Method and system for direct evaluation of operating limit minimum critical power ratios for boiling water reactors

摘要

A method and system for thermal-dynamic modeling and performance evaluation of a nuclear Boiling Water Reactor (BWR) core design is presented. A data processing system is used to execute specific program routines that simultaneously simulate the thermal operating characteristics of fuel rods (or plural groups of fuel rods) within the reactor during a transient operational condition. The data processing system is also used for compilation of a transient response histogram that incorporates the effect of inherent "uncertainties" in various parameters of interest. In an initial phase, the method employs a multi- dimensional approach for the simulation of postulated operational events or an anticipated operational occurrence (AOO) which produces a transient condition in the reactor--such as might be caused by single operator error or equipment malfunction. In a following phase, the operating limit minimum critical power ratio (OLMCPR) of the reactor is directly evaluated from a histogram of probability calculations representing the number of fuel rods subject to a boiling transition (NRSBT) during the transient condition. The histogram may be readily displayed by the data processing system and used to statistically demonstrate an OLMCPR compliance of the reactor core design with USNRC regulations.