Nuclear power systems and containment vessels

Abstract

The present application discloses a nuclear power generation system and a containment vessel that can improve the integrity of the containment vessel. [Solution] This nuclear power generation system comprises a nuclear reactor, a containment vessel that contains the reactor, and a water storage section that stores cooling water for emergencies, wherein the containment vessel is a triple-structure vessel having an inner steel plate that contains the reactor, an intermediate steel plate that is positioned outside the vessel from the inner steel plate, and an outer steel plate that is positioned outside the vessel from the intermediate steel plate, and has an inner flow path formed between the inner steel plate and the intermediate steel plate, and an outer flow path formed between the intermediate steel plate and the outer steel plate, and the outer flow path and the inner flow path are connected to each other at the bottom of the containment vessel and each is connected to the water storage section at the top of the containment vessel.

Description

[Technical field]

[0001] The present invention relates to nuclear power systems and containment vessels. [Background technology]

[0002] Various types of nuclear power generation systems have been proposed (see, for example, Patent Documents 1 to 4). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2023-78930 A [Patent Document 2] JP 2022-109492 A [Patent Document 3] JP 2015-227830 A [Patent Document 4] Special Publication No. 2023-508855 Summary of the Invention [Problem to be solved by the invention]

[0004] Nuclear power generation systems may be provided with a containment vessel to house the reactor equipment. In the case of light water reactors such as boiling water reactors and pressurized water reactors, the containment vessel serves to contain steam and radioactive materials that leak when the reactor equipment is damaged. However, if a large amount of steam leaks from the damaged reactor equipment or if the reactor core is damaged on a large scale, the integrity of the containment vessel may be compromised.

[0005] Therefore, the present application discloses a nuclear power generation system and a containment vessel that can improve the integrity of the containment vessel. [Means for solving the problem]

[0006] In order to solve the above problems, in the present invention, the containment vessel is made into a triple-structure vessel consisting of an inner steel plate, an intermediate steel plate, and an outer steel plate, the float on which the reactor and turbine generator are arranged is made to have a streamlined shape when viewed from above, and the inner flow passage formed between the inner steel plate and the intermediate steel plate and the outer flow passage formed between the intermediate steel plate and the outer steel plate are connected to each other at the bottom of the containment vessel and each is connected to a water storage section at the top of the containment vessel.

[0007] In detail, the present invention is a nuclear power generation system comprising a nuclear reactor, a containment vessel for storing the reactor, and a water storage section for storing cooling water for emergency use, wherein the containment vessel is a triple-structure vessel having an inner steel plate for storing the reactor, an intermediate steel plate arranged outside the vessel from the inner steel plate, and an outer steel plate arranged outside the vessel from the intermediate steel plate, and has an inner flow path formed between the inner steel plate and the intermediate steel plate, and an outer flow path formed between the intermediate steel plate and the outer steel plate, and the outer flow path and the inner flow path are connected to each other at the bottom of the containment vessel and each is connected to the water storage section at the top of the containment vessel.

[0008] In a nuclear power generation system equipped with such a triple-structure containment vessel, in the event of an emergency at the reactor, convection will occur due to the difference in density caused by the temperature difference between the cooling water in the outer flow path and the cooling water in the inner flow path, allowing the natural circulation of cooling water to continue within the containment vessel.

[0009] The outer flow path and the inner flow path each have a vertical partition wall that divides each flow path into a plurality of channels by a wall material extending in the vertical direction. The channels may be connected to each other at the bottom and the top of the containment vessel, and the inner channels formed in the inner flow path by the vertical partitions may be connected to each other at the bottom and the top of the containment vessel. In a nuclear power generation system having a containment vessel of this type, even if the flow of cooling water is hindered in a specific channel due to partial damage to the containment vessel, the flow of cooling water can continue in other channels.

[0010] In addition, the containment vessel may be a circular vessel with the reactor at its center when viewed from above, and the outer channel and the inner channel may be partitioned by vertical partitions extending radially from the center. In a nuclear power generation system having a containment vessel of this type, it is possible to circulate the cooling water approximately evenly through each channel.

