Method for laser-driven thorium-based molten salt reactor u233 online breeding and separation

Abstract

The present application relates to the field of nuclear fuel cycle and advanced nuclear energy technology, and discloses a kind of laser-driven thorium-based molten salt reactor U233 online proliferation and separation method, comprising the following steps: S1 molten salt reactor system initialization;S2 start laser neutron source to realize nuclide conversion;S3 start Pa-233 online extraction process;S4 carry out Pa-233 and U233 separation;U233 salt returns to the core and is recycled in S5;S6 laser power feedback control;S7 safety protection of freeze valve passive safety system.The technical scheme of the present application uses laser neutron source to drive pure Th-232 subcritical molten salt reactor and combines Pa-233 online extraction, which achieves pure thorium zero uranium start and sustainable net proliferation of U233.Compared with the prior art which relies on U235 or Pu-239 as the initial fissile material and cannot achieve pure thorium start, the present application solves the problem of high dependence on traditional fissile nuclides and limited nuclear fuel sources.

Description

Technical Field

[0001] This invention relates to the fields of nuclear fuel cycle and advanced nuclear energy technology, specifically to a laser-driven online breeding and separation method for U233 in a thorium-based molten salt reactor. Background Technology

[0002] Thorium-based molten salt reactors, as one of the core options for fourth-generation advanced nuclear reactors, have become an important technological direction for solving problems such as nuclear safety hazards, nuclear waste disposal difficulties, and low nuclear resource utilization efficiency of traditional nuclear reactors, thanks to their outstanding advantages such as high inherent safety, excellent neutron economy, large nuclear fuel burnup depth, and low nuclear non-proliferation risk. They have significant strategic importance and broad industrial application prospects in the fields of large-scale application of clean energy and independent supply of nuclear fuel. One of their core technologies is to achieve efficient U233 breeding in order to achieve sustainable recycling of nuclear fuel.

[0003] Currently, in existing thorium-based molten salt reactor U233 breeder technology schemes, the core startup and U233 breeder process are highly dependent on traditional initial fission materials such as U235 and Pu239. It is impossible to achieve a startup mode using pure Th-232 as the sole initial nuclear fuel. As a result, the source of nuclear fuel is limited by the reserves of traditional fission materials and international control, making it difficult to achieve independent development of thorium resources and independent recycling of nuclear fuel. This greatly restricts the industrial promotion and application of thorium-based molten salt reactors. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a laser-driven online breeding and separation method for U233 in a thorium-based molten salt reactor, which solves the problems of high dependence on traditional fission nuclides and limited nuclear fuel sources.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a laser-driven online proliferation and separation method for U233 in a thorium-based molten salt reactor, comprising the following steps: S1, Molten salt reactor system initialization: 7LiF-BeF2-ThF4 fuel salt is configured and injected into the thorium-based molten salt reactor core. Pure Th-232 is the only initial nuclear fuel in the fuel salt, and the effective core multiplication factor is set. Controlling the subcritical range provides a foundation for external neutron source driving; S2, activate the laser neutron source, use a high repetition rate laser to generate fast neutrons and inject them into the subcritical core, drive Th-232 to undergo a neutron capture reaction to achieve nuclide conversion in the early stage of U233 breeding; S3 predicts the Pa-233 concentration accumulation pattern through reactor physics calculations and monitors the Pa-233 concentration in the reactor core in real time by combining online measurement. When the Pa-233 concentration reaches the preset threshold, the Pa-233 online extraction process is initiated to extract fuel salt from the reactor core main circulation loop to the separation system. S4. The extracted fuel salt is separated from Pa-233 and U233 by fluorination volatilization or electrochemical separation process, so that the Pa-233 extraction rate is ≥95%, and pure U233 salt and molten salt containing Pa-233 are obtained. S5, the pure U233 salt obtained in S4 is directly returned to the reactor core to participate in the fission reaction, while the molten salt containing Pa-233 is transferred to an off-core decay vessel for isothermal decay, so that Pa-233 is completely decayed into U233 salt and then returned to the reactor core for recycling. S6 monitors the U233 concentration and neutron flux in the reactor core in real time through a laser power feedback control loop, and dynamically adjusts the laser power to ensure that the U233 concentration remains stable within a preset range, so that the net U233 breeding ratio BR is maintained at 1.1–1.2. S7 achieves full safety protection throughout the entire breeding and separation process through a passive safety system of a cryo-valve. When the system malfunctions, the laser neutron source is immediately shut down and the cryo-valve is triggered to drain salt, thus completing the safety emergency handling.

