CN117936148A - Tritium-containing water treatment method and treatment system - Google Patents
Tritium-containing water treatment method and treatment system Download PDFInfo
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- 229910052722 tritium Inorganic materials 0.000 title claims abstract description 161
- YZCKVEUIGOORGS-NJFSPNSNSA-N Tritium Chemical compound [3H] YZCKVEUIGOORGS-NJFSPNSNSA-N 0.000 title claims abstract description 149
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 title claims abstract description 110
- 238000000034 method Methods 0.000 title claims abstract description 46
- 229910052739 hydrogen Inorganic materials 0.000 claims abstract description 119
- 239000001257 hydrogen Substances 0.000 claims abstract description 119
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims abstract description 91
- 239000007787 solid Substances 0.000 claims abstract description 52
- 239000003792 electrolyte Substances 0.000 claims abstract description 29
- 239000004020 conductor Substances 0.000 claims abstract description 28
- 239000007789 gas Substances 0.000 claims abstract description 24
- 238000000926 separation method Methods 0.000 claims abstract description 24
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims abstract description 21
- 239000000446 fuel Substances 0.000 claims abstract description 21
- 229910052760 oxygen Inorganic materials 0.000 claims abstract description 21
- 239000001301 oxygen Substances 0.000 claims abstract description 21
- 239000010416 ion conductor Substances 0.000 claims abstract description 18
- 150000002431 hydrogen Chemical class 0.000 claims abstract description 17
- 239000012528 membrane Substances 0.000 claims abstract description 13
- 238000005119 centrifugation Methods 0.000 claims abstract description 11
- 239000000498 cooling water Substances 0.000 claims abstract description 7
- 238000005868 electrolysis reaction Methods 0.000 claims description 45
- 239000010405 anode material Substances 0.000 claims description 13
- 239000010406 cathode material Substances 0.000 claims description 13
- PACGUUNWTMTWCF-UHFFFAOYSA-N [Sr].[La] Chemical compound [Sr].[La] PACGUUNWTMTWCF-UHFFFAOYSA-N 0.000 claims description 10
- FWLGASJILZBATH-UHFFFAOYSA-N gallium magnesium Chemical compound [Mg].[Ga] FWLGASJILZBATH-UHFFFAOYSA-N 0.000 claims description 10
- 238000011084 recovery Methods 0.000 claims description 10
- 229910052712 strontium Inorganic materials 0.000 claims description 10
- CIOAGBVUUVVLOB-UHFFFAOYSA-N strontium atom Chemical compound [Sr] CIOAGBVUUVVLOB-UHFFFAOYSA-N 0.000 claims description 10
- 229910000859 α-Fe Inorganic materials 0.000 claims description 10
- 239000000126 substance Substances 0.000 claims description 9
- 239000000463 material Substances 0.000 claims description 8
- XLYOFNOQVPJJNP-PWCQTSIFSA-N Tritiated water Chemical compound [3H]O[3H] XLYOFNOQVPJJNP-PWCQTSIFSA-N 0.000 claims description 6
- XRWZBMRLPJNKFR-UHFFFAOYSA-N [Y].[Zr].[Ba] Chemical compound [Y].[Zr].[Ba] XRWZBMRLPJNKFR-UHFFFAOYSA-N 0.000 claims description 5
- 239000011777 magnesium Substances 0.000 claims description 5
- 238000000746 purification Methods 0.000 claims description 3
- 229910002076 stabilized zirconia Inorganic materials 0.000 claims description 3
- RUDFQVOCFDJEEF-UHFFFAOYSA-N yttrium(III) oxide Inorganic materials [O-2].[O-2].[O-2].[Y+3].[Y+3] RUDFQVOCFDJEEF-UHFFFAOYSA-N 0.000 claims description 3
- 241000968352 Scandia <hydrozoan> Species 0.000 claims description 2
- 229910052810 boron oxide Inorganic materials 0.000 claims description 2
- BRPQOXSCLDDYGP-UHFFFAOYSA-N calcium oxide Chemical compound [O-2].[Ca+2] BRPQOXSCLDDYGP-UHFFFAOYSA-N 0.000 claims description 2
- ODINCKMPIJJUCX-UHFFFAOYSA-N calcium oxide Inorganic materials [Ca]=O ODINCKMPIJJUCX-UHFFFAOYSA-N 0.000 claims description 2
- 239000000292 calcium oxide Substances 0.000 claims description 2
- CETPSERCERDGAM-UHFFFAOYSA-N ceric oxide Chemical compound O=[Ce]=O CETPSERCERDGAM-UHFFFAOYSA-N 0.000 claims description 2
- 229910000422 cerium(IV) oxide Inorganic materials 0.000 claims description 2
- JKWMSGQKBLHBQQ-UHFFFAOYSA-N diboron trioxide Chemical compound O=BOB=O JKWMSGQKBLHBQQ-UHFFFAOYSA-N 0.000 claims description 2
- LNTHITQWFMADLM-UHFFFAOYSA-N gallic acid Chemical compound OC(=O)C1=CC(O)=C(O)C(O)=C1 LNTHITQWFMADLM-UHFFFAOYSA-N 0.000 claims description 2
- 229910052746 lanthanum Inorganic materials 0.000 claims description 2
- FZLIPJUXYLNCLC-UHFFFAOYSA-N lanthanum atom Chemical compound [La] FZLIPJUXYLNCLC-UHFFFAOYSA-N 0.000 claims description 2
- HJGMWXTVGKLUAQ-UHFFFAOYSA-N oxygen(2-);scandium(3+) Chemical compound [O-2].[O-2].[O-2].[Sc+3].[Sc+3] HJGMWXTVGKLUAQ-UHFFFAOYSA-N 0.000 claims description 2
- 229910001233 yttria-stabilized zirconia Inorganic materials 0.000 claims description 2