[0011] The present invention may also be a containment vessel comprising a triple-structure vessel body having an inner steel plate for containing a nuclear reactor, an intermediate steel plate arranged outside the vessel from the inner steel plate, and an outer steel plate arranged outside the vessel from the intermediate steel plate, an inner flow path formed between the inner steel plate and the intermediate steel plate, and an outer flow path formed between the intermediate steel plate and the outer steel plate, the outer flow path and the inner flow path being connected to each other at the bottom of the vessel body and each being connected to a water storage section at the top of the vessel body for storing cooling water for emergency use. Effect of the Invention

[0012] The above-described nuclear power generation system and containment vessel can improve the integrity of the containment vessel. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a schematic diagram showing the system configuration of a nuclear power generation system according to an embodiment. [Diagram 2] FIG. 2 is a perspective view showing an outline of the internal structure of the containment vessel. [Diagram 3] FIG. 3 is a perspective view showing details of the internal structure of the containment vessel. [Figure 4] FIG. 4 is a front view showing details of the internal structure of the containment vessel. [Diagram 5] FIG. 5 is a cross-sectional view of the containment vessel taken along the line AA in FIG. [Figure 6] FIG. 6 is a cross-sectional view of the containment vessel taken along the line BB shown in FIG. [Figure 7] FIG. 7 is a cross-sectional view of the containment vessel taken along the line CC shown in FIG. [Figure 8]FIG. 8 is a diagram explaining the flow of cooling water in the containment vessel. [Figure 9] FIG. 9 shows the dimensional conditions of the containment vessel used in the calculations. [Figure 10] FIG. 10 is the first diagram showing the change in temperature distribution of the debris and the steel plate. [Figure 11] FIG. 11 is a second diagram showing the change in temperature distribution of the debris and the steel plate. [Figure 12] FIG. 12 is a diagram showing the temperature distribution in the vicinity of the steel plate. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, an embodiment of the present invention will be described. The embodiment described below is one aspect of the present invention, and is not intended to limit the technical scope of the present invention.

[0015] In the following, a boiling water reactor (BWR) will be taken as an example. However, this embodiment may be a pressurized water reactor (PWR) or other light water reactor, or may be a type of reactor that uses a substance other than light water as a moderator or coolant. In addition, although a form installed on land is exemplified below, this embodiment may be a floating type that can be moored on the sea or the like.

[0016] <System configuration overview> FIG. 1 is a schematic diagram showing the system configuration of a nuclear power generation system 1 according to an embodiment. The nuclear power generation system 1 is mainly composed of a reactor system R and a turbine system T. The turbine generator 4 is a main device of the turbine system T.

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

[0018] The containment vessel 3A is a vessel that contains the pressure vessel 3E that contains the nuclear fuel 3B, etc., 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, etc. The containment vessel 3A is basically made of steel, details of which will be described later. The containment vessel 3A contains the pressure vessel 3E that contains the reactor 3 in its center, and forms an upper dry well 3M above the pressure vessel 3E and a lower dry well 3N below the pressure vessel 3E. The containment vessel 3A also has a suppression pool 3H around the lower dry well 3N.

[0019] The pressure vessel 3E is a container that contains the nuclear fuel 3B and the like, and serves to contain water and steam for cooling the reactor 3. Several hundred nuclear fuels 3B are arranged in the center of the pressure vessel 3E in the form of fuel assemblies to form the main body of the reactor 3. In the main body of the reactor 3, a control rod 3C that can be moved up and down by a drive mechanism provided at the bottom of the pressure vessel 3E is inserted into the gap between the fuel assemblies. When the control rod 3C is withdrawn from the reactor 3 and the reactor 3 goes into a critical state, the reactor 3 continues to generate heat. Also, when the control rod 3C is inserted into the reactor 3 and the reactor 3 goes into a subcritical state, the heat generated by the reactor 3 gradually decays.

[0020] A recirculation pump 3D is provided in the pressure vessel 3E. The recirculation pump 3D is responsible for removing heat from the reactor 3 and controlling the reactor output by forcibly circulating water, which is a reactor coolant, in the liquid phase portion of the pressure vessel 3E. In the nuclear power generation system 1 of this embodiment, an advanced boiling water reactor (ABWR) is assumed, so in FIG. 2 the recirculation pump 3D is provided in the pressure vessel 3E, but the nuclear power generation system 1 is not limited to this. The nuclear power generation system 1 may have a recirculation system in which a recirculation pump and circulation piping are arranged outside the pressure vessel 3E, for example.

