Floating-type nuclear power generation system

Abstract

To provide a floating-type nuclear power generation system capable of advantageously resisting core meltdown.SOLUTION: The floating-type nuclear power generation system includes: a reactor; a turbine generator driven by steam generated by heat of the reactor; and a floating body in which the reactor and the turbine generator are arranged and which is moored on the sea, the floating body having, below the reactor, a core catcher filled with ballast water of a bottom ballast tank formed in the bottom portion of the floating body by a double-hull structure in the lower side.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] The present invention relates to a floating nuclear power generation 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 [Non-patent literature]

[0004] [Non-Patent Document 1] Buongiorno, J. et al. “The Offshore Floating Nuclear Plant Concept.” Nuclear Technology 194.1 (2016) [Non-patent document 2] Seismic response characteristics of floating structures for floating nuclear power plants (part 2) - Vertical seismic isolation characteristics of a floating structure with an air chamber at the bottom - Central Research Institute of Electric Power Industry, Yutaka Hagiwara et al., August 1, 1987 Summary of the Invention [Problem to be solved by the invention]

[0005] In nuclear power generation systems, a core meltdown accident is something that must be avoided at all costs. Therefore, even if all cooling means of the system are lost, it is necessary to attempt to inject water such as seawater. In the case of land-based nuclear power generation systems, attempting to use seawater to counter a core meltdown clearly requires the power of pumps, etc. In this regard, if a nuclear power generation system is floating on the sea, it would seem to have an advantage over land-based nuclear power generation systems in terms of using seawater to counter a core meltdown. However, if a land-based nuclear power generation system is simply floating on the sea, it cannot use seawater advantageously.

[0006] Therefore, the present application discloses a floating nuclear power generation system that can advantageously resist core meltdown. [Means for solving the problem]

[0007] In order to solve the above problems, the present invention provides a core catcher below the reactor, the underside of which is filled with ballast water from a bottom ballast tank formed on the bottom of the floating body by a double hull structure.

[0008] 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, and a float on which the nuclear reactor and the turbine generator are arranged and which is moored at sea, the float having a core catcher below the reactor, the underside of which is filled with ballast water from a bottom ballast tank formed in the bottom part of the float by a double hull structure.

[0009] In the floating nuclear power generation system described above, the underside of the core catcher, which is placed below the reactor, is filled with ballast water from the bottom ballast tank formed in the bottom part of the float by the double hull structure of the float. Because the float of a floating nuclear power generation system is much larger than the reactor, a large amount of ballast water also exists in the bottom ballast tank of the float. Therefore, even if a core meltdown occurs and the molten core falls into the core catcher, the molten core can be cooled by ballast water via the core catcher. Therefore, such floating nuclear power generation systems can be said to be advantageous in countering core meltdowns.

[0010] The core catcher may be made of steel and include a steel plate that forms the bottom of the containment vessel in which the reactor is housed, and a heat transfer plate that is installed upright in the bottom ballast tank on the underside of the steel plate. Steel is strong and has excellent heat transfer properties. Therefore, if the core catcher is made of such steel plate and heat transfer plate, even if the molten core falls into the core catcher due to a core meltdown, the molten core can be effectively cooled by ballast water via the core catcher.

[0011] The floating nuclear power generation system may also have a communication valve that allows water around the float to flow into the containment vessel. In such a floating nuclear power generation system, even in a situation where water is lost from the containment vessel, the communication valve can be opened to allow water around the float to flow into the containment vessel. Therefore, such a floating nuclear power generation system can minimize the loss of water in the containment vessel, which could lead to a core meltdown. Therefore, such a floating nuclear power generation system can be said to be advantageous in countering a core meltdown.

[0012] The floating nuclear power generation system may further include a sinking means for sinking the float. In such a floating nuclear power generation system, the reactor can be sunk together with the float by sinking the float. Therefore, in such a floating nuclear power generation system, the loss of water in the containment vessel, which may lead to a core meltdown, can be minimized. Therefore, it can be said that such a floating nuclear power generation system is advantageously able to counter a core meltdown. [Effects of the Invention]

[0013] The floating nuclear power generation system described above can advantageously withstand a core meltdown. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a schematic diagram showing the arrangement of equipment in a floating nuclear power generation system according to an embodiment. [Figure 2] FIG. 2 is a schematic diagram showing the system configuration of a floating nuclear power generation system according to an embodiment. [Figure 3] Figure 3 shows how a floating body changes direction. [Figure 4] FIG. 4 is a diagram illustrating the situation when a tsunami hits a floating nuclear power generation system. [Figure 5] FIG. 5 is a diagram showing an example of a dust removal device provided in the floating nuclear power generation system 1. As shown in FIG. [Figure 6] Figure 6 shows the IC / PCCS pool from the side. [Figure 7] Figure 7 shows the IC / PCCS pool from above. [Figure 8] FIG. 8 shows the molten core falling from the bottom of the pressure vessel. [Figure 9] FIG. 9 is an explanatory diagram regarding the flooding function of the containment vessel. [Figure 10] FIG. 10 is an explanatory diagram of the sinking function of the floating nuclear power generation system. DETAILED DESCRIPTION OF THE INVENTION

[0015] The following describes an embodiment of the present invention. The embodiment described below is one aspect of the present invention and does not limit the technical scope of the present invention.

[0016] <Outline of equipment layout> 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 purpose, 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 vessel intended for autonomous navigation on the sea. The float 2 floats on the sea while being moored in order to transmit the electricity generated by the floating nuclear power generation system 1 to land. To reduce resistance to tidal currents, the float 2 is moored at only one end in the longitudinal direction and floats on the sea with the other end unmoored. For this reason, the float 2 floats on the sea like a windsock. In other words, when the float 2 is subjected to tidal currents, it floats on the sea with the moored part naturally facing upstream of the tidal current.