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims 1
- 229910052710 silicon Inorganic materials 0.000 claims 1
- 239000010703 silicon Substances 0.000 claims 1
- 238000005372 isotope separation Methods 0.000 abstract description 10
- 238000005265 energy consumption Methods 0.000 abstract description 7
- 230000006378 damage Effects 0.000 abstract description 6
- -1 tritium hydrogen Chemical class 0.000 description 22
- 230000008569 process Effects 0.000 description 12
- 239000002351 wastewater Substances 0.000 description 11
- 239000002826 coolant Substances 0.000 description 7
- 238000002485 combustion reaction Methods 0.000 description 6
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- 239000007788 liquid Substances 0.000 description 6
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- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 4
- 239000013589 supplement Substances 0.000 description 4
- 230000001988 toxicity Effects 0.000 description 4
- 231100000419 toxicity Toxicity 0.000 description 4
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- MYMOFIZGZYHOMD-UHFFFAOYSA-N Dioxygen Chemical compound O=O MYMOFIZGZYHOMD-UHFFFAOYSA-N 0.000 description 2
- XLYOFNOQVPJJNP-ZSJDYOACSA-N Heavy water Chemical compound [2H]O[2H] XLYOFNOQVPJJNP-ZSJDYOACSA-N 0.000 description 2
- MCMNRKCIXSYSNV-UHFFFAOYSA-N Zirconium dioxide Chemical compound O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 description 2
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- 239000003463 adsorbent Substances 0.000 description 1
- 229910021523 barium zirconate Inorganic materials 0.000 description 1
- DQBAOWPVHRWLJC-UHFFFAOYSA-N barium(2+);dioxido(oxo)zirconium Chemical compound [Ba+2].[O-][Zr]([O-])=O DQBAOWPVHRWLJC-UHFFFAOYSA-N 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
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Landscapes
- Electrolytic Production Of Non-Metals, Compounds, Apparatuses Therefor (AREA)
Abstract
The invention discloses a tritium-containing water treatment method and a tritium-containing water treatment system, and relates to the technical field of nuclear science engineering. A method for treating tritium-containing water, comprising the steps of: the method comprises the steps of carrying out electrolytic treatment on tritium-containing water by utilizing a solid oxide electrolytic cell based on an oxygen ion conductor electrolyte to obtain tritium-containing hydrogen, carrying out hydrogen isotope separation on the tritium-containing hydrogen by adopting a gas centrifugation method or an electric separation method based on a solid oxide proton conductor membrane, and utilizing the solid oxide fuel cell based on the oxygen ion conductor electrolyte to generate water from the separated hydrogen. The invention can effectively reduce the tritium content of cooling water in a primary loop of the nuclear power station, help reduce the tritium discharge pressure of the nuclear power station and avoid damage to organisms caused by the radioactivity of the tritium; the extracted and separated high-purity tritium element can be used as a tritium source and applied to the related field of tritium; the separated hydrogen burns to generate water, so that the energy consumption of tritium water treatment can be effectively reduced.
Description
Technical Field
The invention relates to the technical field of design nuclear science engineering, in particular to a tritium-containing water treatment method and a tritium-containing water treatment system.
Background
Nuclear power generation has been developed very rapidly for over half a century as a novel power generation means, and meets a part of the demands of people for electric energy, however, the harm caused by the nuclear power generation is not small.
Nuclear contaminated water and nuclear wastewater contain some radioactive material, tritium (T, an isotope of hydrogen), one of which is mainly derived from the primary loop coolant of the pressurized water reactor, to varying degrees. Generally, methods for treating nuclear wastewater include chemical precipitation, adsorbent treatment, membrane separation permeation, ion exchange, and the like. The main existing form of tritium in nuclear wastewater is tritium water (HTO), and although some radionuclides can be treated by the method, the tritium is difficult to remove, enrich and recycle. Meanwhile, tritium has wide application in nuclear energy as a radioisotope, such as nuclear fuel production, thermonuclear fusion experiments, hydrogen bomb manufacturing and the like, and the nuclear fusion reaction of tritium is also considered as a possible clean energy source in the future. Therefore, the separation of tritium in nuclear wastewater is of great significance.