[0021] A main steam pipe 3L is connected to the pressure vessel 3E to send steam generated in the pressure vessel 3E to a turbine generator 4 of a 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, 3K are provided near the penetrations of the containment vessel 3A to enable isolation of the containment vessel 3A. A safety relief valve 3F is provided midway along 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, 3K are closed. The end of an exhaust pipe 3G downstream of the safety relief valve 3F is disposed in a suppression pool 3H.

[0022] The turbine 4A and the generator 4B constituting the turbine generator 4 are connected by the same rotating shaft. The turbine 4A has a structure in which an impeller is housed in a casing. A condenser 4C is provided below the turbine 4A to condense the steam that has passed through the turbine 4A. A number of thin tubes that form part of the path of the circulating water pipe 4D that connects the water intake and the water discharge port provided below the sea level are provided in the condenser 4C, and the steam is condensed by the cold heat of seawater sent by the circulating water pump 4E provided on the path of the circulating water pipe 4D. Therefore, the power for rotating the generator 4B is applied to the impeller due to the pressure difference between the steam supplied from the reactor 3 through the main steam pipe 3L and the inside of the condenser 4C. This causes the generator 4B to rotate and generate electricity. The condensed water condensed in the condenser 4C is fed again into the pressure vessel 3E via the feed water pipe 4G by the feed water pump 4F.

[0023] Note that FIG. 2 merely shows an outline of the reactor system R and the turbine system T, and in reality, a wide variety of equipment is provided. For example, important equipment such as a steam control valve and a turbine bypass valve are provided near the turbine 4A of the main steam pipe 3L. The turbine bypass valve may be capable of 100% bypass, in which the entire amount of main steam at rated output is sent directly to the condenser 4C without passing through the turbine 4A, or may have a bypass capacity lower than that. In addition, important equipment such as a feedwater flow rate control valve, a condensate demineralizer, and a feedwater heater are provided in the feedwater piping 4G. In addition, piping for an emergency core cooling system is provided inside and outside the containment vessel 3A. In addition, the turbine 4A is a combination of a high-pressure turbine and multiple low-pressure turbines.

[0024] 2, each device is illustrated in a single system, but each device in the nuclear power generation system 1 is multiplexed. For example, there are multiple circulating water pumps 4E and multiple feed water pumps 4F.

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

[0026] The outline of the system configuration of the nuclear power generation system 1 according to this embodiment has been described above. Next, the containment vessel 3A employed in the nuclear power generation system 1 according to this embodiment will be described in detail.

[0027] Fig. 2 is a perspective view showing an outline of the internal structure of the containment vessel 3A. Fig. 3 is a perspective view showing the details of the internal structure of the containment vessel 3A. Fig. 4 is a front view showing the details of the internal structure of the containment vessel 3A. Fig. 5 is a cross-sectional view of the containment vessel 3A taken along line AA in Fig. 4. Fig. 6 is a cross-sectional view of the containment vessel 3A taken along line BB in Fig. 4. Fig. 7 is a cross-sectional view of the containment vessel 3A taken along line CC in Fig. 4.

[0028] The containment vessel 3A is a triple-structure vessel, and has outer passages C1-9 and inner passages H1-7 through which cooling water flows to cool the inside of the vessel. The above-mentioned upper dry well 3M and lower dry well 3N are formed inside the containment vessel 3A. The containment vessel 3A plays a role in containing leaks within the containment vessel 3A when high-temperature steam leaks from the reactor 3 or the like disposed within the containment vessel 3A, or when the nuclear fuel 3B of the reactor 3 leaks from the pressure vessel 3E. For this reason, the containment vessel 3A cools the structural materials of the vessel with the cooling water of the outer passages C1-9 and inner passages H1-7 in order to maintain the integrity of the vessel when the structural materials forming the inner surface of the vessel are exposed to high temperatures.

