Fusion-driven subcritical reactor and its operating method

Abstract

To provide a fusion-driven subcritical reactor that is more efficient and safer. [Solution] A fusion-driven subcritical reactor is a nuclear reactor that starts and operates by amplifying neutrons obtained from nuclear fusion and supplying the amplified neutrons to a reactor that holds subcritical nuclear fuel by external neutrons. It consists of a main neutron source that generates DD neutrons through a nuclear fusion reaction, a cascade member that surrounds the main neutron source, separates fusion / fission neutrons, multiplies the fast fission neutrons generated by nuclear fission, and slows down the fast fission neutrons, and a cascade member that surrounds the cascade member and is mainly made of thorium oxide ( 232 It is equipped with a subcritical main fission blanket made of uranium dioxide (ThO2), and a neutron flattening blanket that has a neutron source located around the outer periphery of the main fission blanket to improve the containment of fission neutrons.

Description

[Technical Field]

[0001] The present invention relates to a fusion-driven subcritical nuclear reactor and a method of operating the same, which uses nuclear fusion as a neutron source for starting and controlling the subcritical nuclear fission reactor. [Background technology]

[0002] Previously, nuclear reactors that use neutrons from nuclear fission reactions and nuclear fusion systems that use nuclear fusion reactions have been proposed as power generation systems that utilize nuclear reactions. Nuclear fission reactors have a drawback that is difficult to solve, namely the accumulation of radioactive waste, while nuclear fusion has problems such as long development times, large equipment size, and high costs.

[0003] Until now, practical nuclear fission reactors have used uranium-238 as the fertile material and uranium-235 as the fissile material. The nuclear fission of uranium-235 produces various fissile materials, and the fertile uranium-238 captures neutrons to produce plutonium-239, which then undergoes complex nuclear reaction pathways to produce long-lived, highly radioactive minor actinides (MAs). Disposal of this reactor waste has therefore become a challenge.

[0004] Furthermore, while nuclear reactors are equipped with various safety measures, the social impact of an accident would be significant. Fundamental improvements in safety can, in principle, be ensured by maintaining the fuel loaded in the reactor in a subcritical state. The reason for this is as follows: Previous nuclear reactors have used a method in which the nuclear fuel is loaded to a supercritical state, and excess neutrons are removed by inserting neutron absorbing means (control rods) between the fuel, thereby forcibly reducing the amount of neutrons in the nuclear fuel to a subcritical state. If the amount of loaded nuclear fuel is maintained subcritically, the nuclear fission chain reaction will not continue and will disappear over time. Therefore, in such a subcritical reactor, it is theoretically impossible to maintain or increase the chain reaction.

[0005] In view of the above, the inventors have developed a technology that uses nuclear fusion as a neutron source for starting and controlling a subcritical nuclear fission reactor (Patent Document 1). This technology is a subcritical reactor in which muon nuclear fusion is installed on the central axis of the subcritical nuclear fission reactor and the amount of nuclear fusion neutrons is electrically adjusted. With this technology, if the nuclear fusion neutrons are cut off, the reactor will automatically return to subcriticality and shut down. In other words, even if an event such as a power loss occurs, the reactor will not go out of control. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] WO2023162286 publication Summary of the Invention [Problem to be solved by the invention]

[0007] The applicant has made further improvements to the fusion-driven subcritical reactor and has conducted intensive research and development into a fusion-driven subcritical reactor that is more efficient and safer by actively controlling neutrons.

[0008] Therefore, an object of the present invention is to provide a fusion-driven subcritical reactor that is more efficient and safer. [Means for solving the problem]

[0009] In order to achieve the above object, the invention described in claim 1 is a fusion-driven subcritical reactor that can electrically control output, amplifies neutrons obtained from fusion, and supplies external neutrons to a reactor that holds subcritical nuclear fuel, thereby starting and operating the reactor. The reactor comprises a main neutron source that generates DD neutrons by fusion reactions, a cascade member that surrounds the neutron source, separates fusion / fission neutrons, multiplies fast fission neutrons generated by fission, and slows down the fast fission neutrons, and a cascade member that surrounds the cascade member and is composed mainly of thorium oxide ( 232The present invention uses the following technical means: a subcritical main fission blanket made of thorium oxide (ThO2); and a neutron flattening blanket that has a neutron source disposed on the outer periphery of the main fission blanket and improves the containment of fission neutrons; and the cascade member has a fast neutron moderator disposed on the outside of the fission cascade made of thorium oxide that prevents the penetration of fast fission neutrons from the main fission blanket.

