SIMEX-77: A FORTRAN-77 Fuel Burnup History and Refuelling Simulation Program for Core Fuel Management at the Gentilly-2Nuclear Generating Station

Abstract

SIMEX is the principal reactor simulation computer code implemented at Gentilly-2 for the purpose of generating fuel management data. It's method combines diffusion calculations with in-core flux detector readings to produce bundle power and fuel neutron flux distributions. The SIMEX code was originally programmed as a module of the Hydro-Quebec version of the FMDP fuel management code, operational on NOS/BE operating systems. A major reprogramming of SIMEX and other FMDP modules used for fuel management at Gentilly-2 has recently been completed. Our original objective was to integrate the SIMEX data base with other fuel management data bases on Hydro-Quebec computers to provide easier access to burnup and power history data while reducing computing costs. The new package, named SIMEX-77, conserves the original FMDP modular framework, data structure and dynamic allocation of data vectors and matrices. The only major changes were the replacement of the original CHEBY method by the TRIVAC nodal collocation method for solving the neutron diffusion equation and the programming of the data base manipulation modules in a separate package, named NSES. This paper presents the modular framework, data structure and methods used in both packages. Results of code commissioning and validation for fuel management and reactor analyses and convergence analysis of the TRIVAC method are also be presented.