Fission reactor adopting lithium-lead alloy as coolant

Abstract

The invention discloses a fission reactor adopting a lithium lead alloy as a coolant, and belongs to the field of nuclear fission reactors. Aiming at the problems of high radiotoxicity of polonium-210 in the existing lead-bismuth cooled reactor and difficulty in engineering realization caused by overhigh melting point of a pure lead cooled reactor, the invention provides a fission reactor scheme taking a lithium-lead alloy as a coolant, and the fission reactor scheme has the following advantages: 1, the generation of polonium-210 is fundamentally eliminated, and the radioactivity safety performance is improved; 2, the melting point of the lithium-lead alloy is lower than that of pure lead, and engineering implementation is more feasible; the invention provides an innovative solution for solving the contradiction between the safety and the engineering feasibility of the current lead bismuth or pure lead cooling reactor, and has important engineering application value.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of nuclear fission reactors, and particularly relates to a fission reactor using lithium-lead alloy as coolant. BACKGROUND

[0002] Lead-cooled reactors have become the focus of the fourth generation nuclear energy system due to their excellent neutron economy, high-temperature operation potential, and safe operation at atmospheric pressure. However, the current use of pure lead or lead-bismuth alloy coolant still faces significant technical bottlenecks in practical application, which are described as follows:

[0003] From the 1950s to the 1980s, the Soviet Union's "Alpha" class nuclear submarine used lead-bismuth eutectic alloy (Pb-44.5Bi) as reactor coolant, becoming the only lead-based reactor system to have been implemented in engineering applications worldwide. The alloy has a melting point of only about 125℃, which allows it to remain in a liquid state without the need for continuous high-temperature operation during frequent start-stop of the submarine, significantly reducing energy consumption and simplifying operation. However, the alloy has serious defects in the irradiation environment: neutrons captured by bismuth-209 generate bismuth-210 with a half-life of 5.01 days, which is converted to polonium-210 through beta decay. As a strong alpha-emitting radionuclide, polonium-210 is not only highly toxic (about 250 million times more toxic than arsenic), but also has a boiling point of only 550℃, making it extremely volatile and easily escaping during system leaks or equipment maintenance, posing a serious risk of radiation contamination. To avoid the radioactive risks posed by polonium-210 in lead-bismuth alloy, the international nuclear energy community is shifting its research focus to pure lead coolant. Pure lead, although free of toxic byproducts, has a melting point of about 327℃, which poses a risk of local solidification under abnormal operating conditions, potentially causing flow channel blockage, equipment damage, and even serious safety accidents such as core overheating. This physical property, combined with the chemical toxicity of lead-bismuth alloy, presents a dual challenge in the development of lead-based coolants.

[0004] Therefore, the purpose of the present application is to overcome the technical defects of the existing lead-based coolant, and to propose an innovative scheme of using lithium-lead alloy as a coolant for a fission reactor, which has multiple advantages: first, compared with lead-bismuth alloy, it fundamentally avoids the generation of strong radioactive nuclides such as polonium-210, significantly improving the radiation safety level; second, compared with pure lead coolant, lithium-lead alloy has a lower melting point, which greatly reduces the risk of operation caused by the solidification of the coolant, providing higher feasibility for engineering implementation. In addition, considering the urgent demand for tritium fuel for the start of a fusion reactor and the extreme scarcity of tritium in nature, it is further proposed to divide the lithium-lead alloy cooled reactor into two types: one is to use lithium-lead alloy with natural lithium abundance, which can control the amount of tritium generated, and is suitable for conventional fission reactors that emphasize radiation safety; the second is to use lithium-lead alloy with high enrichment of lithium-6, which can provide the necessary tritium fuel for the start of a fusion reactor through the 6Li(n, α)T tritium breeding reaction while realizing the function of power generation, realizing the energy development path of fission-fusion cooperation. SUMMARY

[0005] Based on the background art, the present application aims to systematically solve the three core problems of the existing lead-based coolant: eliminate the inherent defect of lead-bismuth eutectic alloy that produces strong radioactive polonium-210 due to neutron irradiation; overcome the safety risk of pure lead coolant that is prone to solidification blockage due to high melting point; and provide a function customizable lithium-lead cooled reactor to adapt to different scene needs of conventional fission power generation and providing tritium fuel for the start of a fusion reactor, thereby improving the safety, functionality and overall benefit of the reactor.

[0006] To achieve the above purpose, the present application proposes a fission reactor using lithium-lead alloy as a coolant, which has multiple advantages: first, compared with lead-bismuth alloy, it fundamentally avoids the generation of strong radioactive nuclides such as polonium-210, significantly improving the radiation safety level; second, compared with pure lead coolant, lithium-lead alloy has a lower melting point, which greatly reduces the risk of operation caused by the solidification of the coolant, providing higher feasibility for engineering implementation. In addition, considering the urgent demand for tritium fuel for the start of a fusion reactor and the extreme scarcity of tritium in nature, it is further proposed to divide the lithium-lead alloy cooled reactor into two types: one is to use lithium-lead alloy with natural lithium abundance, which can control the amount of tritium generated, and is suitable for conventional fission reactors that emphasize radiation safety; the second is to use lithium-lead alloy with high enrichment of lithium-6, which can provide the necessary tritium fuel for the start of a fusion reactor through the 6Li(n, α)T tritium breeding reaction while realizing the function of power generation, realizing the energy development path of fission-fusion cooperation.