[0010] The invention described in claim 2 uses the technical means of the fusion-driven subcritical reactor described in claim 1, in which the main fission blanket has a honeycomb shape.

[0011] The invention of claim 3 uses the technical means that the main fission blanket is a mixture of thorium oxide and silicon carbide, mainly composed of thorium oxide, in the fusion-driven subcritical reactor of claim 2. Here, the term "mixture" is a general term for a state in which thorium oxide and silicon carbide coexist, such as a mixture of thorium oxide and silicon carbide as raw material powder and then sintered, a thorium oxide compact with silicon carbide attached and then sintered, or a thorium oxide sintered body with silicon carbide attached.

[0012] The invention described in claim 4 uses the technical means of providing a fission flattening blanket around the outer periphery of the neutron flattening blanket in the fusion-driven subcritical reactor described in claim 1, and further providing an absorption moderation blanket around the outer periphery of the fission flattening blanket to absorb all used neutrons.

[0013] In a fifth aspect of the present invention, there is provided a method for operating a fusion-driven subcritical reactor according to the second aspect, comprising irradiating the main fission blanket with DD neutrons from the main neutron source through the cascade member to generate DD neutrons in the main fission blanket. 233 The first step is to breed U, and the second step is to produce a predetermined output and consume it through nuclear fission. 233and a second step of operating U at a breeding rate of 1.0, wherein in the first step, the neutron flattening blanket suppresses the generation of thermal neutrons in the main fission blanket or increases the probability that thermal neutrons escape outside the main fission blanket, 233 The first gas is used as a cooling and moderator to reduce the fission of U and increase the breeding rate, and in the second step, a predetermined power is produced and consumed in fission. 233 In order to operate U at a breeding ratio of 1.0, a technical measure is used in which a second gas with a higher moderating power than the first gas is used as a cooling and moderator. [Effects of the Invention]

[0014] According to the fusion-driven subcritical reactor and the method of operating the same having the above configuration, it is possible to provide a fusion-driven subcritical reactor that is more efficient and safer by actively controlling neutrons. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 2 is an explanatory diagram showing the relationship between neutron energy and cross section for the thorium series and the uranium series. [Figure 2] This is an explanatory diagram showing the relationship between neutron energy and neutron reproduction factor. Additional lines have been added for explanatory purposes. [Figure 3] 1 is a perspective, partially cross-sectional view of a fusion-driven subcritical reactor. [Figure 4] 4 is a cross-sectional view of the fusion-driven subcritical reactor of FIG. 3 taken along the line AA. [Figure 5] FIG. 3 is a conceptual diagram for explaining the action and effect of the cascade member. [Figure 6] FIG. 1 is a conceptual diagram of a power generation system. [Figure 7] FIG. 1 is a cross-sectional view of a modified fusion-driven subcritical reactor. DETAILED DESCRIPTION OF THE INVENTION

[0016] (Technical Concept of Fusion-Driven Subcritical Reactor) The inventors have invented a muon-catalyzed fusion reactor as a fusion reactor capable of electrically controlling output and continuous operation. In this invention, muon-catalyzed fusion neutrons generated by injecting slow muons into deuterium (d) gas are used as an external neutron source for nuclear reactions. Furthermore, the inventors have invented a reactor in which the muon-catalyzed fusion reactor is surrounded by fissionable material such as uranium or thorium, and is irradiated with fast neutrons generated by muon-catalyzed fusion (Patent Document 1). According to the above, when the supply of fusion neutrons is cut off, the nuclear fission reaction chain stops.

[0017] The inventors further conducted extensive research and elucidated the interaction between the first-stage fusion neutron supply section and the outer nuclear fission reactor based on reactor physics. As a result, they theoretically derived that, rather than irradiating the nuclear reactor directly with fusion neutrons, a cascade-type connection section acting as a buffer between them is necessary. This invention provides a means for selecting materials and calculating the structure and dimensions related to nuclear fusion and fission reactors and cascades, making it possible to operate nuclear reactors subcritically.

[0018] The fusion neutron source emits deuterium-heavy hydrogen (hereinafter abbreviated as "DD") with an energy of 2.45 MeV, which are then collided with a cascade ring surrounding the monochromatic neutron source. The cascade ring then collided with a non-spontaneously fissionable material, 232 thorium ( 232 Th) or 238 uranium ( 238 When made of uranium, multiple fission antineutrons are emitted for each incident neutron.

