Accurate Reference Gas Mixtures Containing Tritiated Molecules: Their Production and Raman-Based Analysis

Abstract

Highly accurate, quantitative analyses of mixtures of hydrogen isotopologues—both the stable species, H2, D2, and HD, and the radioactive species, T2, HT, and DT—are of great importance in fields as diverse as deuterium–tritium fusion, neutrino mass measurements using tritium β-decay, or for photonuclear experiments in which hydrogen–deuterium targets are used. In this publication we describe a production, handling, and analysis facility capable of fabricating well-defined gas samples, which may contain any of the stable and radioactive hydrogen isotopologues, with sub-percent accuracy for the relative species concentrations. The production is based on precise manometric gas mixing of H2, D2, and T2. The heteronuclear isotopologues HD, HT, and DT are generated via controlled, in-line catalytic reaction or by b-induced self-equilibration, respectively. The analysis was carried out using an in-line intensity- and wavelength-calibrated Raman spectroscopy system. This allows for continuous monitoring of the composition of the circulating gas during the self-equilibration or catalytic evolution phases. During all procedures, effects, such as exchange reactions with wall materials, were considered with care. Together with measurement statistics, these and other systematic effects were included in the determination of composition uncertainties of the generated reference gas samples. Measurement and calibration accuracy at the level of 1% was achieved.

µRA—A New Compact Easy-to-Use Raman System for All Hydrogen Isotopologues

“…For cross-checking, the µRA was mounted to a sampling port of the TTS close to the LARA [ 7 ] system, which has been used for some years for tritium accountancy. High-precision reference gas samples were provided by the TriHyDe facility [ 5 ]. Each gas sample was cross-checked with multiple independent methods and devices for its composition, including the analytical tools of TriHyDe (a 2nd LARA system and a new device utilizing the speed of sound for compositional analysis (BGA) [ 6 ]).…”

“…The calculation of all of the relative concentrations was based on a configuration file containing information about the line position, integration width (ROI), region for background subtraction, and correction factors. For the latter, we used a correction for the relative line strength of all isotopologues [ 5 , 11 ] and calibration values from our in-house calibration using an NIST-certified Raman standard [ 12 ].…”

“…Tritium-compatible gas chromatography (GC) systems are, among other drawbacks, bulky, have a long analysis time, produce radioactive off-gases, and are virtually no longer commercially available [ 2 , 3 , 4 ]. Laser Raman spectroscopy is more suitable for the pressure regimens usually found in a typical tritium-handling system at TLK (50 mbar–900 mbar) [ 5 , 6 , 7 ]. The drawbacks of available systems are often related to either non-tritium compatibility or being a rather bulky and complex system.…”

Demonstration of tritium adsorption on graphene

“…22 In contrast, for the tritiation process utilised during this study selfradiolysis of tritium has been taken advantage of. The tritium loading gas mixture was provided via the TRIHYDE facility 37,38 of the Tritium Laboratory Karlsruhe (TLK) and consisted of 97.2% T 2 with the remaining 2.8% being mainly HT and DT. The pressure in the loading chamber was about 400 mbar during the exposure.…”

Refractive index measurement of hydrogen isotopologue mixture and applicability for homogeneity of hydrogen solid at cryogenic temperature in fusion fuel system

“…Indeed, the isotopic exchange will lead the H 2 -D 2 mixture to reach chemical equilibrium between H 2 , D 2 , and Hydrogen Deuteride (HD); but at ambient temperatures, this exchange reaction is slow (of many weeks) [21]. And the equilibrium constant for H 2 +D 2 ⇌ 2HD decreases with decreasing temperature [22].…”