Floating nuclear power system

Abstract

The present application discloses a floating nuclear power generation system that can utilize the advantages of a floating body for cooling a nuclear reactor. [Solution] A floating nuclear power generation system comprising: a nuclear reactor, a turbine generator driven by steam generated by the heat of the reactor, a float on which the reactor and turbine generator are arranged and moored at sea, a water storage section for storing water to directly or indirectly cool the reactor in an emergency, and a ballast tank that can take in and out seawater from around the float, the water storage section being provided with a connecting valve for directly or indirectly allowing water from around the float to flow in through an inlet provided on the side of the float, and the ballast tank accepting seawater from around the float so that in an emergency the inlet is lower than the waterline of the float.

Description

[Technical field]

[0001] The present invention relates to a floating nuclear power system. [Background technology]

[0002] Nuclear power generation systems have been proposed not only in the form of systems installed on land, but also in the form of floating systems that float on the sea (see, for example, Patent Documents 1 to 3). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 151898 / 1983 [Patent Document 2] Japanese Patent Application Publication No. 151899 / 1983 [Patent Document 3] Japanese Patent Application Publication No. 52-149589 Summary of the Invention [Problem to be solved by the invention]

[0004] When a nuclear power generation system is floated on the sea, the float is surrounded by the sea, which is essentially a favorable environment for cooling the reactor. However, if the emergency seawater intake on the float is higher than the waterline, the reactor cannot be cooled statically with the seawater around the float in the event of an emergency.

[0005] Therefore, the present application discloses a floating nuclear power generation system that can utilize the advantages of a floating body for cooling a nuclear reactor. [Means for solving the problem]

[0006] In order to solve the above problems, in the present invention, a communication valve is provided in a water storage section that stores water for a condenser that condenses steam generated in the pressure vessel or containment vessel in an emergency, allowing water from around the float to flow directly or indirectly through an inlet provided on the side of the float, and in the event of a reactor emergency, a ballast tank is provided to receive seawater from around the float so that the inlet is lower than the waterline of the float.

[0007] In detail, the present invention is a floating nuclear power generation system comprising a nuclear reactor, a turbine generator driven by steam generated by the heat of the reactor, a float on which the nuclear reactor and the turbine generator are disposed and which is moored at sea, a water storage section which stores reserve water for directly or indirectly cooling the reactor in an emergency, and a ballast tank which can take in and out seawater from around the float, the water storage section being provided with a communication valve for allowing water from around the float to flow in directly or indirectly from an inlet provided on the side of the float, and the ballast tank receiving seawater from around the float so that in an emergency the inlet is lower than the waterline of the float.

[0008] In the above-mentioned floating nuclear power generation system, a communication valve is provided to allow water around the float to flow directly or indirectly from an inlet provided on the side of the float into the water storage section that stores reserve water for directly or indirectly cooling the reactor in an emergency. Therefore, by adjusting the draft of the float using a ballast tank so that the inlet is lower than the waterline of the float in an emergency, it becomes possible to receive seawater around the float from the inlet through the communication valve into the water storage section. Therefore, it can be said that such a floating nuclear power generation system makes it possible to utilize the advantages of the float for cooling the reactor.

[0009] The ballast tank may have a water volume within the tank such that the inlet is normally higher than the waterline of the float. This allows the amount of water within the ballast tank to be reduced under normal circumstances. .

[0010] The floating nuclear power generation system may further include a condenser that condenses steam generated in the pressure vessel or containment vessel in which the reactor is located in an emergency using the cold heat of the stored water and returns the condensate to the pressure vessel or containment vessel. In this case, the condenser may be installed at a position on the float that is at least higher than the reactor. This makes it possible to cool the reactor even in the event of a loss of power.

[0011] In addition, the float has at least a side ballast tank formed in the side portion of the float by a double hull structure, and the water storage section may have a second communication valve as a communication valve that connects the inside of the water storage section with the side ballast tank.