[0019] Figure 1 is a graph of the thorium series and uranium series, with neutron energy E on the horizontal axis and cross section on the vertical axis. Figure 2 shows the neutron regeneration rate η. (Japan Atomic Energy Agency public data Jendl-5 file) The differences between the fission reactions of the thorium series and uranium series are the difference in the fission reaction rate (cross section) relative to neutron energy, and the difference in the neutron energy dependence of the capture and fission cross sections.

[0020] In a normal reactor size, when fusion neutrons are placed at the center of the reactor, within the mean free path centered on the fusion source, they decelerate. That is, the collision process moves to the left as shown in Fig. 1. First, focus on the 232 fission cross-section of Th in Fig. 1(a). This fission cross-section is almost zero for neutron energy E < 1 MeV, and rapidly rises at 1 < E.

[0021] The reason is that the ratio η of the macroscopic cross-section Σ of the fission reaction f to the total amount Σ of neutron losses due to various absorptions a (this is called the Neutron Reproduction Factor), η = Σ f / Σ a is calculated by, and below 1 MeV, no neutrons remain due to the fission reaction of the medium.

[0022] 2.45 MeV fusion neutrons leave 232 1.8 neutrons in the Th medium. In contrast, 238 in the U medium, 2.4 neutrons remain. Since 1 fusion neutron is absorbed for one fission to occur, the net increase or decrease in the number of neutrons in the medium due to fusion neutrons is η - 1. Therefore, 232 in Th, 1 neutron enables a chain that is 0.8 times as long each time fission collisions are repeated. On the other hand, 238 in U, since it is 2.4 - 1 = 1.4, the number of fission neutrons increases exponentially and diverges. This is because it has a most probable value near 2.0 MeV and an energy dispersion in the range of about 100 keV to 4 MeV. The generated neutrons undergo various attenuations (absorptions) depending on energy as shown in Fig. 1(a).

[0023] 232 The neutron capture reaction of Th produces 233 U, which becomes the fuel of the fission reactor, and its reaction path is given by the following equation.

[0024] (Equation 1) 232Th +n → 233 Th → β decay (22 minutes) → 233 Pa → β decay (27th) → 233 U (1MeV <E<6MeV)

[0025] (Number 2) 232 Th +n →(n,2n) reaction → 231 Th → β decay → 232Pa → β decay → 232 U → Strong radiation (6MeV <E)

[0026]

number

[0027] Thus, plutonium is produced and, through a complex reaction pathway, leaves behind highly radioactive, long-lived nuclear waste, minor actinides MA.

[0028] When the energy of the fusion neutron source exceeds 6 MeV, the (n, 2n) critical reaction occurs as shown in Equation 1. 231 Th 232 Through Pa 232 U occurs, and this 232 In U-series fission, nuclides with strong gamma-ray emission are formed. 232 Th will also be contaminated. To avoid this, DT fusion neutrons with a neutron energy of 14.1 MeV cannot be directly used as neutrons for fusion control. If DT fusion is to be used as a control factor, the fusion neutron source must be completely surrounded by a moderator to lower the neutron energy, 232 Measures are needed to prevent threshold reactions (n, 2n) from occurring in Th. A material with high moderation capacity and minimal reduction in the number of neutrons must be selected as the moderator. Specifically, heavy water must be filled or circulated between the fusion neutron source and the bonding blanket to prevent the emission of fast neutrons of 4 MeV or higher. This invention applies DD fusion, which does not require a complex structure or mechanism and does not require tritium, a substance that is dangerous to handle, and emits 2.45 MeV neutrons.

[0029] As shown in Figure 5, when neutrons produced by nuclear fusion are irradiated onto the cascade section (cascade blanket core (nuclear fission cascade) 2 and neutron moderation cascade 3 in Figures 3 and 4) and cause nuclear fission, the lifetime of that generation ends and the first generation of fission neutrons is generated. The generated fission neutrons scatter isotropically, so half of the neutrons are dispersed outward from the cascade, and the remaining half are dispersed inside the cascade. Since there is no neutron absorbing material inside the cascade, the neutrons dispersed inside the cascade reach the inner surface of the cascade again, where they cause the next nuclear fusion reaction and are replaced by second-generation fission neutrons.