[0006] Preferably, in step S1, the molten salt reactor system initialization includes: Configure 7LiF-BeF2-ThF4 fuel salt, control the 7Li enrichment in the fuel salt to be ≥99.95%, and use pure Th-232 as the only initial nuclear fuel; The prepared fuel salt is injected into the core of the thorium-based molten salt reactor. Through core structure design and fuel salt ratio adjustment, the effective core multiplication factor is increased. It is controlled within the subcritical range of 0.95–0.98.

[0007] By adopting the above technical solution, and using a 7LiF-BeF2-ThF4 ternary fuel salt system with a 7Li enrichment of ≥99.95%, pure Th-232 is used as the sole initial nuclear fuel, eliminating the dependence on traditional fissile materials. Simultaneously, the core effectively breeds nuclear fuel. Precisely controlling the neutron density within the subcritical range of 0.95–0.98 not only avoids the occurrence of self-sustaining fission reactions in the reactor core, but also provides a stable foundation for external laser neutron source driving. Therefore, the reactor core achieves initial stability, autonomous control of nuclear fuel, and adaptability to external driving requirements.

[0008] Preferably, in step S2, activating the laser neutron source to achieve nuclide conversion includes: High-repetition-rate lasers are activated to accelerate particles to collide with a Li / Be target or directly inject Li / Be components into the reactor core fuel salt to generate fast neutrons, achieving a neutron yield of 10. 8 -10 9 n / s; Fast neutrons are injected into the subcritical reactor core to drive the Th-232 to undergo a neutron capture reaction, completing the nuclide conversion in the early stage of U233 breeding.

[0009] By adopting the above technical solution, a stable fast neutron flux is generated by a high-repetition-rate laser neutron source with specific parameters, ensuring the high efficiency of nuclide conversion. At the same time, the dependence on traditional initial fission materials is avoided. Therefore, a stable and efficient effect of nuclide conversion in the early stage of U233 breeding is obtained.

[0010] Preferably, in step S3, initiating the Pa-233 online extraction process includes: Based on reactor physics calculations and the half-life characteristics of Pa-233, the preset concentration threshold is 0.05-0.1 mol / L; A gamma-ray energy spectrum online monitoring device was used in conjunction with laser-induced breakdown spectroscopy to collect characteristic gamma-ray signals of Pa-233 in real time and quantify the Pa-233 concentration in the reactor core. When the Pa-233 concentration is detected to reach the preset threshold, online extraction is initiated, and the extraction flow rate of the main circulation loop of the reactor core is controlled to be 1–5% of the total circulation volume, and the extraction flow rate is 0.5–2 L / min. The extraction frequency was matched with the half-life of Pa-233 and set to 1–2 times per week.

[0011] By adopting the above technical solution, the timely extraction of Pa-233 is ensured by using precise Pa-233 concentration threshold control, reasonable extraction parameters and extraction frequency adapted to half-life, while avoiding the impact of the extraction process on the main core circulation and reducing the ineffective loss of Pa-233. Therefore, the effect of improving U233 breeding efficiency and reducing nuclide loss is achieved.

[0012] Preferably, in step S4, when a fluorination volatilization separation process is used, the following sub-steps are included: S4101. The extracted fuel salt is introduced into the fluorination reaction tower, the reaction temperature is controlled at 550–650℃, and a mixture of HF and F2 gas is introduced into the reaction tower, wherein the volume ratio of HF to F2 in the mixture is 1:1–1:3. S4102, the U233 in the fuel salt reacts with F2 to generate UF6 gas, and Pa-233 is reduced to non-volatile PaF4 and remains in the molten salt, thus achieving the initial separation of U233 and Pa-233; S4103. UF6 gas is introduced into a condensation recovery tower, and the condensation temperature is controlled at <56℃ to condense UF6 gas into solid UF6. The solid UF6 is then hydrolyzed or reduced to pure U233 salt to complete the fluorination volatilization separation. Under this process, the Pa-233 extraction rate is controlled at 98–99.5%, and the amount of U233 processed per week is 4–8 kg.

[0013] By adopting the above technical solution, and by using precisely controlled reaction temperature, mixed gas ratio, and condensation temperature, efficient separation is achieved by utilizing the difference in volatility between UF6 and PaF4. At the same time, the extraction rate and throughput are strictly controlled. Therefore, the results are good, with high Pa-233 extraction rate, and the efficiency requirements for industrial-scale amplification are met.

