Floating nuclear power system

Abstract

The present application discloses a floating nuclear power system that is advantageously capable of resisting core meltdown. [Solution] This floating nuclear power generation system comprises a nuclear reactor, a turbine generator driven by steam generated by the heat of the reactor, and a float on which the reactor and 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.

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 [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 float with an air chamber at the bottom - Central Research Institute of Electric Power Industry, Yutaka Hagiwara et al., 1987 / 8 / 1 Summary of the Invention [Problem to be solved by the invention]

[0005] In a nuclear power generation system, a core meltdown accident is a situation that must be avoided most. Therefore, even if all cooling means in the system are lost, it is necessary to try to inject seawater or other water. In the case of a nuclear power generation system installed on land, it is clear that the power of a pump or other device is required to try to use seawater to counter a core meltdown. In this respect, if a nuclear power generation system is floated on the sea as a floating body, it seems to have an advantage over a nuclear power generation system installed on land in terms of the use of seawater to counter a core meltdown. However, if a nuclear power generation system installed on land is simply floated on the sea, it is not possible to 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, in the present invention, a core catcher is provided 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.

[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 heat from the reactor, and a float on which the nuclear reactor and the turbine generator are disposed 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 portion of the float by a double hull structure.

[0009] In the above-mentioned floating nuclear power generation system, the underside of the core catcher arranged under 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. Since the float of the floating nuclear power generation system is much larger than the reactor, a large amount of ballast water is also present in the bottom ballast tank of the float. Therefore, even if the molten core falls into the core catcher due to a core meltdown, the molten core can be cooled by ballast water via the core catcher. Therefore, such a floating nuclear power generation system can be said to be advantageously able to counter a core meltdown.

[0010] The core catcher may be made of steel and may have a steel plate forming the bottom part of the containment vessel in which the reactor is housed, and a heat transfer plate 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 a 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 the water around the float to flow into the containment vessel. In such a floating nuclear power generation system, even in a situation where the water in the containment vessel is lost, the water around the float can be allowed to flow into the containment vessel by opening the communication valve. 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 suppressed as much as possible. Therefore, it can be said that such a floating nuclear power generation system is advantageously able to counter 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 sink 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 suppressed as much as possible. Therefore, it can be said that such a floating nuclear power generation system is advantageously capable of countering a core meltdown. Effect of the Invention

[0013] The floating nuclear power generation system described above can advantageously withstand a core meltdown. [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] FIG. 3 shows how a floating body changes direction. [Figure 4] FIG. 4 is a diagram illustrating the state when a tsunami hits a floating nuclear power generation system. [Diagram 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] FIG. 6 shows a side view of the IC / PCCS pool. [Figure 7] FIG. 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 regarding the sinking function of the floating nuclear power generation system. 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 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 ship intended to navigate autonomously on the sea. The float 2 floats on the sea in a moored state in order to transmit the electricity generated by the floating nuclear power generation system 1 to land. The float 2 floats on the sea in a state where only one end in the longitudinal direction is moored and the other end is not moored in order to suppress resistance to the tidal current. For this reason, the float 2 floats on the sea like a windsock. That is, when the float 2 receives a tidal current, it floats on the sea in a position where the moored part naturally faces the upstream side 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 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 arranged. The equipment to be arranged in the reactor equipment areas 5 and 7 includes, for example, pumps and valves of various reactor cooling equipment such as the emergency core cooling system and the residual heat removal system, and a cooling system for cooling the fuel pool. The facility will house pumps and valves for the pool water cooling system, compressed air equipment for control, ventilation and air conditioning equipment, an emergency diesel generator for emergency power supply, 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 in 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 at the top of 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 is equipped with a cleaning system 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 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 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 system 1 receives a tidal current, it floats on the sea with the moored part naturally facing the upstream side of the tidal current. For this reason, 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 FIG. 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, which has the reactor 3, includes a containment vessel 3A, nuclear fuel 3B, control rods 3C, and recirculation poles. The turbine system T, which includes the turbine generator 4, is equipped with various equipment such as a condenser 4C, circulating water piping 4D, a circulating water pump 4E, a feed water pump 4F, etc., 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 and the like, and plays a role in containing radioactive materials released from the pressure vessel 3E in the event of a meltdown accident of the reactor 3, etc. The containment vessel 3A 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 reactor 3 in its center, and forms an upper dry well 3M above the pressure vessel 3E and a lower dry well 3N below the pressure vessel 3E. The containment vessel 3A also has a suppression pool 3H around the lower dry well 3N.

