Optimization and sensitivity analysis of the nitrogen Brayton cycle as a power conversion system for a sodium-cooled fast reactor

Abstract

The sodium-cooled fast reactor (SFR) is a promising next generation reactor type. Existing prototype generation IV nuclear reactors use a steam Rankine cycle for power conversion. However, the reaction between sodium and water presents a major safety issue in the development of SFR. In this aspect, the nitrogen Brayton cycle can be a suitable alternative to the conventional steam Rankine cycle for SFR. Compared to the steam Rankine cycle, the nitrogen Brayton cycle is relatively simple; further, nitrogen does not react with sodium due to its chemically inert feature. Therefore, a nitrogen Brayton cycle coupled with SFR can be a good combination. In this work, the nitrogen Brayton cycle for KALIMER-600 has been studied. In addition, sensitivity analysis, optimization of the cycle, and the preliminary design of components were performed. Mathematical models for conducting sensitivity analysis of the cycles were developed using FORTRAN. Sensitivity studies were carried out by varying the cycle maximum temperature, turbine inlet pressure, and pressure ratio. The optimized results showed that the cycle efficiency is 38.26%. The preliminary design of components was performed to assess the viability of the proposed system. In order to improve cycle thermal efficiency, sensitivity studies of heat exchanger was performed to understand the effects of printed circuit heat exchanger (PCHE) channel shape. The analysis results show that a significant improvement in cycle efficiency (improve 1.3%) was obtained by changing the PCHE channel shape.