[0014] Preferably, in step S4, when an electrochemical separation process is used, the following sub-steps are included: S4201. The extracted fuel salt is introduced into the electrolysis separation system, and the electrolysis temperature is controlled at 25–50℃ to maintain the stability of the electrolysis system. S4202. Apply a DC voltage to the electrolysis system and control the current density to be 10–50 mA / cm². 2 This causes U233 to undergo a reduction reaction and achieves separation; S4203. The separated U233 is purified to obtain pure U233 salt that meets the requirements. The amount of U233 processed per week is 3-7 kg.

[0015] By adopting the above technical solution, selective separation is achieved by using suitable electrode materials, precise voltage and current density control, and utilizing the difference in redox potential between U233 and Pa-233. The equipment is easy to operate, thus achieving the effect of simple separation process, adaptability to small and medium power stacks, and meeting the requirements for Pa-233 extraction rate.

[0016] Preferably, in step S6, the laser power feedback control includes: The preset control range for U233 concentration was set to 3–8%, and monitoring and regulation were carried out through a feedback control loop consisting of a neutron flux detector, an online salt composition spectrometer, and a laser power controller. Neutron flux data and U233 concentration data of the reactor core are collected in real time using a neutron flux detector and an online salt composition spectrometer, and then transmitted to the laser power controller. When the U233 concentration exceeds 8%, the laser power controller automatically reduces the laser power by 10–20%. When the U233 concentration is below 3%, it automatically increases the laser power to the preset range, so that the net proliferation ratio (BR) of U233 is maintained at 1.1–1.2.

[0017] By adopting the above technical solution, and by using a closed-loop control logic of real-time monitoring and dynamic regulation to accurately set the U233 concentration control range and power adjustment range, the effect of stable U233 concentration, maintaining the net proliferation ratio within the design range, and ensuring the continuous stability of the proliferation process is achieved.

[0018] Preferably, in step S7, the safety protection operation of the passive safety system for the refrigeration valve includes: The passive safety system of the refrigeration valve includes a flattened GH3535 alloy refrigeration valve tube, a cooling air duct, a resistance heating strip, and a subcritical shielded storage tank. The refrigeration valve tube is installed in the core salt discharge pipeline and is externally wrapped with a cooling air duct and a resistance heating strip. When the system detects an anomaly, it immediately shuts down the laser neutron source, and simultaneously de-energizes the resistance heating band and activates the cooling gas duct. The refrigeration valve is controlled to complete the molten salt freezing and discharge operation within 9–11 minutes, and all the molten salt is discharged into the subcritical shielded storage tank.

[0019] By adopting the above technical solution, and using a structurally adapted refrigeration valve safety system, emergency response is quickly triggered in case of abnormality, and the salt discharge time is strictly controlled. Therefore, the effects of full-process safety protection, rapid emergency response, and prevention of nuclear safety accidents are achieved.

[0020] Preferably, in S2, the pre-conversion regulation and process continuity control of S1-S7 include: In the early stages of molten salt reactor breeding, the laser power is controlled at 10–30% of full power, so that the neutron capture reaction of Th-232 dominates the core nuclear reaction. The entire process from S1 to S7 was carried out online without stopping the thorium-based molten salt reactor; The separation system is equipped with dual parallel backup extraction circuits. When the main extraction circuit fails, it automatically switches to the backup extraction circuit to maintain the continuous Pa-233 extraction process.

[0021] By adopting the above technical solution, the ineffective consumption of U233 is avoided by using power regulation in the early stage of breeding. Combined with online operation without stopping the reactor and dual backup circuit design, the effects of directional nuclide conversion, strong process continuity and high breeding efficiency are achieved.

[0022] Preferably, in step S5, the process control for recycling U233 salt includes: The molten salt containing Pa-233 is transferred to an off-core decay vessel for isothermal static decay. After the Pa-233 has completely decayed into U233 salt, it is returned to the core to participate in the fission cycle. The breeding cycle of different power modules in molten salt reactors is controlled to be 3–5 months for 10MWth power modules and 6–10 months for 50MWth power modules. The impact of the extraction process on the overall proliferation process is controlled so that the increase in proliferation time due to the extraction process accounts for less than 10%, the increase in total power consumption accounts for less than 8%, and the total power consumption of a single module proliferation process is controlled to be 11,000–36,000 kWh.

