Fracture toughness of irradiated Zr–2.5Nb pressure tube from Indian PHWR

Fracture toughness of irradiated Zr–2.5Nb alloy pressure tube, fabricated by the cold pilgering and stress relieving route, was evaluated using disk compact tension type specimens. These specimens were punched out from the irradiated pressure tube (S-07), which was in service for about 8 effective full power years of reactor operation in the Kakrapar Atomic Power Station-2 (KAPS-2). The tests were carried out remotely inside a lead shielded enclosure. Crack growth during the test was measured using the direct current potential drop technique. The irradiated pressure tube showed low fracture toughness at 25°C. The fracture toughness increased with increase in temperature up to 250°C but was practically unaffected with further increase in temperature up to 300°C. This paper discusses the fracture behavior of irradiated Indian pressure tube material and compares it with other data available.