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Spark source mass spectrometric investigation has been carried out on a thoria-graphite matrix in order to assess the feasibility of characterizing the refractory nuclear material thoria (ThO2) in respect of trace elemental constituents. The sensitivity calibration was used as the method of study. As thorium is monoisotopic and oxygen is subject to some contribution from the instrumental background, these pose the critical problem of selecting a reference element. In order to overcome the problem, Th+, Th3+ and C+ are considered as three independent reference species. A somewhat different approach, effectively without the use of a reference element, is also described. Two specific samples, ThO2 trace constituent material (synthetically doped) and the corresponding blank, are used for the determination of the element specific calibration factors and for the evaluation of unknown blank contributions. The necessary formulations and the related analytical procedure are described and the viability of each of the two methods is outlined. It is shown that the latter method is rather more suitable than the former in the present situation. |
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