[0012] The float may also receive seawater from around the float in a lower part of the float so that the inlet is lower than the waterline of the float in an emergency. With this, even if seawater is received in the ballast tank and the inlet of the communication valve provided on the side of the float does not become lower than the waterline, it is possible to receive seawater from around the float into the water storage section by opening the communication valve. Effect of the Invention

[0013] The floating nuclear power generation system described above makes it possible to utilize the advantages of a floating body for cooling the reactor. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a schematic diagram showing an arrangement of equipment in a floating nuclear power generation system according to an embodiment. [Diagram 2] FIG. 2 is a schematic diagram showing a system configuration of a floating nuclear power generation system according to an embodiment. [Diagram 3] Figure 3 shows the IC / PCCS pool from a lateral perspective. [Figure 4] Figure 4 shows the IC / PCCS pool from above. [Diagram 5] FIG. 5 is a diagram illustrating the manner in which the draft of a floating body changes. [Figure 6] FIG. 6 is a graph showing the stability of the attitude of the floating body. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] 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.

[0016] <Equipment layout overview> Fig. 1 is a schematic diagram showing the arrangement of equipment in a floating nuclear power generation system 1 according to an embodiment. Fig. 1(A) shows the layout of various equipment provided in the floating nuclear power generation system 1 as viewed from above. Fig. 1(B) shows the layout of various equipment provided in the floating nuclear power generation system 1 as viewed from the side.

[0017] The floating nuclear power generation system 1 is a floating power generation system that can be floated on the sea. For this reason, the floating nuclear power generation system 1 includes a float 2. As can be seen from FIG. 1(A), the float 2 is a streamlined float. However, the float 2 is not a ship intended to navigate autonomously on the sea. The float 2 floats in a moored state on the sea in order to transmit the electricity generated by the floating nuclear power generation system 1 to land. In order to suppress resistance to tidal currents, the float 2 floats on the sea with only one end in the longitudinal direction moored by an anchor chain 22 and the other end not moored. For this reason, the float 2 floats on the sea like a windsock. In other words, when the float 2 receives a tidal current, it floats on the sea with the moored part naturally facing the upstream side of the tidal current. This results in a streamlined floating shape. Since the shape of the float 2 reduces resistance, it is possible to minimize the tension applied to the anchor chain 22. In addition, since the float 2 has a streamlined shape, when manufacturing the floating nuclear power system 1 in a general horizontally long shipbuilding dock, the space in the dock can be used to the maximum extent possible, so that the floating nuclear power system 1 can be manufactured efficiently.

[0018] Since the float 2 has such a streamlined shape, in this embodiment, for convenience, the moored portion of the float 2 in the longitudinal direction is referred to as the "bow side" and the unmoored portion is referred to as the "stern side". Therefore, in Fig. 1, the left side of the page is the "bow side" and the right side of the page is the "stern side". Fig. 1(B) shows the internal configuration of the floating nuclear power generation system 1 as viewed from the port side of the float 2.

[0019] In this embodiment, a streamlined float 2 is exemplified, but the float 2 may be a non-streamlined float. The float 2 used in the floating nuclear power generation system 1 may be, for example, a cylindrical float that is circular when viewed from above, a rectangular parallelepiped float that is square when viewed from above, or floats of various other shapes.

[0020] As shown in FIG. 1, the floating nuclear power generation system 1 includes a nuclear reactor 3 disposed near the center of a float 2, and a turbine generator 4 disposed closer to the bow than the nuclear reactor 3. The nuclear reactor 3 generates steam by boiling water with heat generated by nuclear fission. The turbine generator 4 generates electricity by rotating a generator with a steam-driven turbine. Note that in this embodiment, a floating nuclear power generation system 1 using a boiling water reactor (BWR) that drives the turbine generator 4 with steam from the nuclear reactor 3 is illustrated as an example, but the floating nuclear power generation system 1 may be any other type of floating nuclear power generation system. The power system 1 is, for example, a pressurized water reactor (PWR). Alternatively, various other methods may be used.

