Nuclear power generation system and containment vessel

Abstract

This application discloses a nuclear power generation system and a containment vessel capable of improving the integrity of the containment vessel. [Solution] A nuclear power generation system comprising a nuclear reactor, a containment vessel housing the reactor, and a water reservoir for storing emergency cooling water. The containment vessel is a triple-layered vessel having an inner steel plate housing the reactor, an intermediate steel plate positioned outside the inner steel plate, and an outer steel plate positioned outside the intermediate steel plate. It has an inner flow channel formed between the inner steel plate and the intermediate steel plate, and an outer flow channel formed between the intermediate steel plate and the outer steel plate. The outer flow channel and the inner flow channel communicate with each other at the bottom of the containment vessel and communicate with the water reservoir at the top of the containment vessel.

Description

Technical Field

[0001] The present invention relates to a nuclear power generation system and a containment vessel.

Background Art

[0002] Various forms of nuclear power generation systems have been proposed (see, for example, Patent Documents 1-4).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a nuclear power generation system, a containment vessel for storing reactor equipment may be provided. In the case of a light water reactor such as a boiling water reactor or a pressurized water reactor, the containment vessel serves to confine steam and radioactive substances that leak when the reactor equipment is damaged. However, when a large amount of steam leaks from the damaged reactor equipment or when the reactor core is severely damaged, the integrity of the containment vessel may be impaired.

[0005] Therefore, the present application discloses a nuclear power generation system and a containment vessel capable of improving the integrity of the containment vessel.

Means for Solving the Problems

[0006] To solve the above problems, the present invention provides a containment vessel with a triple-layer structure consisting of an inner steel plate, an intermediate steel plate, and an outer steel plate. The floating body on which the reactor and turbine generator are arranged is streamlined when viewed from above. The inner flow channel formed between the inner steel plate and the intermediate steel plate and the outer flow channel formed between the intermediate steel plate and the outer steel plate are connected to each other at the bottom of the containment vessel and to each other at the top of the containment vessel, with the water reservoir being connected to each other.

[0007] More specifically, the present invention relates to a nuclear power generation system comprising a nuclear reactor, a containment vessel housing the reactor, and a water reservoir for storing emergency cooling water. The containment vessel is a triple-layered vessel having an inner steel plate housing the reactor, an intermediate steel plate positioned outside the inner steel plate, and an outer steel plate positioned outside the intermediate steel plate. The containment vessel has an inner flow channel formed between the inner steel plate and the intermediate steel plate, and an outer flow channel formed between the intermediate steel plate and the outer steel plate. The outer flow channel and the inner flow channel communicate with each other at the bottom of the containment vessel and communicate with the water reservoir at the top of the containment vessel.

[0008] In a nuclear power plant system equipped with such a triple-layered containment vessel, if the reactor experiences an emergency, convection will occur due to the difference in density caused by the temperature difference between the cooling water in the outer channel and the cooling water in the inner channel, allowing for the natural circulation of cooling water to continue within the containment vessel.

[0009] Furthermore, the outer channel and the inner channel each have vertical partitions that divide each channel into multiple channels by wall materials extending vertically, and each outer channel formed in the outer channel by the vertical partitions The channels may communicate with each other at the bottom and top of the containment vessel, and each internal channel formed in the internal flow path by the vertical bulkhead may also communicate with each other at the bottom and top of the containment vessel. In a nuclear power generation system with such a containment vessel, even if partial damage to the containment vessel disrupts the flow of cooling water in a particular channel, the flow of cooling water can continue in other channels.

[0010] Furthermore, the containment vessel may be a circular container with the reactor at its center when viewed from above, and the outer and inner channels may be partitioned by vertical bulkheads extending radially from the center. A nuclear power generation system equipped with such a containment vessel can distribute cooling water to each channel in a generally uniform manner.

