KR100444257B1 - A method of seperation for hydrogen isotopes - Google Patents

Abstract

The present invention relates to a method for separating hydrogen isotopes, and specifically, to separate tritium from tritiated heavy water through a multistage adsorption process consisting of a low temperature part and a high temperature part using different adsorption effects between a metal hydride and a hydrogen isotope. The method relates to the separation of hydrogen isotopes, which simplifies the hydrogen isotope separation process, reduces costs and ensures radiochemical safety.

Description

A method of seperation for hydrogen isotopes

The present invention relates to a method for separating hydrogen isotopes, and specifically, to separate tritium from tritiated heavy water through a multistage adsorption process consisting of a low temperature part and a high temperature part using different adsorption effects between a metal hydride and a hydrogen isotope. As for the method, it is possible to separate the hydrogen isotopes, which simplifies the hydrogen isotope separation process, reduces the cost and ensures radiochemical safety.

Hydrogen is an element that is configured from natural with deuterium and tritium gyeongsuso of 99.985%, 0.015%, of which, mass number is 2, heavy hydrogen (deuterium) has ² H with hydrogen isotopes is configured as one proton and one neutron Or D. Isotope tracer that investigates chemical and biochemical reactions containing hydrogen using properties that are slower than light hydrogen, and participates in all chemical reactions like ordinary hydrogen. In order to separate deuterium from natural hydrogen, it can be obtained by using a centrifuge or by electrolyzing heavy water (D ₂ O). In addition, tritium is a hydrogen isotope with a mass number of 3, denoted as ³ H or T, β ^- radioactive and having a half-life of about 12 years transferred to ³ He. Tritium exists naturally despite its short lifespan, which is produced by nuclear reactions in the upper layers of the atmosphere by cosmic rays. It contains 10 ^-19 ~ 10 ^-17 % of hydrogen or rainwater in the atmosphere, and is used as an isotope tracer and the main raw material for fusion reaction.

Currently, the world's commercially available power reactors can be divided into light reactors developed by the United States, hot gas cooling reactors in the United Kingdom and heavy water reactors in Canada, and candu reactors developed in Canada. Both modulators and coolants use heavy water.

Heavy water reactor is a reactor that uses heavy water as a modulator and coolant. Heavy water acts to slow down neutrons compared to hard water and also absorbs neutrons less than hard water. It is used for combustion. However, heavy water is expensive, so the plant design should keep the amount of heavy water injected into the reactor to a minimum and minimize the leakage and loss of heavy water during operation.

Deuterium in the heavy water in the reactor generates a tritium by neutron absorption reaction as shown in Scheme 1 below.

D + n-> T + gamma rays

In Reaction Scheme 1,

D is deuterium, T is tritium and n is neutron.

As shown in Scheme 1, the heavy water in the reactor is changed to tritium by the neutron absorption reaction, resulting in the loss of heavy water. As a method of reducing tritium in deuterium, there are a method of diluting by mixing and diluting heavy water having relatively different concentrations of tritium, and a method of removing tritium in heavy water by chemical exchange.

(1) concentration decrease by tritium substitution

In the case of coolant heavy water, the heavy water is withdrawn from the reactor to increase the purity by the upgrader, and then stored separately without recirculation, and then used as a moderator for the subsequent stage. It is a way to reduce the concentration.

(2) Tritium removal by tritium removal facility

Induces chemical exchange between hydrogen isotopes to extract tritium to remove tritium from deuterium. The tritium separation process consists of a transfer process and a concentration process to remove tritium. The tritium removal process can be divided into water distillation process, electrolysis process and low temperature distillation process. The other complex processes of tritium removal equipment consist of electrolysis and low temperature distillation, liquid phase catalyst exchange and low temperature distillation, electrolytic catalytic exchange and low temperature distillation. The method requires high isotope separation techniques because of the low concentration of tritium in heavy water.

Commercially available methods for the separation of tritium include French I.L.L. There is a method using a tritium removal facility for a reactor and a Canadian candu reactor.

The method comprises the step of performing a hydrogen isotope chemical exchange reaction at a high temperature (step 1); It consists of a cryogenic distillation step (step 2). In step 1, tritiated deuterium and deuterium are subjected to a hydrogen isotope chemical exchange reaction in a platinum catalyst tower loaded with activated carbon in a superheated gas at 200 ° C., and this reaction is repeated several times. Is recycled to the reactor. At this time, the deuterium injected in step 1 is tritiated to become tritium deuterium, and step 2 is a cryogenic distillation process operated at minus 250 ° C. The tritiated deuterium is separated from the ultra low temperature and the tritium is high at the bottom of the tower. And deuterium with low boiling point is separated to the top of the tower. The tritium separated into the bottom of the tower is a radioactive material, so it is either disposed of as waste or recovered as radioactive isotopes, and the deuterium separated into the top of the tower is circulated to step 1. For the high resolution of tritium and deuterium, the cryogenic distillation column is composed of several multi-stage towers.