[0029] Specifically, the outer flow paths C1-9 and the inner flow paths H1-6 of the containment vessel 3A are connected to a water storage means such as an IC / PCCS pool arranged at the same height as the vicinity of the upper part of the containment vessel 3A, and the outer flow paths C1-9 and the inner flow paths H1-7 are constantly filled with water by the head pressure of the stored water. The water filling the outer flow paths C1-9 and the inner flow paths H1-6 exerts a shielding effect that suppresses the radiation emitted from the reactor 3 from leaking outside the containment vessel 3A during normal times and emergency situations. More specifically, the outer flow path C1 is connected to the pool through a pipe not shown, and the inner flow path H6 is connected to the pool through the inner flow path H7. The outer flow paths C1-9 form a flow path in the outer part of the triple-structured vessel that constitutes the containment vessel 3A. The inner flow paths H1-6 form a flow path in the inner part of the triple-structured vessel that constitutes the containment vessel 3A. IC / PCCS The pool contains an isolation condenser (IC) and a passive containment cooling system (PC Although there are heat exchangers for the Passive Containment Cooling System (CS), these are also equipment for cooling the reactor 3 in an emergency, so even if the stored water flows through the outer flow paths C1-9 and the inner flow paths H1-7, it does not interfere with the use of the equipment in the IC / PCCS pool.

[0030] The containment vessel 3A forms a water flow path in which the water flows from the outer flow path C1 at the top of the containment vessel 3A, which communicates with the water storage means, to the outer flow path C9 at the bottom of the containment vessel 3A in the order of the outer flow paths C1, C2, C3, C4, C5, C6, C7, C8, and C9. The containment vessel 3A also forms a water flow path in which the water flows from the outer flow path C9 at the bottom of the containment vessel 3A to the inner flow path H7 at the top of the containment vessel 3A in the order of the outer flow path C9, inner flow paths H1, H2, H3, H4, H5, H6, and H7.

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

[0032] That is, the containment vessel 3A has a cylindrical steel plate K1 forming the outermost peripheral wall surface. The upper end side of the cylindrical steel plate K1 is closed by a steel plate K12. A cylindrical steel plate K15 having a smaller diameter than the steel plate K1 is mounted on the steel plate K12. The upper end side of the steel plate K15 is closed by a steel plate K16. Moreover, the lower end side of the cylindrical steel plate K1 is closed by a steel plate K19. When the nuclear power generation system 1 is a floating body type, the steel plate K19 may be a steel plate constituting the floating body. The outermost shell part of the containment vessel 3A is thus formed by the steel plates K1, K12, K15, K16, and K19.

[0033] Inside the outermost shell portion, steel plates are arranged as follows to form a double-structured containment vessel 3A. That is, inside the steel plate K1, a cylindrical steel plate K2 having a slightly smaller diameter than the steel plate K1 is arranged. Moreover, a steel plate K11 is arranged below the steel plate K12. Moreover, inside the steel plate K15, a steel plate K14 having a slightly smaller diameter than the steel plate K15 is arranged. Moreover, a steel plate K17 is arranged below the steel plate K16. As a result, a space of the outer flow passage C1 is formed between the steel plate K16 and the steel plate K17. Moreover, a space of the outer flow passage C2 is formed between the steel plate K15 and the steel plate K14. Moreover, a space of the outer flow passage C3 is formed between the steel plate K12 and the steel plate K11. Moreover, a space of the outer flow passage C4 is formed between the steel plate K1 and the steel plate K2.

[0034] Inside such a double structure, the steel plates are arranged as follows, thereby forming a triple-structured containment vessel 3A. That is, inside the steel plate K2, a cylindrical steel plate K3 having a slightly smaller diameter than the steel plate K2 is arranged. Moreover, the steel plate K10 is arranged below the steel plate K11. Moreover, inside the steel plate K14, a cylindrical steel plate K13 having a slightly smaller diameter than the steel plate K14 is arranged. Moreover, the steel plate K18 is arranged below the steel plate K17. As a result, the spaces of the outer flow passage C5 and the inner flow passage H4 are formed between the steel plate K2 and the steel plate K3. Moreover, the space of the inner flow passage H5 is formed between the steel plate K11 and the steel plate K10. Moreover, the space of the inner flow passage H6 is formed between the steel plate K14 and the steel plate K13 and between the steel plate K17 and the steel plate K18.

