Integrity assessment on irradiated garter springs

Assuring the integrity of the garter spring is a prerequisite for ensuring the safety of the coolant tube, which is verily one of the most vital components of a Pressurized Heavy Water Reactor (PHWR) system. With this aim in view, twenty one numbers of Zr-2.5% Nb-Cu garter springs (G.S.) which had undergone various Effective Full Power Years of operation (EFPYs) ranging from 1.8 to 8.5, were subjected to detailed mechanical property studies at Post Irradiation Examination Division, BARC. These G.Ss had belonged to Indian PHWRs, namely RAPS, MAPS and NAPS. A report is presented on the basis of the results generated by carrying out a few relevant mechanical tests on the irradiated G.Ss. The study indicated that these garter springs even after 8.5 EFPYs of service in the respective power reactors could exhibit good amount of strength and ductility, much more than what would be required for retaining their integrity during service. (author)