Occupational Thorium Exposure or Self-Poisoning?
Thoriated electrodes are used in TIG (Tungsten Inert Gas) welding [1]. Thorium intake may happen during grinding and welding operations using thoriated electrodes [2]. The use of thoriated tungsten electrodes may be at the origin of a potential hazard [3]. The annual commited effective dose from inhalation of 232Th, 230Th, 228Th and 228Ra is usually below 1mSv for a full-time TIG welder [4]. Electrode consumption during welding was primarily the result of tip sharpening. Indeed, less than 3% of weight loss was attributable to the welding process [5].
Determination of thorium in environmental and workplace materials by ICP-MS.
The paper outlines the advantages of the use of Inductively Coupled Plasma Mass Spectrometry (ICP-MS) over radiometric techniques to measure natural thorium, 232Th. Experimental parameters that must be taken into account in the sample digestion, preparation and ICP-MS analysis of environmental (soils, rocks, sediments) or workplace (thorium oxide, reference solutions) materials are described. The methods presented are applied to various reference materials, with the aim of providing suitable procedures to be useful for other important thorium containing materials (such as monazite sands or welding electrodes). The participation in a European Commission intercomparison exercise is detailed and a comparison with alpha spectrometry is made.
A method for removing the emissions of natural uranium in the analysis of thorium alpha spectra
Abstract In water samples, the radioactive concentrations of uranium are frequently much higher than the thorium concentrations because of uranium's greater solubility in water. In some cases, even though a method of separating out the uranium is used, a part of the emissions corresponding to natural uranium may still contaminate the thorium alpha spectra. Moreover, the separation of uranium from thorium is sometimes inconvenient, because the yield may be greatly decreased. This paper presents a method of analysis which removes the interference between the emissions of thorium and uranium, and calculates accurately the areas in a spectrum corresponding to each thorium isotope: 232Th, 230Th and 228Th. Checks of this method have given very satisfactory results.