Fuel pools, fuel pool operation methods, fuel transport containers

Abstract

To enable temporary storage of spent fuel assemblies in a nuclear reactor facility more safely. [Solution] The system comprises a fuel pool main body and multiple fuel transport containers, and the fuel transport containers have flow ports at the bottom and top to allow pool water in the fuel pool main body to circulate from the bottom to the top of the fuel transport container by convection. When the reactor has completed its specified operating period, spent fuel assemblies removed from the reactor are transferred to the multiple fuel transport containers so that the containers are separated for each specified operating period, and the fuel transport containers within the fuel pool main body are transferred so that the spent fuel assemblies stored in the fuel transport containers are removed from the fuel pool main body in order for each specified operating period.

Description

[Technical Field]

[0001] The present invention relates to a fuel pool for nuclear fuel, a method for operating the fuel pool, and a fuel transport vessel. [Background technology]

[0002] Various methods have been proposed for handling spent nuclear fuel used in nuclear reactors (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-300251 Summary of the Invention [Problem to be solved by the invention]

[0004] Spent fuel assemblies removed from a nuclear reactor are transported outside the nuclear reactor facility in casks (an example of a "fuel transport container" as referred to in this application) after a sufficient cooling period has passed. For this reason, fuel assemblies removed from a nuclear reactor are usually temporarily stored in fuel racks in a fuel pool installed in the nuclear reactor facility and cooled for several years, after which they are transferred into casks and transported outside the nuclear reactor facility.

[0005] However, if spent fuel assemblies are stored in fuel racks in a fuel pool, it is difficult to quickly remove the fuel assemblies from the reactor facility in an emergency, etc. Furthermore, in the case of a floating nuclear power generation system that is operated floating on the sea, for example, there is a possibility that the fuel assemblies will become detached from the fuel racks and scattered if the floater capsizes or sinks for some reason.

[0006] Therefore, the present application discloses a fuel pool for nuclear fuel that can temporarily store spent fuel assemblies more safely in a nuclear reactor facility, a method for operating the fuel pool, and a fuel transport container. [Means for solving the problem]

[0007] In order to solve the above problems, in the present invention, flow ports are provided at the bottom and top of the fuel transport container to allow pool water in the fuel pool main body to circulate from the bottom to the top of the fuel transport container by convection, and spent fuel assemblies removed from the reactor are transferred to multiple fuel transport containers so that the containers are separated for each specified operating period, and the spent fuel assemblies stored in the fuel transport containers are removed from the fuel pool main body in sequence for each specified operating period.

[0008] In detail, the present invention relates to a fuel pool comprising a fuel pool main body attached to a nuclear reactor, a plurality of fuel transport containers capable of storing fuel assemblies, an equipment transfer device capable of transferring the fuel transport containers inside and outside the fuel pool main body, and a fuel transfer device capable of transferring fuel assemblies within the fuel pool main body, wherein the fuel transport containers have flow ports at the bottom and top of the fuel transport containers for circulating pool water within the fuel pool main body from the bottom to the top of the fuel transport container by convection, the fuel transfer device transfers spent fuel assemblies removed from the reactor when the reactor has completed a specified operating period to the plurality of fuel transport containers so that the containers are separated for each specified operating period, and the equipment transfer device transfers the fuel transport containers within the fuel pool main body so that the spent fuel assemblies stored in the fuel transport containers are removed from the fuel pool main body in order for each specified operating period.

[0009] The fuel transport vessel is a vessel that can safely transport spent fuel assemblies. Therefore, the spent fuel assemblies are stored and transported in this way in the fuel pool using the fuel transport vessel. By transporting the spent fuel assemblies, they can be temporarily stored in a safer manner at the nuclear reactor facility.

[0010] All spent fuel assemblies removed from the reactor at the end of one predetermined operating period may be stored in a predetermined number of fuel transport containers, and the fuel pool main body may be large enough to store multiple groups of the predetermined number of fuel transport containers. In this way, the spent fuel assemblies can be stored in separate containers for each predetermined operating period.

