Sebastian Mirz

First Calibration Measurements of an FTIR Absorption Spectroscopy System for Liquid Hydrogen Isotopologues for the Isotope Separation System of Fusion Power Plants

Abstract Fusion facilities like ITER and DEMO will circulate huge amounts of deuterium and tritium in their fuel cycle with an estimated throughput of kg per hour. One important capability of these fuel cycles is to separate the hydrogen isotopologues. For this purpose the Isotope Separation System (ISS), using cryogenic distillation, as part of the TRitium Enrichment Test Assembly (TRENTA) is under development at Tritium Laboratory Karlsruhe. Fourier transform infrared absorption spectroscopy (FTIR) has been selected to prove its capability for inline monitoring of the tritium concentration in the liquid phase at the bottom of the distillation column of the ISS. The actual R&D work is focusing on the calibration of such a system. Two major issues are the identification of appropriate absorption lines and their dependence on the isotopic concentrations and composition. For this purpose the Tritium Absorption IR spectroscopy experiment has been set up as an extension of TRENTA. For calibration a Raman spectroscopy system is used. First measurements, with equilibrated mixtures of H2, D2 and HD demonstrate that FTIR can be used for quantitative analysis of liquid hydrogen isotopologues and reveal a nonlinear dependence of the integrated absorbance from the D2 concentration in the 2nd vibrational branch of D2 FTIR spectra.

How to make Raman-inactive helium visible in Raman spectra of tritium-helium gas mixtures

Abstract Raman spectroscopy, a powerful method for the quantitative compositional analysis of molecular gases, e.g. mixtures of hydrogen isotopologues, is not able to detect monoatomic species like helium. This deficit can be overcome by using radioluminescence emission from helium atoms induced by β-electrons from tritium decay. We present theoretical considerations and combined Raman/radioluminescence spectra. Furthermore, we discuss the linearity of the method together with validation measurements for determining the pressure dependence. Finally, we conclude how this technique can be used for samples of helium with traces of tritium, and vice versa.

First Calibration of an IR Absorption Spectroscopy System for the Measurement of H-2, D-2, and HD Concentration in the Liquid Phase

Abstract Fusion facilities like ITER and DEMO will circulate several kilograms tritium and deuterium per day in their fuel cycle. For the separation of the hydrogen isotopologues the Isotope Separation System (ISS), based on cryogenic distillation, was developed at Tritium Laboratory Karlsruhe (TLK). One challenge is to find and develop an in situ and real time method to analyse the isotopologic composition of the column content. Calibration tests with IR absorption spectroscopy (FTIR) with chemically equilibrated samples have been performed at the Tritium absorption IR Spectroscopy Experiment (TApIR). From this previous work and from literature, it is known that the dependence between IR absorbance and the concentrations is non-linear. This makes it impossible to extrapolate the calibration from equilibrium to non-equilibrium samples. This work shows a full D2, H2, and HD calibration with samples in and off the high temperature. This enables us now to measure composition of inactive liquid hydrogen samples with an accuracy of better than 5%. In addition, one of the main challenges on the way to a calibration with tritiated mixtures is shown, the IR absorbance at molecular dimers, which tremendously increases the complexity of IR absorption spectra.

Design of a Spectroscopy Experiment for All Hydrogen Isotopologues in the Gaseous, Liquid, and Solid Phase

Abstract An integral part of the fuel cycle of future fusion facilities is the isotope separation system (ISS). The Tritium Laboratory Karlsruhe (TLK) is currently developing a system to monitor the concentration of all six hydrogen isotopologues Q2 (H2, HD, D2, HT, DT, T2) in the liquid phase in the cryogenic distillation process of the ISS. Liquid inactive Q2 were already successfully analyzed under cryogenic conditions via infrared (IR) absorption spectroscopy and calibration data for D2 is provided by previous experiments at TLK. The new experiment T2ApIR (Tritium Absorption Infrared Spectroscopy Experiment) is designed to be fully tritium compatible to perform a complete calibration of the IR absorption measurement system with all six hydrogen isotopologues in the liquid phase under conditions similar to the ISS. This provides a unique non-invasive, inline and real-time measurement system for isotopologic concentration determination, ready for implementation in the cryogenic distillation column.