JPS6146226A - Method and apparatus for concentrating tritium in hydrogen isotope by thermodiffusion - Google Patents

Abstract

PURPOSE:To obtain high-purity tritium and simultaneously to reduce the size of a separation tower by adding He to a gaseous mixture of hydrogen isotopes, forming tritium with use of a catalyst, and concentrating the tritium by thermodiffusion. CONSTITUTION:Thermodiffusion separation towers 1, 2, and 3 are connected in series, and the separation towers 1 and 2 and 2 and 3 are connected by pipes furnished with gas circulating pumps 4 and 5. A U-tube 7 having a catalyst bed 7 is connected to a pipe between the separation tower 2 and the circulating pump 5. A gaseous mixture of hydrogenated isotopes added with He is introduced into the separation tower 1, passed through the tower, and brought into contact with the catalyst in the U-tube 7. Consequently, hydrogenated tritium TH and deuterated tritium DH in the gaseous mixture are separated respectively into hydrogen H2 and tritium T2 and into T2 and deuterium D2. Besides, a catalyst bed 8 is also provided between the separation tower 3 and the circulating pump 6. The concd. tritium T2 is taken out from a discharge port 9.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a method for concentrating tritium present in a hydrogen isotope mixed gas by a thermal diffusion method. There are two types of isotopes: light hydrogen (H), deuterium (CD) and tritium (T).

Therefore, there are six types of molecular species in hydrogen molecules, H, D, T, TH, and TDIHD.

A typical method for concentrating and separating monotritium from a mixed gas of these water wing isotopes is the thermal diffusion method, which allows the gas to be handled as is.

A cylindrical thermal diffusion separation column is used as a device for this purpose. This is a double cylinder built vertically.The outer tube is water-cooled from the outside, and the inner tube (heater) is heated from the inside.The mixed gas to be concentrated is passed between these two tubes. As time passes, heavy gas species concentrate at the bottom of this separation column and light gas species condense at the top, reaching equilibrium.The performance of this thermal diffusion separation tube is determined by The distance between the heater (temperature T, ) located on the center line of (
d). In addition, the height h) and the equilibrium separation coefficient ((1) are also related to the design of this tube. This equilibrium separation coefficient is the concentration ratio (separation ability) at equilibrium, and the upper and lower parts of each gas species are It is expressed as a ratio of concentrations, and the higher the number, the better the concentration.Generally, the higher the height of the tower, the better, and there is an optimum value for the width of the tower and the temperature of the heater.Also, the higher the gas pressure, the better the separation. The optimal shape for the tower is small.

(Problem to be solved by the invention) In this way, since the optimal shape of the separation column is uniquely determined regardless of the company of the gas to be concentrated, when there is only a trace amount of the gas to be concentrated, , this tower has the disadvantage of being virtually unusable. For example, when creating a separation column with a large equilibrium separation coefficient and concentrating tritium (T2) present in hydrogen, even if all of the tritium is concentrated at the bottom of the separation column, since tritium has a small volume, it is difficult to extract it. Then, light hydrogen (H2)
It also comes out mixed in. For example 100. If about i amount of tritium existed, the volume would be about 4-1,
At this time, the volume of the separation column is more than 1000, and a large amount of hydrogen also coexists in the lower part, so it is impossible to obtain tritium with high purity. A strategy was taken to add helium (He) to the hydrogen isotope mixture to separate the enriched tritium from other water wing isotopes. That is, when helium is added to a hydrogen isotope mixed gas, hydrogen H, which is lighter than helium (molecular weight M-4), is produced in the separation column.
()(-1), deuterium hydride Dll(M-6) is concentrated on helium ◎Also, TeD('M
-6) 'E and 'l' (K-fin is m under helium)
It is said that tritium can be obtained by at.

However, in this method, even if tritium is concentrated and separated, if TD and TH are mixed in the system, pure tritium cannot be extracted unless one atom is rearranged. This rearrangement of hydrogen atoms is usually carried out using a catalyst.
Ru. In addition, in this method, since TH has the same molecular weight as helium, separation from helium is extremely poor. Further, even if the separation tube is made longer, the purity of tritium is 50% since it is TH.

Therefore, the idea is to use a catalyst to produce TD and TuT.
tT, and 4 and T, Tori, recombination, T, -He and H
, -H13 and -He is a method of concentrating tritium in a thermal diffusion separation tower.

(Means for Solving the Problems) The present invention involves adding helium to the hydrogen isotope mixture gas in advance and using a catalyst when concentrating tritium present in the water wing isotope mixture gas by the thermal diffusion method. Tritium hydride T) IF5 and deuterated tritium TD in the gas, H3 and T.

It is characterized by recombining and concentrating the produced T.

In this method, helium is added in advance to the hydrogen isotope mixture gas in order to keep H2 and T, which interfere with the production of T, away from the catalyst during the recombination reaction of hydrogen atoms on the catalyst surface. The catalyst used for the recombination reaction of hydrogen atoms may be any commonly used metal, but especially platinum,
Niracle, p'' diram, palladium, steel, platinum-rhodium, platinum-palladium, copper-nickel, etc. are preferred.The reaction temperature is 800 to 1000°C, and the reaction vessel is used at a high temperature of, for example, about 1200°C. Use a quartz insulator that can be used.