[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 will be referred to as the "bow side," and the unmoored portion will be 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." Also, Fig. 1(B) shows the internal configuration of the floating nuclear power generation system 1 as seen 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 any other float of various shapes.

[0020] As shown in FIG. 1, the floating nuclear power generation system 1 includes a reactor 3 located near the center of a float 2, and a turbine generator 4 located closer to the bow than the reactor 3. The 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. 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 reactor 3 is exemplified, 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 is equipped with various types of equipment in addition to the float 2, reactor 3, and turbine generator 4 described above. The floating nuclear power generation system 1 is equipped, for example, with 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 is also equipped with a desalination plant 9, an IC / PCCS pool 10, various equipment areas 12, an accommodation area 13, and a waste treatment room 24, which are arranged aft of the reactor 3. The floating nuclear power generation system 1 is also equipped with a condensate storage tank 14 arranged between the reactor 3 and the turbine generator 4. The floating nuclear power generation system 1 is also equipped with a laydown area 18 and an ancillary equipment area 19, which are arranged near the bow of the float 2. A main transformer 20 and an auxiliary boiler 21 are installed in the ancillary equipment area 19. The floating nuclear power generation system 1 is also equipped with 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] The reactor equipment areas 5 and 7 are equipped with various types of reactor equipment that are installed outside the containment vessel of the reactor 3. The equipment that is installed in the reactor equipment areas 5 and 7 includes, for example, pumps and valves for various reactor cooling systems such as the emergency core cooling system and the residual heat removal system, and valves for cooling the fuel pool. The facility will include pumps and valves for the pool water cooling system, compressed air control equipment, ventilation and air conditioning equipment, an emergency diesel generator for emergency power, DC power supply equipment using storage batteries, and various other equipment.

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

[0024] The fuel pool 8 is a pool for storing unused or spent nuclear fuel. The nuclear fuel for the reactor 3 is in the form of fuel assemblies. For this reason, the fuel pool 8 is provided with racks for storing the fuel assemblies at appropriate intervals. In addition, 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. Because the floating nuclear power generation system 1 is used while floating on the sea, it is not possible to obtain freshwater that is almost free of salt from rivers, as is the case with facilities on land. For this reason, the floating nuclear power generation system 1 is equipped 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. Various methods, such as reverse osmosis and evaporation, can be used as the desalination method for the desalination device 9.

[0026] The IC / PCCS pool 10 is equipped with an IC heat exchanger and a PCCS heat exchanger. The IC heat exchanger is an isolation condenser (IC) and is used for all AC power supplies. It cools the reactor 3 in the event of a loss of power or other problem that causes the containment vessel to be isolated. The PCCS heat exchanger is part of 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] The various equipment area 12 is provided with a central control room for operating the floating nuclear power generation system 1, an entrance / exit control room for controlling entry and exit to the radiation controlled area, and various other equipment. 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 living area 13 is provided with living facilities for the operators and others staying on the floating nuclear power generation system 1. Examples of living facilities include private 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 to be 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 before being 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 replenish 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 pieces of 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 is accessible by a cladding installed above the operating floor. The lane facilities make it easy to transport large equipment.

[0032] Various types of auxiliary equipment, such as a main transformer 20 and an auxiliary boiler 21, are located in the auxiliary equipment area 19. The main transformer 20 is a transformer that boosts the voltage of 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 oil.

[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 mentioned above, when the floating nuclear power generation system 1 is subjected to a tidal current, it floats on the sea with the moored part naturally facing upstream of the tidal current. For this reason, the submarine cable for connecting the floating nuclear power generation 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] Furthermore, 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 when the floating nuclear power generation system 1 starts up. For this reason, it is reasonable to place the auxiliary boiler 21 near the turbine generator 4.

[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, the floating nuclear power generation system 1 adopts a configuration in which 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. In addition to the main transformer 20 and the auxiliary boiler 21, the auxiliary equipment area 19 also includes switching equipment such as a line switch (LS) for opening and closing the electrical connection between the submarine cable and the main transformer 20. 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 used to control the attitude of the floating body 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 to cool the reactor 3 in an emergency in the floating nuclear power generation system 1. Water can be injected into the bow ballast tank 25, the bottom ballast tank 26, and the stern ballast tank 27 naturally using the water pressure of seawater, for example, by opening a water intake provided on the bottom of the floating body 2. A pump or the like may also be used for water injection, if necessary. Water can also be discharged from the bow ballast tank 25, the bottom ballast tank 26, and the stern ballast tank 27 using 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-described 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 the 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 reactor 3 described above is a main component of the reactor system R. Furthermore, the turbine generator 4 described above is a main component of the turbine system T.

[0039] The reactor system R, which has the reactor 3, includes a containment vessel 3A, nuclear fuel 3B, control rods 3C, and recirculation pipes. The turbine system T, which includes the turbine generator 4, is equipped with various equipment 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 the turbine generator 4.

[0040] The containment vessel 3A is a vessel that contains a pressure vessel 3E that contains nuclear fuel 3B and the like, and serves to contain radioactive materials that are released from the pressure vessel 3E in the event of a meltdown accident in the reactor 3, etc. The containment vessel 3A may be made of concrete, or may be made of the same steel that constitutes the floater 2. The containment vessel 3A contains the pressure vessel 3E that contains the reactor 3 in its center, and has an upper dry well 3M formed above the pressure vessel 3E and a lower dry well 3N formed 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 nuclear fuel 3B and the like, and serves to contain water and steam for cooling the reactor 3. Several hundred nuclear fuel 3B are arranged in the center of the pressure vessel 3E in the form of fuel assemblies, forming the main body of the reactor 3. Control rods 3C that can move up and down by a drive mechanism provided 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 goes into a critical state, the reactor 3 continues to generate heat. Furthermore, when the control rods 3C are inserted into the reactor 3 and the reactor 3 goes into a subcritical state, the heat generated by the reactor 3 gradually decreases.

