Loading pattern optimization of a PWR reactor fuel assemblies using PESA-II algorithm by considering neutronic and thermal-hydraulic parameters

Abstract

The multi-objective optimization methods are widely used in various areas of science and engineering. In this paper, a multi-objective optimization algorithm has been used to design the optimal placement of fuel assemblies in the KWU reactor with the purposes of power flattening and increasing the multiplication factor. Also, thermal-hydraulic analysis has been performed to investigate the new arrangement during a hypothetical loss of coolant accident. For this purpose, the PESA-II algorithm is coupled with Nodal expansion code (for neutronic calculations) and COBRA-EN code (for thermal-hydraulic calculations). The results showed that the neutronic parameters including power flattening and the multiplication factor (increases from 1.0047 to 1.0058) improved by optimizing the fuel assemblies’ placement. It was also investigated that during a hypothetical loss of coolant accident up to 15%, the reactor could continue to operate in the safe mode. In addition, the results have emphasized the better performance of the PESA-II algorithm than the SPEA algorithm.

Keywords

• pesa-ii algorithm
• arrangement of fuel assemblies
• loss of coolant flow
• nodal expansion and cobra-en codes