[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 Figure 2 only shows the outline of the reactor system R and the turbine system T. In reality, many different types of Various 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, sending the entire amount of main steam at rated output 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 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] 2, each device is illustrated in a single system, but each device of the floating nuclear power generation system 1 is multiplexed. For example, multiple circulating water pumps 4E and multiple feed water pumps 4F are provided.

[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, 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 the streamlined float 2. Since the floating nuclear power generation system 1 is used while being moored 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, thereby greatly improving safety.

[0050] As an example of an offshore floating nuclear facility, the Russian Academician Lomonosov, which has a nuclear power plant mounted on a ship-type barge, began commercial operation in 2020. In Japan, too, designs to install nuclear power plants on floating flat barges were considered in the 1990s. However, in ship-type and flat barge-based nuclear power plants, the reactor is located above sea level, just like land-based nuclear power plants. For this reason, in order to use seawater to cool the reactor in ship-type and flat barge-based nuclear power plants, electricity, engines, and other power sources are required for pumping. For this reason, there is a problem in that electricity and fuel replenishment from outside are required to maintain stable cooling for a long period of time.

[0051] To overcome this problem, Professor Buongiorno and his colleagues at Massachusetts Institute of Technology (MIT) have devised 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. For this reason, it is difficult to realize a structure that supports such heavy objects at the top. In addition, since the cylindrical floating structure is roughly circular when viewed from above, dead space is generated in the dock when it is manufactured in a general horizontal shipbuilding dock, which reduces manufacturing efficiency. In addition, a structure that places the nuclear reactor at the bottom and the steam turbine and generator at the top has problems such as the draft being several times deeper than that of a large ship, making it difficult to manufacture.

[0052] Therefore, in the floating nuclear power generation system 1 of this embodiment, a streamlined float 2 is adopted, and nuclear power generating equipment such as a nuclear reactor 3 and a turbine generator 4 are installed in the float 2 having 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 nuclear reactor 3 is disposed 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 details of the passive heat exchange system realized in the floating nuclear power generation system 1 of this embodiment will be described later.

[0053] As described above, the floating body 2 is moored by the anchor chain 22 on the sea surface, 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 surface with its bow, moored by the anchor chain 22, naturally facing the upstream side of the tidal current. As a result, the streamlined shape of the floating body reduces resistance, and it becomes possible to suppress the tension applied to the anchor chain 22 as much as possible.

[0054] The floating nuclear power system 1 has several advantages due to the use of the streamlined float 2 in addition to the mitigation of resistance to tidal currents when moored as described above. For example, the streamlined shape of the float 2 allows the floating nuclear power system 1 to be manufactured efficiently in a typical horizontally long shipbuilding dock, since the space in the dock can be utilized to the maximum extent possible. That is, by using multiple cranes in the shipbuilding dock, it becomes possible to simultaneously carry out manufacturing work near the reactor 3 and manufacturing work near the turbine generator 4. In addition, by manufacturing the floating nuclear power system 1 at a centralized manufacturing base such as a shipbuilding dock, it is possible to improve manufacturing quality and reduce manufacturing costs. The floating nuclear power system 1 can be easily exported to countries bordering the sea because it can be transported by sea. Therefore, if the floating nuclear power system 1 manufactured at a centralized manufacturing base is exported by sea, it is advantageous in terms of both quality and cost compared to the case of setting up manufacturing bases all over the world.

[0055] Another advantage of the floating nuclear power system 1 due to the use of the streamlined float 2 is, for example, the ease of loading and unloading materials at sea. That is, with the streamlined float 2, the port and starboard sides are generally straight, so it is easy for other ships to come alongside the port or starboard side. If a ship can come alongside the port or starboard side of the float 2, cargo can be transferred with the straight sides touching each other, making it easy to transfer, for example, food for the operators, diesel fuel consumed by the auxiliary boiler 21 and emergency diesel generators, chemicals used for water quality management, 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 the streamlined float 2 is, for example, the advantage of the layout of various facilities 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, the steam generated in the reactor 3 is sent to the turbine generator 4, and the electricity generated in the turbine generator 4 is transformed by the main transformer 20 and sent to the undersea cable. In the floating nuclear power generation system 1 in which each facility is linked in this way, it is more rational to arrange the equipment such as the reactor 3, the turbine generator 4, and the main transformer 20 in order. In this regard, with the streamlined float 2, it is possible to arrange the reactor 3, the turbine generator 4, and the main transformer 20 in order from the stern to the bow. Also, with the streamlined float 2, as shown in FIG. 2, it is possible to arrange the turbine generator 4 so that the rotation axis is along the longitudinal direction of the float 2. Therefore, even if a turbine missile occurs in which the turbine blade breaks during rotation, it is possible to eliminate the possibility that the turbine blade will fly toward the reactor 3. In addition, the floating nuclear power generation system 1 employs a casing that is strong enough that the turbine blades cannot penetrate it, to prevent turbine missiles from occurring.

