JPS62255894A - Method and device for decontaminating waste gas of fuel cycle of fusion reactor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method and apparatus for the decontamination of waste gases of the fuel cycle of a nuclear fusion reactor, preferably containing tritium and/or deuterium in chemically bound form. The present invention relates to a method and apparatus for releasing tritium and/or diuterium from their chemical bonds, separating it from the waste gas and returning it into the fuel cycle for the decontamination of waste gas components.

The waste gas from the technical fusion reactor in Eyomi contains about 85% of rare gases and about 15% of contaminants, as well as a small amount of residual hydrogen. Contaminants include alkylene, tritium-containing M and/or dieutherium metal scrap hydrocarbons, in particular tritiated and/or dieutherium-containing CH4, tritium-containing and/or dieutherium-containing water, and tritiated and/or dieutherium-containing hydrocarbons. Or dieutherium occurs in the form of 100M ammonia. Therefore, the waste gas must be freed of free tritium and tritium-containing contaminants or decontaminated to acceptable emission limits, after which the remaining waste gas can be discharged to the atmosphere. Additionally, recovery of tritium and dieutherium from compounds containing tritium and dieutherium and return of tritium and dieutherium into the fuel cycle is desirable;
The reason is that this method is guaranteed to keep tritium out of the ambient atmosphere.

The method and apparatus for decontamination according to the generic claims are disclosed in 'Proceedings of Tritium Toxicity in Fisheries/Fusion and Isotropic Applications.
dings of Tritium Technology
y in Fission, Fusion and I
"sotropic Application", Dayton-Ohio, April 29, 1980, pp. 115-118. It then passes through a catalytic reactor to reduce the oxygen with hydrogen at 75°C, after which all contaminants are stratified at 75°C in a molecular sheep bed and thus separated from the waste gas. After heating to 400 K, thereby desorbing the contaminants, the contaminants are oxidized at 800 °C in an oxygen-releasing fixed bed to form tritium- or di-eutherium-enriched water and tritium- or di-eutherium-free compounds, i.e. co2.142 and Ar. Tritium or dieutherium f, t
The water is frozen at 160 °C and then periodically evaporated and fed to a hot uranium metal bed which converts the water to dieutherium or tritium-containing hydrogen and solid 002 at 750 °C. Instead of reduction with a uranium metal bed, reduction with electrolysis 4 can also be carried out.

The methods proposed so far have the following drawbacks: - High temperature and with it the risk of loss of tritium due to osmosis - Oxygen release fixation at high temperature, possibly with sintering of the fixed bed particles. IR element excess release (deactivation) loading the bed operation and hot metal blaster - oxidation reactions of ammonia and hydrocarbons and re-reduction of the water formed (loading the hot metal S detter) - oxidation of hydrogen and the water formed reduction (loading of hot metal blister) - Production of chloride compounds during NH3 oxidation in a large radioactive solid waste and - acidic discharge solid bed Problems to be Solved by the Invention The subject matter of the present invention is: From the waste gas of the fuel cycle of a nuclear fusion reactor, tritium and /1 liter are used to decontaminate waste gas components that contain dieutherium in a chemically combined form.
It is an object of the present invention to provide a method and a device in which losses of tritium and/or diuterium due to percolation and loading of the hot metal maple dumper material and the formation of filtrate oxides, as occur in corresponding methods known hitherto, are avoided. . The method should be energy-saving, simple and easy to implement compared to known methods. The liberated tritium and/or deuterium should be able to be returned to the fuel cycle without any other treatment measures other than isotope separation.

Means for Solving the Problem According to the invention, a) passing the waste gas deriving into tritium and/or diuterium through a device for cracking ammonia and hydrocarbons into elements; b) C) decontaminating and discharging the waste gas into the ambient air.

As a device for completely decomposing ammonia, palladium l'J
i3 or a film made of palladium-silver alloy or Ni
A catalyst is used, a Ni catalyst for cracking the hydrocarbons. The decomposition reaction and the separation of liberated hydrogen isotopes are carried out sequentially or in one step. One advantageous mode of implementation of the process of the invention is to carry out the decomposition reaction of ammonia and hydrocarbons using a Ni catalyst on a ceramic support at 250-40%
carried out in a temperature range between 50"C, the membrane is made of palladium or a palladium alloy and surrounds the catalyst,
and is characterized in that the catalyst present inside the membrane is heated together with the gland to the reaction temperature.