The process, commercialized in the early 1970s, consumes excessive energy by repeating the superheated vaporization of tritiated heavy water in step 1, and in step 2, it separates tritium and deuterium at very low temperatures of minus 250 ° C. The technical problems in the distillation column due to the cryogenic coagulation phenomenon of thermal insulation and impurities, and enormous liquefied energy costs in the process of cryogenic liquefaction of a large amount of tritium deuterium. In addition, when tritiated heavy water leaks from the platinum catalyst tower as superheated steam at 200 ° C., or high pressure tritium leaks due to loss of ultra low temperature, there is a risk of environmental pollution and radiation exposure.

Therefore, the present inventors separate tritium from tritiated heavy water through a multistage adsorption process consisting of a low temperature part and a high temperature part using an isotope effect in which adsorption tendencies between hydrogen isotopes to a metal are solved to solve the above problems. As a result of this study, the hydrogen isotope separation method has been completed, which simplifies the hydrogen isotope separation process, reduces the cost, and guarantees radiochemical safety.

An object of the present invention is a method for separating tritium from tritiated heavy water, wherein the fixed metal hydride and the flowing hydrogen isotope are countercurrently contacted in a reactor composed of a low temperature part and a high temperature part using a rotary valve to separate hydrogen isotopes. To provide a way.

1 is a hydrogen isotope separation process diagram consisting of a low temperature portion and a high temperature portion

2 is a heat exchange circuit diagram of a low temperature part and a high temperature part;

3 is tritium separation process diagram

Explanation of symbols on the main parts of the drawings

1 to 8: Reactor 10: Rotary valve

11: rotating part 12: fixed center axis

13: fixed plate 14, 26, 28: injection

15, 16, 25, 27: discharge furnace 31: catalytic reaction tower

32, 35, 36, 37, 41: piping 33: electrolysis tank

34: recombiner 40: rotary valve for hot and cold separation

The present invention is a method for separating tritium from tritiated heavy water, the method of separating the hydrogen isotope by the countercurrent contact of the fixed metal hydride and the flowing hydrogen isotope in a reactor consisting of a low temperature section and a high temperature section using a rotary valve To provide.

Hydrogen isotope separation in the present invention is a metal hydride consisting of palladium and the like, light hydrogen (H ₂ ), deuterated light hydrogen (HD), deuterium (D ₂ ), tritiated light hydrogen (HT), tritium deuterated (DT) and The isotope effect of the adsorption degree of tritium (T ₂ ) is different, and the hydrogen isotope is supplied to the multi-stage fixed bed adsorption tower device composed of a low temperature part and a high temperature part through a rotary valve.

That is, the heavy or light isotopes are gradually concentrated in the solid phase and the gas phase, respectively, via the multi-stage column, and the isotopes are separated to the desired level by allowing the cold and hot portions to proceed in opposite directions.

As a metal used for said metal hydride, the metal and alloy which adsorb | suck hydrogen are used. Preferably, palladium, vanadium, niobium, titanium, uranium and LaNi ₅ , CaNi ₅ , Ti _0.2 V _0.3 , MmNi _2.5 Co _2.5 , MmNi _4.5 Co _2.5 , MmNi _4.5 Al _0.3 , MmNi _4.5 Mn _0.5 , TiCo _0.5 Fe _0.5 , LaCo ₅ , VNb, LaNi _5-x Al _x , TiV, TiCr, TiCr ₂ , TiCrMn, Ti ₂ Mo, TiMo ₂ , TiMn, FeTi, Fe _0.6 TiMn _0.2 , TiCo, TiNi, Mg ₂ Ni, MmNi ₅ , V _0.9 Alloys of Cr _0.1 , Pd _0.75 Al _0.25 and ZrNi are used. Where Mm is an alloy of Ce, La, Nb, Pr and other rare earth metals, for example composed of 50% Ce, 27% La, 16% Nb, 5% Pr and 2% other Rare Earth metals. .

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

1 is a view showing a separation process of the hydrogen isotope using a fixed bed adsorption reaction having a function of the low temperature and high temperature portion according to the present invention.