To separate tritium (in the form of HT O) from the light water reactor coolant (water in the form of H 2 O in large quantities) requires hydrogen isotope separation techniques. The existing technologies for hydrogen isotope separation mainly comprise Vapor Phase Catalytic Exchange (VPCE), liquid Phase Catalytic Exchange (LPCE) and Combined Electrolytic Catalytic Exchange (CECE), which can be theoretically used for tritium removal of a light water reactor, but are mainly applied to a heavy water reactor, and the technology has the advantages of higher energy consumption, lower exchange efficiency and lower separation purity, so that the technology suitable for tritium removal of the light water reactor is particularly urgent to be found.
Disclosure of Invention
The invention aims to provide a treatment method and a treatment system for tritium-containing water, which are used for treating the tritium-containing water by using a solid oxide electrolytic cell based on an oxygen ion conductor electrolyte, reducing the tritium content of cooling water in a primary loop of a nuclear power plant, recycling tritium-containing wastewater after tritium extraction, separation and recovery, realizing harmless treatment and efficient utilization of the tritium water, helping to reduce the tritium discharge pressure of the nuclear power plant, and avoiding damage to organisms caused by the radioactivity of the tritium.
The technical scheme adopted by the invention is as follows:
a method for treating tritium-containing water, which comprises the following three steps:
(1) Electrolysis of tritium-containing water: carrying out electrolytic treatment on tritium-containing water by utilizing a solid oxide electrolytic cell based on oxygen ion conductor electrolyte to obtain tritium-containing hydrogen;
(2) Separation of hydrogen isotopes: carrying out hydrogen isotope separation on tritium-containing hydrogen by adopting a gas centrifugation method or an electroseparation method based on a solid oxide proton conductor membrane;
(3) Hydrogen gas is converted to water: and (3) utilizing a solid oxide fuel cell based on an oxygen ion conductor electrolyte to generate water from the hydrogen obtained by separation in the step (2).
The main components of tritium-containing water include water (H 2 O) and tritium water (HTO).
The invention uses a Solid Oxide Electrolytic Cell (SOEC) based on an oxygen ion conductor electrolyte to carry out electrolytic treatment on tritium-containing water, converts the tritium-containing water into low-toxicity tritium hydrogen, and then uses a hydrogen isotope separation method to repeatedly separate the tritium hydrogen from the hydrogen to obtain high-purity tritium hydrogen, which can be used as a tritium source and applied to the related fields of tritium; the centrifugal separation method adopted by the invention is carried out at normal temperature or high temperature, and the proton conductor membrane separation method can be carried out at normal pressure and high temperature (450-600 ℃).
After tritium is converted from tritium water (HTO) to tritium Hydrogen (HT), its toxicity has been reduced because tritium water exists in liquid form, and is similar to the molecular structure of water molecules (H 2 O) and can be absorbed by organisms, and its radioactivity may cause radiation damage to the cells and DNA of the organisms; whereas tritiated hydrogen exists mainly in gaseous form, like the molecular structure of hydrogen (H 2), firstly the organism is not able to absorb hydrogen in large amounts, and secondly gaseous tritiated hydrogen has a more limited exposure route than liquid tritiated water, and although it may still be absorbed by the organism to have a potential impact on the respiratory system, its toxicity is relatively low.
The invention uses a solid oxide fuel cell, which is used for converting hydrogen with obviously reduced tritium content after hydrogen isotope (mainly hydrogen tritium) separation into water through the fuel cell, supplementing the part of a loop of a nuclear power station where a coolant is electrolyzed, converting the chemical energy of the hydrogen into electric energy through the fuel cell, and providing partial energy for an electrolytic cell in a system, thereby reducing the whole energy consumption in the whole tritium removal process.
The method is suitable for removing tritium from light water piles, can obtain high-purity tritium hydrogen, and has high tritium removal efficiency and low energy consumption in the tritium removal process. By utilizing the tritium water treatment method, only 4.893 ℃ electricity is needed for treating 1kg of tritium water, the energy consumption of the system is greatly reduced, the time needed for electrolyzing 1kg of tritium-containing wastewater is only 5.9 minutes, and the rate is improved. The SOEC has smaller specification, easy replacement, larger power and high cost performance, and has great application prospect.
Further, the oxygen ion conductor electrolyte is selected from yttria stabilized zirconia, scandia stabilized zirconia, yttria doped ceria, lanthanum gallate or lanthanum strontium gallium magnesium.
Because the existing organic proton membrane has poor durability, the inorganic proton membrane has low efficiency. The invention adopts the SOEC oxygen ion exchange membrane based on solid oxygen ion conductor as electrolyte, the power density is high, the electrolysis power of the single symmetrical solid oxide battery adopted by the invention is 2.82W/cm 2 under the conditions of 1.6V and 800 ℃, the electrolysis efficiency is high, more than 70%, the material stability life is long, the boundary between the electrode material and the electrolyte material is obvious under 600 ℃ over 1200 hours, no obvious element diffusion occurs, and the power density fluctuation is less than 5%.
