensitivity analysis, a calibrated set of diffusion coefficients were obtained which gave better predictions. The result of this best-estimate calibration indicates a Ag diffusion pre-factor in the SiC from 3.85 × 10−10 to 3.19 × 10−9 m2/s and Ag activation energy in SiC between 178 and 185 kJ/mole. The outputs are expected to provide the systematic approach for better understanding of Ag transport inside TRISO particle.