Use of neutron noise for diagnosis of in-vessel anomalies in light-water reactors

Abstract

The value of neutron noise analysis for diagnosis of in-vessel anomalies in light-water reactors (LWRs) was assessed by: (1) analyzing ex-core neutron noise from seven pressurized-water reactors (PWRs) to determine the degree of similarity in the noise signatures and the sources of ex-core neutron noise; (2) measuring changes in ex-core neutron noise over an entire fuel cycle at a commercial PWR; (3) applying PWR neutron noise analysis to diagnose a loose core barrel, to infer in-core coolant velocity, and to infer fuel assembly motion; and (4) applying BWR neutron noise analysis to diagnose in-core instrument tube vibrations and bypass coolant boiling, to infer in-core two-phase flow velocity and void fraction, and to infer stability associated with reactivity feedback. This report summarizes these assessments and provides guidance for the acquisition and analysis of neutron noise in LWRs.