Ring Compression Ductility of High-Burnup Fuel Cladding after Exposure to Simulated LOCA Conditions

概要

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Ring compression tests were conducted with specimens sampled from high-burnup PWR and BWR fuel cladding segments that had been ruptured, oxidized at 1,405–1,484 K, and quenched in LOCA-simulated experiments. The calculated oxidation amount for cladding thickness ranged from 11.3 to 25.3% and the hydrogen concentration ranged from 100 to 870 ppm in the ring specimens. The plastic strain to failure and maximum load measured in the ring compression tests decrease with increasing oxidation and hydrogen. Embrittlement of the cladding is seen when the hydrogen concentration is above 300–400 ppm. Although the examined fuel cladding segments did not fracture in the LOCA-simulated experiments, most of the specimens sampled from the segments exhibited a brittle nature in the ring compression tests. This obvious discrepancy between the fracture/no-fracture criterion and the embrittlement criterion is likely caused by a difference in the loading conditions in the two tests. The advantages and drawbacks of the test methodologies should be well considered on application of the test results to the regulatory judgment.
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