[0011] Furthermore, the present invention may also be a containment vessel comprising a triple-layered container body having an inner steel plate for housing a nuclear reactor, an intermediate steel plate positioned outside the container beyond the inner steel plate, and an outer steel plate positioned outside the container beyond the intermediate steel plate, an inner flow channel formed between the inner steel plate and the intermediate steel plate, and an outer flow channel formed between the intermediate steel plate and the outer steel plate, wherein the outer flow channel and the inner flow channel communicate with each other at the bottom of the container body and each communicate with a water storage section for storing emergency cooling water at the top of the container body. [Effects of the Invention]

[0012] With the above-mentioned nuclear power generation system and containment vessel, it is possible to improve the integrity of the containment vessel. [Brief explanation of the drawing]

[0013] [Figure 1] Figure 1 is a schematic diagram showing the grid configuration of a nuclear power generation system according to an embodiment. [Figure 2] Figure 2 is a perspective view showing a schematic representation of the internal structure of the containment vessel. [Figure 3] Figure 3 is a perspective view showing the detailed internal structure of the containment vessel. [Figure 4] Figure 4 is a front view showing the detailed internal structure of the containment vessel. [Figure 5] Figure 5 is a cross-sectional view of the containment vessel at the point indicated by symbol AA in Figure 4. [Figure 6] Figure 6 is a cross-sectional view of the containment vessel at the reference numeral BB shown in Figure 4. [Figure 7] Figure 7 is a cross-sectional view of the containment vessel at the point indicated by the symbol CC in Figure 4. [Figure 8]FIG. 8 is a diagram for explaining the flow of cooling water in the storage container. [Figure 9] FIG. 9 is a diagram showing the dimensional conditions of the storage container used in the calculation. [Figure 10] FIG. 10 is the first diagram showing the change in the temperature distribution of debris and the steel plate. [Figure 11] FIG. 11 is the second diagram showing the change in the temperature distribution of debris and the steel plate. [Figure 12] FIG. 12 is a diagram showing the temperature distribution near the steel plate.

Mode for Carrying Out the Invention

[0014] Hereinafter, embodiments of the present invention will be described. The embodiments shown below are one aspect of the present invention and do not limit the technical scope of the present invention.

[0015] In the following, a boiling water reactor (BWR) will be exemplified. However, this embodiment may be a pressurized water reactor (PWR) or other light water reactors, or may be a type of nuclear reactor that uses a substance other than light water as a moderator or coolant. Further, in the following, a form installed on land will be exemplified, but this embodiment may be a floating type that can be moored on the sea or the like.

[0016] <Outline of System Configuration> FIG. 1 is a schematic diagram showing the system configuration of the nuclear power generation system 1 according to the embodiment. The nuclear power generation system 1 mainly consists of a reactor system R and a turbine system T. The reactor 3 is a main device of the reactor system R. Further, the turbine generator 4 is a main device of the turbine system T. The reactor 3 is a main device of the reactor system R. Further, the turbine generator 4 is a main device of the turbine system T.

[0017] The reactor system R, which includes reactor 3, is equipped with various facilities such as a containment vessel 3A, nuclear fuel 3B, control rods 3C, recirculation pump 3D, and pressure vessel 3E. The turbine system T, which includes turbine generator 4, is equipped with various facilities such as a condenser 4C, circulating water piping 4D, circulating water pump 4E, and feedwater pump 4F, in addition to the turbine 4A and generator 4B that make up turbine generator 4.

[0018] The containment vessel 3A is a vessel that houses the pressure vessel 3E, which contains the nuclear fuel 3B and other materials, and plays a role in containing radioactive materials released from the pressure vessel 3E in the event of a meltdown accident of the reactor 3. The containment vessel 3A is basically made of steel, although details will be described later. The containment vessel 3A encloses the pressure vessel 3E containing the reactor 3 in its center, and forms an upper drywell 3M above the pressure vessel 3E and a lower drywell 3N below the pressure vessel 3E. The containment vessel 3A also has a suppression pool 3H around the lower drywell 3N.

[0019] The pressure vessel 3E is a container that encloses the nuclear fuel 3B and other materials, and plays the role of containing water and steam for cooling the reactor 3. In the center of the pressure vessel 3E, hundreds of nuclear fuel 3B are arranged in the form of fuel assemblies, forming the main body of the reactor 3. Control rods 3C, which can move up and down by a drive mechanism located at the bottom of the pressure vessel 3E, are inserted into the gaps between the fuel assemblies in the main body of the reactor 3. When the control rods 3C are withdrawn from the reactor 3 and the reactor 3 reaches a critical state, the reactor 3 continuously generates heat. When the control rods 3C are inserted into the reactor 3 and the reactor 3 reaches a subcritical state, the heat generated by the reactor 3 gradually decreases.

