Leak before break experiments on H.T.Zr-2.5wt%Nb pressure tubes

not registered; not registered; not registered

Pressure tubes of Advanced Thermal Reactor (boiling-light-water-cooled heavy-water-moderated pressure-tube-type reactor) in Japan are made of Heat Treated Zr-2.5wt%Nb alloy and the both ends are mechanically joined with stainless steel extension tubes. Sharp artificial cracks were introduced in the rolled jointed pressure tube specimen and the cracks were propagated and penetrated the tube wall by fatigue and DHC in high-temperature high-pressure water loop. From the results, it was shown that the LBB phenomena were valid for the rolled jointed pressure tube under the reactor operating conditions and that the critical crack length was more than 50mm. Moreover, calculations were performed about the leak rate using critical flow data.