[0042] 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 power output by forcibly circulating water, which is the reactor coolant, in the liquid phase within the pressure vessel 3E. Note that the floating nuclear power generation system 1 of this embodiment is assumed to be an advanced boiling water reactor (ABWR), and therefore 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, for example, have a recirculation system in which the recirculation pump and circulation piping are arranged outside the pressure vessel 3E.

[0043] A main steam pipe 3L is connected to the pressure vessel 3E to send steam generated in 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 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 and 3K are closed. The end of the exhaust pipe 3G downstream of the safety relief valve 3F is located in a suppression pool 3H.

[0044] The turbine 4A and generator 4B that make up the turbine generator 4 are connected by a common rotating shaft. The turbine 4A has a structure in which an impeller is housed within a casing. A condenser 4C is installed below the turbine 4A to condense the steam that passes through the turbine 4A. The condenser 4C contains numerous thin tubes that form part of the circulating water piping 4D, which connects a water intake located below the waterline on the exterior surface of the floating body 2 to a water outlet. The condenser 4C condenses the steam using the cold heat of seawater pumped by a circulating water pump 4E installed on the circulating water piping 4D. The pressure difference between the steam supplied from the reactor 3 through the main steam pipe 3L and the pressure inside the condenser 4C applies power to the impeller to rotate the generator 4B. This rotates the generator 4B and generates electricity. The condensed water condensed in the condenser 4C is then fed back into the pressure vessel 3E via the feedwater piping 4G by a feedwater pump 4F.

[0045] Note that Figure 2 only shows the outline of the reactor system R and the turbine system T, and in reality, there are many different types. A variety of equipment is installed. For example, important equipment such as a steam control valve and a turbine bypass valve are installed near the turbine 4A on the main steam pipe 3L. The turbine bypass valve may be a 100% bypass valve that sends all of the main steam at rated output directly to the condenser 4C without passing through the turbine 4A, or it may have a lower bypass capacity. In addition, important equipment such as a feedwater flow control valve, a condensate demineralizer, and a feedwater heater are installed on the feedwater pipe 4G. Furthermore, piping for the emergency core cooling system is installed inside and outside the containment vessel 3A. The turbine 4A is a combination of a high-pressure turbine and multiple low-pressure turbines.

[0046] 2, each device is shown in a single system, but the devices in the floating nuclear power generation system 1 are multiplexed. For example, there are multiple circulating water pumps 4E and multiple feedwater pumps 4F.

[0047] In the reactor system R, the position of the control rod 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 rotation 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 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, each characteristic part of the floating nuclear power generation system 1 will be described in detail.

[0049] <Matters concerning the shape of floating body 2> As described above, the floating nuclear power generation system 1 according to this embodiment uses a streamlined float 2. Since the floating nuclear power generation system 1 is used while moored at sea, the decay heat of the reactor 3 can be removed stably over a long period of time by using the surrounding seawater, thereby greatly improving safety.

[0050] An example of an offshore floating nuclear power plant is the Russian Academician Lomonosov, which began commercial operation in 2020. In the 1990s, Japan also considered installing a nuclear power plant on a floating flat barge. However, similar to land-based nuclear power plants, the reactors of nuclear power plants on ship-type and flat barges are located above sea level. Therefore, using seawater to cool the reactor in ship-type and flat barge-type nuclear power plants requires electricity, engines, and other power sources for pumping. Maintaining stable cooling over the long term poses a challenge, as it requires external replenishment of electricity and fuel.

[0051] To overcome this challenge, Professor Buongiorno and his colleagues at the Massachusetts Institute of Technology (MIT) have proposed a design that incorporates a nuclear reactor system into a cylindrical floating structure used for offshore oil drilling. However, the cylindrical floating structure proposed by MIT places the nuclear reactor at the bottom and the steam turbine and generator at the top. The steam turbine and generator are heavy objects. This makes it difficult to realize a structure that supports such heavy objects from above. Furthermore, because the cylindrical floating structure is roughly circular when viewed from above, manufacturing it in a standard shipbuilding dock creates dead space within the dock, reducing manufacturing efficiency. Furthermore, a structure with a nuclear reactor at the bottom and a steam turbine and generator at the top would require a draft several times deeper than that of a large ship, making manufacturing difficult.

[0052] Therefore, the floating nuclear power generation system 1 of this embodiment employs a streamlined float 2, and nuclear power generating equipment such as a nuclear reactor 3 and a turbine generator 4 are housed in the float 2, which has a double hull structure similar to that of a large tanker. In the floating nuclear power generation system 1 of this embodiment, as shown in FIG. 1(B), the reactor 3 is placed below the seawater surface. This makes it possible to realize a passive heat exchange system with seawater that does not require power such as electricity or an engine, which cannot be realized in a ship-type or flat-plate barge. The passive heat exchange system realized in the floating nuclear power generation system 1 of this embodiment will be described in detail later.

[0053] As mentioned above, the floating body 2 is moored on the sea by the anchor chain 22, and therefore floats like a windsock. Figure 3 shows how the floating body 2 changes direction. When the floating body 2 receives a tidal current, it floats on the sea with its bow, moored by the anchor chain 22, naturally facing upstream of the tidal current. As a result, the streamlined shape of the floating body reduces resistance, making it possible to minimize the tension applied to the anchor chain 22.

