Length dependence of fecral accident-tolerant fuel cladding under simulated loss-of-coolant accident testing

The safety of the accident-tolerant fuel (ATF) cladding candidates, must be assessed under simulated conditions of the loss-of-coolant accident (LOCA). During LOCA, the temperature of the cladding and the internal pressure of the fuel rods increase under an oxidizing steam environment. Under these conditions, the cladding experiences mechanical loading due to the internal pressurization, which eventually causes tube burst before quenching. Simulated LOCA tests use 12-inch-long tube segments which are inconvenient for the irradiated ATF cladding candidate of FeCrAl alloys due to the high radiation doses. Therefore, it is useful to reduce specimen size. This study investigates the effect of tube specimen length on burst behavior of the FeCrAl tubes using the severe accident testing system (SATS) at Oak Ridge National Laboratory (ORNL). Specimens of various lengths were subjected to heating experiments until the burst occurred. Specimen surfaces were engraved for strain measurements after the burst, and the tube length effect on the failure behavior of the FeCrAl alloys were investigated by comparing samples of different lengths. Results are interpreted based on changes in the tubes' burst characteristics.