During tritium isotopic labelling reactions of compounds of bio-interest like drugs or relevant materials, isotopic exchanges between the tritium gas phase (T2) and the reaction media (liquid phase or surface for materials) occur, leading to isotopic dilution. This phenomenon is detrimental for obtaining the high isotopic enrichment and the high specific activity needed for applications. Therefore it is of paramount importance to determine the isotopic composition of the gas phase. Methods already exist for the deuterium/hydrogen (D/H) isotopic ratio measurement, but none regarding tritium in a glove box environment. Nowadays, in most fusion facilities, the species-selective (or Optical) Penning gauge [Alcatel CF2P] approach is used for the measurement of H2/D2/T2 fuel isotopic composition  and He/D2 concentration  in the neutralized particle exhaust of fusion devices. For instance, this Optical Penning detection system has already been used in JET Tokamak on tritium campaigns and has been chosen by ITER .
After optimization steps, a new equipment similar to the one used for Fusion was recently installed in the Tritium Labelling Laboratory (LMT) at CEA Saclay inside a glove box, in order to determine precisely the tritium/hydrogen isotopic ratio of gas phases.
A completely new system was designed to fit the requirements of both Optical Gas Analysis (OGA) system and tritium handling. The result is a new metal plate including the Penning gauge for the measurement, a Pirani gauge for the determination of the pressure injected, directly linked to the amount of radioactivity. The total volume is reduced at the maximum limiting thus the overall amount of radioactivity handled. Only the Penning sensor and the optical fiber are in a radioactive environment while the visible spectrometer remains in a non-radioactive one.
This Optical Gas Analysis (OGA) method can be used for many other « species » as 3He (which results from the radioactive decay of tritium). It could equip other CEA nuclear platforms.
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Last update : 09/20 2018 (720)