DT + MD _2- > D ₂ + MDT

D ₂ + MDT-> DT + MD ₂

In the above scheme,

D represents light hydrogen isotopes, T represents heavy isotopes, and M represents metal.

Hydrogen isotope chemical exchange reactions may be represented as in Schemes 2 and 3. Scheme 2 shows the case where heavy hydrogen isotopes are adsorbed better on the metal than light ones, and Scheme 3 shows the case where light hydrogen isotopes are better adsorbed than heavy ones. The reaction follows the reaction formula 2 or 3 depending on the type of metal or the reaction temperature.

The reaction proceeds from reactor 1 to reactor 8 of FIG. 1, the reactor may be installed by adjusting the number to obtain the desired resolution, and the length of the reactor may be different. As the reactor becomes longer, one reactor can serve as a multi-stage theoretical stage, and the reactor is filled with the above-described metal hydride, and is filled in the form of porous particles to increase the reaction surface area.

Specifically, the metal hydride installed in the reactor is installed in a fixed position with the reactor, the hydrogen gas flows in the direction of the reactor 1 to the reactor 8, and also for rotary concentration of hydrogen isotope By installing the valve 10 and rotating the rotation part clockwise, an effect such as that the metal hydride flows from the reactor 8 toward the reactor 1 is obtained. That is, the metal hydride is fixed in appearance, but is in countercurrent contact with the hydrogen gas due to the action of the rotary valve 10.

The rotary valve 10 is comprised by the rotating part 11, the fixed center axis | shaft 12, and the fixed plate 13. As shown in FIG. The rotating part 11 is a rotating part, and a U-shaped flow path and a Y-shaped flow path are provided therein. The U-shaped flow path is a hydrogen gas passage in which opening and closing is repeated as the valve rotates, and the Y-shaped flow path is a hydrogen gas flow path supplied and discharged to the fixed central axis 12. The fixed central axis 12 provides the injection path 14 and the discharge paths 15 and 16 therein in a horizontal independent open space and inside which form three flow paths of the rotary part 11. The injection path 14 is a flow path into which raw hydrogen is introduced, the discharge path 15 is a flow path concentrated and discharged into a heavy hydrogen isotope, and the discharge path 16 is separated into a light hydrogen isotope to discharge the lean product. Represents a flow path. The fixed plate 13 serves to connect the pipes to the inlet and the outlet of each reactor.

A summary of the flow of hydrogen using FIG. 1 is as follows.

Tritiated deuterium is fed to the bottom of the reactor (7), through the reactor (8), some are discharged as lean products, some are sent to the reactor (1), and hydrogen passing through the reactor (1) continues to be reactor (2). Pass through reactor (4) through (3) and (3). A portion of the hydrogen passing through the reactor 4 is concentrated and discharged into a heavy hydrogen isotope, and the remainder is introduced into the reactor 7 through the reactor 5, through the reactor 6, and with the raw hydrogen.

When one cycle of hydrogen circulation is completed, the rotary part 11 of the rotary valve 10 is rotated by an automatic device by 45 ° clockwise to give a countercurrent contact effect to the metal hydride. This rotation produces the effect of continuing countercurrent contact with hydrogen even though the metal hydride is fixed.

Each reactor is temperature controlled as shown in FIG. 2 for the separation of hydrogen isotopes. FIG. 2 is a diagram showing a heat exchange circuit diagram of a low temperature part and a high temperature part, wherein a low temperature heat fluid is supplied to an outer wall of the reactor 1 in a pipe. The low temperature heat fluid continues through reactors 2, 3, and 4 through a rotary valve 24 for the heat exchanger, thereby passing through reactors 1, 2, 3, and 4. Allow cold tower conditions. The fluid exiting the reactor 4 passes through the fixed part 23 of the rotary valve 24, passes through the flow path of the rotary part 21, and then exits the discharge path 25 of the fixed center shaft 22, which is not shown in the drawing. After exchanging heat with the fluid of high temperature exiting the outlet 27 from the heat exchanger, it is again supplied to the reactor 5 via the injection passage 26. This high temperature fluid is then passed through reactors 7 and 8 back to the low temperature in the heat exchanger via outlet 27 of rotary valve 24. This fluid is repeated in a cycle in which the fluid is supplied to the reactor 1 through the injection valve 28 via the rotary valve 24.

In FIG. 2 , the rotary part of the rotary valve 24 is rotated by the automation device counterclockwise by 45 °, which is the hydrogen injection passage 14, the discharge passage 15 and the discharge passage 16 of FIG. 1. It is linked to the automation device of the rotary valve 10 for converting the), and each outlet of the heat exchanger is provided with auxiliary heat exchangers for compensating for the lost heat.