[0054] The floating nuclear power system 1 has several advantages due to the streamlined float 2, in addition to the aforementioned reduction in resistance to tidal currents when moored. For example, the streamlined shape of the float 2 allows for maximum utilization of the space within a typical horizontal shipbuilding dock when manufacturing the floating nuclear power system 1, thereby enabling efficient manufacturing of the floating nuclear power system 1. In other words, by using multiple cranes in the shipbuilding dock, it is possible to simultaneously perform manufacturing work near the reactor 3 and manufacturing work near the turbine generator 4. Furthermore, manufacturing the floating nuclear power system 1 at a centralized manufacturing base such as a shipbuilding dock is expected to improve manufacturing quality and reduce manufacturing costs. Because the floating nuclear power system 1 can be transported by sea, it can be easily exported to countries bordering the sea. Therefore, exporting floating nuclear power systems 1 manufactured at a centralized manufacturing base by sea offers advantages in both quality and cost compared to establishing manufacturing bases around the world.

[0055] Another advantage of the floating nuclear power system 1 due to the use of a streamlined float 2 is the ease of loading and unloading materials at sea. That is, with a streamlined float 2, the port and starboard sides are generally straight, making it easy for other ships to berth alongside the port or starboard side. If a ship can berth alongside the port or starboard side of the float 2, cargo can be transferred with the straight sides touching each other, facilitating the transfer of, for example, food for operators, diesel fuel consumed by the auxiliary boiler 21 and emergency diesel generator, chemicals used for water quality control, casks storing nuclear fuel, and various other maintenance parts.

[0056] Another advantage of the floating nuclear power generation system 1 due to the adoption of a streamlined float 2 is the layout advantage of various components of the floating nuclear power generation system 1, such as the reactor 3 and the turbine generator 4. In the floating nuclear power generation system 1, steam generated in the reactor 3 is sent to the turbine generator 4, and the electricity generated by the turbine generator 4 is transformed by the main transformer 20 and sent to the undersea cable. In a floating nuclear power generation system 1 in which each component is interconnected in this manner, it is more rational to arrange the reactor 3, turbine generator 4, and main transformer 20 in order. In this regard, the streamlined float 2 makes it possible to arrange the reactor 3, turbine generator 4, and main transformer 20 in this order from stern to bow. Furthermore, the streamlined float 2 makes it possible to position the turbine generator 4 so that its rotation axis is aligned along the longitudinal direction of the float 2, as shown in Figure 2. This eliminates the possibility of the turbine blade flying toward the reactor 3, even in the unlikely event of a turbine missile occurring, in which a turbine blade breaks off during rotation. In addition, the floating nuclear power generation system 1 employs a casing strong enough to prevent the turbine blades from penetrating it, to prevent turbine missiles from occurring.

[0057] <Matters regarding the mooring of Floating Body 2> Next, a floating nuclear power generation system 1 is provided with a mooring structure for mooring the streamlined float 2. Some characteristic features will be described. The floating nuclear power generation system 1 employs a form in which a streamlined float 2 is moored, and is therefore equipped with a device for controlling the attitude of the float 2 by itself. An example of a device for controlling the attitude of the float 2 is a thruster. If the float 2 is equipped with an electrically operated screw thruster that can freely turn the propulsion direction, it becomes possible to freely change the direction of the float 2 around the mooring part and to control the position of the float 2. Furthermore, if the float 2 is equipped with a thruster, it becomes possible to continue to maintain the float 2 in a fixed position when the anchor chain 22 breaks.

[0058] Furthermore, a circulating water pump 4E, for example, can be used as a device for independently controlling the attitude of the float 2. The circulating water pump 4E is a pump that supplies seawater to the condenser 4C, which has one of the largest cooling capacities of any nuclear power generation facility. Therefore, the circulating water pump 4E has one of the largest capacities of any pump provided in the floating nuclear power generation system 1, and depending on the arrangement of the water intake and discharge ports of the circulating water piping 4D, the float 2 can be moved at sea. Therefore, in the floating nuclear power generation system 1 of this embodiment, as shown in Figure 3, the circulating water system is configured so that the circulating water pump 4EL, installed in the circulating water piping 4D connecting the port-side intake 4DSL and the starboard-side discharge outlet 4DHR, pumps seawater from the port side to the starboard side, and the circulating water pump 4ER, installed in the circulating water piping 4D connecting the starboard-side intake 4DSR and the port-side discharge outlet 4DHL, pumps seawater from the starboard side to the port side. During normal times when the direction (posture) of the float 2 is left to the tidal current, the flow rates of the circulating water pumps 4EL and 4ER are balanced so that the water is pumped symmetrically by the circulating water pump 4E. When it is desired to move the float 2 to the port side, the flow rate of the circulating water piping 4D is adjusted so that the flow rate of the circulating water pump 4EL is greater than the flow rate of the circulating water pump 4ER. Furthermore, when it is desired to move the float 2 to the starboard side, the flow rate of the circulating water piping 4D is adjusted so that the flow rate of the circulating water pump 4ER is greater than the flow rate of the circulating water pump 4EL. The flow rate of the circulating water piping 4D can be adjusted, for example, by adjusting the opening of a flow control valve provided on the turbine generator 4 or by stopping the circulating water pump 4ER. Controlling the direction of the float 2 by adjusting the flow rate in this manner is effective not only for changing direction around the mooring parts but also for correcting positional deviation of the float 2.

