Radioactivity from Welding Processes, Compare Amateur Welds with Commerial welds

Many nuclear physics research projects require the fabrication of custom-built hardware which often includes welding. Especially for small-scale setups, these hardware components could be produced in-house by amateur welders or in student labs. Low-background experiments, such as High Purity Germanium (HPGe) gamma spectroscopy setups, have stringent requirements on the radiopurity of materials in and around the experimental setup. In this summer student project we investigate the radioactive background introduced by different welding techniques, including non-perfect amateur welds.

We use 2% thoriated tungsten electrodes and Gas Tungsten Metal Arc Welding (GTAW) to create sample welds on a 3’’x3’’ mild steel base plate. We perform a deliberately poor welding technique, dipping the electrode into the molten puddle. This creates tungsten inclusions a welding defect of the GTAW process. We measure the welded plate with a HPGe detector to determine ²³²Th and ²³⁸U contaminants introduced by the “poor” welding process. We also compare the radioactivity of different commercial welding electrodes containing thorium, lanthanum, and cesium. Additionally, we compare our poor welds with welds created by a certified welder.

We also study different stick electrodes used in the Shielded Metal Arc Welding process. We also use deliberately poor welding technique to create slag inclusions, a defect where slag is included in the weld. We measure the radioactivity and compare with welds created by a certified welder.