[0057] <Matters concerning mooring of floating body 2> Next, a floating nuclear power generation system 1 is provided with a mooring device for mooring the streamlined float 2. The following are some characteristic features. The floating nuclear power system 1 has 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 provided with an electric screw thruster that can freely rotate the propulsion direction, it is 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 provided with a thruster, it is possible to continue to maintain the float 2 at a fixed position when the anchor chain 22 breaks.

[0058] Also, as a device for controlling the attitude of the float 2 by itself, for example, a circulating water pump 4E can be used. The circulating water pump 4E is a pump that sends seawater to the condenser 4C, which has the largest cooling capacity of any nuclear power generation facility. Therefore, the circulating water pump 4E has the largest capacity 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 on the sea. In the floating nuclear power generation system 1 of this embodiment, as shown in FIG. 3, the circulating water system is provided such that the circulating water pump 4EL provided in the circulating water piping 4D connecting the port side intake 4DSL and the starboard side discharge port 4DHR pumps seawater from the port side to the starboard side, and the circulating water pump 4ER provided in the circulating water piping 4D connecting the starboard side intake 4DSR and the port side discharge port 4DHL pumps seawater from the starboard side to the port side. In peacetime when the direction (posture) of the float 2 is left to the tidal current, the flow rate of the circulating water pump 4EL and the flow rate of the circulating water pump 4ER are balanced so that the water is symmetrically pumped 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. Such directional control of the float 2 by flow rate adjustment is effective not only for changing the direction around the mooring parts, but also for correcting the positional deviation of the float 2.

[0059] As a device for controlling the attitude of the floating body 2 by itself, in addition to the circulating water pump 4E, for example, a reactor auxiliary cooling water pump for the reactor building cooling water system (RCW) may be used. Seawater pump for turbine cooling (RSW), Turbine auxiliary cooling system (TCW) The present embodiment is a turbine auxiliary cooling seawater pump (TSW) for the Turbine Water System. In the floating nuclear power generation system 1, the reactor auxiliary cooling seawater pump and the turbine auxiliary cooling seawater pump can 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] In the floating nuclear power generation system 1 of this embodiment, it is assumed that the turbine 4A has three low-pressure turbines. The three condensers 4C arranged below each low-pressure turbine are connected to two circulating water pipes 4D for multiplexing. For this reason, six circulating water pipes 4D and circulating water pumps 4E (4EL, 4ER) are shown in FIG. 3. However, the floating nuclear power generation system 1 of this embodiment is not limited to this. The circulating water pipes 4D and the circulating water pumps 4E may be provided symmetrically, and may be, for example, four or less, or eight or more. In addition, in FIG. 3, the water intake 4DSL and the water discharge 4DHL are arranged close to each other, but in order to suppress the short circuit phenomenon, they may be arranged apart from each other, or the opening directions may be staggered, such as to the side and below the float 2.

[0061] Another device for changing the direction of the floating body 2 is a tugboat. If a tugboat is constantly tethered to the floating body 2, not only can the direction of the floating body 2 be changed, but also, for example, when an emergency occurs 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 emergency situations that may occur in a specific sea area include the occurrence of a natural disaster such as an undersea volcanic eruption, and the occurrence of an armed attack by terrorists or the military. In addition, in order to respond to an armed attack situation targeting the floating nuclear power generation system 1, it is desirable to take measures such as setting an area within a predetermined distance from the floating nuclear power generation system 1 to restrict the entry of ships and the like and monitoring 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 it is possible to change the direction of the float 2, the following measures, for example, become possible. Figure 4 is a diagram illustrating the state 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 Fig. 4(A), it is assumed that the tidal current flows toward the lower right on the paper surface of Fig. 4. In this case, the floating nuclear power system 1 moored by the anchor chain 22 floats due to the tidal current in the state shown by symbol P1 in Fig. 4(A), that is, with the bow of the float 2 facing toward the upper left. In this state, it is assumed that, for example, an earthquake or typhoon occurs centered on the left side of the paper surface of Fig. 4, causing a tsunami to flow toward the right.

