Spent Fuel Behaviors under Loss of Cooling/Coolant Accident in A Spent Fuel Pool

Under dry storage conditions for spent nuclear fuels, creep deformation/rupture is the most probable degradation mechanism for the cladding material, because internal pressure of the fuel rod also becomes higher with storage temperature. Thus the integrity of spent fuel during dry storage has been evaluated by predicting creep deformation of Zr alloy claddings. In particular, the hoop-directional creep behavior of high burn-up fuel cladding is concern due to the difference of pressure between fuel-cladding gap and storage environment. Many investigations have been performed in order to validate the hydrogen effect on creep behavior of fuel cladding, because high burn-up fuel cladding contains high concentration of hydrogen absorbed during waterside corrosion during normal operation. But there is no consensus regarding hydrogen effect on creep behavior. Accordingly, it is essential to clarify hydrogen effect on creep behavior of the high burn-up fuel cladding. It was revealed that hydrogen in the Zr alloy plays a role to increase secondary creep rate. The creep rate of irradiated(high burn-up) cladding is highest, and hydrided cladding > un-hydrided cladding.