[0059] In addition to the circulating water pump 4E, other devices for controlling the attitude of the floating body 2 by itself include, for example, a reactor auxiliary cooling water pump for the reactor building cooling water system (RCW). Turbine building cooling seawater pump (RSW), Turbine auxiliary cooling system (TCW) The present embodiment is also applicable to turbine auxiliary cooling seawater pumps (TSW) for the Turbine Seawater System. In the floating nuclear power generation system 1, the reactor auxiliary cooling seawater pump and the turbine auxiliary cooling seawater pump can also be used for position control, similar to the circulating water pump 4E. The floating nuclear power generation system 1 of this embodiment has multiple reactor auxiliary cooling seawater pumps and multiple turbine auxiliary cooling seawater pumps, one seawater pump pumps seawater from the port side to the starboard side, and the other seawater pump pumps seawater from the starboard side to the port side. Therefore, if the flow rate of each seawater pump is adjusted according to the position of the float 2, it is possible to correct the positional deviation of the float 2.

[0060] The floating nuclear power generation system 1 of this embodiment is assumed to have three low-pressure turbines as the turbines 4A. Two circulating water pipes 4D are connected to each of the three condensers 4C located below each low-pressure turbine for multiplexing. Therefore, FIG. 3 illustrates six circulating water pipes 4D and circulating water pumps 4E (4EL, 4ER). However, the floating nuclear power generation system 1 of this embodiment is not limited to this. The circulating water pipes 4D and circulating water pumps 4E may be arranged symmetrically, and may be, for example, four or fewer, or eight or more. While the water intake 4DSL and the water discharge 4DHL are arranged close to each other in FIG. 3, they may be arranged spaced apart from each other or may be arranged so that their opening directions alternate, such as toward the side and downward of the float 2, to prevent short-circuiting.

[0061] Another example of a device for changing the direction of the floating body 2 is a tugboat. By permanently tethering a tugboat to the floating body 2, not only can the direction of the floating body 2 be changed, but also, for example, in the event of an emergency in the sea area where the floating nuclear power generation system 1 is installed, it is possible to cut the anchor chain 22 and quickly move the floating nuclear power generation system 1. Examples of emergencies that may occur in specific sea areas include the occurrence of natural disasters such as the eruption of an undersea volcano, and armed attacks by terrorists or military forces. In response to armed attacks targeting the floating nuclear power generation system 1, it is desirable to take measures such as setting up an area within a predetermined distance from the floating nuclear power generation system 1 to restrict the entry of ships and other vessels and monitor maritime traffic, or setting up a torpedo defense net around the floating nuclear power generation system 1 to prevent the approach of torpedoes and suspicious ships.

[0062] If the direction of the float 2 can be changed, the following measures can be taken, for example. Figure 4 is a diagram illustrating the situation when a tsunami hits the floating nuclear power generation system 1. Figure 4(A) shows the floating nuclear power generation system 1 as seen from above, and Figure 4(B) shows the floating nuclear power generation system 1 as seen from the side.

[0063] For example, as shown in Figure 4(A), assume that the tidal current is flowing downward and to the right on the page of Figure 4. In this case, the floating nuclear power generation system 1 moored by the anchor chain 22 floats due to the tidal current in the state shown by symbol P1 in Figure 4(A), that is, with the bow of the floater 2 facing upward and to the left. In this state, assume that, for example, an earthquake or typhoon occurs centered on the left side of the page of Figure 4, causing a tsunami to flow to the right.

[0064] If the floating nuclear power system 1 receives this tsunami with the bow of the float 2 pointing upward and left, the floating nuclear power system 1 will receive the tsunami from the port side of the float 2. Therefore, the floating nuclear power system 1 may tilt to the starboard side due to the tsunami received from the port side of the float 2. On the other hand, if the generation of the tsunami is detected and the direction of the float 2 is immediately started to change, and the state shown by symbol P2 in Figure 4(A) is reached, that is, the state in which the bow of the float 2 is pointed to the left, the floating nuclear power system 1 will receive the tsunami from the bow side of the float 2. Therefore, the floating nuclear power system 1 can minimize the possibility of the float 2 tilting to either the port side or starboard side. In the floating nuclear power generation system 1, since the float 2 is long from bow to stern, even if a tsunami hits the bow side of the float 2, the floating nuclear power generation system 1 will hardly tilt in the fore-and-aft direction, as shown in Figure 4(B).

[0065] Although Figure 4 shows the floating nuclear power generation system 1 relatively close to land, it is preferable that the floating nuclear power generation system 1 be moored offshore at a distance of several tens of kilometers from land. As shown in Figure 4(B), tsunamis have the tendency to grow larger as they approach land in shallow waters. For this reason, if the floating nuclear power generation system 1 is moored offshore at a distance of several tens of kilometers from land in deep waters, it is possible to relatively reduce the size of the tsunami that the floating nuclear power generation system 1 receives, although this depends on the topography of the seabed.

[0066] A suitable distance from land for mooring the floating nuclear power system 1 is, for example, 30 km or more. If the floating nuclear power system 1 is moored at sea 30 km or more from land, no residential area will be within the area for which evacuation plans are required by Japanese law. In other words, even if a large-scale accident were to occur at the floating nuclear power system 1, it is unlikely that residents on land would need to evacuate.

[0067] Incidentally, it is preferable to provide a dust removal device for removing debris (seaweed, jellyfish, small fish, waste, etc.) from the seawater at the intake port for taking in seawater used in the floating nuclear power generation system 1. Therefore, in the floating nuclear power generation system 1, dust removal devices are provided at the intakes 4DSL and 4DSR of the circulating water pipe 4D and at the intake of the reactor auxiliary cooling seawater system for supplying cold heat to auxiliary machinery around the reactor 3. Fig. 5 is a diagram showing an example of a dust removal device provided in the floating nuclear power generation system 1.

