THE NEED FOR A NEW JOINING TECHNOLOGY FOR THE CLOSURE WELDING OF RADIOACTIVE MATERIALS CONTAINERS
One of the activities associated with cleanup throughout the Department of Energy (DOE) complex is packaging radioactive materials into storage containers. Much of this work will be performed in high-radiation environments requiring fully remote operations, for which existing, proven systems do not currently exist. These conditions demand a process that is capable of producing acceptable (defect-free) welds on a consistent basis; the need to perform weld repair, under fully-remote operations, can be extremely costly and time consuming. Current closure welding technology (fusion welding) is not well suited for this application and will present risk to cleanup cost and schedule. To address this risk, Fluor and the Pacific Northwest National Laboratory (PNNL), are proposing that a new and emerging joining technology, Friction Stir Welding (FSW), be considered for this work. FSW technology has been demonstrated in other industries (aerospace and marine) to produce near flaw-free welds on a consistent basis. FSW is judged capable of providing the needed performance for fully-remote closure welding of containers for radioactive materials for the following reasons: FSW is a solid-state process; material is not melted. As such, FSW does not produce the type of defects associated with fusion welding, e.g., solidification-induced porosity, cracking, distortion due to weld shrinkage, and residual stress. In addition, because FSW is a low-heat input process, material properties (mechanical, corrosion and environmental) are preserved and not degraded as can occur with 'high-heat' fusion welding processes. When compared to fusion processes, FSW produces extremely high weld quality. FSW is performed using machine-tool technology. The equipment is simple and robust and well-suited for high radiation, fully-remote operations compared to the relatively complex equipment associated with the fusion-welding processes. Additionally, for standard wall thicknesses of radioactive materials containers, the FSW process can perform final closure welding in a single pass (GTAW requires multiple passes) resulting in increased productivity. Together, the performance characteristics associated with FSW, i.e., high weld quality, simple machine-tool equipment and increased welding efficiency, are expected to reduce risk to upcoming DOE radioactive materials packaging campaigns. FSW technology requires some development/adaptation for this application, along with approval from the governing code of construction prior to production operations. This paper addresses the need for a new joining technology, a description of the FSW process and why it is well-suited for this application, and several activities required for commercialization.
- Research Organization:
- Hanford Site (HNF), Richland, WA (United States)
- Sponsoring Organization:
- USDOE Assistant Secretary for Environmental Management (EM)
- DOE Contract Number:
- DE-AC06-96RL13200
- OSTI ID:
- 940181
- Report Number(s):
- HNF-39478-FP Rev 0; TRN: US0806891
- Resource Relation:
- Conference: WASTE MANAGEMENT SYMPOSIA INC (WM09) 03/04/2009 PHOENIX AZ
- Country of Publication:
- United States
- Language:
- English
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