Toshihiko Yamanishi

Separation of Hydrogen Isotopes by an Advanced Thermal Diffusion Column Using Cryogenic-Wall

An experiment on the separation of hydrogen isotopes has been carried out by using a thermal diffusion column with a “cryogenic-wall” cooled by liquid nitrogen. The separation factor was compared w...

Separation of hydrogen isotopes by the cryogenic-wall thermal diffusion column

In this paper experimental study for separation of hydrogen isotopes has been performed by using a cryogenic-wall thermal diffusion column refrigerated by liquid nitrogen. The column separated H-D system at total reflux and total recycle operational modes. The dependences of the separation factor on the column pressure and hot wire temperature were examined for the total reflux experiments. The optimum pressure observed was 30 kPa at 1273 K. The maximum separation factor at 473 K was larger than that at 1273 K since HD molecules were not produced on the hot wire by the isotope exchange reaction. The separation factor was exponentially proportion al to the hot wire temperature. In the total recycle experiments, the separation factor was measured under a variety of flow rates, positions and compositions of the feed stream. The increase in the feed flow rate deteriorated the separation factor appreciably.

Analysis of hydrogen isotopes with a micro gas chromatograph

Abstract In the fuel cycle system of fusion reactors, analysis of hydrogen isotopes is very important from the view point of system control. The gas chromatograph (GC) with cryogenic separation column (cryogenic GC) is one of the most extensively used methods for the analysis of hydrogen isotopes. The micro GC with cryogenic column is expected to improve analysis time, that is a major disadvantage of conventional GC. The present authors have modified the micro GC to use its separation column at cryogenic temperature for H2, HD and D2 mixture analysis. Obtained retention time of H2, HD and D2 was about 85, 100 and 130 s, respectively. Peak resolution between H2 and HD, these are nearest each other, was about 1.0. These result suggests that the column developed in this work attained the practical level for the separation of hydrogen isotopes without tritium. Present detection limit of hydrogen isotopes was about 100–200 p.p.m., and it can be improved further by adjustment of separation column.

Characteristics of the ‘Cryogenic-Wall’ Thermal Diffusion Column for Separation of Hydrogen Isotopes

AbstractExperimental study for separation of hydrogen isotopes has been performed by using a ‘cryogenic-wall’ thermal diffusion column. The separation experiments were carried out with H-D system under total reflux and continuous feed operation mode. The dependence of the separation factor on the column pressure were examined for both experiments. In the total reflux experiments, the maximum separation factor of the ‘cryogenic-wall’ column was about 12.4 times larger than for the ‘water cooled-wall’. The effect of the feed flow rate on the separation factor and on the optimum pressure was examined in the continuous feed experiments. As the feed flow rate increased, the separation factor decrease appreciably, and the optimum pressure shift progressively to higher region.

Experimental study of separative characteristics of cryogenic-wall thermal diffusion column for H-D and H-T mixtures

The separative characteristics of H–D and H–T mixtures have been measured by using a cryogenic-wall thermal diffusion column (CTD). The experiments were carried out under a continuous feed operation mode. Steady state was attained within 30 min for the 1.5×0.3 m φ column used. As the feed flow rate increased, the separation factor of the column decreased and the optimum pressure shifted to a larger region both in the H–D and H–T systems. The maximum separation factor was 16.4 for H–D and 26.0 for H–T at a feed flow rate of 25 cm3 min−1 (at 0.1 MPa and 273 K). The optimum pressure, where the maximum separation factor was obtained, was slightly larger in the H–T system than in the H–D system.

Preliminary Experimental Study for Cryogenic Distillation Column with Small Inner Diameter, (I)

A preliminary experimental study was performed by using a cryogenic distillation column which has a small inner diameter (~2 cm). The column separated N2 and Ar at a total reflux operation mode. The experimental column simulates adequately some significant features of a hydrogen isotope distillation column. A significant result obtained is that the mesh of the wire holding the packings was required to be as large as possible and conically-shaped for avoiding the flooding. The dynamic column behavior predicted by computer-aided simulation is in very close agreement with the experimental observation. The HETP value was measured for Dixon Ring under a variety of vapor flow rates within the column. The measured value is approximately 5.5 cm. The over-all HETP value is almost independent of the vapor flow rate. However, if the vapor flow rate is excessively small, the HETP value for the upper half of the column differs slightly from that for the lower half.