[0035] Furthermore, inside the containment vessel 3A having such a triple structure, a cylindrical steel plate K4 is disposed for dividing the space below the upper dry well 3M into a lower dry well 3N and a suppression pool 3H. In addition, at the upper end portion of the steel plate K4, a steel plate K9 for dividing the upper dry well 3M and the suppression pool 3H is disposed in a brim-like shape so as to extend from the upper end of the steel plate K4 toward the inner peripheral surface of the steel plate K3.

[0036] The steel plates K4 and K9 are also arranged as follows to form an upper dry The well 3M and the lower dry well 3N are separated from the suppression pool 3H by a triple-structure partition wall. That is, a cylindrical steel plate K5 having a slightly larger diameter than the steel plate K4 is arranged outside the steel plate K4. Furthermore, a cylindrical steel plate K6 having a slightly larger diameter than the steel plate K5 is arranged outside the steel plate K5. Moreover, a steel plate K8 is arranged below the steel plate K9. Moreover, a steel plate K7 is arranged below the steel plate K8. As a result, a space of the inner flow passage H2 is formed between the steel plate K4 and the steel plate K5. Moreover, a space of the outer flow passage C7 is formed between the steel plate K5 and the steel plate K6. Moreover, a space of the inner flow passage H3 is formed between the steel plate K9 and the steel plate K8. Moreover, a space of the outer flow passage C6 is formed between the steel plate K8 and the steel plate K7.

[0037] The steel plate K20 constituting the bottom surface of the lower dry well 3N is disposed above the steel plate K19. A disk-shaped steel plate K21 having a through hole in the center is disposed between the steel plates K20 and K19. This forms a space for the outer flow passage C8 between the steel plates K19 and K21. At the through hole in the center of the steel plate K21, a space for the outer flow passage C9 is formed between the steel plates K19 and K20. A space for the inner flow passage H1 is formed between the steel plates K20 and K21.

[0038] As can be seen from Figures 3 to 7, the containment vessel 3A is provided with many other steel plates in addition to the above-mentioned steel plates K1 to 21. 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, such steel plates are provided with many through holes at appropriate positions to ensure flow paths, thereby preventing the flow paths of the outer flow paths C1 to C9 and the inner flow paths H1 to H6 from being obstructed.

[0039] Also, as shown in, for example, Figs. 5 to 7, the containment vessel 3A is provided with a large number of radially extending steel plates extending vertically for reinforcement. As a result, the outer flow passages C2 to C8 and the inner flow passages H1 to H5 are partitioned into a plurality of channels. By partitioning the outer flow passages C2 to C8 and the inner flow passages H1 to H5 into a plurality of channels, even if the flow of cooling water is hindered in a specific channel due to partial damage to the containment vessel 3A, the flow of cooling water can be continued in other channels. In addition, the outer channels formed in the outer flow passages C2 to C8 communicate with each other in the outer flow passage C1 and the outer flow passage C9, and the inner channels formed in the inner flow passages H1 to H5 communicate with each other in the outer flow passage C9 and the inner flow passage H6. As a result, it is possible to distribute the cooling water approximately evenly to each channel. Note that the outer flow passages C2 to C8 and the inner flow passages H1 to H5 do not have to be partitioned into a plurality of channels by steel plates extending vertically.

