Thermal-hydraulic analysis of the dual-function gamma thermometer

A computational study was performed to investigate the potential of a modified gamma thermometer (GT) as a monitor of both the localized power level and the core cooling in a PWR. The volumetric heat source within the thermometer was updated to include heat deposited by neutrons as well as heat deposited by decay gammas and neutron-induced gammas. Utilizing this source, along with a more detailed thermal-hydraulics model, a series of thermal-hydraulic calculations were performed to simulate certain reactor transients of interest (i.e., reactor scram, LOCA, etc.) in order to characterize the gamma thermometer response relative to power level monitoring and adequate core cooling indication. Results of this study reaffirm the feasibility of utilizing the GT as a dual-function (power level and adequate core cooling capacity) measurement device, with each function accomplished virtualy independent of the other. The study also indicates that there is a thermal-hydraulic regime for which the GT would no longer give easily interpretable signals.