Fuel-Cladding Mechanical Interaction in LMFBR Fuel Rods

Experimental determinations of cladding plastic deformation in (U,Pu)O₂ fuel rods, clad with annealed Type 316 stainless steel and irradiated in EBR-II, indicate that fuel-cladding mechanical interaction takes place between ∼3 and 8 at.% burnup. At higher burnups, the cladding swelling rate increases markedly resulting in no further fuel-induced plastic deformation. The maximum cladding plastic strain exhibited by several annealed Type 316 stainless-steel-clad rods was 0.4%. Cladding plastic strain was found to be independent of smeared density in the range of 83 to 91% TD.