Facilities for Crack Growth Testing of Neutron-Irradiated Alloys in LWR Environments

Abstract

This paper describes the facilities for conducting crack growth rate (CGR) tests on neutron-irradiated alloys in LWR environments. A set of procedures were developed for using the facilities to test CGRs of neutron-irradiated stainless steel in the Irradiated Materials Testing Complex (IMTC) at the University of Michigan. The DCPD technique was used to monitor the evolution of crack growth under various loading and environmental conditions throughout a CGR test up to 3127 hours. The high resolution of DCPD, the application of a correction factor to crack length, and dK/da control when changing K improved the accuracy of crack length monitoring. A procedure for mounting a neutron-irradiated RCT sample in the hot cell using remote manipulator operation was also developed. Precision design of fixtures helped to overcome the difficulties of spot-welding thin DCPD wires using manipulators. On-the-fly environmental change from BWR NWC to BWR HWC, and then to PWR water at 288°C and 320°C was successfully conducted, and constant K control was maintained throughout the test. As a result, a complete history of crack growth in a neutron-irradiated round compact tension (RCT) sample was reported for the first time.