[0030] By repeating this process, n0 neutrons accumulate in the system, with the fusion neutrons being the first generation. o is expressed as the sum of an infinite series with the number of fusion neutrons produced as the first term S0 and the common ratio r = η / 2.

[0031]

number

[0032] If η>2, i.e., r>1, then Equation 4 diverges and the interior of the cascade goes into a supercritical state.

[0033] On the other hand, if η<2, i.e., r<1, the number of neutrons inside the cascade converges to the value of

[0034]

number

[0035] Since this is the condition for a subcritical reactor to always be realized, the material for the interface between the fusion neutron source and the fission reactor must be selected so that the neutron reuse rate η<2. In particular, when fictitious fusion is used in neutron theory, the energy spectrum of the generated neutrons is monochromatic with no energy spread. If deuterium-deuterium (DD) fusion is used as the external neutron source, the energy is limited to 2.45 MeV. If these fusion neutrons are thorium ( 232 When a neutron collides with a nucleon (Th), the number of neutrons generated, η, is calculated as η = 1.8, or γ ~ 0.9 (η < 2, (γ < 1)) in quantum physics. 232 Th satisfies the condition.

[0036] Fast neutrons radiated from the cascade to the reactor structure are multiplied by the reactor multiplication factor k eff The fast neutrons generated in this fission reactor propagate in the opposite direction ( 232 Collisions from outside the cascade (composed of th) cause fission on the cascade, and half of the fast neutrons are released into the interior of the cascade. These fast neutrons from outside the cascade increase the number of neutrons inside the cascade, which is equivalent to increasing the neutron reproduction factor η of the cascade blanket. At this time, the interior of the cascade may become supercritical. This may increase η to 2<η.

[0037] From Figures 1(a) and 2(a), if the energy of these external fission neutrons is slowed down to 1 MeV or less, 232 In the present invention, nuclear fission does not occur between Th and 232 By placing an appropriate neutron moderator outside the Th cascade, the fast neutrons from the fusion reactor are slowed down and the inside of the cascade is always kept at γ < 1.

[0038] Possible moderators include liquid light water (H2O) and solid graphite or silicon carbide (SiC), but light water causes nucleate boiling and film boiling, and graphite poses the risk of ignition and combustion if air enters the reactor body. Therefore, silicon carbide, which is a solid and has excellent high-temperature stability, can be used.

[0039] From the above, the present invention is based on the idea that in a nuclear fusion-driven subcritical reactor, the parent nucleus of the reactor core 232 The present invention provides a nuclear fusion-fission combined irradiation structure for controlling a nuclear fission reactor, which uses Th and realizes that the nuclear fusion neutral irradiation part is always subcritical.

[0040] (Fusion-powered subcritical reactor) By utilizing the above-mentioned fusion neutrons and thorium, we start from nuclear fusion, which does not rely on a mechanical driving mechanism and can be electrically controlled safely and reliably, and disclose a nuclear fission core based on an operating principle that is completely opposite to the operating principle of forcibly operating it in a subcritical state using moderator absorbers, which was developed in the Manhattan Project.

[0041] In the fusion-driven subcritical reactor S1, the main neutron source 1 is at the center, and the cylindrical cascade blanket core (fission cascade) 2, neutron moderation cascade 3, main fission blanket 4, structural frame 5, fusion neutron source 6, insulating outer tube 7, fission flattening blankets 8, neutron shielding blanket 9, and reactor cavity side wall 10 are arranged in the form of concentric circles in cross section, in this order from the inside out.

[0042] Here, functionally, the main neutron source 1 corresponds to a fusion reactor, and the main fission blanket 4 corresponds to a fission reactor.

[0043] Muon catalyzed fusion using deuterium gas or inertial electrostatic fusion can be used as the main neutron source 1. When muon catalyzed fusion is used, for example, a structure such as that disclosed by the inventors in Patent Document 1 can be provided.

[0044] The cascade blanket core 2 is a sintered body of high-purity thorium oxide. The neutron deceleration cascade 3, which is a moderator installed outside it, desirably does not reduce the neutron energy below 1 MeV. The cascade blanket core 2 and the neutron deceleration cascade 3 together constitute a cascade member.

[0045] The neutron deceleration cascade 3 is a member for preventing the backflow of fission neutrons of 1 MeV or more from the main fission blanket 4, and is formed of silicon carbide in this embodiment.

