| Testing of breeding blanket module (TBM) is one of ITER's important objectives, it consist of tritium extraction system (TES), coolant purification system (CPS) and tritium measurement system (TMS).The major function of TES is to achieve real-time tritium extraction from TBM, and the major function of CPS is to remove tritium and other impurities from helium coolant. For knowing tritium extraction efficiency, tritium purification efficiency and tritium productivity, TMS should analyze concentration of tritium and other impurities quickly and accurately.Present methods for hydrogen isotopes analysis like mass spectrum, ionization chamber, liquid scintillation counter, proportional counter and calorimetric method are not meet requirements of TBM, because it must have fast detection and mini equipment.Micro gas chromatography with small thermal conductivity detector, it just consumes little sample volume, and the retention time became shorter finally. It has been proposed by ITER international organization to on-line analysis of hydrogen isotopes and other impurities in ITER tritium system. But micro gas chromatography technology in our country needs considerable development can meet online tritium measurement.This paper researched the key technology for hydrogen isotope online analysis using micro gas chromatography. They are mainly about the preparation and performance of stationary phase, optimization of conditions and establishment of quantitative methods. Aim for determining the best packing preparation method and instrument parameters, developing a new kind of technique to detect hydrogen isotopes in helium stream, and finally translating this technology into micro gas chromatography. In addition, this paper also researched the gas-solid absorption distribution behavior of hydrogen isotope in column, and predicted tritium component chromatographic retention behavior.(1)Using Al2O3 as base material, modified by MnCl2 and Cr2O3 respectively, prepared two kinds of packing for hydrogen isotopes analysis at 77K.The topography, composition, specific surface area, pore volume, pore size, thermostability and surface combining state of packing were characterized by some instruments. Results showed that, after modification, packing have moderate adsorption activity, the surface is uniformly. Also they have excellent pore size distributing and selectivity of adsorption performance. The hydrogen isotopes adsorption capacities of those packing were researched with static volume device. Adsorption isotherm of H2 and D2 were obtained, it showed that the packing has larger isotope effect. According to capacity factor model, gas-solid adsorption distribution curve of six hydrogen isotope molecules in column were calculated, it indicated that the gas-solid adsorption distribution of hydrogen isotope in column is a liner function, the spectra will show Gaussian shaped, it could helpful for accurate quantitative. (2)Using 0.8 and 2mm inner diameter stainless steel columns packed with modified 5%,19%,30%, 50% particles, respectively installed them on the GC-14C gas chromatography for hydrogen isotopes analysis. In order to determine the 9system's best operating parameters, several rounds of experiment were carried out under different experimental conditions. The results showed that best modification agent is 20%, the best activation temperature and time are at 200 to 250℃and 5 to 12h respectively. Compared with Al2O3, the modified columns restrained the split of para- and ortho-hydrogen, separated He, H2, HD and D2 gas mixture successfully. The separation factor and column efficiency are better than conventional Al2O3 column. Chose Ne to be carrier gas, the sensitivity, retention value and peak shape are all superior to He; the carrier gas flow rate, injection volume and sample content range are also optimized, under this condition, He, H2, HD and D2 could be separated within 120 seconds, the best separation factor of H2/HD is 1.118. The RSD of system's repeatability is less than 3%.(3)For confirming the accuracy quantitative methods about structure of above system, verification test were carried out by two kinds of quantitative methods, it was found that using peak area calibration factor normalization method is more accurate than calibration curve method. The mean relative deviation of analysis results about He, H2 and D2 is 0.0252, it meets the quantitative requirements completely.(4)In order to explain and forecast the retention behavior of tritium gas in the column, this paper proposed a mathematical model about the relationship between reduced mass and retention time, the experimental revealed they fitted linear relation, the related coefficient is greater than 0.97.Using this relationship could predict retention time of tritium gas, it will within 4 minutes for Cr2O3/Al2O3, and 3 minutes for MnCl2/Al2O3. |
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