[0068] As shown in FIG. 5, the dust removal device 29 includes a dust removal pit 29A, an inlet 29C, a cyclone 29D, a settling tank 29E, a discharge door 29G, and an outlet 29H.

[0069] The dust removal pit 29A is a space provided on the bottom or side of the float 2 and is constantly filled with seawater surrounding the float 2. A cyclone 29D is provided in the center of the dust removal pit 29A. The cyclone 29D is located at the open end of an outlet 29H connected to a seawater system pump, such as the circulating water pump 4E. The cyclone 29D has a conical interior shape and an inlet 29C that opens tangentially at its outermost diameter. Therefore, when the seawater system pump is activated while the dust removal pit 29A is filled with seawater and seawater is sucked into the outlet 29H, the seawater flowing in from the inlet 29C generates a spiral water flow within the cyclone 29D. This spiral water flow causes debris D, which has a greater specific gravity than seawater, to be centrifuged within the cyclone 29D and settle into a settling tank 29E located below the cyclone 29D. An openable discharge door 29G is provided at the bottom of the settling tank 29E. Therefore, by opening the discharge door 29G as needed, the debris D accumulated in the settling tank 29E can be discharged from the settling tank 29E. If the water intake is provided at the bottom of the float 2, the water intake will be located at a depth of, for example, approximately 80 to 100 meters, depending on the displacement of the float 2, making it less likely to suck in debris that is abundant near the sea surface. By combining this with the effect of preventing large amounts of migratory fish from entering using the torpedo protection net mentioned above, it is possible to minimize the amount of debris that enters the water intake.

[0070] The dust remover 29 is provided with a strainer 29F that prevents relatively large debris D from flowing into the dust removal pit 29A. The dust remover 29 is also provided with a strainer 29B that prevents relatively large debris D from flowing into the inlet 29C. Therefore, debris D that is not suitable for centrifugation can be removed by the strainer 29F or the strainer 29B.

[0071] It should be noted that the floating nuclear power generation system 1 is not limited to one equipped with such a dust removal device 29. The floating nuclear power generation system 1 may be one that uses, for example, a dust removal device that rotates an endless screen (traveling screen) or other types of dust removal device.

[0072] <Matters related to core cooling> Next, the core cooling equipment provided in the floating nuclear power generation system 1 will be described. 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. Here, particularly characteristic features of the various cooling equipment provided in the floating nuclear power generation system 1 will be described.

[0073] As mentioned above, the floating nuclear power generation system 1 is equipped with an emergency condenser and a passive containment vessel cooling system. Because the floating nuclear power generation system 1 is a floating structure that floats on the sea, it can significantly improve safety by using the surrounding seawater to stably remove decay heat from the reactor 3 for a long period of time. For this reason, the floating nuclear power generation system 1 is capable of letting seawater flow into the IC / PCCS pool 10. The IC / PCCS pool When seawater flows into the IC / PCCS pool 10, cooling can be continued by natural circulation due to the density difference of the seawater. For this reason, the floating nuclear power generation system 1 has the IC / PCCS pool 10 installed as follows.

[0074] Fig. 6 is a side view of the IC / PCCS pool 10. Fig. 7 is a top view of the IC / PCCS pool 10. Fig. 6 shows the positional relationship between the IC / PCCS pool 10 and the pressure vessel 3E in the height direction above sea level.

[0075] 6 and 7, an isolation condenser 30A and a PCCS heat exchanger 30D are disposed in the IC / PCCS pool 10 (the PCCS heat exchanger 30D is not shown in FIG. 6 due to space limitations). The IC / PCCS pool 10, in which the isolation condenser 30A and the PCCS heat exchanger 30D are disposed, is higher than the reactor 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 isolation 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.

[0076] The IC / PCCS pool 10 is normally filled with fresh water. Even if the floating nuclear power generation system 1 experiences a loss of all AC power supplies, the reactor 3 can be cooled by the emergency condenser 30A by opening the pipes 30B and 30C. The IC / PCCS pool 10 also has 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 supplies 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 supplies continues even after the fresh water in the IC / PCCS pool 10 and the condensate storage tank 14 decreases due to boiling, it may become impossible to continue cooling the reactor 3 with fresh water. Even in such a case, the floating nuclear power generation system 1 can fill the IC / PCCS pool 10 with ballast water by opening the communication valve 10A. Furthermore, the floating nuclear power generation system 1 can fill the IC / PCCS pool 10 with seawater around the float 2 by opening the communication valves 10B and 10C. If the IC / PCCS pool 10 is filled with either fresh water or seawater, it is possible to continue cooling the reactor core C using the isolation condenser 30A. The floating nuclear power generation system 1 has valves at appropriate locations for allowing seawater to flow from around the float 2 into the side ballast tanks 28, so that seawater in the side ballast tanks 28 can be replenished as needed even if it decreases.

[0077] The floating nuclear power generation system 1 according to this embodiment is not limited to the configuration in which the isolation condenser 30A condenses steam in the pressure vessel 3E and the PCCS heat exchanger 30D condenses steam in the containment vessel 3A. The isolation condenser 30A, which is used to cool the core C when the primary system boundary is intact, and the PCCS heat exchanger 30D, which is used to cool 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 valves. That is, the isolation condenser 30A may be connected to the upper part (upper dry well 3M) and lower part (suppression pool 3H) of the containment vessel 3A by opening and closing valves. The PCCS heat exchanger 30D may also be connected to the upper part and lower part of the pressure vessel 3E by opening and closing valves. The valves for switching the system configuration may be motor-operated valves using a DC power source or manual valves.