[0064] If the floating nuclear power system 1 receives this tsunami with the bow of the float 2 facing upward and to the 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 occurrence of the tsunami is detected and the direction of the float 2 is immediately started to be changed, and the state shown by symbol P2 in FIG. 4(A), that is, the bow of the float 2 is turned 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 the starboard side. Since the float 2 of the floating nuclear power system 1 is long from bow to stern, even if a tsunami hits the bow side of the float 2, the floating nuclear power system 1 will hardly tilt in the fore-aft direction, as shown in Figure 4(B).

[0065] Although the floating nuclear power system 1 is shown in a location relatively close to land in Fig. 4, it is preferable that the floating nuclear power system 1 be moored offshore at a distance of tens of kilometers or more from land. As shown in Fig. 4(B), a tsunami has the tendency to grow gradually larger as it approaches land in shallow waters. For this reason, if the floating nuclear power system 1 is moored offshore at a distance of tens of kilometers or more from land in deep waters, it is possible to relatively reduce the size of the tsunami that the floating nuclear power 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 away from land, there will be no residential areas within the area required by Japanese law for the formulation of an evacuation plan. In other words, even if a large-scale accident were to occur in the floating nuclear power system 1, it is unlikely that residents on land would be forced 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 the seawater used in the floating nuclear power generation system 1. In the floating nuclear power generation system 1, dust removal devices are provided at the intakes 4DSL, 4DSR of the circulating water piping 4D and at the intake of the reactor auxiliary cooling seawater system for supplying cold heat to auxiliary equipment 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 a portion that is always filled with seawater around 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 that is connected to a seawater system pump such as the circulating water pump 4E. The cyclone 29D has a conical internal shape and has an inlet 29C that opens along the tangential direction at the outermost diameter portion. Therefore, when the seawater system pump operates with the dust removal pit 29A filled with seawater and seawater is sucked into the outlet 29H, a spiral water flow is generated in the cyclone 29D by the seawater flowing in from the inlet 29C. Due to the generation of the spiral water flow, the garbage D, which has a larger specific gravity than seawater, is centrifuged in the cyclone 29D and settles into a sedimentation tank 29E provided 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, about 80 to 100 m, depending on the displacement of the float 2, so there is a low possibility of sucking in debris that is abundant near the sea surface. By combining this with the effect of preventing the intrusion of a large amount of migratory fish by the torpedo protection net described above, it is possible to suppress the intrusion of debris into the water intake as much as possible.

[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 strainer 29B.

[0071] 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 using, for example, a dust removal device that rotates an endless screen (traveling screen) or other types of dust removal devices.

[0072] <Core cooling issues> 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 isolated 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 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, it is possible to significantly improve safety by stably removing the decay heat of the reactor 3 for a long period of time using the surrounding seawater. For this reason, the floating nuclear power system 1 is capable of flowing seawater into the IC / PCCS pool 10. The IC / PCCS pool When seawater is allowed to flow into the IC / PCCS pool 10, cooling can be continued by the natural circulation force caused by the density difference of the seawater. For this reason, in the floating nuclear power generation system 1, the IC / PCCS pool 10 is provided 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] As can be seen from Fig. 6 and Fig. 7, 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 Fig. 6 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.

[0076] 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 after the fresh water in the IC / PCCS pool 10 and the condensate storage tank 14 decreases due to boiling, there may be cases where the cooling of the reactor 3 by the fresh water cannot be continued. 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 core C using the emergency condenser 30A. The floating nuclear power generation system 1 has valves at appropriate locations for allowing seawater to flow into the side ballast tank 28 from around the float 2, so that even if the seawater in the side ballast tank 28 decreases, it can be replenished as needed.

[0077] The floating nuclear power generation system 1 according to the present embodiment is not limited to the 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 emergency condenser 30A used to cool the core C when the primary system boundary is intact and the PCCS heat exchanger 30D 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 the 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 the 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 the valve. The valve for switching the system configuration may be an electric valve using a DC power source or a manual valve.

[0078] In addition, in the floating nuclear power generation system 1, a height difference is provided between the communication 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 density difference in 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] 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.