Further, the structural formula of lanthanum strontium gallium magnesium is La 1-xSrxGa1-yMgyO3-δ, wherein the value range of x is 0.05-0.5, the value of y is 0.05-0.5, and the value of delta is 0-0.5.
Further, both sides of the electrolyte are provided with a cathode material and an anode material, which are identical.
The SOEC and the SOFC in the invention both adopt symmetrical structures, and the polarities can be flexibly changed due to the same cathode and anode materials, so that the electrode structure is prevented from changing.
Further, the cathode material and the anode material are made of strontium ferrite, the chemical formula of the strontium ferrite is SrFe αO3-δ, the value of alpha is 1.01-1.1, and the value of delta is 0-0.5.
Further, the proton conductor can be made of zirconia stabilized by calcium oxide, silicon-doped boron oxide or solid oxide proton conductor material based on barium zirconium yttrium for element doping.
The invention takes into account the application of tritium radioactivity (beta decay) to organics, so a BYN-based solid oxide proton conductor is selected-elemental doping of barium zirconate to give yttria stabilization.
The proton conductor refers to a solid electrolyte capable of conducting hydrogen ions, and tritium as an isotope of hydrogen may also be conducted in the proton conductor. However, due to the fact that molecular masses of hydrogen and tritium are different, the transport energy barrier threshold of hydrogen ions is lower than that of tritium ions at the same temperature, the hydrogen ions can move to the other side of the proton conductor under the action of an electrostatic field with higher probability by precisely controlling the induction voltage, and therefore isotope separation of hydrogen tritium is achieved.
Further, the chemical formula of the solid oxide proton conductor material for element doping based on barium zirconium yttrium is BaZr kYnMpO3-q, wherein k is 0.5-0.95, n is 0.04-0.4, p is 0.01-0.2, q is 0-0.5, and k+n+p=1.
The tritium-containing water treatment system comprises a tritium-containing water circulating electrolysis unit, a tritium hydrogen separation and purification unit and a solid oxide fuel cell unit for converting hydrogen into water, wherein the tritium hydrogen separation and purification unit comprises a proton conductor membrane or a plurality of centrifuges.
Further, the circulating electrolysis unit of tritium-containing water comprises a reactor cooling water loop, a solid oxide electrolysis cell and a circulating pump, wherein the reactor cooling water loop is connected with the solid oxide electrolysis cell, and the circulating pump is used for connecting the solid oxide electrolysis cell with a cathode outlet of the solid oxide electrolysis cell through a pipeline.
Further, the solid oxide fuel cell unit comprises a solid oxide fuel cell, a water recovery tank and a circulating pump, wherein the solid oxide fuel cell is connected with the water recovery tank, and two ends of the circulating pump are respectively connected with an air inlet and an air outlet of the solid oxide fuel cell.
The specific working mechanism is as follows:
(1) Electrolysis process of tritium-containing water: when the tritium content in the primary loop of the reactor is detected to exceed the standard, part of tritium-containing water in the primary loop is decompressed and then moved into the circulating electrolysis unit. In the circulating electrolysis unit, tritium-containing water vapor is firstly mixed with hydrogen to enter a Solid Oxide Electrolysis Cell (SOEC) based on an oxygen ion conductor electrolyte, gaseous tritium water (HTO) and water (H 2 O) in the SOEC are respectively electrolyzed to generate tritium Hydrogen (HT) and hydrogen (H 2), at the moment, the mixed gas at the outlet of the cathode of the SOEC of the electrolysis cell comprises tritium hydrogen, hydrogen and a small part of gaseous tritium water and water which cannot be completely electrolyzed, and the mixed gas is returned to be mixed with the tritium-containing water to be jointly subjected to circulating electrolysis until a new mixed gas containing only hydrogen and hydrogen is obtained.
(2) The invention adopts two methods to realize the separation of tritiated hydrogen and hydrogen gas:
The first is gas centrifugation. The basic principle of gas centrifugation is based on the fact that gas molecules are subjected to different centrifugal forces in a centrifugal field, with different centrifugal sedimentation rates. When the gas mixture is placed in a centrifuge rotating at high speed, centrifugal forces are experienced that cause the molecules to settle in layers within the centrifuge tube according to their mass and molecular size, thereby effecting separation of the gas mixture. Since the relative molecular mass of hydrogen (1H2) is 2 and the relative molecular mass of tritiated hydrogen (1H3 T) is 4, tritiated hydrogen is more easily enriched at the paraxial region. And respectively introducing the gas enriched at the near axis and the far axis into two other different centrifuges to form cascade connection, and repeating the centrifugation process. Repeating the steps, and collecting the separated high-purity tritium hydrogen and hydrogen.