[0011] The fuel pool main body may have a fuel rack capable of temporarily storing fuel assemblies removed from the reactor, adjacent to the container area in which multiple fuel transport containers are arranged, and the equipment transfer device may transfer the fuel transport containers in the container area so that the spent fuel assemblies stored in the fuel transport containers are lined up in order for each predetermined operating period from the fuel rack side in the container area. In this way, the fuel transport containers containing spent fuel assemblies are lined up in the fuel pool main body for each predetermined operating period, making it easy to remove the fuel transport containers.

[0012] The present invention can also be understood from the aspect of a method for operating a fuel pool. For example, the present invention may be a method for operating a fuel pool attached to a nuclear reactor, comprising: a container arranging step of arranging a plurality of fuel transport containers capable of storing fuel assemblies in a fuel pool main body of the fuel pool, a fuel transfer step of transferring spent fuel assemblies removed from the reactor when the reactor has completed a predetermined operating period to the plurality of fuel transport containers so that the containers are divided for each predetermined operating period, and a container transfer step of transferring the fuel transport containers in the fuel pool main body so that the spent fuel assemblies stored in the fuel transport containers are removed from the fuel pool main body in order for each predetermined operating period.

[0013] The present invention can also be seen from the perspective of a fuel transport container. For example, the present invention may be a fuel transport container that can be placed in a fuel pool main body attached to a nuclear reactor, the fuel transport container comprising: a storage main body capable of storing nuclear fuel assemblies; and flow ports provided at the upper and lower parts of the storage main body, for circulating pool water in the fuel pool main body from the lower part to the upper part by convection when the fuel transport container is placed in the fuel pool main body. This makes it possible to cool the fuel assemblies stored in the fuel transport container within the fuel pool main body.

[0014] The fuel transport container may further include a detachable upper lid that can open the upper portion of the storage body, and the upper circulation port provided at the upper portion of the storage body among the circulation ports may be provided in the upper lid. This makes it possible to cool the fuel assemblies in the fuel pool main body even when the opening of the storage body with the fuel assemblies stored therein is closed by the upper lid. [Effects of the Invention]

[0015] The above-described fuel pool for nuclear fuel, fuel pool operating method, and fuel transport container enable safer temporary storage of spent fuel assemblies in nuclear reactor facilities. [Brief explanation of the drawings]

[0016] [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] FIG. 3 is a diagram showing an example of a fuel pool. [Figure 4] FIG. 4 is a diagram showing an example of a cask. [Figure 5] FIG. 5 is a diagram showing an example of the state in which fuel assemblies are stored in a fuel pool. DETAILED DESCRIPTION OF THE INVENTION

[0017] 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.

[0018] <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.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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, 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 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 provided in the ancillary equipment area 19. The floating nuclear power generation system 1 is also equipped with The float 2 is provided with a light oil tank 23 on the deck near the bow. The floating nuclear power generation system 1 also has a bow ballast tank 25, a bottom ballast tank 26, a stern ballast tank 27, and side ballast tanks 28 for controlling the attitude of the float 2.

[0024] 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 of various reactor cooling equipment such as an emergency core cooling system and a residual heat removal system, pumps and valves of a pool water cooling system that cools the fuel pool, compressed air equipment for control, ventilation and air conditioning equipment, an emergency diesel generator that serves as an emergency power source, DC power supply equipment using storage batteries, and various other equipment.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] The condensate storage tank 14 is a tank that stores water that can be supplied to the nuclear reactor 3. The 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.

[0033] 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 for the turbine generator 4, and large pieces of equipment can be easily transported using crane equipment installed above the operating floor.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] <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.

