Mathematical Modelling of Weld Phenomena 12 1 PREDICTION OF STRESS CORROSION CRACKING IN 304 STAINLESS STEEL CANISTERS IN DRY STORAGE OF SPENT FUEL BY MODELING: ANALYSIS OF WELD RESIDUAL STRESS AND SUSCEPTIBLE MICROSTRUCTURE S. GORDON*, X. WU*, Z. YU* and S. LIU* *George S. Ansell Department of Metallurgical and Materials Engineering Center for Welding, Joining and Coatings Research Colorado School of Mines, Golden, CO 80401, U.S.A. DOI 10.3217/978-3-85125-615-4-12 ABSTRACT Atmospheric chloride-induced stress corrosion cracking (CISCC) in the weldments of spent fuel canisters is one of the primary safety concerns during the dry storage of used nuclear fuel at Independent Spent Fuel Storage Installations (ISFSI) in coastal areas. For SCC to occur, three criteria must be met: an aggressive chemical environment, susceptible microstructure, and sufficient tensile stress. Instead of the environment, this paper will focus only on the material microstructure and stress state. Firstly, finite element analysis (FEA) based numerical simulation models were developed for the welding of the mockup canister. Multi-pass arc welding process was considered. The thermal history and residual stress distribution induced by the longitudinal, circumferential, and the intersection between longitudinal and circumferential welds were developed based on a thermal-mechanical coupling model using ABAQUS software. The simulation results were compared with the deep-hole drilling (DHD) and contour measurement data. Based on the model-predicted stress results, a four-point bend (4PB) setup was then designed to duplicate the weld residual stress onto the 4PB specimen, on which the maximum tensile stress is close to the predicted maximum stress level of 250 MPa in the weld heat-affected zone (HAZ). A stress gradient also existed along the thickness of the 4PB specimen which allowed for the consideration of stress variation. The designing of the 4PB test was done by FEA method using ABAQUS software, and verified by digital image correlation (DIC) measurements. Besides, to identify the most susceptible microstructure of the canister to corrosion under the weld residual stress in the controlled environment, the modified implant test (CEMIT) was designed. A FEA model considering the welding process and the following uniaxial tensile load was then developed using the SYSWELD software. The residual stress and thermal history were obtained during and after the CEMIT welding process, and after the uniaxial tensile loading process. These tests yielded instructive information for the prediction of the initiation site of the crack. The initiation of the crack observed in the experiments was explained based on the simulation data. While each of the three simulations provided an independent story, the three together produced a complete