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

[0041] FIG. 8 is a diagram illustrating the flow of cooling water in the containment vessel 3A. When an abnormality occurs in the reactor 3, the cooling water in the inner flow passages H1 to H6 adjacent to the upper dry well 3M and the lower dry well 3N in which the reactor 3 is placed becomes hotter than the cooling water in the outer flow passages C1 to C9. Therefore, when the containment vessel 3A is heated by the heat of the reactor 3, the cooling water in the inner flow passages H1 to H6 becomes less dense than the cooling water in the outer flow passages C1 to C9. As a result, as shown by the dashed arrows in FIG. 8, the cooling water in the outer flow passages C1 to C9 descends from the top to the bottom of the containment vessel 3A, and the cooling water in the inner flow passages H1 to H6 ascends from the bottom to the top of the containment vessel 3A. The cooling water in the inner flow passages H1 to H6 may rise to the top of the containment vessel 3A in a liquid phase, or may rise to the top of the containment vessel 3A while changing to a gas phase state due to boiling on the way. Since the outer flow passage C1 is connected to the IC / PCCS pool 5, the cooling water flows from the IC / PCCS pool 5 to the outer flow passage C1 as the cooling water descends. In addition, since the inner flow passage H7 is connected to the IC / PCCS pool 5, the water that rises in the liquid or gas phase flows from the inner flow passage H7 to the The cooling water flows into the IC / PCCS pool 5. In this triple-structure containment vessel 3A, even without a power source for circulating the cooling water, convection occurs due to the difference in density caused by the temperature difference between the cooling water in the outer flow passages C1-C9 and the cooling water in the inner flow passages H1-H6, and the natural circulation of the cooling water to cool the containment vessel 3A can continue. In addition, since the outer flow passages C1-9 and the inner flow passages H1-6 continue to be filled with water even in an emergency, this water continues to exert a shielding effect that suppresses radiation emitted from the reactor 3 and debris from leaking outside the containment vessel 3A.

[0042] For example, when the core melts in the nuclear 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. When debris accumulates on the steel plate K20 located below the pressure vessel 3E, the steel plate K20 is heated. However, in this embodiment, the steel plate K20 is cooled by the cooling water in the inner flow passage H1. If the debris directly comes into contact with a large amount of water, there is a concern that a steam explosion or a large amount of hydrogen may be generated. For this reason, when attempting to inject water 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 such an amount of water injection during the progression of a severe accident such as a core meltdown. In this regard, in the nuclear power generation system 1 of this embodiment, the steel plate K20 forming the bottom surface of the lower dry well 3N functions not only as a core catcher but also as a heat sink cooled by the cooling water. Therefore, the debris accumulated on the steel plate K20 is stably cooled. In addition, since the debris does not come into direct contact with water during this cooling process, there is little risk of a steam explosion or the generation of large amounts of hydrogen.

[0043] The performance of the containment vessel 3A was calculated, and the results are shown below. In this calculation, the nuclear fuel is dissolved from the reactor 3 and deposited on the steel plate K20 as debris. Figure 9 shows the dimensional conditions of the containment vessel 3A used in the calculation. In this calculation, the steel material used for the steel plates K1 to K21 has a wall thickness of 30 mm and a density of 7.83 g / cm3. 3 of iron (Fe).

[0044] The various conditions in this calculation are as follows: <1.Initial conditions> Debris: Uranium dioxide (UO 2 ) and iron (Fe) Top surface: 3000℃ Bottom surface: 1300℃ (fixed) Inside: Linearly interpolated temperatures on top and bottom surfaces Steel plate K20: Iron plate (Fe): Top surface: 610℃ (fixed) Bottom surface: 94℃ (fixed) Inside: Linearly interpolated temperatures on top and bottom surfaces Cooling water for containment vessel 3A: Water (H 2 O) Bulk temperature: 25℃ <2.Geometric conditions> Debris: Uranium dioxide (UO 2 ) and iron (Fe) Thickness: 1.0m Area (circular plate): diameter 10.6m (area 88.24m 2 ) Steel plate K20: Iron plate (Fe): Thickness: 3cm (0.03m) <3. Thermal boundary conditions> Debris: Uranium dioxide (UO 2 ) and iron (Fe) Top surface: Radiation heat transfer (emissivity 0.9, ambient temperature 25℃) Side: Insulated Steel plate K20: Iron plate (Fe): Side: Insulated Top surface: Solid contact heat transfer coefficient between uranium dioxide and the material is 1000W / m 2 ·K Bottom surface: In contact with water, film boiling heat transfer coefficient 10,000 W / m 2 ·K <4. Heat generation conditions> Heat distribution: Heat is uniformly distributed within the uranium dioxide Total heat output: 60MW Heat density per area: Approx. 680,000W / m 2 5. Material properties Debris: Uranium dioxide (UO 2 ) and iron (Fe) Thermal conductivity (reference value): Approximately 2 to 4 W / m K at high temperatures Melting point of uranium dioxide: 2,865°C Melting point of debris (mixture): 2000℃ (assumed) Steel plate K20: Iron plate (Fe): Thermal conductivity: 40W / mK Melting point of iron: 1,538°C <6.Heat flux conditions> Steel plate K20: Iron plate (Fe): Top of the iron plate (UO2 (interface with): Heat flux: 690,000W / m 2 Underside of steel plate (interface with water): Heat flux: 690,000W / m 2