[0041] The reactor system R containing the reactor 3 is equipped with various facilities such as a containment vessel 3A, nuclear fuel 3B, control rods 3C, a recirculation pump 3D, and a pressure vessel 3E. The turbine system T containing the turbine generator 4 is equipped with various facilities such as a condenser 4C, circulating water piping 4D, a circulating water pump 4E, and a feedwater pump 4F in addition to the turbine 4A and generator 4B that constitute the turbine generator 4.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] The turbine 4A and generator 4B that make up the turbine generator 4 are connected by the same rotating shaft. The turbine 4A has a structure in which an impeller is housed in a casing. A condenser 4C is provided below the turbine 4A to condense the steam that has passed through the turbine 4A. Inside the condenser 4C, there are provided a number of thin tubes that form part of the path of the circulating water piping 4D that connects the water intake and discharge outlets provided below the waterline on the exterior surface of the floating body 2, and The steam is condensed using the cold energy of seawater pumped by a circulating water pump 4E installed on the path of 4D. Therefore, 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, power is applied to the impeller to rotate the generator 4B. This rotates the generator 4B and generates electricity. In addition, the condensed water condensed in the condenser 4C is fed back into the pressure vessel 3E via the feedwater piping 4G by the feedwater pump 4F.

[0047] Note that Figure 2 only shows an outline of the reactor system R and turbine system T, and in reality, a wide variety of equipment is installed. For example, important equipment such as a steam control valve and a turbine bypass valve is installed near the turbine 4A of 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 is installed in the feedwater pipe 4G. In addition, 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.

[0048] 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.

[0049] 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.

[0050] The above is an overview of the system configuration of the floating nuclear power generation system 1 according to this embodiment. Next, the fuel pool 8 employed in the floating nuclear power generation system 1 according to this embodiment will be described in detail.

[0051] Fig. 3 is a diagram showing an example of a fuel pool 8. Fig. 3 shows the fuel pool 8 filled with water (pure water). As shown in Fig. 3, the fuel pool 8 has a fuel pool main body 8P filled with water, a fuel exchange machine 8F (an example of the "fuel transfer device" as defined in the present application) provided above the fuel pool main body 8P, and a polar crane 8R (an example of the "equipment transfer device" as defined in the present application) located above the indoor space in which the fuel pool main body 8P is provided.

[0052] The fuel pool main body 8P has an open-topped, approximately rectangular parallelepiped storage space whose inner surface is lined with stainless steel, and is provided inside with fuel storage racks 8L and casks 8C (an example of the "fuel transport container" in this application) that store fuel assemblies FA of nuclear fuel 3B to be loaded into the reactor 3. The fuel pool main body 8P is provided near the top of the reactor 3, and is designed so that the fuel assemblies FA can be transferred between the reactor 3, whose top is open, and the fuel pool main body 8P during periodic inspection of the floating nuclear power generation system 1.

[0053] The fuel storage rack 8L is a lattice-shaped rack with frames arranged lengthwise and widthwise, into which the fuel assemblies FA can be inserted and removed from above. The fuel storage rack 8L prevents the fuel assemblies FA from going critical by leaving an appropriate distance between the fuel assemblies FA stored in each frame. The fuel storage rack 8L is a rack for storing all the fuel assemblies FA loaded in the reactor 3 in the event of a malfunction in the reactor 3, etc. For this reason, the fuel storage rack 8L is The fuel storage rack 8L has a capacity to store all the fuel assemblies FA currently in use (for example, about 1,000 assemblies). In addition, the fuel storage rack 8L is basically used only for temporary storage of fuel assemblies FA, and is generally always left empty.

[0054] The cask 8C is a container for transporting the fuel assemblies FA inside and outside the floating nuclear power generation system 1. For this reason, the cask 8C can be removed from inside the fuel pool main body 8P. The cask 8C is a container with a roughly cylindrical appearance that can store multiple fuel assemblies FA (for example, 69 assemblies). The cask 8C is a container for safely transporting the stored fuel assemblies FA, and has a shielding function that blocks radiation emitted from the fuel assemblies FA, a heat dissipation function that dissipates heat from the fuel assemblies FA, and an impact resistance function that can withstand impacts applied from the outside.