[0046] 232 The main fission blanket 4 (nuclear fuel body) using Th as a fertile medium has a large number of neutrons as will be described later, 233 Since U is generated and fissions, fast neutrons with 1.0 MeV < E exist. If these fast neutrons directly hit the cascade blanket core 2, surplus fast neutrons will be supplied inside the cascade blanket core 2. This effect causes the neutron amount inside the cascade blanket core 2 to diverge. Since it is essential to prevent this, a neutron deceleration cascade 3 for blocking fast neutrons is arranged outside the cascade blanket core 2.

[0047] If another layer of 232 Th cascade is installed at an appropriate distance outside the cascade structure composed of the cascade blanket core 2 and the neutron deceleration cascade 3, neutrons from the nuclear reactor can penetrate and enhance the neutron amplification by the cascade. This additional outer 232 Th also contributes to the increase in the number of neutrons. The detailed dimensions and structure can be determined using the PHITS window calculation code.

[0048] The main fission blanket 4 is formed of thorium oxide in the form of a perforated block or a honeycomb block 232This core component is made of sintered ThO2, and is configured to allow gas to flow vertically in the diagram. ThO2 has a high melting point, and the sintering temperature is 2000°C or higher. High-temperature sintering of thick ceramics with a diameter of 25 mm or more is difficult, but this can be solved by applying microwave sintering technology such as that proposed in JP 2003-277157 A.

[0049] The honeycomb block structure allows for a large fuel volume-to-surface area ratio, resulting in high cooling efficiency. The fine cells of the honeycomb structure also make the flow of coolant uniform, enabling efficient heat exchange. Using inert gases such as helium or carbon dioxide makes it possible to create a highly efficient high-temperature gas-cooled reactor.

[0050] The main fission blanket 4 can be made from a powder mixture of SiC and ThO2, using silicon carbide as the moderator, or by baking silicon carbide onto the surface of a honeycomb.

[0051] The main fission blanket 4 may also be configured to include a fuel tube-type pellet fuel, a fuel sheath tube, and a blanket.

[0052] The structural frame 5 has a support blanket structure.

[0053] Conventional reactor control is a negative control method that absorbs excess fission neutrons. On the other hand, the function of the fusion neutron source 6 and the insulating outer tube 7 is a positive control that supplies neutrons. The fusion neutron source 6 is generated inside the insulating outer tube 7. The insulating outer tubes 7 are arranged around the outer periphery of the structural frame 5, and for example, 24 of them are arranged at 15° intervals. The insulating outer tubes 7 are 232It consists of an IEC insulator made of ThO2, with the outer surface formed of silicon carbide or graphite layers. Using deuterium gas results in γ ~ 0.9, which can increase the amount of fusion neutrons by 10 times according to equation (5) described below. These act as an active fusion flattening blanket that externally controls the amount of energy spectrum and neutrons in the main fission blanket 4 through external fusion. Compact, inexpensive fusion experimental devices (devices) can be used as fusion neutron sources 6, such as inertial electrostatic confinement fusion (IEC) and Muon Catalyzed Fusion (MuCF) using medical accelerators.

[0054] The dissipation of neutrons from the reactor core is proportional to the density gradient of neutrons at the periphery of the core. The method of reducing the density gradient by placing a fusion neutron source at the periphery of the core is called density flattening. Fusion neutron source 6 is used for density gradient flattening. This changes the density gradient of neutrons flowing out from the core, making it possible to control the neutron energy spectrum and flux distribution within the reactor.

[0055] Fission Flattening Blanket 8 232 It consists of ThO2 and acts as a reflective blanket of thorium. 233 Since fission consumption is greater than the rate of U production, 233 This reduces the accumulation of U. The fission flattening blanket 8 is a passive blanket, and together with the fusion neutron source 6 and the insulating outer tube 7, it acts as a flattening blanket that externally controls the amount of energy spectrum and the amount of neutrons in the main fission blanket 4 by external fusion.

[0056] The neutron shielding blanket 9 is a blanket for absorbing all the used neutrons, and is made of, for example, activated ferritic steel (F82H steel).

[0057] 10 is the reactor side wall, 11 is the reactor wall, 12 is the moderator blanket wall, and 13 is the outermost blanket wall.

[0058] Cooling / moderating gas such as He / CO2 gas is introduced into the main fission blanket 4 through the gas inlet 14, and the gas introduced through the gas inlet 14 is discharged outside the system through the gas outlet 15.

