High temperature properties of J-Alloy^TM

The J-Alloy^TM, Zr-Nb based alloy aiming for expansion of safety margins under high duty operation, is under development as an advanced PWR fuel cladding tube with superior corrosion resistance. In this study, non-irradiated J2 (Zr-1.6Nb-0.1Cr), one of the J-Alloy^TM candidates, was subjected to a series of high temperature tests. In order to obtain high temperature properties of J2, specific heat measurement, high temperature creep test and high temperature burst test were conducted, and it was observed that the high temperature properties of J2 were equivalent to Zircaloy-4 in the α phase and β phase. But difference between J2 and Zircaloy-4 was observed in the temperature range of α+β phase. This difference is due to the alteration of phase transformation temperature caused by Nb addition. Since the difference is slight, it was confirmed that J2 has sufficient properties as an advanced PWR fuel cladding tube. In order to confirm the applicability of J2 cladding tube to LOCA condition, an integral thermal shock test was conducted with parameters of holding temperature, ECR and hydrogen concentration of cladding tube. The test result demonstrated that the fracture limit of J2 meets the 15%-ECR LOCA criterion in Japan. Therefore, the applicability of J-Alloy^TM cladding tube to LOCA condition was confirmed. (author)