The second is to use an electric separation method based on a solid oxide proton conductor film. Tritium can be taken as the isotope of hydrogen through a proton conductor, but due to different molecular masses of hydrogen and tritium, the transportation energy barrier threshold of hydrogen ions is lower than that of tritium ions at the same temperature, and the hydrogen ions can move to the other side of the proton conductor under the action of an electrostatic field with higher probability by precisely controlling the induction voltage, so that the isotope separation of the hydrogen tritium is realized. By utilizing a multistage cascade design, membrane separation of hydrogen tritium isotopes under an electric field can be realized, and separated high-purity tritium hydrogen and hydrogen are obtained.
(3) The process of converting hydrogen into water: high purity hydrogen with extremely low tritium content obtained after separation of hydrogen tritium isotopes is connected to a Solid Oxide Fuel Cell (SOFC) unit based on an oxygen ion conductor electrolyte. The unit includes an SOFC, a water recovery tank and a circulation pump. The SOFC converts hydrogen into water through an electrochemical process, and converts chemical energy of the hydrogen into electric energy to release the electric energy to supply power for an electrolysis process; the water recovery tank collects water formed in the reaction process and is used as a supplement of reactor coolant; the circulating pump ensures that the hydrogen can completely react electrochemically.
The invention not only adds the H 2 with very low tritium content after separation to generate water through the combustion battery to supplement a loop, thus realizing the cyclic treatment of the tritium-containing wastewater of the nuclear power station, but also utilizes the fuel battery to convert the chemical energy of the hydrogen into electric energy to supplement the energy loss of the prior electrolysis process, thereby reducing the energy consumption of the whole system.
The beneficial effects of the invention are as follows:
1. The method can effectively reduce the tritium content of cooling water in a primary loop of the nuclear power station, convert the tritium water with strong radioactivity into tritium hydrogen with the radioactivity reduced by 10000 times, not only can help reduce the tritium discharge pressure of the nuclear power station, but also can avoid damage to organisms caused by the radioactivity of the tritium.
2. The high-purity tritium element (namely tritium hydrogen) extracted and separated by the method can be used as a tritium source and applied to the related field of tritium.
3. The material of the solid oxide electrolytic cell and the proton conductor in the electroseparation method are both made of inorganic materials, so that the problem that the organic materials possibly have reduced performance due to the activity of tritium can be effectively avoided.
4. The SOEC and the SOFC in the invention both adopt symmetrical structures, and the polarities can be flexibly changed due to the same cathode and anode materials, so that the electrode structure is prevented from changing.
Drawings
FIG. 1 is a flow chart of the present invention when gas centrifugation is employed;
FIG. 2 is a flow chart of the proton conductor method of the present invention;
Fig. 3 is a structural view of a battery cell according to the present invention;
FIG. 4 is a graph of maximum power density of a symmetrical cell over time in accordance with the present invention;
Reference numerals: 1-reactor, 2-relief valve, 3-hydrogen, 4-Solid Oxide Electrolytic Cell (SOEC) based on oxygen ion conductor electrolyte, 5-circulation pump, 6-high speed centrifuge, 7-Solid Oxide Fuel Cell (SOFC) based on oxygen ion conductor electrolyte, 8-water recovery tank, 9-circulation pump a, 10-proton conductor membrane, 401-cell electrolyte, 402-cathode material, 403-anode material.
Detailed Description
The following description of the present invention will be made clearly and fully, and it is apparent that the embodiments described herein are only some, but not all, of the embodiments of the present invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to fall within the scope of the invention.
Example 1
In an exemplary embodiment, as shown in fig. 1 and 3, a method and a system for treating tritium-containing water are provided, in this embodiment, a gas centrifugation method is used to perform isotope separation on a new mixed gas containing only hydrogen and tritium obtained in the first step, and the method includes the following steps:
Step one, an electrolysis process of tritium-containing water. When the tritium content in the primary loop of the reactor 1 is detected to exceed the standard, the pressure reducing valve 2 is opened, and part of high-concentration tritium-containing water under the pressure of 15.5MPa is reduced in pressure and then is moved into the circulating electrolysis unit. The water temperature at the outlet of the reactor is about 330 ℃, so tritium-containing water is in a gaseous state after depressurization, is mixed with external hydrogen supply 3, then enters a Solid Oxide Electrolytic Cell (SOEC) 4 based on an oxygen ion conductor electrolyte, tritium water (HTO) and water (H 2 O) in the gaseous state in the SOEC4 are respectively electrolyzed to generate tritium Hydrogen (HT) and hydrogen (H 2), at the moment, mixed gas at the outlet of a cathode of the SOEC4 of the electrolytic cell comprises tritium hydrogen, hydrogen and a small part of gaseous tritium water and water which cannot be completely electrolyzed, and the mixed gas is returned to be mixed with the tritium-containing water through a circulating pump 5 for circulating electrolysis until new mixed gas only containing hydrogen and tritium hydrogen is obtained.
