A Comparison of Two HTO Air Sampling Techniques

Bishop, C.T.; Carfagno, D.G.; Farmer, B.M.; Lacy, V.C.; Yanko, W.H.

doi:10.13182/fst85-a24643

Cited by 2 publications

(2 citation statements)

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“…Tritium oxide (HTO) is adsorbed on silica gel to monitor airborne tritium in the environment. [1][2][3][4] Adsorption of HTO also has been recommended for structural studies of silica gel by measuring surface hydroxyl group concentrations. 5,6 Tracer studies, however, indicate that tritium concentrations measured in water desorbed from the silica gel are consistently lower than in the original tracer solution.…”

Section: Introductionmentioning

confidence: 99%

“…Tritium oxide (HTO) is adsorbed on silica gel to monitor airborne tritium in the environment. − Adsorption of HTO also has been recommended for structural studies of silica gel by measuring surface hydroxyl group concentrations. , Tracer studies, however, indicate that tritium concentrations measured in water desorbed from the silica gel are consistently lower than in the original tracer solution. ,, Presented here is a study to examine the contributions of isotopic exchange and the vapor pressure isotope effect in reducing the tritium concentration of HTO adsorbed on and then desorbed from silica gel.…”

Section: Introductionmentioning

confidence: 99%

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Isotopic Exchange and Vapor Pressure Isotope Effect in Tritium Oxide Adsorption on Silica Gel

1998

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Consistently lower tritium concentrations found in water distilled from silica gel than in the water vapor that had been adsorbed from air stimulated this study of isotopic exchange and the vapor pressure isotope effect for tritiated relative to nontritiated water. Tritium concentrations were compared for various amounts of water vapor adsorbed on and desorbed from a fixed amount of silica gel dried at 100 °C. Tests of the hypothesis that a constant percent water and hydroxyl groups bound in the silica gel undergo isotopic exchange with the adsorbed tritiated water were performed with a type of silica gel generally used in ambient air monitoring. Separate tests were performed to evaluate the additional impact of the vapor pressure isotope effect in reducing the tritium concentration in water vapor relative to the condensed phase. This occurs (1) in the tests when air is swept through tritiated water to generate airborne HTO for adsorption on the silica gel and (2) in distilling water adsorbed on silica gel for tritium analysis. A value for exchangeable water on the silica gel of 5.9 ( 0.2% was found when adsorbing between 7 and 22% water. The isotope effect reduced the tritium concentration in air relative to water by 11% at 20 to 22 °C and by 4% in azeotropic distillation at 80 °C.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Isotopic Exchange and Vapor Pressure Isotope Effect in Tritium Oxide Adsorption on Silica Gel

1998

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Correcting Tritium Concentrations in Water Vapor Monitored with Silica Gel

Rosson

Jakiel²,

Klima³

et al. 2000

Health Physics

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A correction is needed to calculate the activity concentration of airborne tritium oxide when dried silica gel is used as the collector. A tracer study using tritiated water with silica gel showed that the concentration of tritium in desorbed water is lower than that in adsorbed water by a fraction that increases with the amount of adsorbed water. The hypothesis was tested that adsorbed tritiated water is diluted by isotopic exchange with both non-tritiated water and hydroxyl groups within the silica gel matrix. The extent of dilution was measured from 4% to 14% adsorbed water, which is typical of moisture on field collectors for monitoring airborne tritium oxide. For this range of percent adsorbed water, the inferred percent exchangeable water in the silica gel under study was 6.3 +/- 0.1%. This value compares to the silica gel weight loss of 5.3% after heating to 1,050 degrees C. An explanation of the difference between 6.3% and 5.3% is proposed. The contribution of the HTO/H2O vapor pressure isotope effect was considered in calculating isotopic exchange. A curve is presented for correcting the measured tritium concentration in the distillate from the silica gel as a function of the amount of adsorbed water. The tritium tracer procedure is recommended for determining the percent exchangeable water in other silica gels to correct tritium measurements of water vapor collected by them.

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A Comparison of Two HTO Air Sampling Techniques

Cited by 2 publications

References 1 publication

Isotopic Exchange and Vapor Pressure Isotope Effect in Tritium Oxide Adsorption on Silica Gel

Isotopic Exchange and Vapor Pressure Isotope Effect in Tritium Oxide Adsorption on Silica Gel

Correcting Tritium Concentrations in Water Vapor Monitored with Silica Gel

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