Abstract
Multi-pass refueling scheme is a highlighted feature of pebble bed HTGR which spatially mixes the burnup calculation inside core. Such refueling scheme relate burnup calculation in one region of the core to others and thus affects the uncertainty propagation of nuclear data, e.g. fission product yield. In this work, thermal neutron induced U-235 fission product yield uncertainties are propagated in HTR-PM models with various refueling schemes in V.S.O.P. code. And the effect of multi-pass refueling scheme is studied. Bayesian method is applied to estimate the covariance of fission product yield based on ENDF/B-VII.1 fission yield sub-library. Uncertainty quantification is performed with stochastic sampling method and log-normal based correlated sampling method is used to generate reasonable and self-consistent fission product yield samples. The analyzed results indicate that multi-pass refueling scheme could affect the uncertainty propagation of reactor local responses.
Highlights
The continued research and design of pebble-bed High Temperature Gas-cooled Reactor (HTGR) require high-fidelity codes to provide accurate reactor system predictions, and systematic uncertainty analysis to assign confidence bounds to those predictions
This study aims to establish fission yields uncertainty analysis method throughout pebble-bed HTGR burnup calculation based on V.S.O.P. computer code system [5]
As one feature of HTR-PM, the effect of multi-pass refueling fuel management scheme on yields uncertainty propagation is addressed and the following conclusions are drawn from this study: (1) A V.S.O.P. computer code system based fission yields uncertainty analysis framework is proposed in this work to investigate yields uncertainty contribution to reactor responses during burnup simulation
Summary
The continued research and design of pebble-bed High Temperature Gas-cooled Reactor (HTGR) require high-fidelity codes to provide accurate reactor system predictions, and systematic uncertainty analysis to assign confidence bounds to those predictions. Uncertainty analysis of fuel pebble maximum temperature under accidental scenario serves as primary aspect for assessing reactor safety margin and design. Such analysis needs propagate nuclear data’s uncertainty throughout reactor burnup process to released decay heat after accident occurrence. This study aims to establish fission yields uncertainty analysis method throughout pebble-bed HTGR burnup calculation based on V.S.O.P. computer code system [5]. It serves as a preliminary study for further conducting reactor accidental safety analysis
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