JP3406390B2 - Deuterium enrichment method and apparatus - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrolytic concentrator used for concentrating deuterium and deuterium deuterium present in natural water and the like.

[0002]

2. Description of the Related Art Analysis of deuterium in natural water, especially tritium, has become important in the fields of determining the safety of nuclear power plants, predicting crustal movements, measuring hot spring groundwater systems, and the like. Since the tritium concentration is extremely low, it is common to electrolytically concentrate it to improve the measurement accuracy. Conventionally, for the electrolytic concentration of deuterium, a method is known in which a sample solution in which an electrolyte is dissolved is prepared, and plate-like flat plates are opposed to each other for electrolysis. The water contained in the electrolyte is H
_In addition to ₂ O, there are HOD and HOT, which are decomposed into hydrogen and oxygen according to ordinary water electrolysis. However, due to the isotope effect, the decomposition of H ₂ O has priority over the decomposition of HOD and HOT. The concentration of deuterium and tritium in the inside increases and the concentration is performed. Nickel is used as the anode for this electrolysis, and steel, iron, nickel, etc. are used as the cathode, and a sample prepared by washing these electrodes and adding dilute caustic soda as a supporting salt to a water solution containing heavy water. Water is put in a glass container and electricity is applied to carry out electrolysis. Current density from 1
The concentration of deuterium is about 10 A / dm ^2, and the temperature of the liquid is kept below 5 ° C to prevent water from evaporating due to heat generation. To do.

However, this conventional deuterium concentration method has the following problems. Since the sample water is prepared by dissolving the electrolyte in heavy water, the preparation takes time and effort. The electrode is likely to dissolve due to the influence of the electrolyte and the like, and the ionization coefficient fluctuates due to this dissolution. In order to prevent this, pretreatment is necessary, which is troublesome. The generated hydrogen and oxygen reach the opposite electrodes, respectively, and are easily oxidized or reduced, and the electrolysis efficiency is likely to decrease.
Further, the hydrogen and oxygen become explosive and easily explode.

[0004]

It is an object of the present invention to eliminate the drawbacks of the above-mentioned conventional deuterium concentration by electrolysis, in particular the reduction of electrolysis efficiency and the induction of explosion, and to safely and efficiently electrolyze water containing deuterium. It is an object to provide a method and a device that enable concentration.

According to the present invention, the electrolytic solution is divided into an anode chamber and a cathode chamber by an ion exchange membrane, and an electrolytic cell filled with an electrolytic solution which is water containing deuterium is energized to remove the electrolytic solution. A method for concentrating deuterium in which a supporting salt is not dissolved in the electrolytic solution when concentrating the deuterium by electrolyzing to generate hydrogen and oxygen, and an anolyte chamber filled with an anolyte solution containing water containing deuterium. , A cathode chamber filled with catholyte, which is water containing deuterium, partitions the bipolar chamber and adheres to the anode and cathode
And a deuterium concentrating device including an ion exchange membrane and a power supply to both electrodes.

The present invention will be described in detail below. The present invention is
The HOD or HOT is concentrated by electrolyzing water (H ₂ O) containing HOD or HOT and selectively converting H ₂ O into oxygen and hydrogen. When water is electrolyzed, oxygen gas is generated and hydrogen ions are generated in the anode chamber due to the oxidation of water. The produced hydrogen ions reach the cathode through the ion exchange membrane while entraining water molecules, and are reduced at the cathode to generate hydrogen gas. The ionization coefficient in these anode and cathode reactions is
¹ H differs greatly from D ( ² H) and T ( ³ H),
Since depending on the electrolysis conditions to contribute most of the current generation of the ¹ H gas in ¹ H ions and the cathode in the anode, ¹
H ₂ O is reduced by continued electrolysis, resulting in ² H and ³
Concentration of H occurs.

