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 review of NPL Environmental radioactivity measurement intercomparison exercises: 1989–1995
Abstract Since 1989 the National Physical Laboratory (NPL) has conducted a series of five intercomparison exercises directed initially at the environmental radioactivity measurement community in the UK, but now open to overseas participants. The complexity of the intercomparison samples has increased with time. In general the results have been encouraging, but some problems have been highlighted, such as cascade summing and the sources of nuclear data. The intercomparisons are reviewed and the changes and improvement observed over time are discussed. The implications for quality assurance are also addressed.