[0023] By adopting the above technical solution, the effects of high U233 salt recycling rate, high efficiency and energy saving in the proliferation process, and compatibility with different power modules are achieved by using Pa-233 for complete decay and recycling, adapting to the power module for proliferation cycle control, and controlling the energy consumption and time impact of the extraction process.

[0024] This invention provides a laser-driven online propagation and separation method for U233 in a thorium-based molten salt reactor. It offers the following advantages:

[0025] 1. This invention achieves the technical effect of pure thorium zero-uranium start-up and sustainable net breeding of U233 by using a laser neutron source to drive a pure Th-232 subcritical molten salt reactor and combining it with online extraction of Pa-233. Compared with the existing technology that relies on U235 or Pu-239 as initial fission material and cannot achieve pure thorium start-up, this invention solves the problems of high dependence on traditional fission nuclides and limited nuclear fuel sources.

[0026] 2. The present invention employs a technical solution for the precise extraction and off-pile decay of Pa-233 using fluorination volatilization or electrochemical online separation processes. This achieves a significant reduction in Pa-233 neutron capture loss and an increase in the net U233 multiplication efficiency. Compared with existing technologies where Pa-233 accumulates in the pile and is prone to neutron capture, resulting in low U233 multiplication efficiency, this invention solves the problem of severe Pa-233 loss and difficulty in achieving a high net multiplication ratio.

[0027] 3. The present invention adopts a technical solution that combines laser power closed-loop control with a passive safety system for refrigeration valves, achieving precise control of the core reaction state and passive safety protection throughout the process. Compared with the existing technology, which has poor control flexibility and relies on active operation for safety, this invention solves the problems of lagging core state control and slow safety response under abnormal conditions. Attached Figure Description

[0028] Figure 1 This is a flowchart illustrating the steps of a laser-driven online proliferation and separation method for U233 in a thorium-based molten salt reactor according to the present invention. Figure 2 This is a schematic diagram of the fluorination volatilization separation process steps in the laser-driven thorium-based molten salt reactor U233 online breeding and separation method of the present invention; Figure 3 This is a schematic diagram of the electrochemical separation process steps of a laser-driven thorium-based molten salt reactor U233 online breeding and separation method according to the present invention. Detailed Implementation

[0029] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] Please see the appendix Figure 1 This invention provides a laser-driven online proliferation and separation method for U233 in a thorium-based molten salt reactor. The following detailed description, in conjunction with the technical solution of this invention, uses specific embodiments to illustrate the laser-driven online proliferation and separation method for U233 in a thorium-based molten salt reactor. This embodiment focuses on a 50MWth thorium-based molten salt reactor power module as the core implementation object, while also explaining the process adaptability of a 10MWth small-power module. The following embodiments are only for explaining this invention and are not intended to limit the scope of protection of this invention.

[0031] The core of the method described in this invention is to drive a pure Th-232 subcritical molten salt reactor with a laser neutron source, and combine it with an integrated process of online high-efficiency separation of Pa-233, recycling of U233 salt, closed-loop control of laser power and passive safety protection of refrigeration valves to achieve continuous net proliferation of U233.

[0032] Example 1: Laser-driven online proliferation and separation of U233 in a thorium-based molten salt reactor based on fluorination volatilization separation technology. In this example, the fluorination volatilization separation technology is used as the core separation process for Pa-233 and U233. S1, Molten Salt Reactor System Initialization: A 7LiF-BeF2-ThF4 ternary molten salt system is configured as the core fuel salt, controlling the 7Li enrichment in the fuel salt to ≥99.95%. Pure Th-232 is used as the sole initial nuclear fuel, with no other fissile nuclides added. The configured fuel salt is injected into the thorium-based molten salt reactor core via the molten salt delivery system. Through core grid structure design and fuel salt molar ratio adjustments, the effective core multiplication factor is increased. Precise control within the subcritical range provides a foundation for external laser neutron source drive, ensuring that no self-sustaining fission reaction occurs when there is no external neutron input to the reactor core.

[0033] S2, Start the laser neutron source to achieve nuclide conversion: Start the high repetition rate laser neutron source, set the laser process parameters, and convert laser energy into neutrons; Fast neutrons are generated by using laser-accelerated particles to bombard a Be target, keeping the neutron yield within the designed yield range, and the fast neutrons are continuously injected into the subcritical reactor core. Fast neutrons drive neutron capture reactions in Th-232 within the reactor core, completing the stepwise radionuclide conversion during the pre-U233 breeding phase. The radionuclide conversion chain is as follows: Th-232 captures neutrons and is converted into Th-233; Th-233 undergoes β decay to generate Pa-233; and Pa-233 undergoes β decay to generate U233. In the early stages of breeding, the laser power is controlled at a reasonable proportion of full power to make the neutron capture reaction of Th-232 dominate the core nuclear reaction, avoid the fission consumption of the small amount of U233 generated in the early stage, and ensure that the nuclide conversion proceeds in the direction of U233 breeding.