And step two, a hydrogen isotope separation process. The basic principle of gas centrifugation is based on the fact that gas molecules are subjected to different centrifugal forces in a centrifugal field, with different centrifugal sedimentation rates. When the gas mixture is placed in a centrifuge 6 rotating at high speed, the centrifugal force experienced causes the molecules to deposit in layers within the centrifuge tube according to their mass and molecular size, thereby effecting separation of the gas mixture. Since the relative molecular mass of hydrogen (1H2) is 2 and the relative molecular mass of tritiated hydrogen (1H3 T) is 4, tritiated hydrogen is more easily enriched at the paraxial region. And respectively introducing the gas enriched at the near axis and the far axis into two other different centrifuges 6 to form cascade connection, and repeating the centrifugation process. Repeating the steps, and collecting the separated high-purity tritium hydrogen and hydrogen.
And step three, converting the hydrogen into water. High purity hydrogen with extremely low tritium content obtained after separation of hydrogen tritium isotopes is connected to a Solid Oxide Fuel Cell (SOFC) unit based on an oxygen ion conductor electrolyte. The unit includes SOFC7, water recovery tank 8 and circulation pump a9. The SOFC7 converts hydrogen into water through an electrochemical process, and converts chemical energy of the hydrogen into electric energy to be released, so as to supply power for an electrolysis process; the water recovery tank 8 collects water formed during the reaction process as a supplement to the reactor coolant; the circulation pump a9 ensures that the hydrogen can react completely electrochemically.
The SOEC of step one and the SOFC of step three may employ a symmetrical Solid Oxide Cell (SOC) characterized by an electrolyte 401 and cathode material 402 and anode material 403 on either side of the electrolyte, wherein the cathode material 402 and anode material 403 are identical and therefore referred to as symmetrical.
The electrolyte material 401 of the SOC adopts lanthanum strontium gallium magnesium (La 0.9Sr0.1Ga0.8Mg0.2O2.7). The cathode material 402 and the anode material 403 of the SOC use strontium ferrite (SrFe 1.05O2.7).
The main components of tritium-containing water include water (H 2 O) and tritium water (HTO).
After tritium is converted from tritium water (HTO) to tritium Hydrogen (HT), its toxicity has been reduced because tritium water exists in liquid form, and is similar to the molecular structure of water molecules (H 2 O) and can be absorbed by organisms, and its radioactivity may cause radiation damage to the cells and DNA of the organisms; whereas tritiated hydrogen exists mainly in gaseous form, like the molecular structure of hydrogen (H 2), firstly the organism is not able to absorb hydrogen in large amounts, and secondly gaseous tritiated hydrogen has a more limited exposure route than liquid tritiated water, and although it may still be absorbed by the organism to have a potential impact on the respiratory system, its toxicity is relatively low. The present example thus achieves the goal of reducing tritium concentration.
The embodiment adopts a gas centrifugation method to realize the separation of hydrogen and tritium isotopes, extracts high-purity tritium element (tritium hydrogen), and can be used as a tritium source to be applied to the related fields of tritium.
Example 2
Based on example 1, a method and system for treating tritiated water is provided, as shown in FIGS. 2 and 3. In this example, the solid oxide proton conductor membrane 10-based electroseparation method was used to isotopically separate tritium-containing hydrogen. The proton conductor 10 is a solid electrolyte capable of conducting hydrogen ions, and tritium as an isotope of hydrogen may be conducted in the proton conductor 10. However, due to the different molecular masses of hydrogen and tritium, the transport energy barrier threshold of hydrogen ions is lower than that of tritium ions at the same temperature, and the hydrogen ions can move to the other side of the proton conductor 10 under the action of an electrostatic field with higher probability by precisely controlling the induction voltage, so that isotope separation of hydrogen tritium is realized. By utilizing a multistage cascade design, membrane separation of hydrogen tritium isotopes under an electric field can be realized, and separated high-purity tritium hydrogen and hydrogen are obtained.
The solid oxide proton conductor film 10 employs a solid oxide proton conductor material BaZr 0.8Y0.16Ni0.04O2.7 that is element doped based on barium zirconium yttrium.
Example 3
Based on example 1, a method and system for treating tritiated water is provided. The electrical energy required for the Solid Oxide Electrolysis Cell (SOEC) to treat 1kg of water was calculated as follows:
In general, the tritium content of light water stack coolants is severely monitored and controlled because tritium is a radionuclide and can have environmental and human health implications. Under normal operating conditions, the tritium content in the coolant of the light water reactor is often maintained at a very low level to ensure safe operation of the reactor and to meet the emission standards of radioactivity (the requirement of emission of radioactive liquid effluent in nuclear power plants in China states that the tritium concentration in the liquid effluent must not be higher than 100 bellles per liter (100 Bq/L), which is a very small value (ppm level)). The specific tritium content will vary depending on the design and operating conditions of the reactor, but will generally be kept at very low levels. Therefore, tritium water (HTO) in the tritium-containing wastewater can be treated as common water molecules (H 2 O) during electrolysis.
The chemical equation of the electrolytic reaction is: 2H (H) 2O→2H2+O2
From the above reaction formula, 1 water molecule (H 2 O) was electrolyzed to generate 1 hydrogen molecule (H 2) and 0.5 oxygen molecule (O 2).
