THE DESIGN AND INSTALLATION OF A CORE DISCHARGE MONITOR FOR CANDU-TYPE REACTORS

A new type of surveillance system that monitors neutron and gamma radiation in a reactor containment is being installed at the Ontario Hydro Darlington Nuclear Generating Station A, Unit 2. Unlike video or film surveillance that monitors mechanical motion, this system measures fuel-specific radiation emanating from irradiated fuel as it is pushed from the core of CANDU-type reactors. Proof-of-principle measurements have been carried out at Bruce Nuclear Generating Station A, Unit 3. The system uses (y,n) threshold detectors and ionization detectors. A microprocessor-based electronics package, GRAND-II (Gamma Ray And Neutron Detector electronics package), provides detector bias, preamplifier power, and signal processing. Firmware in the GRAND-II controls the surveillance activities, including data acquisition and a level of detector authentication, and it handles authenticated communication with a central data logging computer. Data from the GRAND-II are transferred to an MS-DOS-compatible computer and stored. These data are collected and reviewed for fuel-specific radiation signatures from the primary detector and proper ratios of signals from secondary detectors.