[0020] A recirculation pump 3D is provided in the pressure vessel 3E. The recirculation pump 3D is responsible for heat removal and control of the reactor output of the reactor 3 by forcibly circulating water, which is the reactor coolant, in the liquid phase portion within the pressure vessel 3E. In this embodiment of the nuclear power generation system 1, an Advanced Boiling Water Reactor (ABWR) is assumed, and therefore in Figure 2, the recirculation pump 3D is shown to be installed in the pressure vessel 3E. However, the nuclear power generation system 1 is not limited to this configuration. For example, the nuclear power generation system 1 may have a recirculation system in which the recirculation pump and circulation piping are arranged outside the pressure vessel 3E.

[0021] A main steam pipe 3L is connected to the pressure vessel 3E to send steam generated within the pressure vessel 3E to the turbine generator 4 of the turbine system T. Since the main steam pipe 3L is a pipe connecting the inside and outside of the containment vessel 3A, main steam isolation valves 3J and 3K are provided near the penetration point of the containment vessel 3A to allow for the isolation of the containment vessel 3A. A relief safety valve 3F is provided in the middle of the main steam pipe 3L to prevent the internal pressure of the pressure vessel 3E from becoming excessive when the main steam isolation valves 3J and 3K are closed. The end of the exhaust pipe 3G, located downstream of the relief safety valve 3F, is located in the suppression pool 3H.

[0022] The turbine 4A and generator 4B, which make up the turbine generator 4, are connected by the same rotating shaft. The turbine 4A has a structure in which the impeller is housed within a casing. Below the turbine 4A, a condenser 4C is provided to condense the steam that has passed through the turbine 4A. The condenser 4C has many thin tubes that form part of the path of the circulating water piping 4D, which connects the intake and discharge ports located below sea level. The steam is condensed by the cold heat of seawater supplied by the circulating water pump 4E, which is located along the path of the circulating water piping 4D. As a result, the pressure difference between the steam supplied from the reactor 3 through the main steam pipe 3L and the inside of the condenser 4C applies power to the impeller to rotate the generator 4B. This causes the generator 4B to rotate and generate electricity. The condensed water in the condenser 4C is then supplied back into the pressure vessel 3E via the feedwater piping 4G by the feedwater pump 4F.

[0023] Note that Figure 2 only shows a schematic of the reactor system R and turbine system T, and in reality, a wide variety of equipment is installed. For example, important equipment such as steam control valves and turbine bypass valves are installed near turbine 4A in the main steam pipe 3L. The turbine bypass valve may be capable of 100% bypass, sending the entire amount of main steam at rated output directly to condenser 4C without passing through turbine 4A, or it may have a lower bypass capacity. Also, important equipment such as feedwater flow control valves, condensate demineralizers, and feedwater heaters are installed in the feedwater piping 4G. In addition, piping for the emergency core cooling system is installed inside and outside the containment vessel 3A. Furthermore, turbine 4A is a combination of a high-pressure turbine and multiple low-pressure turbines.

[0024] Furthermore, although Figure 2 shows only one instance of each piece of equipment, each piece of equipment in the nuclear power generation system 1 is redundant. For example, multiple circulating water pumps 4E and feedwater pumps 4F are installed.

[0025] In the reactor system R, the position of the control rods 3C is adjusted so that the reactor 3 maintains a predetermined reactor output. In the turbine system T, the opening of the steam control valve is adjusted so that the turbine generator 4 maintains a predetermined rotational speed, and the feedwater flow rate of the feedwater pump 4F is adjusted so that the reactor 3 maintains a predetermined water level. With this configuration, the nuclear power generation system 1 transmits the thermal energy generated by the nuclear reaction of the reactor 3 as electrical energy to the power grid via the generator 4B, which is synchronized with the grid frequency.

[0026] The general configuration of the nuclear power generation system 1 according to this embodiment is as described above. Next, the details of the containment vessel 3A used in the nuclear power generation system 1 according to this embodiment will be explained.

[0027] Figure 2 is a perspective view showing a schematic of the internal structure of containment vessel 3A. Figure 3 is a perspective view showing a detailed view of the internal structure of containment vessel 3A. Figure 4 is a front view showing a detailed view of the internal structure of containment vessel 3A. Figure 5 is a cross-sectional view of containment vessel 3A at the designation AA shown in Figure 4. Figure 6 is a cross-sectional view of containment vessel 3A at the designation BB shown in Figure 4. Figure 7 is a cross-sectional view of containment vessel 3A at the designation CC shown in Figure 4.