[0055] The refueling machine 8F is a device for transporting fuel assemblies FA within the fuel pool main body 8P and includes a first track 8F1, a second track 8F2, rails 8F3, and a fuel elevator 8F4. The first track 8F1 is a track that can travel along the X direction on the second track 8F2. The first track 8F1 is provided with a fuel elevator 8F4 that is connected to the upper end of the fuel assembly FA and can raise and lower the fuel assembly FA in the Z direction. The second track 8F2 is a rod-shaped body that extends like a beam along the X direction and is a track that can travel along the Y direction on rails 8F3. The rails 8F3 extend from the top of the fuel pool main body 8P to the top of the reactor 3. Therefore, the refueling machine 8F can move the fuel elevator 8F4 to any position in the fuel pool main body 8P or the reactor 3 by appropriately operating the electric motors that drive the first track 8F1 and the second track 8F2. Therefore, the refueling machine 8F can, for example, lift the fuel assembly FA at an appropriate position with the fuel elevator 8F4 while the fuel assembly FA is submerged in water, move the fuel elevator 8F4 to another position with the first tracker 8F1 and the second tracker 8F2, and then lower the fuel assembly FA. In this way, the refueling machine 8F can, for example, transfer the fuel assembly FA that was loaded in the reactor 3 to the cask 8C, or load an unused fuel assembly FA into the reactor 3.

[0056] The polar crane 8R is a device for transporting casks 8C and various other equipment, and includes a trolley 8R1, a crane girder 8R2, rails 8R3, and a hook 8R4. The trolley 8R1 is a traveling body that can travel along the X direction in the upper part of the indoor space where the polar crane 8R is located. The trolley 8R1 is provided with a liftable hook 8R4 that can suspend various equipment. The crane girder 8R2 is a rod-shaped body that extends like a beam along the X direction and is a traveling body that can travel along the Y direction in the upper part of the indoor space where the polar crane 8R is located. The rails 8R3 extend from the top of the fuel pool main body 8P to the top of the reactor 3. Therefore, the polar crane 8R can move the hook 8R4 to any position in the fuel pool main body 8P or the reactor 3 by appropriately operating the electric motors that drive the trolley 8R1 and crane girder 8R2. Therefore, the polar crane 8R can lift the cask 8C at an appropriate position and move it to another position, or move the pressure vessel lid placed on top of the reactor 3 and various other heavy objects.

[0057] The fuel pool 8 is equipped with a circulating cooling system for circulating and cooling the water in the fuel pool main body 8P, and a purification system for maintaining the water quality in the fuel pool main body 8P. Because the fuel pool 8 may be shaken by ocean waves that the floating body 2 receives, a fixing mechanism for detachably fixing the cask 8C is provided on the bottom of the fuel pool main body 8P, and a wave-breaking mechanism for suppressing waves on the water surface in the fuel pool main body 8P is provided on the top of the fuel pool main body 8P. While FIG. 3 shows the fuel storage rack 8L and the cask 8C in direct contact with the bottom of the fuel pool main body 8P, in reality, various support structures are provided on the bottom of the fuel pool main body 8P to support the fuel storage rack 8L and the cask 8C at a distance from the bottom so that the water in the fuel pool main body 8P can flow through the fuel storage rack 8L and the cask 8C.

[0058] FIG. 4 shows an example of a cask 8C. The cask 8C has a hollow cylinder 8C1 and a lid 8C2 that closes the upper opening of the cylinder 8C1. The lid 8C2 is provided with an upper circulation port 8C3 for circulating water inside and outside the cylinder 8C1. The bottom of the cylinder 8C1 is provided with a lower circulation port 8C4 for circulating water inside and outside the cylinder 8C1. Inside the cylinder 8C1, a lattice-shaped partition plate 8C5 is provided, which has vertical and horizontal frames that allow fuel assemblies FA to be inserted and removed from above. The partition plate 8C5 prevents criticality of the fuel assemblies FA by providing an appropriate distance between the fuel assemblies FA housed in each frame.

