Mixed oxide run-beyond-cladding-breach tests in EBR-II

Fuel pin and subassembly design and quality control during fabrication are intended to ensure that fuel pins can reach goal exposure without cladding breach. However, premature random cladding breaches cannot be precluded. Economic commercial operation of sodium-cooled Fast Breeder Reactors may require operation with breached fuel pins in the core. The alternative to this mode of operation is to remove subassemblies with breached fuel pins at the first indication of cladding breach which is both time consuming and costly. An objective of the U.S. Run-Beyond-Cladding-Breach (RBCB) program is to understand the behavior of mixed oxide fuel during continued irradiation in the post-breach condition. The paper presents the results from the initial RBCB tests of mixed-oxide fuels which were conducted in the Experimental Breeder Reactor-II (EBR-II). Tests conducted to calibrate the EBR-II fission product monitors are also briefly described.