Power–feedwater temperature operating domain for a BWR driven by natural convection

Highlights: •Using methodology based on Monte Carlo simulation, NCBWR power as function of feedwater temperature was evaluated. •Sensitivity analysis shows that the reactor power is inversely proportional to feedwater temperature. •Being obtained that a variation of about 2% of the feedwater temperature the response of reactor power is just over 6%. •Found statistically valid correlations to describe the change in power as a function of feedwater temperature. -- Abstract: The aim of this work is to analyze feedwater temperature effects on reactor power in a BWR driven by natural convection (NCBWR) applying a methodology based on Monte Carlo's simulation. The analysis was performed with the reactor operating with different control rod patterns. The Monte Carlo's methodology was applied systematically to establish the operating domain, due that NCBWRs are not yet in operation, the analysis of the nuclear and thermal–hydraulic processes must rely on numerical modeling with the purpose of developing or confirming the design basis. The relative standard deviation obtained with a size of 20,000, data showed that for 2% change in the feedwater temperature, the response in thermal power change is 6.5% for 100% of rated power and 100% of rod pattern. Additionally five more rod patterns are presented in this paper. The regression analysis with the feedwater temperature showed statistically valid linear, quadratic and cubic representations, which are described in this paper for six different arrangements of reactor control rods. The results obtained in this study can be applied to operation and design of NCBWR.