[0028] The containment vessel 3A is a triple-layered vessel with outer channels C1-9 and inner channels H1-7 through which cooling water flows to cool the inside of the vessel. The upper drywell 3M and lower drywell 3N are formed inside the containment vessel 3A. The containment vessel 3A plays the role of containing leaks such as high-temperature steam leaking from the reactor 3 located inside the containment vessel 3A, or nuclear fuel 3B from the reactor 3 leaking from the pressure vessel 3E. For this reason, the containment vessel 3A cools the structural materials forming the inner surface of the vessel with cooling water in the outer channels C1-9 and inner channels H1-7 to maintain the integrity of the vessel when the structural materials are exposed to high temperatures.

[0029] Specifically, the outer channels C1-9 and inner channels H1-6 of the containment vessel 3A are connected to water storage means such as the IC / PCCS pool, which is located at a height equivalent to the upper part of the containment vessel 3A. The hydrostatic pressure of the stored water keeps the outer channels C1-9 and inner channels H1-7 constantly filled with water. The water filling the outer channels C1-9 and inner channels H1-6 provides a shielding effect that suppresses the leakage of radiation emitted from the reactor 3 to the outside of the containment vessel 3A, both under normal and emergency conditions. More specifically, the outer channel C1 is connected to the pool through piping (not shown), and the inner channel H6 is connected to the pool through inner channel H7. The outer channels C1-9 form the channels in the outer part of the triple-layered vessel that constitutes the containment vessel 3A. The inner channels H1-6 form the channels in the inner part of the triple-layered vessel that constitutes the containment vessel 3A. IC / PCCS The pool contains emergency condensers (IC: Isolation Condenser) and static containment vessel cooling systems (PC). Although heat exchangers for the CS (Passive Containment Cooling System) are installed, these are also facilities for cooling reactor 3 in emergencies, so even if the stored water flows through the outer channels C1-9 and inner channels H1-7, it does not interfere with the use of equipment in the IC / PCCS pool.

[0030] Furthermore, the containment vessel 3A forms water channels in the order of outer channels C1, C2, C3, C4, C5, C6, C7, C8, C9, flowing from the upper outer channel C1 of the containment vessel 3A, which is in communication with the water storage means, to the lower outer channel C9 of the containment vessel 3A. Additionally, the containment vessel 3A forms water channels in the order of outer channel C9, inner channels H1, H2, H3, H4, H5, H6, H7, flowing from the lower outer channel C9 of the containment vessel 3A to the upper inner channel H7 of the containment vessel 3A.

[0031] The containment vessel 3A is formed from steel plates as follows, with a structure having such a flow path.

[0032] In other words, the containment vessel 3A has a cylindrical steel plate K1 that forms the outermost outer perimeter wall. The upper end of the cylindrical steel plate K1 is closed by a steel plate K12. A cylindrical steel plate K15, which has a smaller diameter than steel plate K1, is mounted on steel plate K12. The upper end of steel plate K15 is closed by a steel plate K16. The lower end of the cylindrical steel plate K1 is closed by a steel plate K19. If the nuclear power generation system 1 is a floating type, steel plate K19 may be a steel plate that constitutes the floating body. Thus, the outermost shell of the containment vessel 3A is formed by steel plates K1, K12, K15, K16, and K19.

[0033] Inside this outermost shell, a double-layered containment vessel 3A is formed by arranging steel plates as follows: Inside steel plate K1, a cylindrical steel plate K2, slightly smaller in diameter than steel plate K1, is placed. Below steel plate K12, steel plate K11 is placed. Inside steel plate K15, steel plate K14, slightly smaller in diameter than steel plate K15, is placed. Below steel plate K16, steel plate K17 is placed. This creates a space for the outer channel C1 between steel plate K16 and steel plate K17. A space for the outer channel C2 is also created between steel plate K15 and steel plate K14. A space for the outer channel C3 is also created between steel plate K12 and steel plate K11. A space for the outer channel C4 is also created between steel plate K1 and steel plate K2.

[0034] Inside this double structure, a triple-layered containment vessel 3A is formed by arranging steel plates as follows: Inside steel plate K2, a cylindrical steel plate K3 with a slightly smaller diameter than steel plate K2 is placed. Below steel plate K11, steel plate K10 is placed. Inside steel plate K14, a cylindrical steel plate K13 with a slightly smaller diameter than steel plate K14 is placed. Below steel plate K17, steel plate K18 is placed. As a result, a space for an outer channel C5 and an inner channel H4 is formed between steel plate K2 and steel plate K3. A space for an inner channel H5 is formed between steel plate K11 and steel plate K10. A space for an inner channel H6 is formed between steel plate K14 and steel plate K13, and between steel plate K17 and steel plate K18.