The molar mass of water was 18g/mol, and the molar masses of hydrogen and oxygen were 2g/mol and 32g/mol, respectively. Thus 1kg of water contains 1000.18=55.56 mol of water and electrolysis produces 55.56mol of hydrogen and 55.56×0.5=27.78 mol of oxygen.
The ionization of 1 hydrogen molecule requires 2 electrons and the ionization of 1 oxygen molecule requires 4 electrons, so the total number of electrons required is 2×55.56+4×27.78= 222.24mol. And the charge carried by 1mol of electrons is
N=n×n A×e＝1×6.02×1023×10-19＝9.632×104 C, where N A is an avogalileo constant, e is a basic charge, and C is a unit of charge amount, coulomb.
The amount of charge required for electrolysis of 1kg of water was 222.24X 9.632X 10 4＝2.14×107 C.
From the electric energy (J) =charge amount (C) ×voltage (V) and the experimental electrolysis voltage of 1.6V, the required electric energy is 2.14×10 7 ×1.6= 3.424 ×107J, which is converted into kilowatt-hours (i.e., degree, 1 kilowatt-hour=1 degree electricity) for daily use, 1 kwh=3.6×10 6 J is known, so the electric energy required for 1kg of water to be electrolyzed is 3.424 ×10 7 ++3.6
×106)＝9.51kwh。
Namely 9.51 DEG electricity is needed for electrolysis of 1kg tritium-containing wastewater.
The electrical energy released by the combustion of hydrogen in the Solid Oxide Fuel Cell (SOFC) 6 is calculated as follows:
Since the partial pressure of external hydrogen and tritium-containing wastewater during electrolysis is set to be 1:1, the amount of hydrogen fed to the SOFC can be considered to be 2×55.56= 111.12mol. The heat energy released by combustion of 1mol of hydrogen is known to be 286 kilojoules (kJ), so that the heat energy released by combustion of 111.12mol of hydrogen is 111.12X 286X 10 3＝3.18×107 J. SOFCs have a cell efficiency of about 55% and thus have 3.18×10 7×55％＝1.75×107 J of energy converted to electrical energy, also in kwh, with a released electrical energy of 1.75×10 7÷(3.6×106) =4.86 kwh.
I.e. the electrical energy generated during combustion is 4.86 degrees electricity.
Considering the energy loss (5%) in the electrolysis and combustion processes, about 95% of the electrical energy released by SOFC6 can be supplied to SOEC3 for electrolysis, i.e. 4.86×95% = 4.617kwh, so that the electrical energy requirement of 4.617 +.9.51×100% = 48.55% in the electrolysis process, i.e. 9.51-4.617 = 4.893 degrees of electricity is required for electrolysis of 1kg of water, greatly reducing the energy consumption of the system.
Meanwhile, the current density of the single symmetrical solid oxide cell adopted by the invention is 1778mA/cm 2 at the temperature of 1.6V and 800 ℃, so that the electrolysis power is 2.84W/cm 2. Consider a SOEC of 100 10 layers of 5cm by 5cm of this cell composition, with a power of about 71kW. The efficiency of the electrolytic cell is about 70%, so that the time required for electrolysis of 1kg of tritium-containing wastewater is 4.893 ×60 × (71×70%) =5.9 minutes, which is quite fast. The SOEC has smaller specification and is easy to replace; the power is larger, the cost performance is high, and the application prospect is very good.
The foregoing detailed description of the invention has been presented for purposes of illustration and description, but it is not intended that the invention be limited to the details of this description, but rather that it be understood that the invention is capable of numerous and simple embodiments and substitutions by those skilled in the art without departing from the spirit of the invention.
Example 4
Based on the embodiment 1 and the embodiment 3, a tritium-containing water treatment method and a tritium-containing water treatment system are provided, wherein the adopted electrolyte material is lanthanum strontium gallium magnesium (La 0.9Sr0.1Ga0.8Mg0.2O2.7), the cathode material 402 and the anode material 403 are SOCs of strontium ferrite (SrFe 1.05O2.7), the current density of the SOCs is 921mA/cm 2 under the conditions of the electrolysis voltage of 1.3V and the temperature of 800 ℃, and the electrolysis power of the SOCs is about 1.20W/cm 2; comparative examples 1 and 2 were prepared by changing the electrolyte material or the electrode material, and the electrolytic power of the batteries of different electrolytes and electrode materials at an electrolytic voltage of 1.3v and a temperature of 800 c were compared, and the results are shown in table 1.
TABLE 1 electrolytic Power of batteries with different electrolytes and electrode materials at an electrolytic voltage of 1.3V at 800 ℃
As can be seen from table 1, under the same conditions, the battery power of the SOC of example 1 of the present invention was 1.92 times that of comparative example 1 and 2 times that of comparative example 2. It can be seen that the battery electrolysis power of the example 1 and the comparative example 2 of the present invention is significantly improved compared with the battery electrolysis power of the example 3, so that the optimum electrolyte material of the present invention selects lanthanum strontium gallium magnesium (La 0.9Sr0.1Ga0.8Mg0.2O2.7), and the optimum cathode material 402 and anode material 403 select the SOC of strontium ferrite (SrFe 1.05O2.7).
