Evaluating the effect of using different sets of enrichment for FAs on fuel management optimization using CA

Abstract

In nuclear reactor core design, achieving the optimized arrangement of fuel assemblies (FAs) is the most important step towards satisfying safety and economic requirements. In most studies, nuclear fuel optimizations have been performed by using a finite number of different types of FAs. However the effect of FA numbers with different enrichments and the difference between their maximum and minimum enrichment values can be important and should be evaluated in the optimization process. This research is aimed at evaluating the effect of using different enrichment values for FAs. This issue has been investigated by focusing on two parameters, namely, the initially selected enrichment and the difference between the minimum and maximum enrichments applied in the core design. In the previous studies of nuclear fuel management, these parameters have been kept as fixed quantities and considered as initial assumptions in the optimization process. Therefore, to achieve an optimized arrangement of the core, the proper values of these parameters have to be determined. For this purpose a parameter ( δ) served through the optimization process to show the effect of the difference between the enrichment values of FAs. Another parameter named ε 0 shows the minimum enrichment of FAs. These parameters are defined based on a factor named Fuel Quality Factor (FQF) as a characteristic of fuel composition. FQF is shown by Z( r) is also used through the optimization process for achieving the smooth distribution of power. The values of Z( r) are calculated using the MCNP code. This methodology is applied to a VVER-1000 nuclear reactor core in order to minimize the local power peaking factor ( P q ). For finding the best configuration of FAs in the core, Cellular Automata (CA) is applied as a powerful and reliable tool. The computer codes WIMS and CITATION are used for core calculations. The results provide a comprehensive view of VVER-1000 reactor core configuration for different groups of δ and ε 0 and provide a useful database for designers and engineers.