Review of borssele PWR noise experiments, analysis and instrumentation

Abstract

The paper reviews the experience obtained in the Borssele reactor noise measurements during eight core cycles and describes the developments in instrumentation. In the first part of the paper, measurements under various experimental conditions are described: - measurements at full reactor power for each core cycle, and during the stretch-out operation of the 7th core; - measurements during the reactor start-up and stop procedure under different operating conditions. The instrumentation for these measurements consisted of several ex-core and in-core neutron detectors, pressure transducers in the primary coolant loops, and thermocouples situated in both cold and hot legs and also at the core exit. During one period of measurements, one hundred signals from the reactor were recorded and analysed in order to obtain base-line information. The noise signals were analysed in terms of auto- and cross-power spectral densities, phases and coherences. The noise patterns of many sensors have been followed closely; separated core support barrel motion- and reactivity-noise spectra have been obtained; several effects have been parameterized as a function of boron concentration and primary coolant temperature; primary loop pressure noise has been shown to give excellent possibilities of detecting the state of the reactor; base-line information has been obtained for several reactor conditions. In the second part of the paper, a description is given of the system for real-time processing of multi-channel ( > 10) noise signals using an array processor coupled to a mini-computer. This system, located at Petten, has been recently connected to the Borssele reactor via a 200 km telephone link.