Oxidation and embrittlement behaviors of Zry-4 cladding in air-containing atmospheres at high temperatures

空気混入雰囲気下におけるZry-4の高温酸化及び脆化挙動

Negyesi, M.

Negyesi, M.

The presentation deals with oxidation behavior of Zry-4 alloy during severe accidents of LWR. Zry-4 fuel cladding was exposed in steam-air mixtures at temperatures of 1000-1200 C. Specimen weight gain was measured, metallographic observations were carried out, hydrogen uptake was determined and ring compression tests were conducted. The oxidation kinetics of Zry-4 was significantly affected by the air fraction in steam at 1000 C in the post-transient regime and at 1200 C. The effect of air fraction was diminished at 1000 C in the pre-transient regime. Metallographic examination revealed severe oxide layer cracking and nitride formation. Substantial hydrogen pick-ups were measured, especially at 1000 C after 60 min, strongly depending on the air fraction. They probably led to the significant decrease in plastic strain at 1000 C after 60 min. The effect of air fraction on plastic strain has been hardly observed at 1200 C.