[0021] The floating nuclear power generation system 1 includes various equipment and the like in addition to the float 2, the reactor 3, and the turbine generator 4 described above. The floating nuclear power generation system 1 includes, for example, reactor equipment areas 5 and 7, a pit 6, and a fuel pool 8 around the reactor 3. The floating nuclear power generation system 1 also includes a desalination device 9, an IC / PCCS pool 10, various equipment areas 12, a living area 13, and a waste treatment room 24, which are arranged aft of the reactor 3. The floating nuclear power generation system 1 also includes a condensate storage tank 14 arranged between the reactor 3 and the turbine generator 4. The floating nuclear power generation system 1 also includes a laydown area 18 and an auxiliary equipment area 19, which are arranged near the bow of the float 2. A main transformer 20 and an auxiliary boiler 21 are provided in the auxiliary equipment area 19. The floating nuclear power generation system 1 also includes a light oil tank 23 on the deck near the bow of the float 2. The floating nuclear power generation system 1 also includes a bow ballast tank 25, a bottom ballast tank 26, a stern ballast tank 27, and a side ballast tank 28 for controlling the attitude of the float 2.

[0022] In the reactor equipment areas 5 and 7, various reactor equipment to be installed outside the containment vessel of the reactor 3 is disposed. The devices disposed in the reactor equipment areas 5 and 7 include, for example, pumps and valves of various reactor cooling equipment such as an emergency core cooling system and a residual heat removal system, pumps and valves of a pool water cooling system that cools the fuel pool, compressed air equipment for control, ventilation and air conditioning equipment, an emergency diesel generator that serves as an emergency power source, DC power supply equipment using storage batteries, and various other equipment.

[0023] The pit 6 is a pit for temporarily storing various items during periodic inspections and fuel replacement. Examples of items to be stored in the pit 6 include a steam separator and a steam dryer that are placed above the nuclear fuel inside the reactor 3.

[0024] The fuel pool 8 is a pool for storing unused or spent nuclear fuel. The nuclear fuel of the reactor 3 is in the form of fuel assemblies. A rack is provided to store the combined fuel assemblies at an appropriate interval. A fuel exchange machine for transferring the fuel assemblies between the reactor 3 and the fuel pool 8 is provided above the fuel pool 8.

[0025] The desalination device 9 is a device that desalinates seawater. Since the floating nuclear power generation system 1 is used while floating on the sea, it is not possible to obtain fresh water that contains almost no salt from a river, as is the case with facilities on land. For this reason, the floating nuclear power generation system 1 is provided with a desalination device 9 that removes salt from seawater to desalinate it, in order to secure reactor cooling water and various other types of water. As a desalinization method for the desalination device 9, various methods such as reverse osmosis membrane method and evaporation method can be applied.

[0026] An IC heat exchanger and a PCCS heat exchanger are arranged in the IC / PCCS pool 10. The IC heat exchanger is an isolation condenser (IC) equipment, and is used for all AC power sources. In the event of a loss of power or other accident that causes the containment vessel to be isolated, the PCCS cools the reactor 3. The PCCS heat exchanger is a piece of equipment in the Passive Containment Cooling System (PCCS), and cools the steam that is released into the containment vessel in the event of a severe accident.

[0027] In the various equipment area 12, a central control room for operating the floating nuclear power generation system 1, an entrance / exit control room for controlling entrance / exit to the radiation controlled area, and various other equipment are provided. The emergency diesel generator and DC power supply equipment described above may be provided in the various equipment area 12 instead of the reactor equipment areas 5 and 7.

[0028] The accommodation area 13 is provided with accommodation facilities for the operators and others staying on the floating nuclear power system 1. Examples of the accommodation facilities include individual rooms with berths, a dining room with cooking equipment, bathing facilities, recreational facilities, and various other facilities.

[0029] Various facilities for treating radioactive waste are installed in the waste treatment room 24. Examples of radioactive waste treated in the waste treatment room 24 include liquid waste such as wastewater generated in radiation controlled areas and miscellaneous solid waste such as waste materials generated in various operations. These wastes are reduced in volume in the waste treatment room 24 by evaporation and concentration, compression, incineration, etc., and stored within the float 2, and then transported from the float 2.