[0059] (Method of operating a fusion-driven reactor) 232 Th has a neutron capture cross section of 1 to 10 barn between energies of 20 eV and 10 keV. 233 Th, and then undergoes beta decay with a delay of 22 minutes. 233 It is converted to Pa and has a half-life of 27 days. 233 This nuclear transformation is used to create nuclear fission fuel. 233 Manufacture U. 233 U is fissile over the entire energy range of neutrons, and has a large cross section of 10 to 100 barn for thermal neutrons. 233 As soon as U is produced in the main fission blanket 4, it is fissioned by thermal neutrons. 232 The number density of Th is 10 22 cm -3 is dominantly high, on the order of . 232 Th→ 233 The rate of U production is highest in the capture reaction due to the resonance region (approximately 10 eV to 10 keV epithermal neutrons), and in the lower energy thermal neutron region, nuclear fission becomes dominant. 233 U and 232 Generated from Th 233 If U is balanced, the reactor will become a breeder reactor capable of steady-state operation with a breeding rate of 1.0.

[0060] We present a method to ensure that only neutrons up to the epithermal level, which has neutron energy higher than the thermal region, remain in the blanket (discarding them before thermal neutrons are produced).

[0061] First, when the fusion neutron source 6 is shut down, the buckling of the fission reactor expands, and the neutron velocity distribution changes to one where the epithermal component is high, resulting in an in-reactor environment where thermal neutrons are dissipated significantly.

[0062] The probability that a thermal neutron escapes from a nuclear reactor is P Tloss is expressed by the following equation:

[0063]

number

[0064] When deuterium gas is flowed into the main fission blanket 4, and the coolant is helium, and DD neutrons from nuclear fusion are irradiated onto the main fission blanket 4 before it cools down to thermal neutrons, uranium 233 ( 233 U) is generated. 233 U is 232 Th is captured and stored in the skeletal material

[0065] (Number 1) n+ 232 Th → 233 Th → (β-decay protactinium ( 233 Pa)) → β decay → 233 U

[0066] The refrigerant is helium or carbon dioxide. Since it does not use water, there is no latent heat loss. It is highly efficient because it can reach high temperatures. It is small, compact, and quiet, making it suitable for marine use, such as submarines, naval vessels, and offshore power generation platforms. If carbon dioxide is used as the cooling gas, it also acts as a neutron moderator, increasing the number of thermal neutrons in the reactor. Furthermore, if the cooling gas is a mixture of helium and carbon dioxide, the neutron energy spectrum in the reactor can be adjusted. The cooling gas component ratio can be controlled by diverting the circulating gas outside the reactor to a pipe whose temperature is lower than the liquefaction temperature of carbon dioxide, recovering the carbon dioxide, and increasing the helium component ratio.

[0067] 232Th + 233 If you use a U-series fission chain, harmful 239 The amount of highly radioactive long-lived nuclear waste generated by the production of Pu and minor actinides can be reduced to 1 / 1,000 to 1 / 10,000,000.

[0068] 233 When U has accumulated, the cooling gas is changed from helium to carbon dioxide. As the number of thermal neutrons cooled by the carbon in the carbon dioxide increases, 233 The thermonuclear fission of U becomes larger, nuclear fission progresses, and reproduction and consumption become balanced.

[0069] When the uranium concentration in the main fission blanket 4 increases, the fusion neutron source 6 is activated to reduce the neutron density gradient dn / dr, and the reactor is switched to operation in which the neutron confinement rate within the main fission blanket 4 is increased. When a nuclear reaction occurs within the honeycomb-structured main fission blanket 4, neutrons fly through the space within the honeycomb structure. The dissipation of neutrons from the core of the main fission blanket 4 is proportional to the density gradient of neutrons at the periphery of the neutrons. The fusion neutron source 6 is placed on the periphery to reduce the density gradient and perform density flattening, thereby controlling the rate of the fission reaction and the amount of neutrons generated. The fusion neutron source 6 also supplies neutrons to the outer fission flattening blanket 8 and neutron shielding blanket 9, 233 This causes the production and proliferation of U.

[0070] Accumulated in main fission blanket 4 233 In the stage of extracting exergy from the main fission blanket 4 by bombarding U with thermal neutrons, the reactor as a whole consumes 233 Compensate for U and transition to operation at a breeding rate of 1.

[0071] In energy extraction operation, the reactor buckling is modified to increase the equivalent radius of the reactor by reducing the neutron density gradient with fusion neutron sources6 arranged along the periphery.

