Fuel R&D at Studsvik III. Studies of special phenomena in fuel behaviour: lift-off and defect fuel degradation Original Research Article

Two different types of research and development programmes at Studsvik are discussed. Cladding lift-off studies have been pursued, where a high end-of-life overpressure in high burn-up fuel rods may cause outward creep and consequently an increased pellet-cladding gap. Primary defects, mainly caused by debris fretting, may lead to large secondary failures due to internal hydriding. These problems have been studied in the R2 test reactor.