Overview of Structural Integrity Related Research on Alloy 800 Steam Generator Tubing between 2006 and 2012

Abstract

Canadian utilities have been actively supporting structural integrity related research on Alloy 800 Steam Generator (SG) tubing through the Chemistry, Materials and Components (CM and C) research program of CANDU Owners Group (COG). The present paper summarizes the results from a variety of work packages funded under CM&C and Ontario Power Generation (OPG) between 2006 and 2012. The topics include: Revision of Canadian Industry Fitness-For-Service Guidelines for Steam Generator and Preheater Tubes; Characterization of cold work and residual stresses in straight SG tubes; Tension tests to characterize material stress-strain curves Tension test of SG tube with a circumferential slot; Burst-pressure tests of defect-free archive and ex-service SG tubes; Burst-pressure tests of SG tubes with different circumferential slot morphologies; Development of advanced finite element method; Residual stresses in hydraulically and mechanically expanded SG tube joints; Validation of flaw models for structural integrity assessments of degraded SG tubes. These research results are being used by Candu Energy Inc. and the Canadian utilities to develop strategies to manage any emerging degradation mechanisms in Alloy 800 SG tubing in CANDU reactors to meet the requirements of the Canadian Industry’s Fitness-For-Service Guidelines for Steam Generator and Preheater Tubes.