The process of separating tritium from the tritiated heavy water of the reactor will be described in detail with reference to FIG. 3 .

Making a hydrogen isotope chemical exchange reaction by countercurrent contact in the catalytic reaction tower 31 (step 1);

Generating tritiated deuterium in the electrolysis tank 33 (step 2);

Concentration and removal using rotary valve 40 (step 3); And

It is composed of the step (step 4) of synthesizing heavy water by the combination of deuterium and oxygen in the recombiner (34).

Step 1 is a step of increasing the concentration of tritium by the hydrogen isotope chemical exchange reaction while the tritiated heavy water produced in the reactor in the catalytic reaction tower 31 undergoes a countercurrent contact reaction with the tritiated deuterium.

Step 2 is a step of generating tritium deuterated by the following Scheme 4 in the electrolysis tank (33).

2DTO-> 2DT + O ₂

In Scheme 4,

DTO is tritiated deuterium and DT is tritiated deuterium.

Step 3 is a step of injecting tritium deuterium into a rotary valve 40 for separating a hot and hot tower hydrogen isotope and concentrating and removing it at a high concentration.

Step 4 is a step of recombining with oxygen generated in the reaction formula 4 and deuterium in the catalytic reaction tower (31) after the hydrogen isotope chemical exchange reaction is synthesized in heavy water.

In the catalytic reaction column 31, a catalyst material coated with a periodic group 8 metal such as platinum and rhodium on a hydrophobic porous carrier such as polystyrene divinylbenzene and hydrophobic carbon, and a liquid filler to help spread tritiated heavy water. The recombiner 34 is filled with a catalyst using a Group 8 metal on the periodic table to promote the oxidation reaction of deuterium, and the heavy water produced by the recombination reaction has a very low tritium content. Is fed back to the reactor via [M. Benedict, TH Pigford & HW Levi, Nuclear Chemical Engineering , McGraw-Hill Book Campany 2th, p756].

The tritium separation process of the present invention will be described in detail as numerical values of the examples.

The amount of tritiated heavy water supplied to the catalytic reaction tower 31 through the pipe 32 is 20 gmol / h, the concentration of tritium is 10 ppm in atomic fraction, and the radioactivity concentration of the raw water is 29 Ci / kg.

The amount of heavy water having a low tritium concentration after treatment which is recycled to the reactor through the pipe 35 is 19.98 gmol / h, and the concentration of tritium is 1 ppm in atomic fraction.

The amount of concentrated tritiated deuterium gas supplied to the rotary valve 40 through the pipe 36 is 0.342 gmol / h, and the concentration of tritium is 1,000 ppm in atomic fraction.

The flow rate of deuterium gas recycled from the rotary valve 40 to the catalytic reaction tower 31 is 0.324 gmol / h, and the concentration of tritium is 500 ppm in atomic fraction.

The flow rate of the heavy water flowing down the upper layer of the catalytic reaction tower 31 is 50 gmol / h.

The tritium concentration in deuterium in the pipe 32 is 7.43 ppm in atomic fraction.

The tritium concentration in the heavy water in the pipe 37 is 502.44 ppm in atomic fraction.

The tritium concentration of the tritiated deuterium gas supplied to the rotary valve 40 is 1.000 ppm in atomic fraction, which is from the pipe 36 through the pipe of the fixed shaft 12 of the rotary valve 40 to run the cold and hot hydrogen. It flows into the element separation process.

The tritium gas concentrated in the cold / hot tower hydrogen isotope separation cavity is produced at a concentration of 0.018 gmol / h, a tritium atomic fraction of 10,000 ppm, through a pipe 41 installed on the fixed shaft 12, and the pipe 41. The radioactivity of the tritium gas produced at is equivalent to 145 kCi / kg.

The tritium concentration of another tritiated deuterium gas discharged from the fixed shaft 12 of the rotary valve 40 is 500 ppm in atomic fraction, and is recycled to the catalytic reaction tower 31 through the pipe 37.

The catalytic reaction tower 31 is operated at a temperature of 80 ° C., and the value of the hydrogen isotope separation coefficient α between deuterium and tritiated heavy water is 1.4232. In addition, the total required theoretical stage is 38 stages, 19 stages from the upper part to the piping 32, 17 stages from the piping 32 to the piping 37, and two stages from the piping 37 to the lower part are comprised. .