[0078] In addition, in the floating nuclear power generation system 1, a difference in height is provided between the communicating valves 10B and 10C. Therefore, convection occurs in the seawater in the IC / PCCS pool 10 heated by the isolation condenser 30A due to a difference in density of the seawater caused by a temperature difference. Due to the difference in elevation, it is expected that the seawater in the IC / PCCS pool 10 will be naturally replaced with the seawater around the floating body 2.

[0079] Note that salt deposition on the surfaces of the isolation condenser 30A and the PCCS heat exchanger 30D may reduce heat exchange capacity. Therefore, when seawater is introduced into the IC / PCCS pool 10, it is preferable to prevent salt deposition due to evaporation of the seawater. Salt deposition can be suppressed by preventing boiling of seawater (the generation of voids) on the heat exchange surfaces of the isolation condenser 30A and 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 communicating valves 10A, 10B, and 10C. For example, using large-diameter valves for the communicating valves 10B and 10C makes it easier for the seawater in the IC / PCCS pool 10 to be replaced with seawater around the floating body 2, thereby suppressing the temperature rise of the seawater in the IC / PCCS pool 10 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. Therefore, 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 high, and then 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.

[0080] As described above, the floating nuclear power generation system 1 is provided with various facilities that make it easier to cool it with seawater, taking advantage of the floating structure compared to land-based nuclear power plants. Therefore, it can be said that the floating nuclear power generation system 1 can stably remove decay heat from the reactor 3 for a long period of time by using the surrounding seawater. The function of using seawater by opening the communication valves 10A, 10B, 10C can be used not only in the IC / PCCS pool 10 but also in the fuel pool 8, for example.

[0081] The design concept of introducing seawater into the IC / PCCS pool 10 can also be applied to pressurized water reactors. For example, if 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.

[0082] <Matters related to accident prevention measures> Next, we will explain the accident countermeasure equipment provided in the floating nuclear power generation system 1. As mentioned above, the floating nuclear power generation system 1 is equipped with sufficient equipment to cool the reactor 3, but various countermeasures are also taken in anticipation of a serious accident, as described below.

[0083] <Core Catcher> FIG. 8 illustrates the molten core falling from the bottom of the pressure vessel 3E. If the reactor core melts in the reactor 3, the bottom of the pressure vessel 3E may be damaged, causing the molten core to fall below the pressure vessel 3E, as shown in FIG. 8. If the molten core falls below the pressure vessel 3E, the structural materials of the floater 2 below the pressure vessel 3E will be heated. However, as mentioned above, the floater 2 has a double-hull structure, and a bottom ballast tank 26 is provided at its bottom. Furthermore, a number of heat transfer plates 26B are attached to the underside of the steel plate 26A of the floater 2, which forms the bottom of the lower dry well 3N. Therefore, the steel plate 26A is strongly reinforced by the heat transfer plates 26B. Although FIG. 8 illustrates the inside of the bottom ballast tank 26 as being partitioned by the heat transfer plates 26B, water ports are provided at various locations in the heat transfer plate 26B for circulating ballast water. Therefore, the ballast water can flow freely within the bottom ballast tank 26 without being obstructed by the heat transfer plate 26B.

[0084] The bottom surface of the lower dry well 3N, which is formed by the steel plate 26A and the heat transfer plate 26B, functions as a core catcher. The steel plate 26A and the heat transfer plate 26B are in contact with the ballast water in the bottom ballast tank 26. Therefore, the bottom of the lower dry well 3N functions as a heat sink for dissipating heat to the ballast water in the bottom ballast tank 26. Therefore, if the molten core falls from the pressure vessel 3E due to a core meltdown, the heat of the molten core that has fallen from the pressure vessel 3E is transferred to the ballast water in the bottom ballast tank 26 via the steel plate 26A and the heat transfer plate 26B.

[0085] If the molten core falling from the bottom of Pressure Vessel 3E were to come into direct contact with a large amount of water, there is a concern that a steam explosion or a large amount of hydrogen would be generated. For this reason, if an attempt is made to inject water into the molten core, measures must be taken to limit the amount of water injected. However, it is not easy to control the amount of water injected in this way while a severe accident such as a core meltdown is progressing.

[0086] In this regard, in the floating nuclear power generation system 1 of this embodiment, the steel plates 26A and heat transfer plates 26B that form the bottom surface of the lower dry well 3N function not only as a core catcher but also as a heat sink for dissipating heat to the ballast water in the bottom ballast tank 26. Therefore, the molten core that falls to the bottom surface of the lower dry well 3N is stably cooled and solidified, and then deposited as fuel debris. Furthermore, in this cooling method, the molten core does not come into direct contact with a large amount of water, so there is a low possibility of a steam explosion or the generation of a large amount of hydrogen.

[0087] Furthermore, in the floating nuclear power generation system 1 of this embodiment, the pedestal supporting the pressure vessel 3E is made of steel, so that the heat of the molten core in the pressure vessel 3E is also transferred to the suppression pool 3H via the pedestal. As such, in the floating nuclear power generation system 1 of this embodiment, even in the event of a core meltdown, passive countermeasures against the molten core are implemented, utilizing the water in the bottom ballast tanks 26 and the water in the suppression pool 3H. Note that, in order to minimize the impact of the pedestal coming into contact with fuel debris, a cylindrical bulkhead may be installed inside the pedestal, and the heat of the fuel debris may be transferred to the suppression pool 3H via a heat transfer tube or the like. If such a bulkhead and heat transfer means are provided, the integrity of the pedestal can be maintained even in the unlikely event of a core meltdown.