In addition to this, the transport number between isotopes when passing through the ion exchange membrane is slightly different, and the concentration of ² H and ³ H is promoted. However, in the actual reaction, ² H and ³ H are lost by the reaction or are lost as water accompanying gas. Therefore, not all of the deuterium present in the initial electrolytic solution is present in the concentrated solution after concentration, but deuterium that is lost is far less than the concentration rate of the electrolytic solution, and therefore effective deuterium is not available. Concentration of hydrogen can be achieved. In the present invention, unlike the conventional deuterium concentration, since an ion exchange membrane is used, the generated hydrogen gas and oxygen gas are mixed or the generated gas is contacted with the counter electrode to be oxidized or reduced to the original water. With almost no returning, efficient concentration can be achieved, and since there is no danger of detonation, a highly safe concentration operation can be performed.

Further, when both electrodes are brought into contact with the ion exchange membrane of the present invention, the ion exchange groups contained in the ion exchange membrane function as an electrolyte to promote the electrolysis of water, so that the conductivity of water is improved as in the conventional case. It is not necessary to add a supporting salt for the purpose, and thus it is not necessary to prepare an electrolytic solution in which the supporting salt is dissolved. Furthermore, some supporting salts contain components that deteriorate the electrodes and ion exchange membranes, and in conventional deuterium concentration, the exchange of electrodes and ion exchange membranes during long-term operation was essential. On the other hand, in the aspect in which the ion exchange membrane of the present invention is brought into contact with both electrodes, it is not necessary to add a supporting salt, and substantially the same as in pure water electrolysis, there is no component that deteriorates the electrode or the ion exchange membrane. No need to replace. Further, since it is not necessary to remove the supporting salt from the concentrated electrolytic solution and impurities such as electrodes deteriorated by the supporting salt are not mixed into the electrolytic solution, highly concentrated deuterium was easily dissolved. A solution can be obtained.

In the present invention, the ion exchange membrane may be installed vertically or horizontally, but if it is installed horizontally, the electrolysis conditions such as the gas generation amount on the surface of the ion exchange membrane are kept constant, Therefore, the operating conditions are stable and the efficiency is further improved. For the anode used in the present invention, it is desirable to use a metal such as titanium or stainless steel having excellent conductivity and chemical stability or carbon, and to form it as a structure having fine through holes having excellent gas-liquid permeability. . It is also possible to use a mesh, a perforated plate, or a commercially available product in the form of a fabric, which is obtained by processing fibers, a powder sintered body, and a metal plate to make holes. The pore size is 0.001 to 1
mm, and the thickness is preferably about 1 to 10 mm.

As the ion exchange membrane, it is desirable to use a fluororesin type ion exchange membrane which is stable under the generation of oxygen and hydrogen. Examples of commercially available products include Nafion manufactured by DuPont, Aciplex manufactured by Asahi Kasei Corporation, and Flemion manufactured by Asahi Glass Co., Ltd. In the present invention, when the supporting salt is not added to the electrolytic solution, the both electrodes are brought into close contact with the ion exchange membrane.
At that time, since the resistance of the electrolytic solution is large, it is desirable that both electrodes are sufficiently adhered to the ion exchange membrane at a pressure as high as possible.
The pressure required for this is about 1 to 100 kg / cm ² . As the catalyst substance, carbon, noble metal, or the like can be used in addition to nickel and iron. The catalyst may be supported on the electrode, or the catalyst itself may form the electrode, or may be supported on the ion exchange membrane in some cases. As a supporting method, there is a method in which a paste-like substance obtained by kneading fluororesin fine particles such as PTFE and a catalyst powder is applied to an electrode or the like and fixed by a hot pressing method.

Each of these members is placed in an electrolytic cell to electrolytically concentrate deuterium. It is desirable that the electrolytic cell body be made of corrosion-resistant Pyrex glass, and that it has a capacity of about 100 ml to 10 liters in order to improve the concentration ratio, that is, to prevent the amount of the electrolyte solution after concentration from becoming too small. Is desirable. In the present invention, the ion exchange membrane prevents the mixing of hydrogen gas and oxygen gas,
A slight problem does not occur even if both gases are mixed slightly. Therefore, it is not necessary to strictly seal the compartments of the anode chamber and the cathode chamber other than the ion exchange membrane.

