Fuel irradiation experiments by JAERI for light water reactor

The approach of JAERI's study on fuel safety for the investigation of the fuel failure mechanisms are as follows: 1. Pellet-cladding mechanical interaction at high heat rating (a cause of failure when the cladding becomes deteriorated by irradiation). 2. Cladding deterioration by hydriding and irradiation (the irradiation effect on the mechanical properties tends to saturate with neutron fluence, therefore it was postulated that the hydrogen addition to the cladding and irradiation of intermediate period of time will contribute to get the information on the high burnup state of the cladding). 3. Fuel failure by moisture in the fuel (considered as one of the major mechanisms of failure in the early life of the fuel): moisture was intentionally added to the fuel and the pin pressure was measured to study the rate of absorption of moisture)