Analytical and Experimental Assessment of CANDU Fuel Sheath Integrity Under Post Dryout Conditions

Abstract

The experiments that investigated the CANDU fuel sheath behavior under different pressures, temperatures, oxidizing environment, material structure (as-received or thermally treated to attach appendages), and heating rates were reviewed and assessed to determine the limits of postdryout duration, sheath temperature, and pressure difference across the sheath required to ensure the fuel sheath integrity. A number of burst curves at different heating rates were studied. Time-at-temperature fuel sheath failure maps were developed based on temperature ramp and isothermal experiments for the 28-element fuel bundle. Analytical time-at-temperature fuel sheath failure maps were also developed for both of 28- and 37-element fuel bundles using the ELOCA fuel analysis computer code and were compared to the experimental time-at-temperature sheath failure maps. Time-at-temperature sheath failure maps could be used as a simple and effective screening tool to demonstrate fuel sheath integrity during postulated design basis accident.