[0035] Furthermore, inside the triple-layered containment vessel 3A, a cylindrical steel plate K4 is positioned to partition the space below the upper drywell 3M into a lower drywell 3N and a suppression pool 3H. Additionally, a steel plate K9 is positioned at the upper end of the steel plate K4 in a flange-like manner, extending from the upper end of the steel plate K4 toward the inner circumferential surface of the steel plate K3, to further partition the upper drywell 3M and the suppression pool 3H.

[0036] The steel plates K4 and K9 are arranged as follows, and the upper dry Well 3M and the lower drywell 3N are separated from the suppression pool 3H by a triple-layered partition wall. Specifically, a cylindrical steel plate K5, slightly larger in diameter than steel plate K4, is placed outside steel plate K4. Furthermore, a cylindrical steel plate K6, slightly larger in diameter than steel plate K5, is placed outside steel plate K5. In addition, steel plate K8 is placed below steel plate K9. Furthermore, steel plate K7 is placed below steel plate K8. As a result, an inner flow channel H2 space is formed between steel plate K4 and steel plate K5. An outer flow channel C7 space is formed between steel plate K5 and steel plate K6. An inner flow channel H3 space is formed between steel plate K9 and steel plate K8. An outer flow channel C6 space is formed between steel plate K8 and steel plate K7.

[0037] Furthermore, the steel plate K20 that forms the bottom surface of the lower drywell 3N is positioned above the steel plate K19. Between the steel plate K20 and the steel plate K19, there is a disc-shaped steel plate K21 with a through hole in the center. This creates a space for the outer flow channel C8 between the steel plate K19 and the steel plate K21. Also, at the through hole in the center of the steel plate K21, a space for the outer flow channel C9 is created between the steel plate K19 and the steel plate K20. In addition, a space for the inner flow channel H1 is created between the steel plate K20 and the steel plate K21.

[0038] As can be seen in Figures 3 to 7, the containment vessel 3A is provided with numerous steel plates in addition to the steel plates K1 to 21 mentioned above. For example, as shown in Figures 4 to 7, reinforcing steel plates are provided in various places in the containment vessel 3A. As shown in Figure 3, these steel plates are provided with numerous through holes in appropriate locations to secure the flow paths, thereby preventing them from obstructing the flow paths of the outer flow paths C1 to C9 and the inner flow paths H1 to H6.

[0039] Furthermore, as shown in Figures 5-7, for example, the containment vessel 3A is provided with numerous steel plates extending radially and vertically for reinforcement. This divides the outer channels C2-C8 and the inner channels H1-H5 into multiple channels. By dividing the outer channels C2-C8 and the inner channels H1-H5 into multiple channels, even if partial damage to the containment vessel 3A disrupts the flow of cooling water in a particular channel, the flow of cooling water can continue in other channels. In addition, each outer channel formed in the outer channels C2-C8 communicates with each other in outer channels C1 and C9, and each inner channel formed in the inner channels H1-H5 communicates with each other in outer channel C9 and H6. This makes it possible to distribute cooling water to each channel fairly evenly. Note that the outer channels C2-C8 and the inner channels H1-H5 do not necessarily need to be divided into multiple channels by vertically extending steel plates.

[0040] In a containment vessel 3A of this structure, if high-temperature steam leaks from the reactor 3 or the nuclear fuel 3B of the reactor 3 leaks from the pressure vessel 3E, and the structural material forming the inner surface of the containment vessel 3A is exposed to high temperatures, cooling water will flow through the outer channels C1-9 and inner channels H1-7 as follows.