The power source of the device of the present invention is not particularly limited,
It is desirable to use a constant-voltage constant-current power supply, and a direct current integrating ammeter is convenient for calculating the electrolysis amount and yield. The current density was set to 1 to 100 A / dm ² during operation, and to prevent evaporation of the electrolytic solution, it is preferred to perform electrolysis while maintaining the below 5 ℃ liquid temperature.

Next, an example of a deuterium concentrating apparatus according to the present invention will be described with reference to the accompanying drawings, but the embodiments do not limit the present invention. FIG. 1 is a vertical sectional front view showing an example of a deuterium concentrator according to the present invention. The deuterium concentrator 1 is immersed in a constant temperature bath 3 in which the cooling water 2 is maintained at a liquid temperature such as 1 ° C. at which it does not freeze. The deuterium concentrating device 1 is housed in a cylindrical or box-shaped main body 4 having an open top, and the device 1 is a horizontal disk-shaped anode 5 and a cathode 6 located below the anode 5. Is fastened with bolts 8 in the vertical direction with the ion exchange membrane 7 interposed therebetween. An anode power feed 9 and a cathode power feed 10 are connected to the left end of the anode 5 and the right end of the cathode 6, respectively, and both the power feeds 9 and 10 are lids 11 fitted into the upper opening of the body 4. Through the hole of the main body 4. A small-diameter cylindrical hydrogen gas outlet is provided in the hole near the left end of the lid 11.
12 is installed, and a cylinder 13 for taking out oxygen gas is placed on the upper surface of the membrane 7. The inside of the main body 4 and the cylindrical body 13 are filled with sample water 14 containing deuterium.

When the temperature of the cooling water 2 in the constant temperature bath 3 is maintained at about 1 ° C. and current is applied between the power feeding bodies 9 and 10 of the concentrating device 1 having such a configuration, the upper surface of the ion exchange membrane 7 is exposed. Electrolysis of the sample water 14 occurs on the lower surface of the contacting anode 5, and oxygen gas and hydrogen ions are generated. The generated oxygen gas rises as it is inside the cylindrical body 13 and is taken out of the system, and hydrogen ions pass through the ion exchange membrane 7 and reach the surface of the cathode 6 in contact with the lower surface of the ion exchange membrane 7. Hydrogen ions are reduced on the surface of the cathode 6 to generate hydrogen gas, which is taken out of the system through the hydrogen gas outlet 12. Generation of hydrogen and oxygen gas by such water electrolysis proceeds more easily in species that are more likely to be ionized (having a larger ionization coefficient),
That is, the three isotopes of hydrogen, ¹ H, ² H and ³ H
Of ¹ H out of ¹ H is almost selectively eliminated and the concentration of ² H and ³ H in the rest of the sample water is increased, so that heavy water containing deuterium ² H and ³ H is concentrated. .

In the apparatus of this embodiment, both electrodes 5 and 6 are in contact with the ion-exchange membrane 7 and the ion-exchange groups of the ion-exchange membrane are used as an electrolyte to allow the electrolytic reaction to proceed, so that it is supported in the sample water. salts no need to add, reduce a large labor for water sample preparation.

FIG. 2 is an enlarged view of a connecting portion between a power feeder and an electrode of another deuterium concentrator. In FIG. 1, the ion exchange membrane, the bolts for fastening both electrodes, and the power feeds to both electrodes are provided separately, but in FIG. 2, a single member that serves as both members is used. Anodes 22 located above and below the ion exchange membrane 21.
Also, the lower ends of the anode power supply 26 and the cathode power supply 27 are screwed into holes 24 and 25 formed in the cathode 23 to support the electrodes and supply power. In the example shown in the figure, since each power feeding body contacts both the anode and cathode electrodes, it is necessary to insulate the other electrodes. Therefore, a thin insulating layer is formed on the inner surface of each of the holes 24, 25 which are in contact with both the power supply members 26.
28 and 29 are formed, and the power supply 26 for the anode is the cathode 23.
Insulators 30 and 31 are arranged on the surface that contacts with the cathode and the surface that the cathode power supply 27 contacts with the anode 22, respectively. Figure 2
The device of (1) has a smaller number of parts than the device of FIG. 1, and can provide a device having a simpler structure.