Example 5
A 1200 hour stability test was performed on a symmetrical cell with strontium ferrite as the cathode and anode and lanthanum strontium gallium magnesium as the electrolyte:
Experimental conditions: the atmosphere on one side of the battery is dry pure hydrogen, the atmosphere on the other side is air, and the temperature is 600 ℃. Data were recorded every 10 hours and the maximum power density was plotted as a function of time as shown in fig. 4.
An EDS line scan inset of the electrode-electrolyte interface before and after the 1200 hour stability test is attached to fig. 4. In the illustration, the left side is a strontium ferrite electrode, the right side is an LSGM electrolyte, a gray broken line represents Fe, the ordinate is the intensity unit CPS of Fe element signals, and the abscissa is the depth from the surface of a sample, and the unit is microns.
As can be seen in fig. 4, after 1200 hours of continuous testing, the iron element is still mainly distributed on one side of the electrode, no iron element diffusion occurs between the strontium ferrite electrode and the electrolyte lanthanum strontium gallium magnesium, and the boundary is still obvious and clear. The material has long stable life, obvious boundary between the electrode material and the electrolyte material at 600 ℃ for more than 1200 hours, no obvious element diffusion and less than 5 percent of power density fluctuation.
Claims (10)
1. A method for treating tritium-containing water, which is characterized by comprising the following three steps:
(1) Electrolysis of tritium-containing water: carrying out electrolytic treatment on tritium-containing water by utilizing a solid oxide electrolytic cell (4) based on an oxygen ion conductor electrolyte (401) to obtain tritium-containing hydrogen;
(2) Separation of hydrogen isotopes: separating hydrogen isotopes from tritium-containing hydrogen by adopting a gas centrifugation method or an electroseparation method based on a solid oxide proton conductor membrane (10);
(3) Hydrogen gas is converted to water: the hydrogen gas separated in the step (2) is utilized to generate water by a solid oxide fuel cell (7) based on an oxygen ion conductor electrolyte (401).
2. A method of treating tritiated water according to claim 1, characterized in that the oxygen ion conductor electrolyte (401) is selected from yttria stabilized zirconia, scandia stabilized zirconia, yttria doped ceria, lanthanum gallate or lanthanum strontium gallium magnesium;
further, the oxygen ion conductor electrolyte (401) is lanthanum strontium gallium magnesium.
3. The method for treating tritium-containing water according to claim 2, wherein the lanthanum strontium gallium magnesium has a structural formula of La 1-xSrxGa1-yMgyO3-δ, wherein x has a value ranging from 0.05 to 0.5, y has a value ranging from 0.05 to 0.5, and δ has a value ranging from 0 to 0.5.
4. A method of treating tritiated water according to claim 1, characterized in that both sides of the electrolyte are provided with a cathode material (402) and an anode material (403), the cathode material (402) and the anode material (403) being identical.
5. The method for treating tritium-containing water according to claim 4, wherein the cathode material (402) and the anode material (403) are made of strontium ferrite, the chemical formula of the strontium ferrite is SrFe αO3-δ, the value of alpha is 1.01-1.1, and the value of delta is 0-0.5.
6. The method of claim 1, wherein the proton conductor is one of a calcium oxide stabilized zirconia, a silicon doped boron oxide, or a solid oxide proton conductor material based on elemental doping of barium zirconium yttrium.
7. The method according to claim 6, wherein the solid oxide proton conductor material based on barium zirconium yttrium for element doping has a chemical formula BaZr kYnMpO3-q, wherein k has a value of 0.5 to 0.95, n has a value of 0.04 to 0.4, p has a value of 0.01 to 0.2, q has a value of 0 to 0.5, and k+n+p=1.
8. The tritium-containing water treatment system of any one of claims 1 to 7, comprising a circulating electrolysis unit for tritium-containing water, a hydrogen tritide separation and purification unit comprising a proton conductor membrane (10) or a plurality of centrifuges, and a solid oxide fuel cell unit for converting hydrogen gas to water.
9. The tritium-containing water treatment system of claim 8, wherein the tritium-containing water circulating electrolysis unit comprises a reactor cooling water loop, a solid oxide electrolysis cell (4) and a circulating pump (5), the reactor (10) cooling water loop is connected with the solid oxide electrolysis cell (4), and the circulating pump (5) connects the solid oxide electrolysis cell (4) and a cathode outlet of the solid oxide electrolysis cell (4) through a pipeline.
10. The tritium-containing water treatment system of claim 8, wherein the solid oxide fuel cell unit comprises a solid oxide fuel cell (7), a water recovery tank (8) and a circulating pump a (9), wherein the solid oxide fuel cell (7) is connected with the water recovery tank (8), and two ends of the circulating pump a (9) are respectively connected with an air inlet and an air outlet of the solid oxide fuel cell (7).
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