Fusion Science and Technology / Volume 54 / Number 1 / July 2008 / Pages 186-188
Technical Paper / Tritium Measurement
The measurement of the amount of impurities in tritiated gases can be achieved by means of mass spectrometry or gas phase chromatography.
A growing number of disadvantages associated to the "life expectancy" of the mass spectrometer and its tricky maintenance (when enclosed in a gloves box) have led us to acquire a micro gas phase chromatograph. This device is based on a modular concept with the injector, the column and the detector packed in a compact unit which is easy to replace. Thanks to constant improvement in the field of capillary column, new micro chromatographs are now able to perform measurement in absence of pre-column and presence of argon instead of nitrogen as a carrier gas. Of importance, this new apparatus allow better performances (running time: 1 m 30 sec, limit of detection: < 10 ppm).
However, in normal use, this apparatus requires 800 millibar in the inlet, a pressure that doesn't match with the feature of our process gas. To overcome this inconvenience, we have developed an automatic functioning system with a bellows that samples and compresses the gas to pressures compatible with the micro gas chromatograph.
The apparatus and the experimental procedures will be presented as well as experimental performances (reproducibility, detection limits. . .) for some impurities such as nitrogen, oxygen and helium.