JPS62210039A - Method for extracting and transferring tritium - Google Patents

Abstract

PURPOSE:To extract and transfer the following tritium to the other side of a diaphragm from a medium contg. tritium of one side of the diaphragm which is pure and has easily utilizable pressure by using the diaphragm wherein an electrically-conductive substance for hydrogen ion is sandwiched by hydrogen permeable metallic membrane electrodes are conducting current between both electrodes. CONSTITUTION:A diaphragm is formed by sandwiching both sides of a substance 1 such as ion exchange resin and beta''-alumina which is an electric charge carrier of hydrogen ion by means of metallic membranes 2, 3 (electrodes) such as Pd and Pt wherein hydrogen is selectively permeated and it is no permeable for the other substance. When conducting current between both electrodes, tritium <3>H contained in a medium 4 is dissociated and dissolved in the electrode 2, reaches the interface of the electrode 2 and a proton electric conducto4 1, is ionized and migrated in the electric conductor, reaches the electrode 3, and again becomes at atomic state. This tritium is permeated through the electrode, thereafter made into gaseous tritium, and discharged to 5. In such a way, low-partial pressure tritium contained in the medium is extracted as gaseous tritium which is pure and has easily utilizable pressure by utilizing the simple elecrochemical cell structure.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention is based on a medium containing tritium, which is low in volume. The present invention relates to a method for obtaining a pure gas by continuous separation and recovery, and is characterized by the use of a diaphragm sandwiched between a hydrogen ion conductive substance and a hydrogen permeable metal membrane electrode.

Extraction of an isotopic mixed gas of the chemical form of hydrogen (hereinafter referred to as tritium gas) from a medium containing the isotope (hereinafter simply referred to as tritium) in a form that is particularly easy to reuse, that is, as a pure gas near normal pressure. There is no such method, and only the method described below, which is technically complex, difficult, and disadvantageous in terms of safety and economy, is possible in principle.

First, it is possible to separate and extract tritium using a hydrogen-permeable metal membrane such as palladium or niobium, and it has been put into practical use as a hydrogen purification method.

This method utilizes the selective permselectivity of the membrane for tritium, and there are no problems in terms of operational continuity and the purity of the tritium gas obtained. However, since permeation occurs due to the difference in hydrogen partial pressure on both sides of the membrane, in the case of separation and extraction from a medium with a low tritium partial pressure, the pressure of tritium gas on the permeate side will be even lower, but the tritium recovery rate from the medium will be lower. In order to obtain a sufficient value, the amount of tritium gas on the permeation side must be extremely low and maintained in a vacuum.

In other words, this method requires a combination with a powerful vacuum pump that pumps up the tritium gas to a usable pressure while evacuating the permeate side, but it can be used in a tritium radiation environment and does not contaminate the tritium obtained. In order to do this, a type of pump that does not use oil must be used, which is technically extremely difficult and expensive.

Active metal packed columns that utilize metal hydrogenation reactions can also be used to separate and recover tritium, depending on the conditions. However, this method is essentially a batch operation, and tritium can only be recovered up to the capacity of the filled metal, and tritium cannot be absorbed and released at the same time. Therefore, multiple packed columns are connected in parallel to constantly recover tritium. It is necessary to perform switching operations for alternate collection and discharge while monitoring the volume. Tritium gas is generated by heating and regenerating the gas after once exhausting the tower that has completed this absorption operation, but it is only obtained intermittently due to the operation of the system, and a considerable amount of tritium is always unused and converted into hydride. It is accumulated at ℃. Currently, the only metal that can be used in this law is uranium metal, which is a nuclear fuel material and its acquisition and handling are regulated. The disadvantage is that it is necessary to avoid

In addition, the method of oxidizing tritium using a catalyst, converting it to water, and recovering this water in a °C drying tower or cold trap is widely used as a method for separating and removing tritium from air or inert gas. However, it is extremely difficult to reuse the recovered tritium.

(Problems to be Solved by the Invention) The above-mentioned conventional methods include a selective permeation method using a hydrogen-permeable diaphragm made of palladium, niobium, etc., a method using a hydrogenation reaction using an active metal packed column, and a method using a catalyst. The law is
As mentioned above, it is technically complex.

In addition to being difficult, there were various problems in terms of safety and economy.

(Means for Solving the Problems) As described above, the purpose of the present invention is to carry out the separation, extraction, pressurization, and transfer of tritium using V - simple devices, which were extremely difficult in the conventional methods. Yes, it can be considered as a method of constructing a tritium selective pump.