[0007] The technical scheme of the present application is as follows:

[0008] A fission reactor using a lithium-lead alloy as a coolant, wherein liquid lithium-lead alloy is used as the primary coolant for the reactor core and main circulation loop; the lithium-lead alloy is a eutectic with a melting point range of 220-250℃; the lithium-lead alloy does not contain bismuth to eliminate the generation of polonium-210.

[0009] In the above technical solution, the lithium-lead alloy contains 0.6-0.8% lithium by mass and 99.2-99.4% lead by mass.

[0010] In the above technical solutions, two types are classified according to the abundance of lithium-6 isotopes:

[0011] Natural lithium abundance type: Lithium-6 abundance is 7.5%-7.6%;

[0012] Highly enriched lithium-6 type: lithium-6 abundance ≥ 60%.

[0013] In the above technical solution, the naturally lithium-abundant lithium-lead alloy is used in a conventional fission reactor, and its tritium formation rate is ≤1×10⁻⁶. 12 atoms / s·m 3 .

[0014] In the above technical solution, the highly enriched lithium-6 lithium-lead alloy breeds tritium through the 6Li(n,α)T reaction, with a tritium yield ≥5×10⁻⁶. 13 atoms / s·m 3 It is used to provide tritium fuel for fusion reactors.

[0015] In the above technical solution, the total amount of impurity elements in the lithium-lead alloy is <300 ppm, of which nitrogen, molybdenum, niobium, cobalt and copper are ≤5 ppm individually.

[0016] The above technical solution also includes a passive coolant solidification blocking system that automatically activates the external heating system when the temperature is below 220°C.

[0017] In the above technical solution, the inner wall of the main circulation loop pipe is covered with a coating resistant to liquid metal corrosion, and the coating composition is FeCrAlY alloy.

[0018] In the above technical solution, the preparation method of the lithium-lead alloy includes: mixing lithium powder and lead powder under the protection of high-purity argon gas; melting and electromagnetic stirring at a temperature below 470°C; and dynamic rotary cooling casting.

[0019] In the above technical solution, tritium fuel is separated and extracted from the coolant by helium purging and molecular sieve adsorption.

[0020] Beneficial effects:

[0021] 1. Lithium-lead alloys retain the advantages of lead-based coolants, such as good neutronic properties and high thermal conductivity. At the same time, compared to lead-bismuth alloys, they fundamentally avoid the generation of highly radioactive nuclides such as polonium-210, significantly improving radiation safety. Compared to pure lead coolants, lithium-lead alloys have a lower melting point, greatly reducing operational risks caused by coolant solidification and providing greater feasibility for engineering implementation.

[0022] 2. Based on the abundance level of lithium-6 in lithium-lead alloys, lithium-lead cooled reactors are divided into high-enriched lithium-6 type and natural lithium-enriched type. If a lithium-lead alloy with natural lithium-6 abundance is used as a coolant, the generation of tritium can be effectively suppressed and the material cost can be reduced, making it suitable for conventional fission reactors where radiation safety is the primary consideration. If a lithium-lead alloy with high lithium-6 enrichment is used as a coolant, the tritium breeding reaction of 6Li(n,α)T can be used to achieve fission power generation while providing the necessary tritium fuel for the start-up of fusion reactors. Detailed Implementation

[0023] The present invention will now be described in detail with reference to specific embodiments. However, the following embodiments are only for illustrative purposes, and the scope of protection of the present invention should include all the contents of the claims. Moreover, through the description of the following embodiments, those skilled in the art can fully implement all the contents of the claims of the present invention.

[0024] Example 1

[0025] The preparation method of lithium-lead alloy is as follows:

[0026] 1. Argon gas with a purity ≥ 99.999% is purified by removing water and oxygen, and the entire process is carried out under the protection of this high-purity argon gas;

[0027] 2. High-purity lithium and high-purity lead are selected as raw materials, and impurity elements (such as N, Mo, Nb, Co, Cu, etc.) are strictly controlled to ensure that the total impurities are <300 ppm and individual impurities are ≤5 ppm. The two materials are separately processed into fine powders in an argon atmosphere;

[0028] 3. According to the mixing ratio, separate the lead powder and lithium powder into independent hoppers. When mixing, first add a portion of the lead powder and start stirring, then simultaneously add the lithium powder and the remaining lead powder, and continue mechanical stirring for 20 minutes until the mixture is uniform;

[0029] 4. The melting furnace is subjected to a vacuum-argon circulation treatment at 400℃, and the mold is baked at 450℃ to remove residual gas adsorbed on the inner surface of the system.