[0059] When the fuel assembly FA is put into or taken out of the cylinder 8C1, the lid 8C2 is removed from the top of the cylinder 8C1, as shown in Fig. 4(A). On the other hand, when the fuel assembly FA is stored or transported while housed in the cylinder 8C1, the lid 8C2 is attached to the top of the cylinder 8C1, and the top opening of the cylinder 8C1 is closed. Because the cylinder 8C1 is provided with an upper circulation port 8C3 and a lower circulation port 8C4 at its bottom, even when the top opening of the cylinder 8C1 is closed by the lid 8C2, the water of the fuel pool main body 8P can flow through the inside of the cask 8C placed underwater in the fuel pool main body 8P. Therefore, even if the spent fuel assemblies FA removed from the reactor 3 are stored in the tubes 8C1 in the fuel pool main body 8P and the upper opening of the tubes 8C1 is closed by the lid 8C2, the water in the fuel pool main body 8P that enters from the lower circulation port 8C4 rises inside the tubes 8C1 and naturally flows out from the upper circulation port 8C3 due to convection caused by the decay heat of the fuel assemblies FA stored inside the cask 8C. As a result, the fuel assemblies FA that generate decay heat inside the cask 8C are cooled, and the cold state of the spent fuel assemblies FA is maintained.

[0060] In the fuel pool 8 of this embodiment, by providing space to store a plurality of such casks 8C within the fuel pool main body 8P, it becomes possible to handle spent nuclear fuel as follows. Figure 5 is a diagram showing an example of the storage state of fuel assemblies FA in the fuel pool 8. In Figure 5, in order to identify specific casks 8C, the casks 8C are suffixed with the symbols A to L. Hereinafter, when "cask 8C" is mentioned, it will refer to any unspecified one of the casks 8CA to 8L.

[0061] In a typical commercial ABWR, for example, the core is loaded with 872 fuel assemblies, and the fuel pool is approximately 10m square. The frequency of replacement of the fuel assemblies loaded in the core depends on the core design and operating conditions, but about one-third of the fuel assemblies in the core are removed as spent nuclear fuel every two years. The casks used for storing spent nuclear fuel in commercial reactors are approximately 2.5m in outer diameter and can hold around 69 fuel assemblies.

[0062] Therefore, assuming that the floating nuclear power generation system 1 according to this embodiment is such an ABWR plant, the fuel storage rack 8L will have storage space for approximately 1,000 fuel assemblies, which is sufficient to store the fuel assemblies for the entire reactor core as required by laws and regulations, etc. Then, in the remaining space of the fuel pool main body 8P, which is approximately 10 m square, excluding the space for the fuel storage rack 8L, which has storage space for approximately 1,000 fuel assemblies, space will be secured to accommodate 12 casks 8C (casks 8CA-L), each with an outer diameter of approximately 2.5 m.

[0063] Therefore, for example, 12 casks 8CA-L can be arranged in three rows of four casks in each row in the fuel pool main body 8P, as shown in Fig. 5. If fuel assemblies FA, which account for about one-third of the entire core, are removed from the reactor 3 as spent nuclear fuel every two years, a maximum of 276 spent fuel assemblies FA removed from the reactor 3 when the floating nuclear power generation system 1 completes its specified operating period and undergoes a periodic inspection can be directly stored in the four casks.

[0064] There are various orders for storing the spent fuel assemblies FA stored in the 12 casks 8CA to 8L, but for example, if the spent fuel assemblies FA removed from the reactor 3 during a specific periodic inspection are stored in one group of casks 8C (four casks: 8CI, 8CJ, 8CK, and 8CL), the spent fuel assemblies FA removed from the reactor 3 during the next periodic inspection are stored in another group of casks 8C (four casks: 8CE, 8CF, 8CG, and 8CH), and the spent fuel assemblies FA removed from the reactor 3 during the next periodic inspection are stored in another group of four casks 8C (casks 8CA, 8CB, 8CC, and 8CD), the casks 8C of each group will be lined up in the fuel pool main body 8P in order of the magnitude of their decay heat. Then, after the casks 8CI, 8CJ, 8CK, and 8CL with the smallest decay heat are removed from the fuel pool main body 8P, the newly delivered cask 8C can be carried into the fuel pool main body 8P, and the spent fuel assemblies FA removed from the reactor 3 during the next periodic inspection can be stored in the casks 8C within the fuel pool main body 8P. If the spent fuel assemblies FA are transported in this manner using the refueling machine 8F, the spent fuel assemblies FA can be stored in 12 casks 8CA-L so that they are separated for each specified operating period. By carrying out the casks 8C from the fuel pool main body 8P in order starting with the casks 8C with the smallest decay heat, the casks 8C within the fuel pool main body 8P will be carried out of the fuel pool main body 8P in order for each specified operating period.

