Patent ID: 6611572
Filing Date: 2003-08-26
Classification: G21D,Y02E

Abstract:
A method for determining an operating margin for a nuclear fuel core of a Boiling Water Reactor (BWR), wherein fuel design or core configuration are contingent upon an operating margin for the reactor, said operating margin being determined by a process for evaluating an operating limit minimum critical power ratio (OLMCPR) comprising:a) developing in a memory of a computer system distributions of values for a change in critical power ratio to initial critical power ratio (&Dgr;CPR/ICPR) corresponding to a plurality of generic computer simulations of a plurality of transient operational reactor occurrences, said simulations each providing a &Dgr;CPR/ICPR distribution with respect to a corresponding generic transient operational reactor occurrence; b) selecting, from the &Dgr;CPR/ICPR distributions generated by the simulations, the &Dgr;CPR/ICPR distribution corresponding to the generic transient operational reactor occurrence related to the BWR operating limit determination; c) for the operating limit determination, developing in the memory of the computer system a histogram of NRSBT (number of fuel rods subject to boiling transition) corresponding to a plurality of transient minimum critical power ratios (CPRs) by determining initial critical power ratios (ICPRs) for one or more fuel rods and applying the selected &Dgr;CPR/ICPR to determine the transient minimum CPRs for said BWR; d) selecting a nominal NRSBT value, based on a central tendency of NRSBT distribution, statistically determined by said computer system from the histogram of the developed NRSBT values; e) selecting a confidence interval for the nominal NRSBT value; f) selecting an OLMCPR value from a minimal CPR such that during a simulation of a limiting transient operational reactor occurrence the nominal NRSBT value remains less than a predetermined cutoff value; and g) effecting said Boiling Water Reactor operation by applying the selected OLMCPR as an operational control parameter.