(3)He mass spectrometry for very low-level measurement of organic tritium in environmental samples.
ABSTRACT The design, setup and performance of a mass spectrometric system for the analysis of low to very low-level tritium in environmental samples are described. The tritium concentration is measured indirectly by the (3)He ingrowth from radioactive decay after complete initial degassing of the sample. The analytical system is fully computer-controlled and consists in a commercial helium isotope mass spectrometer coupled with a high vacuum inlet system. A detection limit of 0.15 Bq/kg is routinely obtainable for sample sizes of 20g of water equivalent and an accumulation time of three months. Larger samples (and/or longer accumulation time) can be used to obtain lower detection limits. In addition to the benefit of a lower detection limit, another advantage of this non-destructive method lies in the simplicity of the analytical procedure which strongly limits the risk of contamination. An inter-comparison was successfully performed with the conventional beta counting technique on lyophilized grass samples, in a range of tritium concentrations of environmental interest. It shows that the (3)He mass spectrometry method yields results that are fully consistent with the conventional liquid scintillation technique over a wide range of tritium concentrations.
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ABSTRACT: The island of Guadeloupe is located in the middle of the 850 km long Lesser Antilles island arc. Present-day volcanic and geothermal activity is concentrated in two systems both located in the southwestern part of the island (Basse Terre): the La Soufrière volcanic complex and the Bouillante hydrothermal system, some 20 kilometers to the northwest of the volcano. We report here the largest isotopic data set for helium isotopes in hydrothermal gases and waters from both systems, acquired between 1980 to 2012. 3He/4He ratios in the fumarolic gases of La Soufrière volcano have been quite homogeneous and stable over the last thirty years. The average ratio of 8.2 ± 0.2 Ra confirms that the volcano is tapping a MORB-like mantle source. In contrast, the nearby Bouillante geothermal system displays a much lower 3He/4He ratio (4.5 ± 0.1 Ra). He-C elemental and isotopic relationships show that both systems are actually fed by the same magmatic source, and that their marked difference in 3He/4He results from the 4He contamination of the Bouillante deep aquifer by the surrounding wallrock. This conclusion is strengthened by the spatial distribution of 3He/4He ratios which shows that La Soufrière fumaroles and the Bouillante geothermal system are the two end-members of a spatial trend of decreasing 3He/4He ratio with distance from La Soufrière summit dome, implying an increasing addition of radiogenic 4He from the host rocks away from the present-day active volcanic edifice.Journal of Volcanology and Geothermal Research 08/2014; 283. DOI:10.1016/j.jvolgeores.2014.07.003 · 2.52 Impact Factor
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ABSTRACT: A pilot study aimed on possible occurrence of elevated activity of non-exchangable organically bound tritium (NE-OBT) in biota was performed. The first results showed a significant surplus of NE-OBT activity in biota of the valley of Mohelno reservoir and Jihlava river. The liquid releases of HTO from the nuclear power plant Dukovany is the source of tritium in this area. This area can be a source of various types of natural samples for future studies of tritium pathways.Applied radiation and isotopes: including data, instrumentation and methods for use in agriculture, industry and medicine 11/2014; 93. DOI:10.1016/j.apradiso.2014.01.027 · 1.09 Impact Factor
01/2014; International Atomic Energy Agency Vienna., ISBN: 978–92–0–102814–3