Advantageously, the waste gas is first subjected to oxidation of the component CO to 002 using an oxidation catalyst, and then at a temperature in the range of 200"C to 300"C for the removal of 02k and for the reduction of water. Hydrogen isotopes are brought into contact with 0.2 Determetal and treated with a membrane and a Ni catalyst at temperatures in the range of 600 to 45 [J'O] to subtly decompose ammonia and hydrocarbons.

The apparatus according to the invention intended to carry out the entire process comprises a buffer vessel, a catalyst bed and a heatable metal bed.
In the direction of flow of the waste gas in 1, a buffer vessel 1 for compensating the gas pressure, a catalyst bed 2 for selective oxidation to colco 2
, a heatable metal bed 3 for removal from the waste gas by a chemical reaction of 02 and H20'i, a hydrogen isotope outlet 22 containing a heatable membrane for selectively passing: hydrogen isotope f7r
one or several containers 5 containing renewable Nil
It is characterized in that a heatable bed 10 is arranged, which drains the medium 6 and has an inlet T and an outlet 8 M for the regenerant, as well as one or several bonders 23.

Advantageous implementation of this device! In the case of A4, an externally coolable vessel 611 is arranged at the base of the combination of the vessel 5 and the catalyst bed 10, the outer surface of which is cooled to a temperature of 200 ''O, and is cooled from the waste gas for 11 minutes. Gas outlet 12 for hydrogen isotope
A container 14 which is made of palladium or palladium-silver alloy containing Ni catalyst 13 and has a decontamination pot 1kjM gas supply pipe 15 and a decontaminated waste gas discharge pipe 16 is placed in a container 11 having seven shoulders. The container 11 has a container heating device 18 between its inner wall 17 and the container 14. It is particularly advantageous if the container 14 is designed as a helical tube.

The waste gas from the fuel cycle of the fusion reactor has approximately the following composition tM: 80-85 mol% He, Ar 15-20 mol% N(DIT)3*C(DIT
)4 @(n,'r)2o 1 (D,T)a l
co.

Of course, some of the deuterium isotopes may also be substituted by light hydrogen (near "rotium") in the corresponding compounds.

The advantages of the process according to the invention and the device according to the invention are that: a) a slight reduction in steps is achieved; b) the maximum working temperature in the circulation system, except for the decomposition temperatures of NH3 and CH4, does not exceed 300"Ck; This results in no loss of tritium due to penetration through the metal walls, c) minimization of radioactive waste is achieved, and d) reduction of the load on the elementary decker (metal bed) to a minimum value. [Basic release fixed bed (c.

'6 In-situ 0. No formation: no Hzflllation and no re-reduction], e) no formation of tritium oxides; f) decomposition of tritium and/or dieutherium contaminants ammonia and hydrocarbons and formation of tritium or dieutherium; When summarizing the separation of: the thermodynamics and kinetics of a chemical reaction are seen to shift in favor of the method.

One level up to the technical level! In the mentioned process, no percolation losses of deuterium occur during the catalytic oxidation of the oxidizable waste gas components and the reduction of water to hydrogen in the uranium bed.

In the process according to the invention, the waste gas is introduced as feed gas into the conduit of the m-ring, flows through the buffer vessel and then passes at about room temperature (20° C. to 25° C.) through a fixed bed acting as a catalyst. . The fixed bed is, for example, fobcalide (Cuo/
MnO2) or perovskite. Thereby, the oxygen and carbon monoxide present in the waste gas are selectively converted to CO2. In the case of oxygen deficiency in the gas, the fixed bed liberates the chemical catalytic gas, the gas emanating from this catalyst, which then forms a layer of uranium 44 or titanium gold. 'k, 200-600
At temperatures between 20 °C and 20 °C, water is decomposed with the formation of hydrogen and, for example, uranium oxide is formed,
In some cases, oxygen that has not been converted to carbon is collected. The waste gas from this tIit getter is then passed through a container with an Iig made of palladium or a palladium-silver alloy at a temperature between 3UO and 450°C, in particular 400-450"C, and the waste gas is removed. The ammonia contained in the gas is decomposed by the membrane in the form of a directly heated tube or bundle of tubes.
It may be surrounded by an outer container (tank) that can be cooled. From this vessel, the specific gravity produced during decomposition is discharged and, if necessary, a hydrogen isotope separator fl
After passing through the fuel cycle V of the fusion reactor, it is sent back.

