Exposures from thorium contained in thoriated tungsten welding electrodes

Area of Science:

• Industrial Hygiene
• Radiological Health
• Materials Science

Background:

• Thoriated tungsten electrodes are widely used in tungsten inert gas welding.
• Understanding thorium particulate generation is crucial for radiation dose estimation.
• Previous studies have not fully quantified thorium exposure during welding and electrode maintenance.

Purpose of the Study:

• To quantify thorium particulate concentrations and particle sizes during welding and electrode sharpening.
• To assess the contribution of welding versus sharpening to overall thorium exposure.
• To provide data for estimating radiation doses for welders using thoriated tungsten electrodes.

Main Methods:

• Analysis of thorium isotopes (232Th, 230Th, 228Th) in electrodes from different manufacturers.
• Measurement of airborne thorium concentrations in the breathing zone during welding and sharpening.
• Particle size analysis of aerosols generated during welding and sharpening.

Main Results:

• Electrode consumption is mainly due to sharpening (<3% from welding).
• Respirable thorium particulate concentrations were 0.002 x 10(-12) microCi 232Th/mL during welding and 1.3 x 10(-12) microCi 232Th/mL during sharpening.
• Activity median aerodynamic diameters for respirable aerosols were 3.5 microns (welding) and 5 microns (sharpening).

Conclusions:

• Electrode sharpening is the dominant source of thorium particulate exposure.
• Data supports the estimation of radiation doses associated with thoriated tungsten electrode use.
• Further research may focus on alternative electrode materials to minimize exposure.