Method of WWER active core power parameters evaluation by readings of ex-core neutron flux monitoring system using additional information

Abstract

Ex-core neutron flux monitoring system (ENFMS) is designed to control nuclear reactor core power, its change rate and reactivity. Problem of core power evaluation by readings of the ENFMS is considered in this paper.Readings of ex-core ionisation chambers is main information source of the ENFMS on core state. But the ex-core ionisation chambers readings aren’t the only information source on core power level. Control rods positions, fuel burnup and several other physical parameters characterizing the state of the core have an impact on the ex-core ionisation chambers readings. The ENFMS has to take into account these parameters for evaluation of the core power with high precision.Power reading correction method (PRCM) for evaluation of the core power and other power parameters by the ENFMS using additional in-core information is discussed in this paper. Besides the ENFMS detectors readings this method takes into consideration control rods positions, coolant properties in downcomer region, xenon distribution, fuel burnup and decay heat power.Model tests demonstrated that the PRCM allows evaluating the power level and other power parameters of interest with high precision. Power evaluation error is reduced by factor 2–3 as compared to traditional method.