The wheat, thus ammonia removed, and the waste gases are used to decompose hydrocarbons, especially methane, from 2501E to 450.
A fixed bed of nickel catalyst heated to a temperature of -0 is allowed to flow freely. ◎Decomposition is carried out according to the following formula, and since it is simple in the abdominal method, all hydrogen isotopes are expressed together as H or N2 (this The written method is maintained below): cnH2n+X -m-'/2 (2n+J N2
+ 0n(Ni) Over time the catalyst is exhausted and must be discarded or regenerated over light hydrogen at a sufficiently high temperature according to the formula: C(N') + 2 N2-+ CH, (2 ) Depending on its purity, the residual gas can either be discharged directly into the ambient air or recycled until the required purity is reached, in which case it is again initially drained into the buffer vessel' and then recorded. It passes through the catalyst bed, oxygen blister and vessel.

Whereas the known process consists of at least seven steps, the individual working temperatures of which are well apart from each other, the maximum temperature difference between two successive steps being 640°C, the process of the invention
The six or four steps are designed to have very small temperature differences exclusively on the ascending line. Whereas in processes belonging to the state of the art the catalytic oxidation of all oxidizable constituents of the waste gas is carried out at 527°C, in the process of the invention the catalytic oxidation is carried out selectively with respect to CO between 20°C and 2
It is only applied at low temperatures in the range of 5°C. The process according to the invention allows the step of D) decomposition of ammonia and hydrocarbons by subsequent reduction of water and removal of the Blatter metal sludge at a suitable temperature, e.g. 250'C. In this case, for the stationary decomposition of ammonia, it is immaterial whether the ammonia is decomposed with a membrane made of palladium-free luca or a palladium-silver alloy or with a Ni catalyst.

The present invention will now be described in detail with reference to some drawings and illustrative examples.

The example devices from FIGS. 1 and 2 are generally
In the embodiment shown, the combination of an externally cooled 1 vessel 5 carrying a heated membrane at 450° C. and an externally cooled catalyst bed 10 with an internal heated stone at 450° C. In the illustrated embodiment, there is only one structure, namely 4[
The only difference is that it is replaced by an externally cooled vessel 11 heated to 10° C. and surrounding the tubular membrane 14. The spirally rotating tubular membrane 14 contains a nickel catalyst 13 supported on a ceramic support in the latter embodiment. Regeneration of the Ni catalyst, which has lost 1 # of carbon, is carried out by introducing a regenerant, for example, consisting of light hydrogen, through the total gas outlet 12 and passing it through the tubular membrane 14.

For this reason, the square 24 in the smooth damp guide 121 is closed and the valve 27 is opened. At approximately equal working temperatures, about 450°C, the formula (
2) Carbon reacts with N2. The resulting methane-hydrogen mixture 28 is discharged via the regenerant outlet 26 of the conduit 21. The other components of both devices are listed in the following table and need not be described in detail.

Table: 1. Buffer vessel 2, Catalyst bed 3, for example with hozocalite, Metal bed 4, for example with M uranium, Metal bed 3, for example made of palladium, Nickel catalyst l B main agent population to catalyst bed 10 8, Catalyst bed 10 Regenerant outlet 9 (4) for raw material, e.g.
) 13. Discharge pipe 1Z from the container 11 for decontaminated gaseous gases.Inner wall 18. of the container 11. A heating device 19 for the vessel 14, a cooling device 21 for the vessel 11, a circulation conduit 22, a gas outlet 23 for the hydrogen isotope from the vessel 5, Bonde. Examined. For this reason, as a substitute for genuine waste gas from the fuel cycle of a fusion reactor, the process gas to be treated can be replaced with ammonia and/or methane, respectively.
A gas mixture consisting of helium containing up to mol % was simulated by using with or without the addition of small amounts of other expensive gases. This gas mixture is supplied as a gas in the experimental apparatus by supplying helium via inlet valve 31, ammonia via inlet valve 32, and methane via inlet valve 30.
:, I did it.