Tritium behavior in the Caisson, a simulated fusion reactor room

Abstract In order to confirm tritium confinement ability in the deuterium–tritium (DT) fusion reactor, intentional tritium release experiments have been started in a specially fabricated test stand called ‘Caisson’, at Tritium Process Laboratory in Japan Atomic Energy Research Institute. The Caisson is a stainless steel leak–tight vessel of 12 m3, simulating a reactor room or a tritium handling room. In the first stage experiments, about 260 MBq of pure tritium was put into the Caisson under simulated constant ventilation of four times air exchanges per h. The tritium mixing and migration in the Caisson was investigated with tritium contamination measurement and detritiation behavior measurement. The experimental tritium migration and removal behavior was almost perfectly reproduced and could almost be simulated by a three-dimensional flow analysis code.

Single column and two-column H-D-T distillation experiments at TSTA

Cryogenic distillation experiments were performed at TSTA with H-D-T system by using a single column and a two-column cascade. In the single column experiment, fundamental engineering data such as the liquid holdup and the HETP were measured under a variety of operational conditions. The liquid holdup in the packed section was about 10--15% of its superficial volume. The HETP values were from 4 to 6 cm, and increased slightly with the vapor velocity. The reflux ratio had no effect on the HETP under the condition that the vapor velocity was almost constant. For the two-column experiment, dynamic behavior of the cascade was observed.

Simulation of Tritium Behavior after Intended Tritium Release in Ventilated Room

At the Tritium Process Laboratory (TPL) at the Japan Atomic Energy Research Institute (JAERI), Caisson Assembly for Tritium Safety study (CATS) with 12 m3 of large airtight vessel (Caisson) was fabricated for confirmation and enhancement of fusion reactor safety to estimate tritium behavior in the case where a tritium leak event should happen. One of the principal objectives of the present studies is the establishment of simulation method to predict the tritium behavior after the tritium leak event should happen in a ventilated room. The RNG model was found to be valid for eddy flow calculation in the 50m3/h ventilated Caisson with acceptable engineering precision. The calculated initial and removal tritium concentration histories after intended tritium release were consistent with the experimental observations in the 50 m3/h ventilated Caisson. It is found that the flow near a wall plays an important role for the tritium transport in the ventilated room. On the other hand, tritium behavior intentionally released in the 3,000 m3 of tritium handling room was investigated experimentally under a US-Japan collaboration. The tritium concentration history calculated with the same method was consistent with the experimental observations, which proves that the present developed method can be applied to the actual scale of tritium handling room.

Hydrogen isotope separation characteristics of cryogenic distillation column

Abstract Cryogenic distillation is a promising method for a hydrogen isotope separation system in the fuel cycle of nuclear fusion reactors. However, sufficient experimental information has not yet been obtained to enable us to achieve the cascade operation of cryogenic distillation columns. The present study aims to obtain such information. The experimental apparatus used in the present study is composed of a cryogenic distillation column, gas chromatographs and a helium refrigerator. The cryogenic distillation column can be operated in three modes; the total reflux mode, the total recycle mode and the total recycle mode with a feedback stream. In each experiment, the gas in the condenser and the gas or liquid in the reboiler are sampled and analyzed with gas chromatographs after the column pressure, the pressure drop in the packed section, and other operating conditions reach a steady state. The experimental results are arranged with the pressure drop in the packed section and the height equivalent to a theoretical plate (HETP). As a result of the total reflux experiments, it should be noted that the pre-flooding operation of the distillation column before the total reflux operation improves the separating efficiency of the distillation column and reduces the HETP value. The experimental results also show that the pressure drop increases with vapor velocity. The flooding point or the loading point is not observed with vapor velocity lower than 20 cm/s. As a result of the total recycle experiments, the HETP value is observed to decrease with reflux ratio.