High Temperature Creep Behavior of N36 Zirconium Alloy Cladding Tubes

Abstract:

High temperature tensile creep behavior of N36 zirconium alloy cladding tubes in the temperature range from 593 K to 723 K and the stress range from 60 MPa to 160 MPa was investigated. The results show that there are three distinct rate-controlled creep mechanisms for N36 zirconium alloy cladding tubes. In the temperature range from 593 K to 673 K the stress exponent n is ~3 and creep activation Q≈150 kJ·mol-1 is found in the low applied stress region, which means the dominant process is viscous-glide-controlled. But in the high applied stress region the stress exponent n is 5~6 and the creep activation Q≈170 kJ·mol-1 is found, which obeys the typical five power law creep mechanism controlled by the climb of edge dislocations. At 723 K and with high applied stress the power law breakdown appears and the exact mechanism is not clear by now. In the test condition N36 zirconium alloy cladding tubes exhibit a type of creep behavior similar to that noted in class-I(A) alloys, which is very different from zircaloy.

Key words:N36 zirconium alloy cladding tube; high temperature creep; creep mechanism