[0088] <Flooding function of Containment Vessel 3A> 9 is an explanatory diagram of the flooding function of the containment vessel 3A. The floating nuclear power generation system 1 is designed so that the reactor 3 is located below sea level. For this reason, the floating nuclear power generation system 1 is equipped with a function to fill the containment vessel 3A with seawater. That is, the floating nuclear power generation system 1 is equipped with a seawater inlet pipe 3AP that connects the inside of the containment vessel 3A with the surroundings (sea) of the float 2. A seawater inlet valve 3AV is provided midway along the seawater inlet pipe 3AP.

[0089] Under normal conditions, the seawater inlet valve 3AV is closed, and as shown in Figure 9(A), seawater does not flow into the containment vessel 3A. If all means for injecting water into the pressure vessel 3E are lost due to some kind of accident, the seawater inlet valve 3AV is opened. When the seawater inlet valve 3AV is opened, seawater around the float 2 flows into the containment vessel 3A. As mentioned above, the reactor 3 is located below sea level. Therefore, by opening the seawater inlet valve 3AV, most of the containment vessel 3A is filled with seawater, as shown in Figure 9(B), and the reactor core C inside the pressure vessel 3E can be indirectly cooled from outside the pressure vessel 3E. Note that, in order to vent air from the containment vessel 3A when filling it with seawater, the floating nuclear power generation system 1 is provided with two seawater inlet pipes 3AP, one above the other. As a result, in the initial state when seawater begins to flow into the containment vessel 3A, the upper seawater inlet pipe 3AP serves as the air vent. This forms a path through which the air inside the containment vessel 3A is discharged. When the containment vessel 3A is filled with seawater, the containment vessel 3A becomes flooded. Note that a vent valve other than the seawater inlet valve 3AV may be provided to vent the air inside the containment vessel 3A. A filter vent device may be provided along the air vent path to remove radioactive materials contained in the air.

[0090] <Sinking function of floating nuclear power generation system 1> 10 is an explanatory diagram of the sinking function of the floating nuclear power generation system 1. The floating nuclear power generation system 1 has a function of sinking the float 2. The float 2 can be sinking by, for example, opening a valve that connects the inside and outside of the float 2, destroying the bottom of the vessel, or filling the inside of the float 2 with seawater by various other methods.

[0091] Because the floating nuclear power generation system 1 is designed to float on the sea, if all means for injecting water into the pressure vessel 3E are lost due to some kind of accident, the floating nuclear power generation system 1 may be sunk, for example, as shown in FIG. 10(A). If the floating nuclear power generation system 1 is sunk, the reactor 3 can be cooled with seawater. If it is desired to raise the floating nuclear power generation system 1 from the seabed, a floating float F is prepared to raise the floating nuclear power generation system 1, as shown in FIG. 10(B), once several years have passed since the floating nuclear power generation system 1 was sunk and the decay heat of the reactor 3 has become sufficiently small. The floating float F is a hollow body with an airtight structure, and it is possible to inject seawater into the floating float F and drain the seawater from the inside of the floating float F.

[0092] After preparing such a floating float F, as shown in FIG. 10(C), seawater is poured into the floating float F above the floating nuclear power generation system 1 that is submerged on the seabed, and the floating float F is submerged on the seabed. Then, the floating float F is connected to the floating nuclear power generation system 1. Next, the seawater inside the floating float F is discharged. Once the seawater inside the floating float F is discharged, the buoyancy of the floating float F causes the floating float F to rise to the sea surface together with the floating nuclear power generation system 1. This makes it possible to attempt various disposal methods, such as dismantling the floating nuclear power generation system 1 and removing the nuclear fuel.

[0093] In this way, even if the floating nuclear power generation system 1 were to encounter a situation where it were unable to inject water into the reactor 3, it would be possible to use the above-mentioned various functions that take advantage of the floating design 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 land-based nuclear power plants. [Explanation of symbols]

[0094] R··Reactor system: T··Turbine system: F··Floating float: C··Reactor core: D··Refuse: 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··Diesel tank: 24··Waste treatment room: 25··Bow ballast tank: 26··Bottom ballast tank Tank: 27··Stern ballast tank: 28··Side ballast tank: 29··Dust removal system: 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: 3AP··Seawater inlet pipe: 3AV··Seawater inlet valve: 4DS· ·Intake: 4DH··Outlet: 10A··Communicating valve: 10B··Communicating valve: 10C··Communicating valve: 10D··Atmospheric vent pipe: 26A··Steel plate: 26B··Heat transfer plate: 29A··Dust removal pit: 29B··Strainer: 29C··Inlet: 29D··Cyclone: ​​29E··Settling tank: 29F··Strainer: 29G··Discharge door: 29H··Outlet: 30A··Immunity condenser: 30B··Piping: 30C··Piping: 30D··Heat exchanger for PCCS

Claims

1. A nuclear reactor and 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, the floating body being moored on the sea; The float has a core catcher below the reactor, the underside of which is filled with ballast water from a bottom ballast tank formed in a bottom portion of the float by a double hull structure. Floating nuclear power generation system.

2. the core catcher is made of steel; a steel plate forming a bottom portion of a containment vessel in which the reactor is housed; a heat transfer plate provided upright in the bottom ballast tank on the underside of the steel plate, 2. The floating nuclear power generation system according to claim 1.

3. a communication valve for allowing water around the floating body to flow into the containment vessel; 2. The floating nuclear power generation system according to claim 1.

4. Further provided is a sinking means for sinking the floating body.

4. The floating nuclear power generation system according to claim 1.

Images