Hydrogen Ingress Mechanisms in ZR-2.5 wt% Nb Pressure Tubes-An Overview of Some Recent Progress

Abstract

This paper provides simplified illustrations ofsome of the important physical processes involved,and selected examples of progress toward identifyingand understanding hydrogen ingress mechanismsassociated with Zr-2.5 wt% Nb (Zr-Nb) alloy pressuretubes (PTs) operating in CANDU PHW' nuclear powerreactors. (1) The material is drawn mostly from thecurrent CANDU Owners Group (COG), Fuel Channel R&Dprograms, which are being carried out principally atthe research laboratories of Ontario Hydro (OH) andAtomic Energy of Canada Limited (AECL). A briefstatus of the current hypotheses for explaining theincreased hydrogen content observed in the recentlyremoved surveillance PT from Pickering Unit 3Channel L09 (P3L09), is also given.