Dynamic Response and Relative Sensitivity of Vanadium In-Core Flux Detectors and Lead Cables in Pt. Lepreau

Abstract

The Pt. Lepreau core-monitoring group has developed a program5 to use the signals from vanadium in-core flux detectors to accurately map the flux and power distribution inside the core, in real time, including periods of reactor power transients. In order to construct an accurate real-time flux map, the vanadium detector signals, which have a dominant(- 93%) delayed component, have to be dynamically compensated; and the signal contribution from the lead-cable, which amounts to approximately 25% of the prompt detector signal, has to be properly accounted for. Data from vanadium detectors was acquired during a recent run-down test in order to assess the detector and lead-cable response parameters to be used in the dynamic compensation and flux-mapping algorithms. The run-down data for individual detectors exhibit systematic variations in the values of prompt fraction and amplitudes for delayed terms. A statistical analysis of the distributions of these amplitudes allows the separation of dynamic response terms due to the lead-cable and the detector itself. An average value for the relative sensitivity (compared to the detector) of the lead-cable is also extracted. This paper presents the methodology and the results of analyzing the run-down test data from the vanadium flux mapping detectors at Pt. Lepreau.