[0072] In summary, the fusion-driven subcritical reactor of the present invention allows for electrical control of output. Neutrons obtained from fusion are amplified using a cascade element, and the amplified neutrons are treated as external neutrons. These external neutrons are then supplied to a subcritical thorium-decay-chain fuel reactor, which starts and operates the reactor. In other words, the reactor is loaded with fuel only up to the subcritical level, and fast neutrons produced by fusion are injected into the core to excite the subcritical fission reactor to criticality (or near criticality). The neutron yield is stably controlled by fusion neutrons, enabling steady nuclear energy generation. This method realizes an efficient subcritical reactor that does not undergo chain reactions, ensuring safety. It also enables the development of a small, highly efficient, and safe subcritical reactor that does not generate radioactive waste.

[0073] This reactor has a highly purified core (nuclear fuel assembly) at the factory. 232 First, fusion neutrons are emitted only from the main neutron source 1, and the peripheral fusion neutron source 6 is turned off. At this time, the radius of the core is small compared to the Fermi age, so the neutron energy spectrum is dominated by fast neutrons. 233 The probability of fast neutrons being accumulated in the core is higher than the probability of fission of U. When the amount of neutrons accumulated in the main fission blanket 4 increases, the fusion neutron source 6 is turned on to increase the thermal neutrons. 233 Operate so that the growth rate and proportion of U are balanced.

[0074] Main fission blanket 4 232 By using Th as the main component, external neutron irradiation can be performed to form n+ 232 Th → 233 Th → β decay → protactinium ( 233 Pa) → β decay → Uranium 233 ( 233 U). 232 Th + 233 If U-series fission reaction chains are used, the amount of highly radioactive long-lived nuclear waste generated by the production of harmful plutonium-239 and minor actinides can be reduced to 1 / 1,000 to 1 / 10,000,000.

[0075] (Power generation method) The power generation system S of the present invention will be described with reference to FIG.

[0076] The power generation system S comprises a fusion-driven subcritical reactor S1 and a fusion system S2. The fusion system S2 is integrally formed such that the communication between the fusion reactor structure of the fusion system S2 and the fusion-driven subcritical reactor S1 is separated via a structural partition 20, which is a pipe wall of the gas flow path, and fusion neutrons pass through the structural partition 20 and are irradiated from the fusion system S2 to the fusion-driven subcritical reactor S1.

[0077] The fusion system S2 may employ the configuration of a muon catalyzed fusion system proposed by the inventors and described in Patent Document 1 and the like.

[0078] The power generation system S includes a reaction vessel R, a structural partition 20, and a power generation means 30.

[0079] The reaction vessel R is partitioned from the muon catalyzed fusion system S2 via a structural partition 20, and is arranged to surround the fusion core.

[0080] The structural partition 20 separates the circulation wind tunnel system, through which deuterium gas flows at supersonic speed, from the fusion-driven subcritical reactor S1, through which coolant gas flows.

[0081] The power generating means 30 is of a known configuration that is provided in a high temperature gas reactor using nuclear fission.

[0082] In the muon catalyzed fusion system S1, neutrons generated in the main neutron source 1 and emitted isotropically induce a fission reaction in the main fission blanket 4.

[0083] The heat generated in the main fission blanket 4 is transported by the coolant gas flowing through the fusion-driven subcritical reactor S1, and this high-temperature heat source can be used in the power generation means 30 to generate, for example, high-temperature steam, which can then be used to generate turbine power.

[0084] (Example of change) As shown in Figure 7, a configuration can be adopted in which seven sets of the reactor cores shown in Figure 4 are bundled together, housed in a calandria-type vessel, and integrated with a fission flattening blanket 8 and a neutron shielding blanket 9. This makes it possible to provide a small-sized, high-power fusion-driven subcritical reactor.

[0085] (Effects of the embodiment) The fusion-driven subcritical reactor of the present invention, with the above-mentioned configuration, realizes an efficient subcritical reactor that does not undergo chain reactions and ensures safety. It also makes possible a highly efficient, safe, small-scale subcritical reactor that does not generate radioactive waste.