[0030] The condensate storage tank 14 is a tank that stores water that can be supplied to the reactor 3. The condensate storage tank 14 is connected to the condenser of the turbine generator 4 and an emergency core cooling system, and is used to supply water to the condenser during normal operation and to inject water into the reactor 3 in an emergency.

[0031] The laydown area 18 is a work space for disassembling and inspecting various large equipment such as the turbine generator 4. The laydown area 18 is on the same floor as the operating floor of the turbine generator 4, and large equipment can be easily transported using crane equipment installed above the operating floor.

[0032] Various types of auxiliary equipment, such as a main transformer 20 and an auxiliary boiler 21, are arranged in the auxiliary equipment area 19. The main transformer 20 is a transformer for stepping up the electricity generated by the turbine generator 4 to the voltage of the power grid. The auxiliary boiler 21 is a boiler that generates steam using heat generated by burning diesel fuel.

[0033] The floating nuclear power generation system 1 is moored on the sea by an anchor chain 22 attached to the bow side of the float 2. As described above, when the floating nuclear power generation system 1 receives a tidal current, it floats on the sea with the moored part naturally facing the upstream side of the tidal current. Therefore, the submarine cable for connecting the floating nuclear power system 1 to the onshore power grid is suspended from near the bow of the float 2 toward the seabed, similar to the anchor chain 22. For this reason, it is reasonable to place the main transformer 20 for stepping up the electricity generated by the turbine generator 4 to the voltage of the power grid near the bow of the float 2 close to the submarine cable, as shown in Figure 1.

[0034] In addition, the auxiliary boiler 21 is used to provide steam for the ground of the turbine generator 4 and to heat the steam equipment around the turbine during startup of the floating nuclear power generation system 1. For this reason, it is reasonable to place the auxiliary boiler 21 near the turbine generator 4 as well.

[0035] For this reason, the floating nuclear power generation system 1 adopts a configuration in which the main transformer 20 and the auxiliary boiler 21 are arranged in an auxiliary equipment area 19 provided on the bow side of the float 2. Also, in the floating nuclear power generation system 1, a light oil tank 23 for storing light oil to be supplied to the auxiliary boiler 21 is arranged above the auxiliary equipment area 19. Note that in the auxiliary equipment area 19, not only the main transformer 20 and the auxiliary boiler 21 but also switching equipment such as a line switch (LS) for opening and closing the electrical connection between the submarine cable and the main transformer 20 can be installed. may be installed.

[0036] The bow ballast tank 25, the bottom ballast tank 26, the stern ballast tank 27, and the side ballast tank 28 are tanks for receiving ballast water for controlling the attitude of the float 2. The ballast water in the bow ballast tank 25, the bottom ballast tank 26, and the stern ballast tank 27 can also be used as seawater for cooling the reactor 3 in an emergency of the floating nuclear power generation system 1. Water can be naturally injected into the bow ballast tank 25, the bottom ballast tank 26, and the stern ballast tank 27 by the water pressure of seawater, for example, by opening a water intake provided on the bottom of the float 2. A pump or the like may be used in combination for water injection, if necessary. In addition, water can be discharged from the bow ballast tank 25, the bottom ballast tank 26, and the stern ballast tank 27 by a pump or an ejector.

[0037] The outline of the equipment layout of the floating nuclear power generation system 1 according to this embodiment has been described above, but the above-mentioned equipment layout is only an example, and other equipment layouts may be adopted. Next, an outline of the system configuration of the floating nuclear power generation system 1 will be described.

[0038] <System configuration overview> 2 is a schematic diagram showing a system configuration of a floating nuclear power generation system 1 according to an embodiment. The floating nuclear power generation system 1 is mainly composed of a reactor system R and a turbine system T. The above-mentioned reactor 3 is a main device of the reactor system R. Also, the above-mentioned turbine generator 4 is a main device of the turbine system T.

[0039] 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.

