Abstract
Transient separation behavior in tritiated water distillation tower packed with materials having ability to adsorb water is investigated analytically and experimentally for nuclear reactor safety. Analytical equations based on the stage model are set up for simulation of the transient behavior of tritium (T) separation from wastewater. It is found that a dimensionless time defined in terms of the inside vapor flow rate and the liquid holdups in tower, reboiler and condenser can correlate variations over time to achieve a steady-state T concentration. However, when mixing with different T concentrations at a feed point occurs, the transition time period becomes longer than expected. Effects of the reflux ratio, the stage separation factor and the total stage number on the transient and steady-state T concentrations are numerically calculated. Variations over time to achieve each steady-state value are compared with experimental data using a small-scale tower. Long time distillation experiment for one month has been completed, and it is confirmed that a distillation column packed with ceramic Raschig rings coated with zeolite 13X adsorbent is hardly affected by water corrosion.
Highlights
Tritium (T) is an evaporable radioisotope having half-decay time of 12.3 years
Long time distillation experiment for one month has been completed, and it is confirmed that a distillation column packed with ceramic Raschig rings coated with zeolite 13X adsorbent is hardly affected by water corrosion
With the increase in the holdup in the condenser and reboiler, mixing at the feed point becomes larger and continues longer. This is because the T concentration at the feed point becomes slightly different from the feed T concentration in the earlier time due to time delay from the transient T concentration to the steady-state one
Summary
Tritium (T) is an evaporable radioisotope having half-decay time of 12.3 years. T is a research target as a fuel for the future fusion reactor. The isotopic chemical exchange system between H2 and HDO shows a comparatively larger isotope separation factor, it needs a special Pt catalyst when it is operated around at 70 ̊C It may not be suitable for large-scale detritiation of wastewater. On the other hand, when packing materials have ability to adsorb water, slightly larger isotope effect is observed in its adsorption or desorption process It was found in our previous studies [14] [15] [16] that enhancement of the isotope separation factor by use of adsorptive packing is possible. Our group has clarified that mesoporous zeolite has shown the larger enhancement of the separation factor in water distillation system and the separation performance for detritiation is improved significantly after various intensive trials These results are applied for an international patent [17]. One month continuous operation of water distillation is tested using a distillation tower packed with ceramic Raschig ring coated with zeolite 13X
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