In the reactor of FIG. 1 provided in the present invention, a palladium-based adsorbent for forming a metal hydride is filled, and the adsorbent has a composition of 75 wt% palladium and 25 wt% aluminum. Palladium having a particle size of several tens of micrometers and aluminum powder are mixed, compacted to pellets, and then obtained in a powder obtained by crushing the solid produced by heating in an inert gas atmosphere to obtain only those having a particle size of 0.5 to 1.0 mm. The powder is heated to 250 ° C. in an argon atmosphere, degassed in a vacuum of 1 Pa, and then charged and used in the reactor of FIG. 1 through an activation process of repeating adsorption and desorption several times with hydrogen isotopes.

The tritiated deuterium supplied through the rotary valve 40 of FIG. 3 reacts at 90 ° C., and the hydrogen isotope separation coefficient αH between the solid phase and the gas phase is 1.275. On the other hand, the separation coefficient αC in the reactor operated at 10 ° C. in which tritium is transferred from the solid phase to the gas phase is 1.5223.

The required number of theoretical stages of the reactor is 70 stages in total, and the on-top portion of 90 ° C is 37 stages in total, with 9 stages at the top and 28 stages at the bottom of the supply pipe 36. It consists of. Of course, this calculation is just one example and the cost can be minimized by performing an optimization design.

In the process of separating tritium as in the above example, by continuing to install the separation process as shown in Figure 1 in series series of several stages can be concentrated tritium in high purity, triple in the tritium process diagram as shown in FIG. In moving tritium from hydrogenated heavy water to deuterium, a process using a gas phase catalyst reaction or a pure liquid phase catalytic reaction may be used, and the tritiated heavy water coming from a reactor without electrolysis without the catalytic reaction tower of FIG. The generated tritium deuterium may be directly supplied through the rotary valve 40 to separate tritium.

The above example is a process of separating tritium, but can be used as a method of separating light hydrogenated deuterium using the process of FIG. 1 , and in this case, the process of FIG. By concentration, natural or partially concentrated mixtures of deuterium and light hydrogen can be separated into high concentrations of deuterium and light hydrogen. In addition, the apparatus is an example for applying the method of the present invention, it is applicable to the appropriate apparatus as needed.

As described above, the present invention utilizes an isotope effect in which the adsorption tendency between hydrogen isotopes to the metal is different, and the hydrogen isotope gas passes through a multistage reactor composed of a low temperature part and a high temperature part, and the stationary multistage reactor is a rotary valve ( Through the effect of making the countercurrent contact with the hydrogen isotope gas by the action of 10), it is possible to provide the separation method of the hydrogen isotope which simplifies the tritium separation, the cost reduction effect and the radiochemical safety.

Claims (5)

Hydrogen isotrope, comprising a low temperature part and a high temperature part, in which a flowing hydrogen gas is introduced through a rotary valve to adsorb and separate hydrogen isotopes from the hydrogen gas into a reactor having metal hydride fixed therein. Separation method of elements. The metal used as the metal hydride is palladium, vanadium, niobium, titanium, uranium, LaNi ₅ , CaNi ₅ , Ti _0.2 V _0.3 , MmNi _2.5 Co _2.5 , MmNi _4.5 Co _2.5 , MmNi _4.5 Al _0.3 , MmNi _4.5 Mn _0.5 , TiCo _0.5 Fe _0.5 , LaCo ₅ , VNb, LaNi _5-x Al _x , TiV, TiCr, TiCr ₂ , TiCrMn, Ti ₂ Mo, TiMo ₂ , TiMn, FeTi, Fe _0.6 TiMn _0.2 , TiCo, TiNi , Mg ₂ Ni, MmNi ₅ , V _0.9 Cr _0.1 , Pd _0.75 Al _0.25 and ZrNi alloy, wherein Mm is selected from Ce, La, Nb, Pr and rare earth metals . 2. The method for separating hydrogen isotopes according to claim 1, wherein a rotary valve (10) and a reactor device composed of a low temperature part and a high temperature part are connected in series and installed in several stages. The method of claim 1, wherein the hydrogen isotope is produced by the tritized deuterium by directly electrolyzing tritiated deuterium water, or by contacting deuterium by a gas phase catalytic reaction or a liquid phase catalyst reaction, or in the electrolysis tank 33 after the liquid phase catalyst reaction. Separation method of hydrogen isotope characterized by using tritiated deuterium produced by electrolysis of concentrated tritium deuterium. 2. The method of claim 1, wherein the hydrogen isotope is a mixture of natural hydrogen or partially concentrated deuterium with light hydrogen.