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| Figure 1 - Sketch of a 3013 outer container (right) and photograph of the container after welding. |
A key element in the Department of Energy (DOE) strategy for the stabilization, packaging, and storage of plutonium-bearing materials involves closure welding of DOE-STD-3013 outer containers. The 3013 container provides the primary barrier and pressure boundary for preventing release of plutonium-bearing materials to the environment. The final closure weld of the 3013 container must be leaktight, structurally sound, and meet DOE-STD 3013-specified criteria.
In February 2001, the Savannah River Technology Center (SRTC) supplied a welding system to the Hanford Plutonium Finishing Plant (PFP), located near Richland, Wash., for the closure of 3013 containers. Efforts to supply this system included development, qualification, and demonstration of an automatic gas tungsten arc welding (GTAW) process for making the closure weld. GTAW was chosen for its demonstrated history in critical applications, ease of remote operation, and ability to make high-integrity welds.
The 3013 container, made of Type 316/316L stainless steel and measuring almost 5 inches in diameter and approximately 10 inches in length, is closure-welded at the lid/container interface – Fig. 1. The corner joint is formed by pressing an interference-fit lid into the 3013 container, creating a square groove weld preparation. The closure is made autogenously (without addition of filler) using a modified AMI© 9 Series orbital weld head with a Model 227 power supply. The modified weld head (Fig. 2) includes an integral chill block.
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Figure 2 - The modified orbital weld head.
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An encoder and shunt were added for weld travel speed and arc current measurements, respectively. In addition, the weld head rotor was adapted to receive a specially designed snap-in tungsten electrode for ease of replacement.
This article focuses on the development, qualification, and demonstration of the welding process for the closure welding of Hanford PFP 3013 containers.
Reprinted from the Welding Journal
July, 2002
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