Study on highly-efficient enrichment of tritium water by use of distillation column packed with hydrophilic adsorbent

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Tritium-waste water will be drained from facilities for a tritium fuel cycle of a future fusion reactor or is presently exhausted from uranium fuel reprocessing plant for a fission reactor. When its concentration is lower than the legally regulated one (60Bq/cm^3), it can be drained from the facilities as it is. When it is higher than the legal value, the drain water has to be diluted by a large amount of fresh water or has to be enriched/separated in the facilities. There is less difficulty in the dilution process. However, when its tritium concentration is much higher than the regulated level, we need to develop a new isotope separation system to decontaminate the tritium-waste water drain at a lower level than the regulated level and to separate a small amount of high-level tritium water. Although the H_2H_2O isotopic exchange method that was used for a heavy water separation of CANDU reactor can be applied to the tritium enrichment, the facilities for the deuterium separation are h … More uge, and they need a special and expensive Pt catalyst. In addition, the Pt catalyst performance is deteriorated by CO that will be included in the exhaust gas of fusion facilities. Therefore, the process needs pretreatment to reduce some pollutants. In the present study, a new isotope separation method to enhance the performance of a classical distillation column with use of hydrophilic adsorbents. As candidates for the hydrophilic adsorbent, silica-gel and zeolite adsorbents were comparatively experimented in the present study. The original isotope separation factor based on the difference in vapor pressure between H_2O and HTO is 1.028. It was found that the isotope separation factor was enhanced to 1.1 to 1.2 with the use of the hydrophilic adsorbent, and therefore it can downsize the scale of the tritium enrichment and separation. The silica-gel column attained the comparatively large separation performance in the various ranges of vapor flow rate. On the other hand, the zeolite column (commercial name Linde molecular sieve 13X) attained the largest isotope separation performance at very small vapor flow rate, but the separation factor decreased at higher flow rate. This is because the exchange reaction between HTO in the vapor phase and H_2O on the adsorbent is comparatively slow. Therefore, the number of transfer unit (NTP) of the zeolite column was much smaller than that of the silica-gel column. The zeolite column is considered to be effective especially for the very small vapor flow rate. The transient tritium enrichment performance was experimentally determined, and it was found that the numerical calculation based on the plate model that uses the number of transfer unit fitted the experimental ones. The experimental and numerical results were presented in the research papers listed in the next page. The abstract of the present scientific research is summarized in a report. Less