[0041] Figure 8 illustrates the flow of cooling water in the containment vessel 3A. If an abnormality occurs in the reactor 3, the cooling water in the inner channels H1-H6 adjacent to the upper drywell 3M and lower drywell 3N where the reactor 3 is located will be hotter than the cooling water in the outer channels C1-C9. Therefore, when the containment vessel 3A is heated by the heat of the reactor 3, the density of the cooling water in the inner channels H1-H6 will be lower than that of the cooling water in the outer channels C1-C9. As a result, as shown by the dashed arrows in Figure 8, the cooling water in the outer channels C1-C9 will descend from the top to the bottom of the containment vessel 3A, and the cooling water in the inner channels H1-H6 will rise from the bottom to the top of the containment vessel 3A. The cooling water in the inner channels H1-H6 may rise to the top of the containment vessel 3A in a liquid phase state, or it may rise to the top of the containment vessel 3A while changing to a gaseous phase state due to boiling along the way. Since the outer channel C1 is connected to the IC / PCCS pool 5, the cooling water flows from the IC / PCCS pool 5 to the outer channel C1 as it descends. Also, since the inner channel H7 is connected to the IC / PCCS pool 5, the water that rises in liquid or gaseous state flows out of the inner channel H7. The water flows into IC / PCCS pool 5. In this triple-layered containment vessel 3A, even without power to circulate the cooling water, convection occurs due to the difference in density caused by the temperature difference between the cooling water in the outer channels C1-C9 and the cooling water in the inner channels H1-H6, allowing for the natural circulation of cooling water to continue within the containment vessel 3A. Furthermore, even in an emergency, the outer channels C1-C9 and inner channels H1-H6 remain filled with water, and this water continues to provide a shielding effect that prevents radiation emitted from reactor 3 and debris from leaking outside the containment vessel 3A.

[0042] For example, if the reactor core melts in reactor 3, the bottom of the pressure vessel 3E may be damaged, and debris, which is molten nuclear fuel, may fall below the pressure vessel 3E. If the debris accumulates on the steel plate K20 located below the pressure vessel 3E, the steel plate K20 will be heated. However, in this embodiment, the steel plate K20 is cooled by the cooling water in the inner flow channel H1. If the debris comes into direct contact with a large amount of water, there is a concern that a steam explosion or a large amount of hydrogen will be generated. For this reason, if water is to be injected into the debris, it is necessary to take measures such as considering the appropriate timing and amount of water. However, it is not easy to control the amount of water injected in this way during the progression of a severe accident such as a core meltdown. In this respect, in the nuclear power generation system 1 of this embodiment, the steel plate K20 that forms the bottom surface of the lower drywell 3N functions not only as a core catcher but also as a heat sink that is cooled by the cooling water. Therefore, the debris accumulated on the steel plate K20 is cooled stably. Furthermore, in this cooling process, since the debris and water do not come into direct contact, the possibility of a steam explosion or the generation of large amounts of hydrogen is low.

[0043] The following calculations were performed on the performance of containment vessel 3A, and the results are shown below. These calculations assume that nuclear fuel leaches from reactor 3 and accumulates as debris on steel plate K20. Figure 9 shows the dimensional conditions of containment vessel 3A used in the calculations. In these calculations, the steel used for steel plates K1-K21 had a thickness of 30 mm and a density of 7.83 g / cm³. 3 It is iron (Fe).

[0044] The various conditions used in this calculation are as follows: <1.Initial conditions> Debris: A mixture of uranium dioxide (UO2) and iron (Fe). Top surface: 3000℃ Bottom surface: 1300℃ (fixed) Internal: Linear interpolation of the temperatures of the upper and lower surfaces. Steel plate K20: Iron plate (Fe): Top surface: 610℃ (fixed) Bottom surface: 94℃ (fixed) Internal: Linear interpolation of the temperatures of the upper and lower surfaces. Cooling water for containment vessel 3A: Water (H2O) Bulk temperature: 25℃ <2.Geometric conditions> Debris: A mixture of uranium dioxide (UO2) and iron (Fe). Thickness: 1.0m Area (circular slab): Diameter 10.6m (Area 88.24m²) 2 ) Steel plate K20: Iron plate (Fe): Thickness: 3cm (0.03m) <3. Thermal boundary conditions> Debris: A mixture of uranium dioxide (UO2) and iron (Fe). Top surface: Radiant heat transfer (emissivity 0.9, ambient temperature 25°C) Side: Insulation Steel plate K20: Iron plate (Fe): Side: Insulation Top surface: Solid contact heat transfer coefficient with uranium dioxide: 1000 W / m 2 ·K Bottom surface: In contact with water, with a film boiling heat transfer coefficient of 10,000 W / m 2 ·K <4. Conditions for generating heat> Heat generation distribution: Heat is generated uniformly within uranium dioxide. Total heat output: 60MW Heat density per unit area: Approximately 680,000 W / m² 2 <5. Material Properties> Debris: A mixture of uranium dioxide (UO2) and iron (Fe). Thermal conductivity (reference value): Approximately 2-4 W / m·K at high temperatures. Melting point of uranium dioxide: 2,865°C Melting point of the debris (mixture): 2000°C (assumed) Steel plate K20: Iron plate (Fe): Thermal conductivity: 40 W / m·K Melting point of iron: 1,538℃ <6.Heat flux conditions> Steel plate K20: Iron plate (Fe): Top surface of the iron plate (interface with UO2): Heat flux: 690,000W / m 2 Underside of the iron plate (interface with water): Heat flux: 690,000W / m 2