[0040] 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 nuclear reactor 3, etc. The containment vessel 3A may be made of concrete, or may be made of the steel material that constitutes the float 2. The containment vessel 3A contains the pressure vessel 3E that contains the nuclear reactor 3 in the center, and has 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.

[0041] 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.

[0042] The pressure vessel 3E is provided with a recirculation pump 3D. 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 inside the pressure vessel 3E. In the floating 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 floating nuclear power generation system 1 is not limited to this. The floating 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.

[0043] 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.

[0044] 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 for condensing the steam that has passed through the turbine 4A is provided below the turbine 4A. A number of thin tubes that form part of the path of the circulating water piping 4D that connects the water intake and the water discharge port provided below the water line on the exterior surface of the float 2 are provided in the condenser 4C, and the steam is condensed by the cold heat of seawater pumped by the circulating water pump 4E provided on the path of the circulating water piping 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 piping 4G by the feed water pump 4F.

[0045] 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.

[0046] In addition, although only one system of each equipment is shown in Figure 2, Each device is multiplexed. For example, there are multiple circulating water pumps 4E and multiple water supply pumps 4F.

[0047] 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 floating 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.

[0048] The outline of the system configuration of the floating nuclear power generation system 1 according to this embodiment has been described above. Next, the emergency cooling function provided in the floating nuclear power generation system 1 will be described in detail.

[0049] As described above, the floating nuclear power generation system 1 according to this embodiment is used while moored on the sea, and therefore safety can be significantly improved by stably removing the decay heat of the reactor 3 for a long period of time using the seawater around the float 2. Furthermore, when using the seawater around the float 2, safety can be further improved by realizing passive use of seawater without requiring power such as electricity or an engine. Therefore, the various cooling facilities provided in the floating nuclear power generation system 1 are configured as follows in order to use the seawater around the float 2.

[0050] During normal operation, the reactor 3 is cooled by the cold heat of the condenser 4C, but during normal shutdown or emergency shutdown, the reactor 3 is cooled by various cooling equipment other than the condenser 4C. The cooling equipment used in an emergency for the reactor 3 is called the emergency core cooling system (ECCS), and is composed of various cooling equipment such as a high-pressure water injection system, an isolation cooling system, and a low-pressure water injection system.

[0051] As described above, the floating nuclear power system 1 is equipped with an emergency condenser and a passive containment vessel cooling system. Since the floating nuclear power system 1 is of a floating type that floats on the sea, the decay heat of the reactor 3 can be stably removed for a long period of time by using the surrounding seawater, greatly improving safety. For this reason, the floating nuclear power system 1 is capable of flowing seawater into the IC / PCCS pool 10. When seawater is flowed into the IC / PCCS pool 10, cooling can be continued by the natural circulation force due to the density difference of the seawater. For this reason, in the floating nuclear power system 1, the IC / PCCS pool 10 is provided as follows.

[0052] Fig. 3 is a side view of the IC / PCCS pool 10. Fig. 4 is a top view of the IC / PCCS pool 10. Fig. 3 shows the positional relationship between the IC / PCCS pool 10 and the pressure vessel 3E in the height direction above sea level.

[0053] As can be seen from Figures 3 and 4, an emergency condenser 30A and a PCCS heat exchanger 30D are arranged in the IC / PCCS pool 10 (the PCCS heat exchanger 30D is omitted in Figure 3 due to space limitations). The IC / PCCS pool 10 in which the emergency condenser 30A and the PCCS heat exchanger 30D are arranged is higher than the core C. The IC / PCCS pool 10 is provided with a communication valve 10A for communicating with the side ballast tank 28, communication valves 10B and 10C for communicating with the periphery (sea) of the floating body 2, and an atmosphere release pipe 10D for communicating with the atmosphere. The emergency condenser 30A is connected to the inside of the pressure vessel 3E via a pipe 30B connected to the vicinity of the upper part of the pressure vessel 3E and a pipe 30C connected to the vicinity of the lower part of the pressure vessel 3E.