The enrichment cap used in the present invention consists of an inner H15 equipped with an internal heater and an outer cylinder equipped with an external cooling device. This thermal diffusion separation column, the gas introduction part that introduces helium gas into this separation column, and tritium hydride TH and deuterated tritium DI in the hydrogen isotope mixed gas
Take the molecules T, and ■, and T, and rearrange the catalyst layer into ttr.

Hereinafter, the present invention will be described in detail based on the drawings.

(Example) FIG. 1 shows a schematic diagram of a separation column and a gas treatment device connected thereto used in an example of the present invention.

In FIG. 1, a plurality of thermal diffusion separation columns 1.2.8 are connected in series. This separation column is classified as 1III because of its ease of handling.
Eight pieces were connected to give an effective length of 3+a. The lower part of separation column 1 and the upper part of separation column 2 are connected by two pipes, and the lower part of separation column 2 and the upper part of separation column 3 are connected by two pipes, one of which is pipe 1, in order to equalize the gas concentration. gas circulation pump 4
So 5 was inserted n times. A pipe between the separation column 2 and the gas circulation pump 6 for the purpose of decomposing the foliated tritium TH and deuterated tritium DH in the hydrogen isotope mixed gas into molecules T, H2 and T. Has a catalyst layer on
The U-shaped tubes 7 were connected. Further, a U-shaped pipe 8 having a catalyst layer was similarly connected to the pipe between the separation column 3 and the gas circulation pump 6. 9 is a condensed gas outlet.

Examples, l.

The diameter of each outer cylinder of separation towers 1, 2, and 8 is 4 Q vupr.
The internal heater in the inner cylinder was a quartz tube with a nichrome tube that was moved back and forth twice, and had a diameter of 7111B. The volume of the gas reservoir at the top of the separation column was 0.5 t. First, in separation column 1
! After introducing 10 nol of tritium hydride TH, helium was introduced to bring the pressure to 1 atmosphere. Alumina-supported platinum 0.2 was used as the catalyst, and after evacuation in advance,
While contacting the sample gas at 550°C, the outer cylinder was water-cooled to 20°C, and the internal heater was heated at 860°C overnight at the bottom of the O separation tower 8. could be confirmed using a radiogas chromatograph.

Example 2 The same procedure as in Example 1 was carried out, except that copper was used instead of alumina-supported platinum as a catalyst.

FIGS. 2 and 8 are graphs showing the relationship between tritium concentration and time.

The results using the catalyst Pt/Al, O, Tr at 55°C are shown in Figure 2. TH is concentrated in the upper part (△ mark) and q is about 2
It is. τ is not seen at all in the upper part (○ mark), but in the lower part (e mark), it has already formed and concentrated after 1 hour, and hardly any increase or decrease is seen after that. However, after 24 hours, T in the lower part , is almost no longer visible, and the lower TH (0 mark) has also decreased. - As a result of measuring the amount of tritium remaining in the contact K after use and not being exhausted using a 2π-counter, 0.2μC1 of tritium was detected. Figure 8 shows the results using the mouth catalyst at 0uTt550℃.
) As in the case of t/al, o, T, is seen after 1 hour at the bottom mark and increases slightly thereafter.

In these Examples, similar results were obtained using tritium hydride T)I and tritium deuteride DH.

(Effects of the Invention) As explained above, according to the present invention, tritium hydride Tit and deuterated tritium DH are converted into tritium T
Highly purified tritium can be obtained.

Furthermore, since the total pressure increases with the addition of helium, the shape of the separation column can be made smaller than in conventional methods.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a self-network device according to an embodiment of the present invention, and FIG. 2 is a diagram of a 0.5% Pt/Al2O according to an embodiment of the present invention. FIG. 8 is a graph showing the concentration of T by the metal steel catalyst according to the embodiment of the present invention. 1, 2.8... Separation column 4.5.6... Gas circulation pump 7, 8... Catalyst layer U-shaped tube 9... Concentrated gas outlet 1G, 11.12... Gas Tame Patent Applicant President, Toyama University Figure 1

Claims (1)

[Claims] 1. When concentrating tritium present in a hydrogen isotope mixture gas by the thermal diffusion method, helium is added to the hydrogen isotope mixture gas in advance, and a catalyst is used to concentrate the hydrogen in the hydrogen isotope mixture gas. Tritium oxide TH and tritium deuteride TD are converted into tritium (
T_2) and hydrogen (H_2) and tritium (T_2)
and deuterium (D_2), producing tritium (T
A method for concentrating tritium in a hydrogen isotope by a thermal diffusion method, characterized by concentrating _2) by a thermal diffusion method. 2. At least one cylinder consisting of an inner cylinder equipped with an internal heater and an outer cylinder equipped with an external cooling device, for introducing the hydrogen isotope mixed gas to be concentrated between the inner cylinder and the outer cylinder for concentration processing.
This thermal diffusion separation tower, a gas introduction part that introduces helium gas into this separation tower, and tritium hydride TH and deuterated tritium TD in the hydrogen isotope mixed gas are
2) and a catalyst layer for recombining hydrogen (H_2), tritium (T_2), and deuterium (D_2) using a thermal diffusion method for concentrating tritium in hydrogen isotopes. 3. The concentrating device according to claim 2, wherein the gas introduction section comprises at least a gas circulation pump and a gas reservoir. 4. The concentrating device according to claim 2, wherein the catalyst layer is interposed between the separation column and the gas circulation pump.