Session: CS-01-02 Structural Integrity of Pressure Components-2

Paper Number: 154006

154006 - Flaw Stability Analysis of Surface Cracks in Doe Standard Canisters Under Operation Loads and Welding Residual Stresses 

Abstract: 

There are over 3000 commercial spent nuclear fuel (SNF) storage canisters that are made of stainless steel and planned for multipurpose functions of SNF handling: interim storage, transportation, and ultimate disposal at a future SNF disposition location (e.g., deep geologic repository). However, the United States currently has not determined a permanent SNF disposition location, and thus many multipurpose canisters (MPC) are located in coastal regions for de facto long-term storage. The MPC canisters are fabricated by welding, and post-welding heat treatment (PWHT) is not required for relieving the welding residual stresses (WRS). As a result, these canisters may be susceptible to chloride indued stress corrosion cracking (CISCC) due to the deliquescence of chloride-bearing marine salts or dusts that enter the overpack system and deposit on the canister external surface. Previous work (PVP2016-63887) performed the flaw stability analysis of a MPC canister with consideration of influence of WRS in terms of the failure assessment diagram (FAD)-based fracture mechanics method, as codified by API 579-1/ASME FFS-1-2007 Edition. However, API 579-1/ASME FFS-1-2016 and 2021 editions recommend the WRS distributions through thickness that are totally different from those in API 579-1/ASME FFS-1-2007. Accordingly, the newly recommended WRS distributions are adopted in this work. In addition, an equivalent residual stress distribution is proposed with WRS reduction with distance from the weld centerline to reduce the over-conservatism embedded in the previous work. Moreover, the closed-form solutions of stress intensity factor K are developed in terms of the tabular data of the K factor provide in API 579-1/ASME FFS-1 and used to determine more accurate flaw sizes at flaw instability. With these three updates, the flaw instability sizes are redetermined for the surface cracks in the MPC canister with consideration of normal and accident operation loads combined with WRS.

Presenting Author: Xian-Kui Zhu Savannah River National Laboratory

Presenting Author Biography: Dr. Xian-Kui Zhu is a Principal Engineer at US DOE Savannah River National Laboratory. His research focuses on structural integrity and assessment for oil/gas transmission pipelines, pressure vessels, spent nuclear fuel storage canisters, underground nuclear waste tanks, and transfer lines. Dr. Zhu is an international recognized specialist at the advanced plasticity theory, the elastic-plastic fracture mechanics theory, fracture toughness testing method and evaluation, fitness for service evaluation, and their applications to various engineering structures and components.

Authors:

Xian-Kui Zhu Savannah River National Laboratory
Robert Sindelar SRNL
Andrew Duncan SRNL
Bruce Wiersma SRNL