[0054] The IC / PCCS pool 10 is usually filled with fresh water. Even if the floating nuclear power generation system 1 experiences a loss of all AC power sources, the reactor 3 can be cooled by the emergency condenser 30A by opening the pipes 30B and 30C. The IC / PCCS pool 10 is also provided with a path for connecting to the condensate storage tank 14. Therefore, even if the floating nuclear power generation system 1 experiences a loss of all AC power sources and the fresh water in the IC / PCCS pool 10 decreases, the reactor 3 can continue to be cooled by the fresh water stored in the condensate storage tank 14. However, if the loss of all AC power sources continues even if the fresh water in the IC / PCCS pool 10 and the condensate storage tank 14 decreases due to boiling, there may be a case where the cooling of the reactor 3 by the fresh water cannot be continued.

[0055] Therefore, in the event of an emergency, the floating nuclear power generation system 1 changes the draft of the float 2 by receiving seawater around the float 2 into a ballast tank, and slightly sinks the float 2 so that the inlet of the communication valve 10B provided on the outer surface of the float 2 is lower than the waterline (sea surface). Figure 5 is a diagram illustrating an example of how the draft of the float 2 changes.

[0056] When the floating nuclear power generation system 1 is in a normal operating state or in a stopped state, for example, as shown in Fig. 5(A), the amount of water in the ballast tank is adjusted so that the waterline (sea surface) of the float 2 is lower than the inlet of the communication valve 10B. When the waterline of the float 2 is in such a state, the floating nuclear power generation system 1 cannot allow seawater around the float 2 to flow into the IC / PCCS pool 10 even if the communication valve 10B is opened.

[0057] Therefore, in the floating nuclear power generation system 1, when an emergency occurs or when it is judged that an emergency is likely to occur, the draft of the float 2 is changed by receiving seawater around the float 2 into the ballast tank, and the float 2 is slightly submerged so that the inlet of the communication valve 10B provided on the outer surface of the float 2 is lower than the waterline (sea surface) as shown in Fig. 5(B). The ballast tank that receives seawater to change the draft of the float 2 may be any of the bow ballast tank 25, the bottom ballast tank 26, the stern ballast tank 27, or the side ballast tank 28, but it is important to change the draft while keeping the attitude of the float 2 stable.

[0058] The stability of the attitude of the float 2 is greatly related to the draft. FIG. 6 is a graph showing the stability of the attitude of the float 2. The horizontal axis of the graph shown in FIG. 6 represents the draft depth (height from the bottom of the vessel to the waterline). The vertical axis of the graph shown in FIG. 6 represents the GM height (height from the center of gravity to the metacenter). The force that tries to return the attitude of the float to its original state when it tilts increases as the metacenter position becomes higher than the center of gravity position. For this reason, the float is less likely to tilt when the GM height is high than when it is low. As can be seen from the graph in FIG. 6, when the draft depth is deep or shallow, the force that tries to return the attitude of the float to its original state when it tilts acts more strongly than when the draft depth is between them. Therefore, when changing the draft of the float 2 to sink the float 2, it is preferable to adjust the draft so that the attitude of the float 2 is stable while taking into consideration the characteristics of the graph shown in FIG. 6.

[0059] Seawater can be received into the ballast tank simply by opening a valve that communicates between the sea around the float 2 and the ballast tank. In addition, after the inlet of the communication valve 10B becomes lower than the waterline (sea level), seawater around the float 2 can be received into the IC / PCCS pool 10 simply by opening the communication valve 10B. Therefore, for example, even if the electric pump cannot be operated due to a total loss of AC power, it is possible to continue cooling the core C using the isolation condenser 30A.

[0060] The floating nuclear power generation system 1 according to this embodiment is not limited to a configuration in which the emergency condenser 30A condenses the steam in the pressure vessel 3E and the PCCS heat exchanger 30D condenses the steam in the containment vessel 3A. The service condenser 30A and the PCCS heat exchanger 30D used for cooling the containment vessel 3A when the primary system boundary is damaged may complement or exchange each other's functions by switching the system configuration by opening and closing a valve. That is, the emergency condenser 30A may be connected to the upper part (upper dry well 3M) and the lower part (suppression pool 3H) in the containment vessel 3A by opening and closing a valve. Also, the PCCS heat exchanger 30D may be connected to the upper part and the lower part in the pressure vessel 3E by opening and closing a valve. The valve for switching the system configuration may be an electric valve using a DC power source or a manual valve.

