Session: OAC-04-02 Storage and Transportation of Radioactive and other Hazardous Materials - 2

Paper Number: 106680

106680 - Mechanical Responses of 316l Stainless Steel Printed by Wire Arc Additive Manufacturing With Different Thermal Histories 

Wire arc additive manufacturing (WAAM) is a wire-based direct energy deposition (DED) approach that uses an electric arc as the energy source to melt wire feedstocks for layer-by-layer deposition of desired geometries. Compared to other DED processes such as laser powder bed additive manufacturing (AM), advantages of WAAM include low capital investment, ability to fabricate in ambient atmosphere, high deposition rate, and open architecture controls. These advantages marked WAAM as an economic and cost-effective technique to print large structures, such as spent nuclear fuel (SNF) canisters.

 

Current standard SNF canisters fabrication procedures include rolling stainless steel (SS) plates (304L or 316L stainless steel), fusion welding the rolled cylinder along the height direction, and along the circumference direction if necessary, assembling associated structures such as the internal basket, etc. Besides the multiple steps of fabrication and assembling, relatively high tensile residual stresses in the fusion welded zone and heat affected zone, as well as, the canister storage environment resulted in a major concern of canister chloride-induced stress corrosion cracking (CISCC) with the extended storage plan.

 

In this paper, we demonstrated the production of a 316L SS mockup SNF canister integrated with an internal basket using WAAM, and both the canister and the internal basket were printed in one step. From the SNF canister design, there is a significant thickness difference between the canister wall (0.5 – 0.75 in.) and the internal basket (~0.3 in.), therefore, welding passes needed to produce the wall and the basket are different, which means thermal histories received by the printed wall and basket in WAAM are different. To understand the thermal history difference impact, we studied mechanical responses of the printed wall and internal basket, and the microstructure differences caused by different thermal histories. Tensile tests at room temperature and elevated temperatures were performed on longitudinal and vertical specimens extracted from thick and thin WAAM printed walls. Scanning electron microscopy (SEM) was used to characterize specimens removed from both builds. Results showed that tensile properties and grain structures are affected by different thermal histories received in multi- and single-bead WAAM.

 

This is a technical paper that does not take into account contractual limitations or obligations under the Standard Contract for Disposal of Spent Nuclear Fuel and/or High-Level Radioactive Waste (Standard Contract) (10 CFR Part 961). For example, under the provisions of the Standard Contract, spent nuclear fuel in multi-assembly canisters is not an acceptable waste form, absent a mutually agreed to contract amendment. To the extent discussions or recommendations in this paper conflict with the provisions of the Standard Contract, the Standard Contract governs the obligations of the parties, and this paper in no manner supersedes, overrides, or amends the Standard Contract. This paper reflects technical work which could support future decision making by the U.S. Department of Energy (DOE or Department). No inferences should be drawn from this paper regarding future actions by DOE, which are limited both by the terms of the Standard Contract and Congressional appropriations for the Department to fulfill its obligations under the Nuclear Waste Policy Act including licensing and construction of a spent nuclear fuel repository.

Presenting Author: Wei Tang Oak Ridge National Laboratory

Presenting Author Biography: Dr. Wei Tang is a R&D staff in Materials Science and Technology Division at Oak Ridge National Laboratory. His research interests include materials additive manufacturing, welding and processing, microstructure characterization, mechanical properties evaluation, and residual stress characterization. Specific to waste management, he has been performing R&D on spent nuclear fuel canister repair welding, additive manufacturing, and products characterization and evaluation for several years. Currently he is a member of American Welding Society (AWS) and a member of the technical paper committee (TPC) of AWS.

Authors:

Wei Tang Oak Ridge National Laboratory
Dominic Giuliano Oak Ridge National Laboratory
Oscar Martinez Oak Ridge National Laboratory
Maxim Gussev Oak Ridge National Laboratory
Andrzej Nycz Oak Ridge National Laboratory
Ke An Oak Ridge National Laboratory
Luke Meyer Oak Ridge National Laboratory
Chris Masuo Oak Ridge National Laboratory
Dunji Yu Oak Ridge National Laboratory
William Carter Oak Ridge National Laboratory
Alex Walters Oak Ridge National Laboratory
Riley Wallace Oak Ridge National Laboratory
Derek Vaughan Oak Ridge National Laboratory