[0065] When the cask 8C containing the fuel assemblies FA is removed from the fuel pool main body 8P by the polar crane 8R, the water inside the cask 8C is drained, the air inside the cask 8C is replaced with helium gas, and the upper circulation port 8C3 and lower circulation port 8C4 are closed. This keeps the inside of the cask 8C containing the spent fuel assemblies FA dry. The cask 8C containing the fuel assemblies FA is then lifted using a crane located on the deck of the float 2 through a hatch on the deck of the float 2, and is removed outside the float 2 on the deck of the float 2.

[0066] The arrangement order of the casks 8C in the fuel pool main body 8P does not necessarily have to be in order of the decay heat of the fuel assemblies FA, but if it is desired to place the fuel assembly FA with the smallest decay heat in the lowest cask 8C in Figure 5 and the fuel assembly FA with the largest decay heat in the highest cask 8C in Figure 5, then after casks 8CI, 8CJ, 8CK, and 8CL are removed from the fuel pool main body 8P, the four casks 8CE, 8CF, 8CG, and 8CH are moved by polar crane 8R to the locations of casks 8CI, 8CJ, 8CK, and 8CL, and then the four casks 8CA, 8CB, 8CC, and 8CD are moved by polar crane 8R to the locations of casks 8CE, 8CF, 8CG, and 8CH. Then, the four casks 8C newly transported to the floating nuclear power generation system 1 are placed in the locations of casks 8CA, 8CB, 8CC, and 8CD in the fuel pool main body 8P. In this way, even if periodic inspections are repeated, it is possible to maintain the state in which the fuel assembly FA with the smallest decay heat is placed in the lowest cask 8C in Figure 5, and the fuel assembly FA with the largest decay heat is placed in the highest cask 8C in Figure 5.

[0067] Incidentally, in Figure 5, the eight casks 8C (8CE-8CL) that have already housed the fuel assemblies FA are shown with their interiors exposed. However, in reality, as described above, the casks 8C that have completed housing the fuel assemblies FA have the lids 8C2 attached, and the upper openings of the cylinders 8C1 are closed. Water from the fuel pool main body 8P passes through the interior of the cask 8C through the lower circulation port 8C4 at the bottom of the cylinder 8C1 and the upper circulation port 8C3 at the lid 8C2, removing decay heat from the fuel assemblies FA. Furthermore, the cask 8C is fixed to the bottom of the fuel pool main body 8P. Therefore, if this method of operating the fuel pool 8 is adopted, the fuel assemblies FA can be stably cooled by the pool water within the fuel pool main body 8P, and the cask 8C can safely protect the fuel assemblies FA even if the floating body 2 tilts due to waves on the sea surface, etc. Furthermore, even if the floater 2 were to capsize or sink, the cask 8C would be able to prevent the fuel assemblies FA from scattering.

[0068] In addition, when attaching or detaching the cask 8C to the bottom of the fuel pool main body 8P while it is submerged in the water of the fuel pool main body 8P, it is preferable that this be done remotely from outside the fuel pool main body 8P rather than manually. For this reason, the cask 8C is preferably provided with, for example, a remote engagement mechanism that can remotely move an L-shaped fixing member to engage with the bottom of the fuel pool main body 8P. Furthermore, when attaching or detaching the lid 8C2 to or from the tube 8C1 of the cask 8C while it is submerged in the water of the fuel pool main body 8P, it is preferable that this be done remotely from outside the fuel pool main body 8P rather than manually. For this reason, the cask 8C is preferably provided with a remote opening / closing mechanism that can remotely move the lid 8C2 to engage with the tube 8C1.