[0034] S3 predicts the Pa-233 concentration accumulation pattern through reactor physics calculations and monitors the Pa-233 concentration in the reactor core in real time by combining online measurement. When the Pa-233 concentration reaches the preset threshold, the Pa-233 online extraction process is initiated to extract fuel salt from the reactor core main circulation loop to the separation system. Open the connection pipeline between the reactor core main circulation loop and the separation system, extract fuel salt from the main circulation loop to the fluorination volatilization separation system, and control the extraction flow rate and extraction velocity. Extraction operations should be performed at a reasonable frequency to match the half-life of Pa-233, so as to avoid excessive accumulation of Pa-233 in the reactor core, which could lead to neutron capture reactions and the generation of U234, resulting in the effective loss of Pa-233. Through reactor physical burnup calculations, combined with laser neutron source intensity, core power, and kJ / kJ / kE, e Based on ff and fuel salt components, solve the nuclide transformation kinetics of Th-232 to Th-233, Th-233 to Pa-233 via β decay, and Pa-233 to U-233 via β decay, and predict the time interval for Pa-233 concentration to reach a preset threshold. A bypass online monitoring device is installed in the main circulation loop of the reactor core. The characteristic rays and spectral signals of Pa-233 are measured in real time using gamma spectroscopy and laser-induced breakdown spectroscopy, and the molar concentration of Pa-233 is quantitatively monitored online. When the Pa-233 molar concentration in the 5–100 MWth power module reaches the preset threshold of 0.05–0.1%, the online extraction process is initiated. Fuel salt is extracted from the main circulation loop of the reactor core to the separation system, and the extraction flow rate is controlled to be 1–5% of the core circulation flow rate, with an extraction velocity of 0.5–2 L / min. Extraction should be performed 1–2 times per week, in accordance with the half-life of Pa-233.

[0035] Please see the appendix Figure 2S4, Fluorination volatilization separation process for separating Pa-233 and U233: A fluorination volatilization separation process is used to achieve efficient separation of UF6 and PaF4 by utilizing the difference in volatility, including: S4101. The extracted fuel salt is introduced into a fluorination reaction tower made of nickel-based alloy material. The temperature inside the reaction tower is controlled within the reaction range by a heating system. A mixture of HF and F2 gas is continuously introduced into the reaction tower. The volume ratio of HF to F2 in the mixture is within a reasonable range. In S4102, UF4 in fuel salt undergoes an oxidation reaction with F2 to generate UF6 gas. The core reaction formula is: UF4 + F2 → UF6↑. Simultaneously, Pa-233 is reduced to non-volatile PaF4 and remains stably in the molten salt phase, achieving phase separation between U233 and Pa-233. The reaction conditions are determined by calculation using molten salt chemical thermodynamic formulas to ensure that the redox reaction proceeds in a directional and efficient manner. S4103. The UF6 gas generated in the fluorination reaction tower is introduced into the condensation recovery tower, and the temperature in the condensation recovery tower is controlled to be lower than the boiling point of UF6, so that the UF6 gas is condensed into solid UF6; the solid UF6 is converted into 7LiF-BeF2-UF4 pure U233 salt through hydrolysis or reduction process, thus completing the fluorination volatilization separation.

[0036] S5, U233 salt recycling: The pure U233 salt obtained in S4 is directly returned to the reactor core through the molten salt transport system to participate in the core fission reaction, providing fission nuclides for core energy output and continuous nuclide conversion; After the fluorination volatilization separation, the molten salt containing Pa-233 is transferred to an external constant temperature decay tank. The temperature inside the decay tank is controlled to carry out constant temperature static decay. The decay time is consistent with the half-life of Pa-233 to ensure that Pa-233 completely decays into U233 salt. The U233 salt generated during decay is returned to the reactor core via a molten salt transport system, completing a closed-loop recycling of the U233 salt and continuously replenishing the reactor core with fission fuel.