[0045] If nuclear fuel leaches from reactor 3 and deposits on steel plate K20, the calculated temperature changes of each part based on the above conditions are as follows. Figure 10 is the first figure showing the temperature distribution changes of the debris and the steel plate. Figure 11 is the second figure showing the temperature distribution changes of the debris and the steel plate. Figure 12 is a figure showing the temperature distribution near the steel plate.

[0046] As can be seen from the six graphs shown in order of elapsed time in Figures 10(A), 10(B), and 11(A), 11(B), and 11(C), the top surface temperature of steel plate K20 remains well below its melting point for 1000 seconds after the nuclear fuel leached from reactor 3 accumulates on steel plate K20. In other words, as shown in the graph in Figure 12, the top surface temperature of steel plate K20, which is the hottest structural material of containment vessel 3A, is approximately 610°C, well below its melting point. From this, it can be seen that the triple-layered, water-cooled containment vessel 3A can remove heat from the debris while maintaining its integrity as a vessel, even when exposed to high temperatures, thanks to the cooling water in the outer channels C1-C9 and inner channels H1-H6, even without power to circulate the cooling water.

[0047] Furthermore, the containment vessel 3A is not limited to the above configuration. The containment vessel 3A may have any shape as long as it is a triple-layered container capable of forming an outer flow channel and an inner flow channel. [Explanation of Symbols]

[0048] R··Reactor system T-Turbine System F·· Floating body for buoyancy 1. Nuclear power generation system 3...nuclear reactor 4. Turbine Generator 5. IC / PCCS Pool 3A Containment Vessel 3B·Nuclear fuel 3C Control Rods 3D Recirculation Pump 3E Pressure Vessel 3F · Relief safety valve 3G·Exhaust pipe 3H Suppression Pool 3J Main steam isolation valve 3K Main steam isolation valve 3L Main steam pipe 3M Upper Drywell 3N ·· Lower drywell 4A Turbine 4B Generator 4C Condenser 4D...Circulating water piping 4E ·· Circulating water pump 4F Water supply pump 4G ··Water supply piping C1~C9...Outer flow path H1~H7...Inner channel K1~21...Steel plate

Claims

1. Nuclear reactor and A containment vessel for housing the reactor, It is equipped with a water storage section for storing cooling water for emergencies, The aforementioned storage container is The container has a triple-layer structure, comprising an inner steel plate for housing the reactor, an intermediate steel plate positioned outside the container beyond the inner steel plate, and an outer steel plate positioned outside the container beyond the intermediate steel plate. An inner flow channel formed between the inner steel plate and the intermediate steel plate, It has an outer channel formed between the intermediate steel plate and the outer steel plate, The outer channel and the inner channel communicate with each other at the bottom of the containment vessel and communicate with the water reservoir at the top of the containment vessel. Nuclear power generation system.

2. The outer channel and the inner channel each have vertical partitions that divide each channel into multiple channels by wall materials extending in the vertical direction. Each outer channel formed in the outer flow path by the vertical bulkhead communicates with each other at the bottom and top of the containment vessel, Each internal channel formed in the internal flow path by the vertical bulkhead communicates with each other at the bottom and top of the containment vessel. The nuclear power generation system according to claim 1.

3. The containment vessel is a circular container with the reactor as its center point when viewed from above. The outer channel and the inner channel are separated by the vertical partition wall extending radially from the central point. The nuclear power generation system according to claim 2.

4. A triple-layered container body having an inner steel plate for housing the reactor, an intermediate steel plate positioned outside the container beyond the inner steel plate, and an outer steel plate positioned outside the container beyond the intermediate steel plate, An inner flow channel formed between the inner steel plate and the intermediate steel plate, The system comprises an outer channel formed between the intermediate steel plate and the outer steel plate, The outer channel and the inner channel are in communication with each other at the bottom of the container body and are in communication with a water reservoir for storing emergency cooling water at the top of the container body. Containment vessel.

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