Behavior of high-burnup advanced LWR fuels under accident conditions
- Nuclear Safety Research Center, Japan Atomic Energy Agency - JAEA, Tokai-mura, Naka-gun, Ibaraki, 319-1195 (Japan)
Advanced fuels for LWRs which consist of cladding materials with high corrosion resistance and pellets with lower fission gas release have been developed by utilities and fuel vendors to improve the fuel performance even in the high burnup region and also raise the safety level of current nuclear power plants to a higher one. In order to evaluate the adequacy of present safety criteria and safety margins in terms of such advanced fuels and provide a database for future regulation of them, JAEA has started a new extensive research program called ALPS-II program. The ALPS-II program is primarily composed of tests simulating a RIA (Reactivity Initiated Accident) (VA-5 and -6 tests) and a LOCA (Loss Of Coolant Accident) on high burnup advanced fuels irradiated in commercial PWR or BWRs and started in JFY 2008. Recently, post-test examinations on the fuel rods after the pulse irradiation tests of VA-5 and -6 were performed and the relationship between the failure limits of the high burnup advanced fuels with M-MDA{sup TM} cladding and the morphology of the hydrides precipitated in the cladding during normal operation was investigated. The difference in the crack surface morphology was observed between tests VA-5 and-6, which seemed to reflect the difference in the direction along which hydrides precipitate in the cladding. This indicates that the hydride precipitated in the cladding, which is considered to be dependent on the final heat treatment at fabrication, affects the fuel enthalpy at failure. In terms of the simulated LOCA test, integral thermal shock tests and high temperature oxidation tests have been conducted on high burnup PWR and BWR fuel cladding with advanced materials, and their fracture limits, high temperature oxidation rates, etc. were investigated. In the recent integral thermal shock tests for high burnup BWR cladding, namely Zry-2/LK3 material, no fractures were observed. In terms of the oxidation rate tests, the oxidation rate of irradiated M5{sup TM} was similar to those of unirradiated Zry-4 and M5{sup TM} and lower than the values estimated by the Baker-Just equation. From the results of these tests, it was found that in terms of these materials the fracture boundaries do not decrease and the oxidation does not significantly accelerate in the burnup level examined.
- Research Organization:
- American Nuclear Society - ANS, 555 North Kensington Avenue, La Grange Park, IL 60526 (United States)
- OSTI ID:
- 22750091
- Country of Publication:
- United States
- Language:
- English
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