Validating the History -Based Diffusion Methodology for Core Tracking Using in-Corc Detectors

Abstract

A refinement of the three-dimensional diffusion reactor fuelling simulation program for CANDU reactors (RFSP) was developed and has been described in Reference 1. This refinement, called the history-based local-parameter methodology, allows core tracking with lattice properties which take into account the history of local conditions at each individual fuel bundle, including (in addition to fuel irradiation) local values of fuel temperature, coolant density, power level, and concentration of saturated fission products. This paper presents a validation of the history-based methodology, performed by comparing flux shapes calculated for the Point Lepreau CANDU 6 reactor over a tracking period of about 1.5 years (1991 September-1993 April) to the core fluxes measured by means of in-core vanadium detectors. The results were compared with those obtained from a conventional, i.e., non-history-based, calculation. The standard deviation of differences between calculated and measured fluxes is significantly improved (reduced) when using the history-based methodology.