[0016]

EXAMPLES Examples of deuterium concentration by the deuterium concentration apparatus of the present invention will be described below, but the examples do not limit the present invention.

Example 1 Using iridium oxide powder (200 mesh under) as a catalyst, PTFE aqueous suspension (Mitsui Fluorochemical Co., Ltd.) and Nafion liquid (Aldrich 117) were used as binders, and these were used as naphtha as a solvent. The mixture was kneaded to obtain a pasty substance. After applying this paste on a titanium fiber sintered substrate, at 80 ° C for 5 minutes at 80 kg /
It was fixed at a pressure of cm ² to form an anode.

Platinum particles (100 mesh under) were used as a catalyst, and an aqueous PTFE suspension and a Nafion solution were used as a binder as in Example 1, and these were kneaded with naphtha as a solvent to obtain a paste-like substance. After coating this paste on titanium fiber sintered substrate, at 120 ℃ for 5 minutes,
It was fixed at a pressure of 80 kg / cm ² to form a cathode. The electrode area of these electrodes was 15 cm ² . Use Nafion 117 as an ion exchange membrane, contact the anode and cathode on both sides of the ion exchange membrane, and use bolts and nuts.
It was fastened and pressure-welded at a pressure of 30 kg / cm ² .

As shown in FIG. 1, this clamped electrode was set in a glass body having an inner diameter of 5.5 cm and a height of 15 cm, and 280 ml of sample water (tritium concentration: 0.5 Bq / Kg) was added to generate further generation. A cylinder for separating oxygen gas and hydrogen gas was erected on the anode surface. This cylinder,
A lid body in which a power feeder to both electrodes and a hydrogen gas outlet were fitted was set in the glass main body, the inside of the main body was sealed, and the main body was immersed in a constant temperature bath (1 ° C.).

While measuring the current value using an ammeter,
When continuous electrolysis was performed until the integrated current value reached 750 AH, the amount of sample water decreased to 20 ml. Considering a slight amount of evaporation and the amount of water retained in the electrode, the amount of decrease in this water was a value almost equal to the theoretical value. Concentration factor is 14 and liquid scintillation counter (Packard 2250
From the tritium concentration measurement by type A), it was found that the recovery rate (measured 10 times and averaged) was 0.60. This electrolysis operation was repeated twice more under the same conditions, and the respective recovery rates were measured to be 0.62 and 0.59, indicating good reproducibility.

[0020]

According to the method of the present invention, the electrolytic cell is divided into an anode chamber and a cathode chamber by an ion exchange membrane and filled with an electrolytic solution which is water containing deuterium, and the electrolytic solution is electrolyzed to produce hydrogen and hydrogen. Concentrate the deuterium by generating oxygen
In the method, the supporting salt is not dissolved in the electrolytic solution, which is a method for concentrating deuterium. According to the method of the present invention, the ionization coefficient of ¹ H in water containing hydrogen isotopes consisting of ¹ H, ² H and ³ H is larger than that of other isotopes.
^Since only ¹ H water is almost selectively electrolyzed and converted into hydrogen gas and oxygen gas to disappear, ² H and ³ H concentrations increase and deuterium concentration is achieved. Since an ion exchange membrane is used, the generated hydrogen gas and oxygen gas hardly reach the counter electrode and return to the original water by oxidation or reduction, so that the concentration efficiency can be kept high and by mixing both gases. Safe operation is possible because there is no explosion noise.

