Influence of Framework Silica-to-Alumina Ratio on the Tritiated Water Adsorption and Desorption Characteristics of NaX and NaY Zeolites

The fixed-bed adsorption process has been studied as one of the promising processes for the recovery of tritiated water in the field of nuclear fusion. The influence of the framework SiO₂/Al₂O₃ ratio ranging from 2.0 to 10.0 on the tritiated water adsorption and desorption characteristics in the H₂O-HTO binary systems was systematically examined using NaX and NaY zeolites. A large difference in isotherm was observed by changing the SiO₂/Al₂O₃ ratio from 7.0to 10.0. The framework SiO₂-to-Al₂O₃ ratio has a slight effect on the isotope separation factor. The capacity of removable water from NaY10.0 around room temperature is approximately four times larger than that from NaA2.0 even though both zeolites have nearly the same capacity for absorbable H₂O at nearly P=P0= 1:0. The weaker interaction generates the isotope effect on desorption. The HTO dehydration ratio has a strong interrelation with the accumulative amount of purge gas. Dehydration is independent of the flow rate of the purge gas. On the design side of the water adsorption process with multi-absorber systems, the size of the water absorber such as a dryer or dehumidifier can be downscaled with NaY10.0 as the adsorbent since the consideration of the heating and cooling periods necessary for the temperature swing desorption process is not required in the NaY10.0 column.     

Separation Factor of Hydrogen and Deuterium by Suspension Electrolysis Using Mercury Cathode

The electrolytic separation factor between hydrogen and deuterium was examined using mercury or else platinum cathode immersed in IF NH₄Cl in 10v/oD₂O water containing cobalt sulfide powder in suspension. Several other kinds of powdered materials in suspension were also studied. In the case of mercury pool electrode, the materials added in suspension were effective in enhancing the hydrogen/deuterium separation factor, but powder suspension was ineffective on platinum plate electrode. The powdered material added in suspension served as catalyst on the hydrogen evolution reaction at the mercury cathode. The influence of the applied potential on the separation factor was studied over the temperature range of 15°~80°C. The results provided an indication of the rate-determining steps governing the electrolytic hydrogen evolution.

The experimental values obtained for the separation factor and activation energy gave an insight into the mechanism of the rate-determining step of the hydrogen evolution at the working electrode.     

Measurement of HETP of SUS Dixon Ring and Porcelain Packing in Small-Scale Water Distillation Column for H2O-HTO Isotope Separation

Series of water distillations in a total reflux mode have been performed in a 100cm height column of 1.6cm I. D. in order to measure values of HETP for various packings, that is, one brass or three SUS Dixon rings and three porcelain packings. The HETP were measured by changing the vapor flow rate within the column. The SUS Dixon ring of 1.5 mm diameter and the porcelain packing of 1.2 mm O. D. had a small HETP (～5cm), but could not meet a large vapor flow rate because of a large pressure drop. The SUS Dixon ring of 6.0 mm diameter had a small HETP (～6cm) in the vapor flow rate under 2g/min, but the HETP value increased with increasing the vapor flow rate. The pressure drop for the ring, however, was almost constant in the range of these measurements.