[0069] In this embodiment, an example has been given in which 12 casks 8C are arranged in the fuel pool main body 8P, but the present disclosure is not limited to this. The fuel pool 8 may be arranged, for example, in a form in which another number of casks 8C are arranged in the fuel pool main body 8P. Furthermore, the fuel pool 8 may be arranged in a form in which the area in which the casks 8C are arranged and the area in which the fuel storage racks 8L are arranged can be separated. Furthermore, this embodiment may be modified as appropriate within the scope of the present disclosure. [Explanation of symbols]

[0070] R··Reactor system: T··Turbine system: F··Floating float: C··Reactor core: 1··Floating nuclear power system: 2··Float: 3··Reactor: 4··Turbine generator: 5··Reactor equipment area: 6··Pit: 7··Reactor equipment area: 8··Fuel pool: 9··Desalination plant: 10··IC / PCCS pool: 12··Various equipment areas: 13··Accommodation area: 14··Condensate storage tank: 18·· Laydown area: 19 · Auxiliary equipment area: 20 · Main transformer: 21 · Auxiliary boiler: 22 · Anchor chain: 23 · Diesel oil tank: 24 · Waste treatment room: 25 · Bow ballast tank: 26 · Bottom ballast tank: 27 · Aft ballast tank: 28 · Side ballast tank: 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:8P··Fuel pool body:8L··Fuel Storage rack: 8F · Fuel exchange machine: 8C · Cask: 8R · Polar crane: FA · Fuel assembly: 8C1 · Cylinder: 8C2 · Lid: 8C3 · Upper flow port: 8C4 · Lower flow port: 8C5 · Partition plate: 8F1 · First running body: 8F2 · Second running body: 8F3 · Rail: 8F4 · Fuel elevator: 8R1 · Trolley: 8R2 · Crane girder: 8R3 · Rail: 8R4 · Hook:

Claims

1. The fuel pool body attached to the reactor, a plurality of fuel transport containers capable of accommodating fuel assemblies; an equipment transfer device capable of transferring the fuel transport container into and out of the fuel pool main body; a fuel transfer device capable of transferring the fuel assemblies within the fuel pool main body, the fuel transport container is provided with flow ports at its bottom and top for allowing pool water in the fuel pool main body to flow from the bottom to the top of the fuel transport container by convection, the fuel transfer device transfers spent fuel assemblies removed from the reactor when the reactor has completed a predetermined operating period to the plurality of fuel transport containers such that the containers are separated for each predetermined operating period; the equipment transfer device transfers the fuel transport container in the fuel pool main body so that the spent fuel assemblies stored in the fuel transport container are transported out of the fuel pool main body in order for each of the predetermined operating periods. Fuel pool.

2. all of the spent fuel assemblies removed from the reactor upon completion of one of the predetermined operating periods are stored in a predetermined number of the fuel transport containers, the fuel pool main body has a size capable of accommodating a plurality of groups of the predetermined number of fuel transport containers, The fuel pool of claim 1.

3. the fuel pool main body has a fuel rack capable of temporarily storing the fuel assemblies removed from the reactor, the fuel rack being adjacent to a container area in which the plurality of fuel transport containers are arranged, the equipment transfer device transfers the fuel transport container in the container area so that the spent fuel assemblies stored in the fuel transport container are lined up in order for the predetermined operating period from the fuel rack side in the container area.

3. The fuel pool of claim 2.

4. A method for operating a fuel pool attached to a nuclear reactor, comprising: a container placement step of placing a plurality of fuel transport containers capable of accommodating fuel assemblies in a fuel pool main body of the fuel pool; a fuel transfer step of transferring spent fuel assemblies removed from the reactor when the reactor has completed a predetermined operating period to the plurality of fuel transport containers such that the containers are separated for each predetermined operating period; a container transfer step of transferring the fuel transport container in the fuel pool main body so that the spent fuel assemblies stored in the fuel transport container are carried out from the fuel pool main body in order for each predetermined operating period. How to operate the fuel pool.

5. A fuel transport container that can be placed in a fuel pool main body attached to a nuclear reactor, a storage unit main body capable of storing nuclear fuel assemblies; a circulation port provided at each of the upper and lower parts of the storage body, for circulating pool water in the fuel pool body from the lower part to the upper part of the storage body by convection when the fuel transport container is placed in the fuel pool body; Container for transporting fuel.

6. Further provided is a detachable upper cover that can open the upper portion of the storage body, The upper circulation port provided at the top of the storage body is provided in the upper cover. It is being The fuel transport container according to claim 5.

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