[0086] The fusion-driven subcritical reactor of the present invention can be operated as follows. First step: DD neutrons are irradiated from the main neutron source 1 to the main fission blanket 4 via the cascade member, and the neutrons are generated in the main fission blanket 4. 233 Multiply U. Second step: A predetermined output is produced and consumed through nuclear fission. 233 U is operated at a breeding rate of 1.0. In the first step, the neutron flattening blanket is used to suppress the generation of thermal neutrons in the main fission blanket 4 or to increase the probability that thermal neutrons escape outside the main fission blanket 4; 233 The second step is to reduce the fission of U to increase the breeding rate, and use helium gas as a coolant and moderator. 233 Carbon dioxide is used as a coolant and moderator to operate U at a breeding ratio of 1.0.

[0087] Because gas is used for cooling, there is no latent heat of vaporization compared to water cooling, so the heat capacity of the core is smaller. As a result, even if gas circulation stops, cooling is possible through natural convection caused by the temperature difference between the inlet and outlet. This, in principle, makes it possible to realize a highly safe reactor core. There is no risk of the core becoming unable to be cooled due to a loss of power or water supply, as is the case when high-pressure circulating water is used for cooling.

[0088] The fusion-driven subcritical reactor of the present invention does not contain any uranium or plutonium before operation. It can be operated without shutdown from the initial start-up of the reactor until its decommissioning. In principle, the reactor of the present invention is operated in a sealed state from a non-radioactive or very low radioactivity state, and continues exergy extraction operation. When the life of the reactor's nuclear fuel expires, the nuclear fuel multiplication operation is terminated, and the remaining nuclear fuel is consumed through a certain period of non-breeding operation, after which operation is suspended. When the operation of the reactor is terminated, 233 The furnace body can be replaced by ensuring that no U remains inside the furnace. [Explanation of symbols]

[0089] 1…Main neutron source 2...Cascade blanket core (cascade member) 3...Neutron moderation cascade (cascade component) 4...Main fission blanket 5...Structural frame 6…Fusion neutron source 7...Insulating outer tube 8...Flattening blanket 9...Neutron shielding blanket 10…Reactor cavity side wall 14...Gas inlet 15...Gas exhaust hole 20…Structural bulkhead 30...Means of power generation S1...Fusion-driven subcritical reactor S2...Nuclear fusion system

Claims

1. A fusion-driven subcritical reactor capable of electrically controlling output, amplifying neutrons obtained from fusion, and supplying the amplified neutrons to a reactor holding subcritical nuclear fuel, thereby starting and operating the reactor, a main neutron source that generates DD neutrons through a nuclear fusion reaction; a cascade member surrounding the neutron source, separating fusion / fission neutrons, multiplying fast fission neutrons generated by fission, and slowing down the fast fission neutrons; The cascade member is surrounded by a gas containing mainly thorium oxide ( 232 ThO 2 a subcritical main fission blanket consisting of a neutron flattening blanket that provides improved containment of fission neutrons by disposing a neutron source around the outer periphery of the main fission blanket; Equipped with The cascade member is configured by arranging a fast neutron moderator on the outside of a fission cascade made of thorium oxide, the fast neutron moderator preventing the penetration of fast fission neutrons from the main fission blanket. A fusion-driven subcritical nuclear reactor.

2. 10. The fusion-driven subcritical nuclear reactor of claim 1, wherein said primary fission blanket is honeycomb shaped.

3. 2. The fusion-driven subcritical nuclear reactor of claim 1, wherein the primary fission blanket is a mixture of thorium oxide and silicon carbide.

4. The fusion-driven subcritical reactor of claim 1, further comprising a fission flattening blanket on the outer periphery of the neutron flattening blanket, and an absorption moderation blanket on the outer periphery of the fission flattening blanket for absorbing all used neutrons.

5. 3. A method for operating a fusion-driven subcritical nuclear reactor according to claim 2, comprising: DD neutrons are irradiated from the main neutron source through the cascade member to the main fission blanket, and 233 a first step of propagating U; A given output is produced and consumed through nuclear fission 233 the second step of operating U at a breeding rate of 1.0; Equipped with In the first step, the neutron flattening blanket suppresses the generation of thermal neutrons in the main fission blanket or increases the probability that thermal neutrons escape outside the main fission blanket; 233 Reduce U fission to increase breeding rate, and use the first gas as a coolant and moderator; In the second step, a predetermined output is produced and consumed by nuclear fission. 233 To operate the U at a breeding ratio of 1.0, a second gas having a higher moderating power than the first gas is used as a coolant and moderator. A method for operating a fusion-driven subcritical nuclear reactor, comprising:

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