In-core assessment of defective fuel in CANDU-600 reactors

The gamma ray and delayed neutron activities of the coolant in a CANDU-600 reactor are monitored continuously to detect and locate fuel defects as they occur. The gamma activities of various fission products are interpreted to estimate the number of defective rods and to determine the condition of the defects. The delayed neutron activities are analyzed to locate defective fuel and to determine when to remove it in order to avoid significant releases of uranium to the heat transport system. The techniques can be used to keep the reactor system clean while avoiding premature discharge of fuel. Operational data from the Point Lepreau Nuclear Generating Station are used to demonstrate the interpretative methods. (author)