[0080] In this way, the floating nuclear power generation system 1 is provided with various facilities for facilitating cooling with seawater by taking advantage of the advantages of a floating structure compared to nuclear power plants 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 the surrounding seawater. The function of using seawater by opening the communication valves 10A, 10B, 10C can be used not only for the IC / PCCS pool 10 but also for the fuel pool 8, for example.

[0081] 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.

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

[0083] <Core Catcher> FIG. 8 is a diagram showing a state where a molten core falls from the bottom of the pressure vessel 3E. When the core melts in the nuclear reactor 3, the bottom of the pressure vessel 3E may be damaged, and the molten core may fall below the pressure vessel 3E as shown in FIG. 8. When the molten core falls below the pressure vessel 3E, the structural material of the float 2 below the pressure vessel 3E is heated. However, as described above, the float 2 has a double hull structure, and the bottom of the float 2 is provided with a bottom ballast tank 26. A large number of heat transfer plates 26B erected in the bottom ballast tank 26 are joined to the lower surface of the steel plate 26A of the float 2 forming the bottom surface of the lower dry well 3N. For this reason, the steel plate 26A is firmly reinforced by the heat transfer plate 26B. Note that, in FIG. 8, the inside of the bottom ballast tank 26 is shown as being partitioned by the heat transfer plate 26B, but water passages for circulating ballast water are provided at various points of the heat transfer plate 26B. Therefore, the ballast water can flow freely within the bottom ballast tank 26 without being impeded 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, when 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, when attempting to inject water into the molten core, measures must be taken such as limiting the amount of water injected to an appropriate amount. However, it is not easy to control the amount of water injected 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 plate 26A and the heat transfer plate 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 has fallen to the bottom surface of the lower dry well 3N is stably cooled and solidified, and accumulates as fuel debris. In addition, 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 generation of a large amount of hydrogen.

[0087] In addition, 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. In this way, in the floating nuclear power generation system 1 of this embodiment, even if a core meltdown occurs, a passive molten core countermeasure is implemented using the water in the bottom ballast tank 26 and the water in the suppression pool 3H. In addition, in order to minimize the effect of the pedestal coming into contact with the 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 by a heat transfer tube or the like. If such a bulkhead and heat transfer means are provided, the soundness of the pedestal can be maintained even if a core meltdown occurs.

[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 provided with a function to fill the containment vessel 3A with seawater. That is, the floating nuclear power generation system 1 is provided 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] In a normal state, the seawater inlet valve 3AV is closed, and as shown in FIG. 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 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 described 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 FIG. 9(B), and it becomes possible to indirectly cool the core C in the pressure vessel 3E from the outside of the pressure vessel 3E. Note that, in order to allow the air in the containment vessel 3A to be vented when the containment vessel 3A is filled 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 for removing radioactive materials contained in the air may be provided midway along the air vent path.

[0090] <Sinking function of floating nuclear power 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] Since the floating nuclear power generation system 1 is adapted to float on the sea, if all means for injecting water into the pressure vessel 3E are lost due to some 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. When it is desired to raise the floating nuclear power generation system 1 from the seabed, a floating float F for floating the floating nuclear power generation system 1 is prepared as shown in FIG. 10(B) at a timing when 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 a sealed structure, and it is possible to inject seawater into the floating float F and to drain the seawater from the floating float F.

[0092] After preparing such a floating float F, seawater is poured into the floating float F above the floating nuclear power generation system 1 sunk to the seabed, as shown in FIG. 10(C), to sink the floating float F to 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. When the seawater inside the floating float F is discharged, the floating float F rises to the sea surface together with the floating nuclear power generation system 1 due to the buoyancy of the floating float F. This makes it possible to attempt various disposal operations, 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 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. [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·Light oil tank:24·Waste treatment room:25·Bow ballast tank:26·Bottom ballast tank Tank: 27·Aft 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 port: 4DH··Outlet port: 10A··Communicating valve: 10B··Communicating valve: 10C··Communicating valve: 10D··Atmospheric release 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··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 the sea, on which the nuclear reactor and the turbine generator are arranged, 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 system.

2. the core catcher is made of steel; A steel plate forming a bottom portion of a containment vessel in which the nuclear reactor is housed; A heat transfer plate is provided upright in the bottom ballast tank on the lower surface of the steel plate.

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

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

4. The floating body further includes a sinking means for sinking the floating body.

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

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