Development of fuel failure detection system for a high temperature gas cooled reactor. IV

For pt.III see ibid., vol.36, p.1261, (1989). A fuel failure detection (FFD) system using a wire-precipitator has been developed for a high-temperature gas-cooled reactor. For actual application of the FFD system, the response data to a precipitator for noble-gas fission products (FPs) released from coated particle fuels were measured under various in-core irradiating conditions. The dependency of precipitator counting rates on the fuel temperature and the reactor power was obtained by analyzing measured data. A model of the response function of a precipitator to the noble-gas FP nuclides was developed and its validity has been examined. By integrating these results, a state equation for the fuel failure detection can be determined. The response of a Ge gamma-ray spectrometer and a precipitator for a failed fuel sample was measured. The response curves of long-life nuclides are different from those of short-life nuclides. Using this difference, the fuel failure detection can be carried out