[0061] Furthermore, in the floating nuclear power generation system 1, there is a height difference between the communicating valves 10B and 10C. Therefore, although convection occurs in the seawater in the IC / PCCS pool 10 heated by the isolation condenser 30A due to the density difference in the seawater caused by the temperature difference, the height difference between the communicating valves 10B and 10C is expected to naturally replace the seawater in the IC / PCCS pool 10 with the seawater around the float 2.

[0062] In addition, in the floating nuclear power generation system 1, if the inlet of the communication valve 10B provided on the outer surface of the float 2 does not become lower than the waterline (sea level) even when seawater is received in the ballast tank, seawater may be poured into the lower part of the float 2 to further sink the float 2. In this case, the amount of seawater received in the lower part of the float 2, which determines the height of the waterline, may be adjusted to an amount that fits within the volume of the cabin by pouring seawater into the cabin closed by a watertight door, or may be adjusted by opening and closing a valve provided in a path for introducing seawater into the lower part of the float 2. According to this, even if the inlet of the communication valve 10B provided on the outer surface of the float 2 does not become lower than the waterline (sea level) even when seawater is received in the ballast tank, it becomes possible to receive seawater around the float 2 into the IC / PCCS pool 10 by opening the communication valve 10B.

[0063] In addition, if salt is deposited on the surface of the emergency condenser 30A or the PCCS heat exchanger 30D, the heat exchange capacity may be reduced. Therefore, when seawater is flowed into the IC / PCCS pool 10, it is preferable to prevent salt deposition due to evaporation of the seawater. The deposition of salt can be suppressed by preventing boiling (generation of voids) of seawater on the heat exchange surface of the emergency condenser 30A or the PCCS heat exchanger 30D. Therefore, in order to suppress the temperature rise of the seawater in the IC / PCCS pool 10, it is preferable to use large-diameter valves for the communication valves 10A, 10B, and 10C. For example, if large-diameter valves are used for the communication valves 10B and 10C, the seawater in the IC / PCCS pool 10 is easily replaced with the seawater around the floating body 2, so that the temperature rise of the seawater in the IC / PCCS pool 10 can be suppressed as much as possible. Furthermore, when seawater is used to cool the emergency condenser 30A or the PCCS heat exchanger 30D, such salt precipitation may occur, so it is preferable to attempt cooling with fresh water in the initial stage immediately after an emergency shutdown of the reactor 3 when the decay heat is relatively large, and to start cooling with seawater when the amount of fresh water has decreased due to evaporation, etc. and the decay heat of the reactor 3 has also decreased.

[0064] In this way, the floating nuclear power generation system 1 is provided with various facilities for facilitating cooling with seawater, taking advantage of the advantages of a floating system compared to a nuclear power plant installed on land. Therefore, it can be said that the floating nuclear power generation system 1 can stably remove decay heat of the reactor 3 for a long period of time by using surrounding seawater. The function of using seawater by opening the communication valves 10A, 10B, and 10C may be used not only for the IC / PCCS pool 10, but also for the fuel pool 8, for example. Regarding the change in the waterline (sea surface) of the float 2 by adjusting the amount of water in the ballast tank, in the above embodiment, the inlet corresponding to the communication valve 10B is lower than the waterline, but the inlet corresponding to the communication valve 10C may be lower than the waterline. In addition, the inflow path of seawater from the periphery of the float 2 to the IC / PCCS pool 10 may be a path that directly connects the periphery of the float 2 to the IC / PCCS pool 10, like the communication valves 10B and 10C, or may be an indirect path via a ballast tank or the like.