That is, the present invention uses a diaphragm made of a proton-conductive electrolyte in which a substance serving as a charge carrier for hydrogen ions Z is sandwiched between hydrogen-permeable metal membrane electrodes, and a current is passed between the two electrodes to raise the temperature at °C.
Tritium is continuously separated and extracted from a medium containing tritium gas in contact with one electrode, while pure tritium gas is released from the other electrode into a space separated from the medium by the diaphragm. It's a method.

The present invention makes it possible to extract and transfer tritium Z at a low partial pressure in a medium to tritium gas at a pure and easily available pressure without using complicated equipment or operations.

(Example) An example of the present invention will be described based on FIG. 1. In the figure, 1 is a substance mainly used as a charge carrier for hydrogen ions (hereinafter referred to as a proton conductor), and 2 and 3 are metal membranes that selectively permeate hydrogen 1 and are airtight to other substances. This is a type of electrochemical device, with the upper layer acting as an electrolyte and 2.3 acting as an electrode.It is operated by an external power source and has no mechanically moving parts. ) from which tritium dissociates and dissolves into the electrode g,
It reaches the interface between the electrode 2 and the proton conductor Yu by diffusion permeation. Here, tritium is ionized, migrates through the proton conductor 1 according to the potential difference applied between the two electrodes, and reaches the electrode 3.

Tritium becomes atomic again at electrode 3, becomes tritium gas after passing through the electrode, and is released to 5. Through this series of processes, tritium is transferred to each other,
Separation and extraction from the soil medium, purification into pure tritium gas, and pressurization are performed.

In implementing the present invention, the combination of proton conductors and electrodes can be selected as appropriate depending on the target medium and operating temperature. When using an ion exchange resin as a proton conductor and a platinum film formed on the resin surface by electroless plating as an electrode, the temperature was at room temperature, and when a concentrated potassium hydroxide aqueous solution and palladium foil were used, the temperature was 200°C. The transfer operation was confirmed. At this time, hydrogen was transferred in accordance with the current flowing in the circuit, and transfer in the opposite direction was also possible. The hydrogen pressure difference corresponded to the potential difference and required only about 40 V at room temperature for 10 times the hydrogen pressure ratio on both electrodes.

Possible media from which tritium can be extracted in the present invention include pure tritium gas at low pressure or near vacuum, mixed gases containing tritium, liquids such as molten metals and salts, and solids in which tritium is dissolved. In principle, illegality can be enforced against any of them. Furthermore, even if tritium is a compound such as H2O or NH3, only tritium can be recovered from the compound by electrolysis if a sufficient voltage is applied. In addition to the substances used in the above-mentioned examples, solid electrolytes such as β''-alumina, montmorillonite, and hydrogenated uranyl phosphate hydrate can be used as proton conductors.
In addition to palladium and platinum, the electrode material may also include niobium, vanadium, nickel, etc. depending on the conditions. In addition to the above-mentioned applications, the present invention is also applicable to tritium, which has a relatively small difference in power between 4 and 5. When used as a gas, it can be used as a transfer pump, when used as a Fl sealed container, it can be used as a tritium recovery, storage, and supply device, and when the 5 side is a solid surface, it can be used as a method to prevent tritium permeation leakage in solids. It seems possible to do so.

(Effects of the Invention) According to the present invention, tritium at a low partial pressure in a medium can be converted into pure tritium at a pressure that is easy to use by using a device with a simple electrochemical cell structure without using complicated devices or operations. 0 that can be extracted or transferred into gas

[Brief explanation of drawings]

FIG. 1 shows the configuration of an apparatus for extracting and transporting tritium according to the present invention. What is the number in the diagram? Hail. ■... Proton conductor 2... Hydrogen extraction electrode 3.
・Hydrogen release electrode 4 ・Medium containing low partial pressure hydrogen 5 ・Pure hydrogen 6 ・Power source patent applicant Japan Atomic Energy Research Institute 10 −

Claims (1)

[Claims] Using a diaphragm in which a substance whose charge carrier is mainly hydrogen ions is sandwiched between hydrogen-permeable metal membrane electrodes, tritium is continuously separated and extracted from a tritium-containing medium in contact with one electrode by passing an electric current between the two electrodes, while the other A tritium extraction and transfer method characterized by releasing pure tritium gas from an electrode into a space separated from a medium by the diaphragm.