[0037] The power module's growth cycle is determined through process design. The total power consumption of a single module throughout the growth process is within a reasonable range. The percentage of growth time added by the extraction process and the percentage of total power consumption both meet design requirements. The growth cycle is calculated using the growth time calculation formula recorded in the disclosure documents. in, Proliferation time (days) The total mass (kg) of U233 required for the reactor core. The decay constant of Pa-233 (days) -1 ), , The effective neutron flux of the reactor core (n·cm) -2·s -1 ), The thermal neutron capture cross section (barn) for Th-232. The atomic number density of Th-232 (atoms·cm) -3 ), Subcritical multiplication factor, To improve the efficiency of online extraction and separation.

[0038] S6, Laser Power Feedback Control: Real-time monitoring and dynamic adjustment of core U233 concentration and neutron flux are achieved through a laser power feedback control loop. The net breed ratio BR is calculated using the formula recorded in the disclosure materials. in, Net growth ratio Effective neutron flux (n·cm) -2 ·s -1 ), The neutron capture section (barn) for Th-232 The atomic number density of Th-232 (atoms·cm) -3 ), For Pa-233 online extraction rate, The cross section (barn) of U233 fission. The atomic number density of U233 (atoms·cm) -3 ), The decay constant of Pa-233 (days) -1 ), The atomic number density at Pa-233 (atoms·cm) -3 ); A preset control range for the U233 concentration in the reactor core is set. The laser power feedback control loop consists of a neutron flux detector, an online salt composition spectrometer, and a laser power controller. The three components are linked in real time through a data transmission module. The neutron flux detector is used to collect neutron flux data in the reactor core in real time, and the salt composition online spectrometer is used to collect U233 concentration data in the reactor core fuel salt in real time. Both types of data are transmitted to the laser power controller in real time. The laser power controller adjusts the power in real time based on the received data: when the U233 concentration reaches the upper limit, it automatically reduces the laser power; when the U233 concentration drops to the lower limit, it automatically increases the laser power to the preset range.

[0039] S7, Safety Protection of the Passive Safety System for the Refrigeration Valve: Throughout the entire propagation and separation process, the passive safety system for the refrigeration valve remains in standby mode, providing comprehensive safety protection, including: The passive safety system of the refrigeration valve consists of a flat GH3535 alloy refrigeration valve tube, a cooling air passage, a resistance heating belt, and a subcritical shielded storage tank. The refrigeration valve tube is located in the core salt discharge pipeline and is tightly wrapped with the cooling air passage and resistance heating belt. The resistance heating belt works continuously to keep the molten salt in the refrigeration valve tube in a molten state. When abnormal situations such as abnormal spikes in core neutron flux, molten salt overheating, or separation system failure are detected, the control system immediately issues an instruction to shut down the laser neutron source, while simultaneously de-energizing the resistance heating band and rapidly activating the cooling gas duct. The cooling duct achieves rapid cooling of the refrigeration valve tubes through forced air cooling, controls the refrigeration valve tubes to complete the molten salt freezing and salt discharge operations within the design time, and discharges all the fuel salt in the reactor core into the subcritical shielded storage tank to complete the safety emergency treatment and ensure that no nuclear safety accident occurs in the reactor core.

[0040] Furthermore, in this embodiment, the entire process of S1-S7 is carried out online without shutting down the thorium-based molten salt reactor. The separation system is equipped with dual parallel backup extraction loops. When the main extraction loop fails, the control system automatically switches to the backup extraction loop to maintain the Pa-233 extraction process and ensure process continuity.

[0041] Please see the appendix Figure 3 Example 2: Online breeding and separation of U233 in a laser-driven thorium-based molten salt reactor based on electrochemical separation technology. This example uses electrochemical separation technology as the core separation process between Pa-233 and U233, and is suitable for small and medium-sized modular thorium-based molten salt reactors. S4, Electrochemical separation process to separate Pa-233 and U233: S4201. The fuel salt extracted from the reactor core is introduced into an electrolytic cell resistant to molten salt corrosion. An inert electrode assembly is installed in the electrolytic cell. The cathode is made of graphite and the anode is made of platinum. The electrode assembly is connected to an external DC power supply and current controller. S4202. Apply a DC voltage to the electrode assembly within a reasonable voltage range. Control the current density within a reasonable range using a current controller. These voltage and current density parameters are determined by calculation using the molten salt electrochemical formula to precisely match the redox potential difference between U233 and Pa-233. Under the action of the electric field, U233 in the fuel salt is reduced to metallic U and deposited on the cathode surface, while Pa-233 remains stably in the molten salt phase of the anode, achieving the initial separation of U233 and Pa-233. S4203. The metallic U deposited on the cathode surface is dissolved in 7LiF-BeF2 basic molten salt through a molten salt dissolution process to prepare 7LiF-BeF2-UF4 pure U233 salt, thus completing the electrochemical separation.