[0045] When nuclear fuel elutes from the reactor 3 and accumulates on the steel plate K20, the calculation results of the temperature change of each part based on the above conditions are as follows. Fig. 10 is a first diagram showing the change in temperature distribution of the debris and the steel plate. Fig. 11 is a second diagram showing the change in temperature distribution of the debris and the steel plate. Fig. 12 is a diagram showing the temperature distribution near the steel plate.

[0046] As can be seen from the six graphs shown in order of elapsed time in (A), (B), and (C) of FIG. 10 and (A), (B), and (C) of FIG. 11, the upper surface temperature of the steel plate K20 is kept at a temperature sufficiently lower than the melting point until 1000 seconds have passed since the nuclear fuel eluted from the reactor 3 was deposited on the steel plate K20. That is, as shown in the graph of FIG. 12, the upper surface temperature of the steel plate K20, which is the hottest among the structural materials of the containment vessel 3A, is about 610°C, which is sufficiently lower than the melting point. From this, it can be seen that the water-cooled containment vessel 3A with a triple structure can remove heat from the debris while maintaining the integrity of the vessel even when exposed to high temperatures, by the cooling water in the outer flow paths C1 to C9 and the inner flow paths H1 to H6, even without a power source for circulating the cooling water.

[0047] The containment vessel 3A is not limited to the above-mentioned form, and may have any shape as long as it is a triple-structure vessel capable of forming an outer flow path and an inner flow path. [Explanation of symbols]

[0048] R··Reactor system T·Turbine system F··Floating float 1. Nuclear power generation system 3...nuclear reactor 4. Turbine generator 5. IC / PCCS Pool 3A··Containment vessel 3B·Nuclear fuel 3C··Control rod 3D Recirculation Pump 3E Pressure vessels 3F: Safety relief 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 Dry Well 4A·Turbine 4B Generator 4C··Condenser 4D...Circulating water piping 4E··Circulating water pump 4F: Water supply pump 4G Water supply pipe C1~C9...Outer flow path H1~H7 Inner passage K1~21...Steel plate

Claims

1. A nuclear reactor, a containment vessel for containing the nuclear reactor; A water storage section for storing cooling water for emergency use, The containment vessel comprises: A triple-structure vessel having an inner steel plate for housing the reactor, an intermediate steel plate arranged on the vessel outer side than the inner steel plate, and an outer steel plate arranged on the vessel outer side than the intermediate steel plate, An inner flow passage formed between the inner steel plate and the intermediate steel plate; an outer flow passage formed between the intermediate steel plate and the outer steel plate; The outer flow path and the inner flow path communicate with each other at a bottom of the containment vessel, and each communicate with the water storage section at an upper part of the containment vessel. Nuclear power system.

2. The outer flow path and the inner flow path each have a vertical partition wall that divides each flow path into a plurality of channels by a wall material extending in a vertical direction, the outer channels formed in the outer flow passage by the vertical partitions communicate with each other at a bottom and an upper portion of the containment vessel; The inner channels formed in the inner flow passage by the vertical partitions communicate with each other at the bottom and the top of the containment vessel. The nuclear power generation system according to claim 1 .

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

4. a triple-structure vessel body having an inner steel plate for housing a nuclear reactor, an intermediate steel plate disposed on the vessel outer side than the inner steel plate, and an outer steel plate disposed on the vessel outer side than the intermediate steel plate; An inner flow passage formed between the inner steel plate and the intermediate steel plate; An outer flow passage formed between the intermediate steel plate and the outer steel plate, The outer flow path and the inner flow path communicate with each other at the bottom of the container body, and communicate with a water storage section that stores cooling water for emergency use at an upper part of the container body. Storage vessel.

Images