In-core fuel management for AHWR

Abstract

The primary aim for the in-core fuel management in a nuclear reactor is to achieve higher fuel utilization without compromising the safety during operation. Loading pattern optimization during each refueling stage is the main challenge in light water reactors like pressurized water reactors (PWRs) and boiling water reactors (BWRs). Whereas, in case of heavy water reactors like pressurized heavy water reactors (PHWRs), the development of refueling scheme is relatively simple mainly due to on-line refueling, use of small length bundle and natural uranium as fuel. The use of small length bundle and flexibility of multi-bundle shift scheme helps in controlling the ripples in power due to refueling. Even though the PHWRs possess best neutron economy, the use of natural uranium fuel in PHWRs limits the achievable burn-up to 7500MWd/Te and as a result large amount of waste management is a serious concern. In Indian advance heavy water reactor (AHWR), both the features of PWRs (high discharge burn-up fuel) and PHWRs (on-power refueling) are being included along with advanced safety features. The AHWR shall possess good neutron economy and owing to higher discharge burn-up, lower waste is expected. However, during on-power refueling with full length channel and high enrichment fuel, the challenge is to control the refueling ripples and maintaining the operational parameters under their design limits. This necessitates the implementation of a special refueling strategy to control the power peaking due to on-power refueling. This paper describes about the special refueling strategy for this kind of problems. A computer code based on the heuristic approach has been developed for facilitation of on-power refueling in automatic manner for high discharge burn-up fuel in AHWR core. Further, parallel processing on shared memory architecture (personal computer) has been employed to enhance the efficiency of this code.