ELESTRES Code Upgrades

Abstract

The fuel-performance code ELESTRES (ELEment Simulation and sTRESses) models the in-reactor and on-power behaviour of CANDU fuel elements under normal operating conditions. The code also provides initial conditions for evaluating fuel behaviour during high-temperature transients. The CANDU® fuel community uses the ELESTRES-IST (Industry Standard Toolset) version of the code to assess the performance of CANDU fuel designs (e.g., standard natural uranium CANDU fuel, CANFLEX® fuel, and low-void-reactivity fuel (LVRF)).

The CANFLEX fuel design is evolving to meet more demanding requirements, such as higher burnup operations and higher coolant temperatures and pressures, compared to the current CANDU fuel designs. LVRF uses a burnable poison, (U,Dy)O₂ in the central element of the CANFLEX bundle, to achieve lower void reactivity during a postulated loss-of-coolant accident. The ELESTRES code must be capable of simulating these more demanding CANDU fuel applications. A version of the ELESTRES code based on the ELESTRES-IST code version is under development to provide a tool that is qualified to model CANDU fuel performance under these more demanding reactor operating conditions.

This paper describes recent ELESTRES code capability upgrades. The paper identifies the key model enhancements, and the implementation, verification and validation activities that are being performed in accordance with the AECL software quality assurance program.