Sensitivity Analysis of Thermal-Hydraulic Parameters and Probability Estimation of Boiling Transition in a Standard BWR/6

A model correlating the minimum critical power ratio (MCPR) of standardized boiling water reactors (BWRs) to a set of thermal-hydraulic variables in parameter space is developed. A statistical approach with fractional factorial sampling along with response surface methodology and orthogonal central composite design are employed. The COBRA-II computer code, after modifications to include MCPR calculation, is used to simulate the thermal hydraulics of the BWR/6. The sensitivity is obtained by differentiating a quadratic equation that represents the state of the system with respect to its constituent variables. Taking this correlation as a joint multivariable probability distribution function and using crude Monte Carlo integration techniques, the probability of boiling transition during normal operation in a standardized BWR/6 is estimated. The result agrees very well with data available in open literature.