[0042] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for online proliferation and separation of U233 in a laser-driven thorium-based molten salt reactor, characterized in that, Includes the following steps: S1, Molten salt reactor system initialization: 7LiF-BeF2-ThF4 fuel salt is configured and injected into the pure thorium molten salt reactor core. Pure Th-232 is the only initial nuclear fuel in the fuel salt, and the effective core multiplication factor is set. Controlling the subcritical range provides a foundation for external neutron source driving; S2, activate the laser neutron source, use a high repetition rate laser to generate fast neutrons and inject them into the subcritical core, drive Th-232 to undergo a neutron capture reaction to achieve nuclide conversion in the early stage of U233 breeding; S3 predicts the Pa-233 concentration accumulation pattern through reactor physics calculations and monitors the Pa-233 concentration in the reactor core in real time by combining online measurement. When the Pa-233 concentration reaches the preset threshold, the Pa-233 online extraction process is initiated to extract fuel salt from the reactor core main circulation loop to the separation system. S4. The extracted fuel salt is separated from Pa-233 and U233 by fluorination volatilization or electrochemical separation process, so that the Pa-233 extraction rate is ≥95%, and pure U233 salt and molten salt containing Pa-233 are obtained. S5, the pure U233 salt obtained in S4 is directly returned to the reactor core to participate in the fission reaction, while the molten salt containing Pa-233 is transferred to an off-core decay vessel for isothermal decay, so that Pa-233 is completely decayed into U233 salt and then returned to the reactor core for recycling. S6 monitors the U233 concentration and neutron flux in the reactor core in real time through a laser power feedback control loop, and dynamically adjusts the laser power to ensure that the U233 concentration remains stable within a preset range, so that the net U233 breeding ratio BR is maintained at 1.1–1.

2. S7 achieves full safety protection throughout the entire breeding and separation process through a passive safety system of a cryo-valve. When the system malfunctions, the laser neutron source is immediately shut down and the cryo-valve is triggered to drain salt, thus completing the safety emergency handling.

2. The method for online proliferation and separation of U233 in a laser-driven thorium-based molten salt reactor according to claim 1, characterized in that, In step S1, the initialization of the molten salt reactor system includes: Configure 7LiF-BeF2-ThF4 fuel salt, control the enrichment of 7Li in the fuel salt to be ≥99.95%, and use pure Th-232 as the only initial convertible nuclear material; The prepared fuel salt is injected into the core of the thorium-based molten salt reactor. Through core structure design and fuel salt ratio adjustment, the effective core multiplication factor is increased. It is controlled within the subcritical range of 0.95–0.

98.

3. The method for online proliferation and separation of U233 in a laser-driven thorium-based molten salt reactor according to claim 1, characterized in that, In step S2, activating the laser neutron source to achieve nuclide conversion includes: High-repetition-rate lasers are activated to accelerate particles to collide with a Li / Be target or directly inject Li / Be components into the reactor core fuel salt to generate fast neutrons, achieving a neutron yield of 10. 8 -10 9 n / s; Fast neutrons are injected into the subcritical reactor core to drive the Th-232 to undergo a neutron capture reaction, completing the nuclide conversion in the early stage of U233 breeding.

4. The method for online proliferation and separation of U233 in a laser-driven thorium-based molten salt reactor according to claim 1, characterized in that, In step S3, initiating the Pa-233 online extraction process includes: Based on reactor physics calculations and the half-life characteristics of Pa-233, the preset concentration threshold is 0.05-0.1 mol / L; A gamma-ray energy spectrum online monitoring device was used in conjunction with laser-induced breakdown spectroscopy to collect characteristic gamma-ray signals of Pa-233 in real time and quantify the Pa-233 concentration in the reactor core. When the Pa-233 concentration is detected to reach the preset threshold, online extraction is initiated, and the extraction flow rate of the main circulation loop of the reactor core is controlled to be 1–5% of the total circulation volume, and the extraction flow rate is 0.5–2 L / min. The extraction frequency was matched with the half-life of Pa-233 and set to 1–2 times per week.