The method of the present invention uses an ion exchange membrane as an electrolyte and eliminates the need for adding a supporting salt as in the conventional case.
And, the operation time-consuming that dissolution into the electrolyte of the support salt it is not required. The apparatus of the present invention comprises an anode chamber filled with an anolyte solution that is water containing deuterium, a cathode chamber filled with a catholyte solution that is water containing deuterium, and an anode and
A concentrator of deuterium, characterized in that it comprises a feeder to the ion exchange membrane and the electrodes in close contact with the cathode. According to the device of the present invention, the concentration efficiency can be maintained high and safe operation can be performed as in the case of the method of the present invention.

Further, the anode and the cathode are adhered to the ion exchange membrane.
Since the ion-exchange group of the ion-exchange membrane can be used as the electrolyte, the troublesome operation of adding the supporting salt becomes unnecessary. Furthermore, some supporting salts contain components that deteriorate the electrodes and ion-exchange membranes, and in conventional deuterium concentration, it was essential to replace the electrodes and ion-exchange membranes during long-term operation. the contact with the electrodes then, since the component of the addition of the support salt is deteriorating becomes electrode or ion exchange membrane is unnecessary is not present, replacement of the electrodes and the like become unnecessary. Further, since it is not necessary to remove the supporting salt from the concentrated electrolytic solution and impurities such as electrodes deteriorated by the supporting salt are not mixed into the electrolytic solution, highly concentrated deuterium was easily dissolved. A solution can be obtained. When the ion exchange membrane is installed horizontally, the electrolysis conditions on the entire surface of the ion exchange membrane are substantially equal, and stable electrolysis can be performed.

[Brief description of drawings]

FIG. 1 is a vertical sectional front view showing an example of a deuterium concentrator according to the present invention.

FIG. 2 is an enlarged view of a connecting portion between a power feeder and an electrode of another deuterium concentrator.

[Explanation of symbols]

1 ... Deuterium concentrator 2 ... Cooling water 3 ... Constant temperature bath 4 ... Main body 5 ... Anode 6 ... Cathode 7 ... Ion exchange membrane
8 ... Bolt 9, 10 ... Feeder 11 ... Lid
12 ・ ・ ・ Hydrogen gas outlet 13 ・ ・ ・ Cylinder 14 ・ ・ ・ Sample water 21 ・ ・ ・ Ion exchange membrane 22 ・ ・ ・ Anode 23 ・ ・ ・
Cathode 24, 25 ... Hole 26 ... Anode power supply 27 ...
・ Cathode power supply 28, 29 ... Insulating layer 30, 31 ... Insulator

─────────────────────────────────────────────────── --- Continuation of front page (72) Inventor Takayuki Shimamune 3006 Hommachida, Machida City, Tokyo 30 (56) References JP 54-49498 (JP, A) JP 40-20000 (JP, B1) (58) Fields surveyed (Int.Cl. ⁷ , DB name) C01B 5/02 B01D 59/40 B01J 47/12

Claims (4)

(57) [Claims] 1. An electrolyzer, which is divided into an anode chamber and a cathode chamber by an ion exchange membrane and is filled with an electrolytic solution which is water containing deuterium, is electrolyzed to electrolyze the electrolytic solution to generate hydrogen and oxygen. In the method of concentrating the deuterium according to
A method for concentrating deuterium, wherein a supporting salt is not dissolved in the electrolytic solution . 2. An anode chamber filled with an anolyte solution containing water containing deuterium, a cathode chamber filled with a catholyte solution containing water containing deuterium, and both electrode chambers are defined so as to adhere to the anode and the cathode. Characterized by comprising an ion exchange membrane and a power supply to both electrodes
Deuterium enrichment equipment to. 3. The deuterium concentrator according to claim 2 , wherein the ion exchange membrane is horizontally positioned. 4. Adhering the anode and cathode to the ion exchange membrane
The pressure according to claim 2 or 3 is 1 to 100 kg / cm ^2.
The deuterium concentrator described .