[0030] 5. Add the mixed powder to the melting furnace in batches and heat to melt under electromagnetic stirring. Monitor the temperature in real time (≤470℃). After the exothermic reaction phase ends, continue stirring for 20 minutes and let it stand at 400℃ for 3 hours.

[0031] 6. Detect alloy composition online and adjust the batching ratio accordingly. After passing the test, filter the melt at 400℃ to remove high-melting-point impurities, ensuring the total impurities in the finished product are <290 ppm.

[0032] 7. The 270℃ liquid alloy is injected into a horizontally rotating mold and solidified during dynamic cooling, which effectively suppresses the gravitational segregation of lithium elements and obtains an alloy ingot with uniform composition.

[0033] Example 2

[0034] Currently, lead-based reactors commonly use lead-bismuth or pure lead as coolants. In lead-bismuth reactors, bismuth reacts with neutrons to produce polonium-210, a strong alpha radionuclide. Polonium-210 is not only extremely toxic (approximately 250 million times more toxic than arsenic), but also has a boiling point of only 550°C. It is highly volatile and easily volatilizes during system leaks or equipment maintenance, posing a serious risk of radiation contamination. While pure lead does not produce highly toxic byproducts, its melting point is as high as approximately 327°C. Under abnormal operating conditions, it poses a risk of localized solidification, which could lead to blockage of flow channels, equipment damage, or even induce serious safety accidents such as core overheating.

[0035] This invention proposes a fission reactor using a lithium-lead alloy as a coolant. While retaining the excellent neutronic properties and high thermal conductivity of lead-based coolants, the lithium-lead alloy, because it does not contain bismuth, fundamentally avoids the generation of highly radioactive nuclides such as polonium-210 compared to lead-bismuth reactors, significantly improving radiation safety. Furthermore, the lithium-lead alloy has a melting point of approximately 235°C, far lower than pure lead (approximately 327°C), greatly reducing the operational risks caused by coolant solidification and providing greater feasibility for engineering implementation.

[0036] Based on the abundance level of lithium-6 in lithium-lead alloys, lithium-lead alloy cooled reactors are divided into two types: First, lithium-lead alloys with natural lithium abundance can control the amount of tritium generated, which is suitable for conventional fission reactors that emphasize radiation safety; Second, lithium-lead alloys with high lithium-6 enrichment can provide the necessary tritium fuel for fusion reactor startup through the 6Li(n,α)T tritium breeding reaction, while realizing the power generation function, thus achieving a fission-fusion synergistic energy development path.

[0037] The comparison in this embodiment fully demonstrates that the present invention provides an innovative solution to the contradiction between safety and engineering feasibility in current lead-bismuth or pure lead-cooled reactors, and also has the function of providing the necessary tritium fuel for fusion reactor startup, thus having significant engineering application value.

[0038] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A fissile reactor using lithium-lead alloy as coolant, characterized in that: liquid lithium-lead alloy is used as primary coolant for the reactor core and the main circulation loop; the lithium-lead alloy is eutectic with a melting point range of 220-250℃; the lithium-lead alloy does not contain bismuth to eliminate the production of polonium-210.

2. The fission reactor of claim 1, wherein: the lithium-lead alloy contains 0.6-0.8% lithium and 99.2-99.4% lead by mass fraction.

3. The fission reactor of claim 1, wherein: the lithium-6 isotope abundance is divided into two types: natural lithium abundance type: lithium-6 abundance is 7.5%-7.6%; highly enriched lithium-6 type: lithium-6 abundance is ≥60%.

4. The fission reactor of claim 3, wherein: The natural lithium abundance type lithium-lead alloy is used in a conventional fission reactor, and the tritium generation rate is ≤1×10 12 atoms / s·m³.

5. The fission reactor of claim 3, wherein: The high lithium-6 type lithium-lead alloy is prepared by 6 The Li(n, alpha)T reaction is used to breed tritium, and the tritium yield is greater than or equal to 5*10 13 atoms / s*m3, and is used to provide tritium fuel for a fusion reactor.

6. The fission reactor of claim 1, wherein: the total amount of impurities in the lithium-lead alloy is <300 ppm, and the single impurities of nitrogen, molybdenum, niobium, cobalt, and copper are ≤5 ppm.

7. The fission reactor of claim 1, wherein: a passive coolant solidification blocking system is also included, which automatically starts the external heating system when the temperature is below 220℃.

8. The fission reactor of claim 1, wherein: the inner wall of the main circulation loop pipe is covered with a liquid metal corrosion resistant coating, and the coating composition is FeCrAlY alloy.

9. The fission reactor of claim 1, wherein: the preparation method of the lithium-lead alloy includes: mixing lithium powder and lead powder under high-purity argon protection; smelting below 470℃ and electromagnetic stirring; dynamic rotation cooling casting forming.

10. The fission reactor of claim 5, wherein: tritium fuel is separated and extracted from the coolant by helium purging and molecular sieve adsorption.