Updating of a gamma spectroscopy-based failed fuel monitor

In 1978, an automated gamma spectrometer which views sample tubes of flowing reactor coolant was developed to detect the onset of fuel failure for CANDU nuclear power plants. This Gaseous Fission Product Monitor (GFPM) was installed in four CANDU plants, and has logged more than 50 reactor years of operation. An updated version of the monitor has been developed in which the need for a moving collimator is eliminated, and an industrial grade PC and I/O control system are added. Routine operator interaction is provided by a virtual instrument control panel which displays a 24-hour histogram of critical concentration results and the status of selected system parameters. An upgraded GFPM system in operation for nine months at the Point Lepreau Nuclear Generating Station delivers a typical detection sensitivity for 20-minute count cycles in the range of 1E-02 to 3E-03 MBq/kg for Xe-133, Xe-135, Kr-88 and I-131. The new GFPM has demonstrated the ability to identify fuel leaks rapidly enough to allow correlation with operational changes in the fuel, and has successfully monitored other radionuclide concentrations for special diagnostic applications