In-core coolant flow monitoring of pressurized water reactors using temperature and neutron noise

Abstract

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Analysis of in-core dynamics in pressurized water reactors with application to parameter monitoring

“…The results of modeling analysis of the LOFT reactor showed that (a) there is a range of frequencies in which the phase between the in-core neutron detector noise and core-exit temperature noise is linear, (b) the frequency range of the linear phase behavior is limited by the primary sink frequency of the corresponding transfer function, (c) for the case when o c is negative, the phase angle at low frequencies approaches -180 deg, (d) the phase angle approaches zero-degree when cc c is positive, and (e) the results from the model study and from PWR operational data, it can be concluded that in the LOFT reactor the primary perturbation source is the core coolant flow rate fluctuation. This last conclusion was recently established by a multivariate autoregressive analysis of pump Ap, core Ap, in-core neutron detector and core-exit thermocouple signal analysis , and by experimental measurements at LOFT and commercial PWRs (Sweeney et al, 1985 In order to establish the phase behavior between the neutron noise signal and the core-exit thermocouple signal at low frequencies we will present results of data analysis from different PWRs. We want to emphasize that the higher frequency behavior of calculated phase will be affected by the location of the detectors (in-core, ex-core neutron detectors and the location of thermocouples from the core-exit).…”

“…Similar behavior was observed at power levels 25%, 50% and 75%, and at different flow rates. As the flow rate decreases, the phase slope increases, indicating larger transit time (Sweeney et al, 1985). Figure 2 shows the neutron-temperature CPSD phase relationship in a 1140 MW (electric) commercial PWR at 100% power.…”

“…In-core dynamics of fluctuations in process variables in pressurized water reactors (PWRs) was studied in the past by several investigators Sweeney et al, 1985;, with primary applications to flow monitoring, and detecting the effects of reactivity changes on neutron noise spectrum. Recent research in this area revealed the connection between neutron noise and core-exit coolant temperature noise cross power spectral density (CPSD) phase behavior as a function of the moderator temperature coefficient of reactivity (a c ) in a PWR.…”