5. The method for online proliferation and separation of U233 in a laser-driven thorium-based molten salt reactor according to claim 1, characterized in that, In step S4, when a fluorination volatilization separation process is used, the following sub-steps are included: S4101. The extracted fuel salt is introduced into the fluorination reaction tower, the reaction temperature is controlled at 550–650℃, and a mixture of HF and F2 gas is introduced into the reaction tower, wherein the volume ratio of HF to F2 in the mixture is 1:1–1:

3. S4102, the U233 in the fuel salt reacts with F2 to generate UF6 gas, and Pa-233 is reduced to non-volatile PaF4 and remains in the molten salt, thus achieving the initial separation of U233 and Pa-233; S4103. UF6 gas is introduced into a condensation recovery tower, and the condensation temperature is controlled at <56℃ to condense UF6 gas into solid UF6. The solid UF6 is then hydrolyzed or reduced to pure U233 salt to complete the fluorination volatilization separation. Under this process, the Pa-233 extraction rate is controlled at 98–99.5%, and the amount of U233 processed per week is 4–8 kg.

6. The method for online proliferation and separation of U233 in a laser-driven thorium-based molten salt reactor according to claim 1, characterized in that, In step S4, when an electrochemical separation process is used, the following sub-steps are included: S4201. The extracted fuel salt is introduced into the electrolysis separation system, and the electrolysis temperature is controlled at 25–50℃ to maintain the stability of the electrolysis system. S4202. Apply a DC voltage to the electrolysis system and control the current density to be 10–50 mA / cm². 2 This causes U233 to undergo a reduction reaction and achieves separation; S4203. The separated U233 is purified to obtain pure U233 salt that meets the requirements. The amount of U233 processed per week is 3-7 kg.

7. The method for online proliferation and separation of U233 in a laser-driven thorium-based molten salt reactor according to claim 1, characterized in that, In step S6, the laser power feedback control includes: The preset control range for U233 concentration was set to 3–8%, and monitoring and regulation were carried out through a feedback control loop consisting of a neutron flux detector, an online salt composition spectrometer, and a laser power controller. Neutron flux data and U233 concentration data of the reactor core are collected in real time using a neutron flux detector and an online salt composition spectrometer, and then transmitted to the laser power controller. When the U233 concentration exceeds 8%, the laser power controller automatically reduces the laser power by 10–20%. When the U233 concentration is below 3%, it automatically increases the laser power to the preset range, so that the net proliferation ratio (BR) of U233 is maintained at 1.1–1.

2.

8. The method for online proliferation and separation of U233 in a laser-driven thorium-based molten salt reactor according to claim 1, characterized in that, In step S7, the safety protection operation of the passive safety system for the refrigeration valve includes: The passive safety system of the refrigeration valve includes a flattened GH3535 alloy refrigeration valve tube, a cooling air duct, a resistance heating strip, and a subcritical shielded storage tank. The refrigeration valve tube is installed in the core salt discharge pipeline and is externally wrapped with a cooling air duct and a resistance heating strip. When the system detects an anomaly, it immediately shuts down the laser neutron source, and simultaneously de-energizes the resistance heating band and activates the cooling gas duct. The refrigeration valve is controlled to complete the molten salt freezing and discharge operation within 9–11 minutes, and all the molten salt is discharged into the subcritical shielded storage tank.

9. The method for online proliferation and separation of U233 in a laser-driven thorium-based molten salt reactor according to claim 1, characterized in that, In S2, the pre-conversion regulation and process continuity control from S1 to S7 include: In the early stages of molten salt reactor breeding, the laser power is controlled at 10–30% of full power, so that the neutron capture reaction of Th-232 dominates the core nuclear reaction. The entire process from S1 to S7 was carried out online without stopping the thorium-based molten salt reactor; The separation system is equipped with dual parallel backup extraction circuits. When the main extraction circuit fails, it automatically switches to the backup extraction circuit to maintain the continuous Pa-233 extraction process.

10. The method for online proliferation and separation of U233 in a laser-driven thorium-based molten salt reactor according to claim 1, characterized in that, In step S5, the process control for recycling U233 salt includes: The molten salt containing Pa-233 is transferred to an off-core decay vessel for isothermal static decay. After the Pa-233 has completely decayed into U233 salt, it is returned to the core to participate in the fission cycle. The breeding cycle of different power modules in molten salt reactors is controlled to be 3–5 months for 10MWth power modules and 6–10 months for 50MWth power modules. The impact of the extraction process on the overall proliferation process is controlled so that the increase in proliferation time due to the extraction process accounts for less than 10%, the increase in total power consumption accounts for less than 8%, and the total power consumption of a single module proliferation process is controlled to be 11,000–36,000 kWh.

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