The gas mixture is passed through the nickel catalyst bed 36 at a high flow rate, i.e. 150 J/h.

The catalyst present in the quartz tube is heated to the desired total temperature in a tube furnace that can be opened from the outside (not shown in the drawing, but indicated by heating device 37). The tube furnace is connected to an I11 electronic control unit (not shown in the drawings).

Thereafter, the gas mixture passed through a Pd/Ag membrane 41, while the membrane was used at a temperature of 450° C. by means of a heating device 38, and the hydrogen produced from the catalytic decomposition of methane or ammonia was passed through an outlet 42 in a four-dimensional manner. Separated. The catalyst vessel 36 as well as the pa/Agm 41 can each be routed through one bypass t. In this case, the composition of the gas to be dived was determined using a gas graphite rough 43 connected to a self-recording integrator 44 for evaluation.
pak) Qs Bora Park R Mayu was analyzed using a Molekier Sheep 5A column. Additionally, a quadrupole mass spectrometer 46 is directly connected to the #ring 52 via the gas intake $45. Height 8 using gas suction system 45
: A gas mixture at (even atmospheric pressure) can be fed to a commercial analyzer used in a high vacuum without changing its percentage composition. The gas suction system was heated (not shown) to avoid Jl contraction effects.

For data evaluation a calculator 48 was used which was connected via a coupler 47 to a quadrupole mass spectrometer 46. Due to the high sensitivity of mass spectrometry, only a very small amount of sample is required for each analysis, so that it is possible to withdraw the sample practically continuously from the circuit over several hours, with pressure No descent occurs. A very high throughput was selected for the test strategy. As a result, the change in the passing time of 11 White is slight. D) The interpretation of the measurement results is easy.
It can be carried out according to the JIA theory of batch reactors.

The experimental equipment also includes several pressure regulators 34, manometers 35, expansion containers 49, and flow meters 50j? and several Bon F51s, as well as Masuzen.

Experiment A: Catalytic decomposition of methane into the elements.
A nickel catalyst on a ceramic carrier of SF type G1-22t'' was circulated through 9 bonders.The volume of the circulating flow was 6!D) The catalyst volume was 5d.

Part 1 of the experiment: A friend who keeps the temperature of the container containing the palladium membrane at 25°C. Detection of methane decomposition in helium as carrier gas was verified by mass spectrometric analysis of methane and hydrogen content. Figure 4 shows the results in the three-sided section of the curve (up to 4 hours). At the beginning of the experiment, instructions were given to decompose methane, but after about two hours, the vessel stopped working. XP on catalyst surface
S analysis (XP8 photoelectron spectrometer) revealed that the carbon produced was present in elemental form and not in carbide form. Part 2 of the experiment: However, palladium g'(I-4oo'c When the system is heated to (Figure 4, right part of the curve, 4 hours and 6 hours)
(see Between Time).

Part 6 of the experiment: Regeneration of the nickel catalyst The elemental carbon deposited on the nickel catalyst is converted into hydrogen by total introduction of light hydrogen in the temperature range between 2500 and 450 °C in helium as a carrier gas. The supply V was converted into methane and transported from the Sotai equipment. Methane production has been demonstrated.

Experiment B: Catalytic decomposition of ammonia into elements A gas mixture consisting of helium and about 15 mol% ammonia was passed through the experimental apparatus at a flow rate of 181/h. in this case,
Ammonia is decomposed at 400 °C in a container covered with a Pd/Ag film (surface area 1.2 m2). Figure 5 shows wi
Figure 4 shows the dependence of the decomposition rate on four ammonia source concentrations, as determined by t-analysis. The ammonia partial pressure at the original level is 0
It was 87.10 mbar*, 35.48 mbar Δ, 14.14 mbar, and 9.33 mIJ bar.

The reaction rate constant determined from ammonia decomposition was 4 x 101 F' molecules per 2.1 seconds. The conversion rate is quantitative.

Comparative Example for a Helium-Methane Mixture: A mixture of about 15 mol% helium and methane was passed through a palladium membrane in a bonder in an fcpm loop for 4 hours at a flow rate of "h", with the exception of nickel-catalyzed gold. The temperature is 400″C and 9. No decrease in methane concentration could be detected by mass spectrometry. This means that palladium membranes decompose only ammonia, but not methane. In contrast, nickel catalysts decompose not only methane but also ammonia.