[0065] The design concept of introducing seawater into the IC / PCCS pool 10 can also be applied to the case of a pressurized water reactor. For example, when the floating nuclear power generation system 1 is a pressurized water reactor, seawater is introduced into the secondary side of the steam generator, which exchanges heat between the primary cooling system in which the reactor is installed and the secondary cooling system in which the turbine is installed, instead of the condensate of the secondary cooling system. This makes it possible to cool the coolant of the primary cooling system with the seawater introduced into the secondary side of the steam generator, even if the condensate of the secondary cooling system is lost.

[0066] In this way, even if the floating nuclear power generation system 1 falls into a situation where the means of injecting water into the reactor 3 is lost, it is possible to use the above-mentioned various functions that take advantage of the floating type to cool the reactor 3 with seawater and sufficiently prevent radioactive materials from being released from the reactor 3. Therefore, it is possible to use nuclear energy more safely than in nuclear power plants installed on land.

[0067] Furthermore, since the floating nuclear power system 1 is designed so that it can be used in a state where the waterline (sea surface) of the float 2 is lower than the inlet of the communicating valve 10B, as shown in Figure 5(A) while it is in a normal operating state or in a stopped state, it can be manufactured in a shipbuilding dock with a relatively shallow depth. [Explanation of symbols]

[0068] R··Reactor system:T··Turbine system:F··Floating float:C··Core:1··Floating nuclear power system:2··Float:3··Reactor:4··Turbine generator:5··Reactor equipment area:6··Pit:7··Reactor equipment area:8··Fuel pool:9··Desalination plant:10··IC / PCCS pool:12··Various equipment area:13··Accommodation area:14··Condensate storage tank:18··Laydown area:19··Ancillary equipment area:20··Main transformer:21··Auxiliary boiler:22··Anchor chain:23··Light oil tank:24··Waste treatment room:25··Bow ballast tank:26··Bottom ballast tank:27··Stern ballast tank:28··Side ballast tank: 30··Emergency condenser system: 3A··Containment vessel: 3B··Nuclear fuel: 3C··Control rods: 3D··Recirculation pump: 3E··Pressure vessel: 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 dry well: 3N··Lower dry well: 4A··Turbine: 4B··Generator: 4C··Condenser: 4D··Circulating water piping: 4E··Circulating water pump: 4F··Feedwater pump: 4G··Feedwater piping: 10A··Communicating valve: 10B··Communicating valve: 10C··Communicating valve: 10D··Atmospheric release pipe: 30A··Emergency condenser: 30B··Pipe: 30C··Pipe: 30D··Heat exchanger for PCCS:

Claims

1. A nuclear reactor, a turbine generator driven by steam generated by the heat of the nuclear reactor; a floating body on which the nuclear reactor and the turbine generator are disposed and which is moored on the sea; a water storage section for storing water for directly or indirectly cooling the reactor in an emergency; A ballast tank capable of taking in and taking out seawater around the floating body, The water storage section is provided with a communication valve for allowing water around the float to flow directly or indirectly through an inlet provided on a side surface of the float, The ballast tank receives seawater around the float in an emergency so that the inlet is lower than the waterline of the float. Floating nuclear power system.

2. The ballast tank has a water volume therein such that the inlet is normally higher than the waterline of the float.

2. The floating nuclear power system according to claim 1.

3. Further comprising a condenser that condenses steam generated in a pressure vessel or a containment vessel in which the nuclear reactor is located in an emergency using cold heat of the stored water and returns the condensate to the pressure vessel or the containment vessel, 2. The floating nuclear power system according to claim 1.

4. The condenser is installed at a position on the floating body that is at least higher than the reactor.

4. The floating nuclear power system according to claim 3.

5. The float has at least a side ballast tank formed in a side portion of the float by a double hull structure, The water storage section has a second communication valve as the communication valve, which communicates between the inside of the water storage section and the side ballast tank.

2. The floating nuclear power system according to claim 1.

6. The float receives seawater around the float in a lower part of the float in an emergency so that the inlet is lower than the waterline of the float.

6. A floating nuclear power generation system according to any one of claims 1 to 5.

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