Session: MF-05-02 Fitness-For-Service and Failure Assessment-2

Paper Number: 154690

154690 - Assessment of Adequacy of Upper-Shelf Fracture Toughness Model for Zr-2.5nb Pressure Tubes for Fitness-for-Service Evaluations 

Abstract: 

A probabilistic predictive model for fracture toughness of irradiated Zr-2.5%Nb pressure tubes in CANDU^Ò reactors in the upper-shelf temperature region was developed in 2014. The model was then incorporated into the Canadian Standards Association (CSA) Standard N285.8 as the reference model in the evaluations of pressure tube material surveillance measurements as well as in fitness-for-service evaluations that use the upper-shelf fracture toughness as an input.  Based on the range of bulk equivalent hydrogen concentration, H_eq, in the data set used in the model development, the upper validity limit on H_eq is set to 120 ppm by weight. New burst-test data for upper-shelf fracture toughness have been obtained from ex-service surveillance pressure tubes and other testing programs since the upper-shelf fracture toughness model was developed.  Evaluation of pressure tube material surveillance measurements and assessment of the adequacy of the upper-shelf fracture toughness model for Zr-2.5%Nb pressure tubes for continued use in fitness-for-service evaluations were performed, as documented in this paper. The upper validity limit on H_eq was also assessed in the current work by performing additional analyses with an expanded data set that includes burst-test results for the upper-shelf fracture toughness obtained from the material with high bulk equivalent hydrogen concentrations.

Presenting Author: Cheng Liu Kinectrics

Presenting Author Biography: Dr. Cheng Liu has received his Ph.D. degree in applied mathematics from York University. He joined Kinectrics Inc. in 2011 and worked as a research scientist in the department of materials and major components. The main business of his department is to provide consulting service to complex technical problems associated with structural integrity assessment of critical components in CANDU reactors. Dr. Liu’s expertise is in model development, flaw evaluation and uncertainty analysis. He serves as a member of CSA N285 technical committee, and also as a member of several working groups under ASME Section XI.

Authors:

Cheng Liu Kinectrics
Leonid Gutkin Kinectrics Inc.