Slow heat-up PWR test CORA-30: test results

The CORA out-of-pile experiments are part of the international Severe Fuel Damage (SFD) Program. They were performed to provide information on the damage development of Light Water Reactor (LWR) fuel elements in loss-of-coolant accidents in the temperature range 1200 C to 2400 C. Test CORA-30 should investigate the fuel element damage behaviour with reduced initial heat-up rate of about 0.2 K/s compared to the normally used value of 1 K/s. The lower initial heat-up rate is representative for a loss-of-coolant accident which may develop after a shutdown of the reactor. The initial increase rate of the cladding temperature influences the thickness of the oxide layer reached at a given temperature. The thickness of the protective oxide layer influences the temperature time behaviour and the extent of the temperature escalation. Test CORA-30 showed that the temperature escalation takes place also for an initial heatup rate of 0.2 K/s. The temperature at the start of the escalation was about 150 K higher than in tests with 1 K/s initial heatup. The increase rate of the temperature reached a maximum of about 2 K/s, a value much less than about 20 K/s reached for an initial temperature increase of 1 K/s. This result is important for accident management considerations. (orig./GL)