Evaluation of the maximum bending stress of pre-hydrided Zircaloy-4 cladding tube after simulated loss-of-coolant-accident test

Abstract

After the accident at Fukushima dai-ichi nuclear power station, the fracture resistance of fuel rods against aftershock became a concern in the safety evaluation of reactor core during the long-term cooling after a loss-of-coolant-accident (LOCA). In this study, the maximum bending stresses of pre-hydrided cladding tubes which experienced simulated LOCA tests were investigated. The obtained results suggested that the decrease in the maximum bending stress of the cladding tube experienced LOCA conditions was mainly determined by the hydrogen content in the cladding tube after simulated LOCA test, irrespective of initially hydrogen content. It was also suggested that the decreasing trend of the maximum bending stress with the increasing hydrogen content would be expressed by a form of exponential function, in which the maximum bending stress at a hydrogen content of 1500 ppm was estimated to be about a half of that at 0 ppm.