[Brief explanation of drawings]

1 is a schematic cross-sectional view of an embodiment of the apparatus according to the invention, in which the decomposition of ammonia and the decomposition of hydrocarbons take place in two different parts of the apparatus; FIG. Figure 3 is a schematic cross-section showing another embodiment of the apparatus according to the invention, in which hydrogen is simultaneously carried out in the same component of the apparatus; FIG. 4 is a curve diagram showing the effectiveness of the decomposition reaction in the case of methane, and FIG. 5 is a curve diagram showing the effectiveness of the decomposition reaction in the case of ammonia.

Claims (1)

[Claims] 1. In order to decontaminate waste gas components containing tritium and/or dieutherium in a chemically bonded form from the waste gas of the fuel cycle of a nuclear fusion reactor, released from binding,
A method for separating from the waste gas and returning it into the fuel cycle, comprising: a) removing ammonia and hydrogen bromide from the waste gas, leading together with tritium- and/or di-eutherium-containing ammonia and/or tritium- and/or di-eutherium-containing hydrocarbons; Decomposition into elements (cratsking)
b) passing the liberated hydrogen isotopes through a membrane and separating them from the residual waste gas stream, and c) discharging the decontaminated waste gas into the ambient atmosphere. A method for decontaminating waste gas from a fusion reactor fuel cycle. 2. As an ammonia decomposition device, a membrane made of palladium or a palladium-silver alloy or a Ni catalyst is used,
2. A method as claimed in claim 1, in which a Ni catalyst is used for the decomposition of hydrocarbons, and the decomposition reaction and the separation of liberated hydrogen isotopes are carried out sequentially or in one step. 3. The decomposition reaction of ammonia and hydrogen bromide is carried out in the temperature range of 250°C to 450°C using a Ni catalyst on a ceramic carrier, and the membrane is made of palladium or palladium-silver alloy and surrounds the catalyst. 2. The method of claim 1, wherein the catalyst present inside the membrane is heated together with the membrane to the reaction temperature. 4. CO of the component CO using an oxidation catalyst in the waste gas
Selective oxidation to _2 followed by contact with O_2 getter metal at a temperature in the range of 200°C to 300°C to remove O_2 and reduce water and finally decompose ammonia and hydrocarbons. Therefore, 300℃～
2. The method of claim 1, wherein the hydrogen isotope is contacted with the permeable membrane and the Ni catalyst at a temperature in the range of 450<0>C. 5. It has a buffer vessel, a catalyst bed, and a heatable metal bed in order to decontaminate waste gas components containing tritium and/or deuterium in chemically bonded form from the waste gas of the fuel cycle of a fusion reactor. In the device, in the flow direction of the exhaust gas, in the circulation conduit (21), a buffer vessel (1) for compensating the gas pressure, a catalyst bed (2) for the selective oxidation of CO to CO_2, a catalyst bed (2) for selectively oxidizing CO to CO_2 from the exhaust gas. and a metal bed (3) for removing H_2O by chemical reaction, a hydrogen isotope product outlet (22) containing one or several heatable membranes (4) selectively passing hydrogen isotopes. a heatable catalyst bed (10) with an inlet (7) and an outlet (8) for a regenerant (9), containing a regenerable Ni catalyst (6), and one or more An apparatus for decontaminating waste gas from a fuel cycle of a nuclear fusion reactor, characterized in that a pump (23) is disposed therein. 6. Instead of the combination of vessel (5) and catalyst bed (10),
An externally coolable container (11) is arranged, inside the container (11) having a gas outlet (12) for hydrogen isotopes separated from the waste gas, the outer surface of which is cooled to a temperature ≦200°C. D) A container (14) made of palladium or a palladium-silver alloy containing a Ni catalyst (13) and having a supply pipe (15) for the waste gas to be decontaminated and a discharge pipe (16) for the decontaminated waste gas. ) is arranged, and the container (11) has a heating device (18) for the container between its inner wall (17) and the container (14).
Apparatus described in section. 7. Device according to claim 6, characterized in that the container (14) is constructed as a helical tube.