PERFORMANCE OF UNENCAPSULATED (U, Pu) O2 FUEL PINS (SERIES F3A) IRRADIATED IN EBR-11 to 50,000 MWd/Te

摘要

Sixteen unencapsulated mixed-oxide fuel pins were irradiated in EBR-I J to approximately 5atomic percent burnup at 16 kW'tt nominal peak linear power. The fuel fabrication parameters were varied within the ranges proposed for commercial liquid metal fast breeder reactors (LMFBRl except that pin diameter was approximately 75* larger than usually specified. No cladding failures occurred. Pin swelling was substantially greater in Type-304L stainless steel clad fuel pins than in Type-316 clad elements .Mission gas release to the internal void volume ranged from 73 to 97%. Experimental burnup values were 10 to 12% less than calculated values and varied across the subassembly m a manner that suggested some fission rote elevation from an adjacent extra-worth driver subassembly Substantial attack was found in the cladding at its inside surface and the extent of this attack (up to 0.009 inch mtergranular penetration at about ' 158 Pi correlated with temperature but not with any fuel fabrication parameter The penetrating fission product material contained Cs. Mo. and To. The unusually, large amount of fuel/fission product/cladding reaction may be related to the high carbon content in the mixed oxides and/or to a short high temperature operating period.