Fuel Failure Detection Experiment Using UO2-Loaded Sodium in-Pile Loop

Performance of various types of fuel failure detection systems has been studied using a uranium oxide loaded sodium in-pile loop located in Japan Research Reactor 2. The detection systems include a delayed neutron monitor(graphite or polyethylene moderator ), a moving-wire precipitator(detecting beta-and gamma-rays separately ), a cover gas gamma-ray spectrometer (single Ge(Li) or an anticoincidence hyperpure Ge ), and a Si(Li)-precipitator. Construction and performance of these detection systems are described as well as the methods of the detection efficiency determination. A method is introduced, which gives the fission product release fraction from the fuels and the fission product transfer rate from sodium to cover gas, using only the fission product concentrations in the cover gas.