Nuclear reactor cooling system

Abstract

To remove decay heat, and to prevent air and liquid metal from coming into contact with each other also in the event of double breakdown of a nuclear reactor vessel and a reactor containment vessel, and prevent occurrence of a fire disaster.SOLUTION: A nuclear reactor cooling system includes: a reactor core installed in a nuclear reactor vessel; a nuclear reactor cooling material filled in the nuclear reactor vessel; a reactor containment vessel containing the nuclear reactor vessel; a concrete silo housing the reactor containment vessel; a collector cylinder forming an air upflow passage and an air downflow passage in a space between the reactor containment vessel and the concrete silo, wherein air for cooling the reactor containment vessel, whose temperature has risen to a high temperature due to heat from the reactor containment vessel, flows upward and passes through the air upflow passage, and wherein ambient air descends, passes and is led to the air upflow passage in the air downflow passage communicating with the air upflow passage; a thermal insulation material installed so as to be in contact with an exterior side of the collector cylinder in a radial direction; and a liquid nitrogen supply system which is installed at an upper part of the concrete silo in order to supply liquid nitrogen to the air upflow passage and the air downflow passage.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a reactor cooling system, and more particularly to a reactor cooling system suitable for use in the core of a fast reactor equipped with a reactor cooling device. [Background technology]

[0002] A fast reactor, which uses high-speed neutrons to sustain a nuclear fission reaction, generally comprises a reactor core installed in a reactor vessel and a liquid metal coolant filled in the reactor vessel.

[0003] The reactor vessel is contained within a containment vessel, which provides a space filled with an inert gas, and is mounted within a concrete silo lined with a steel liner.

[0004] The core of a fast reactor continues to generate residual decay heat even when the reactor is shut down. To cool this, a turbine bypass system is generally used. However, in case the normal decay heat removal system cannot be used, a separate system for removing the decay heat is also required.

[0005] For example, in Patent Document 1, a function called a reactor vessel auxiliary cooling system (hereinafter referred to as RVACS) is provided that uses air, that is, atmospheric air, to remove decay heat.

[0006] The RVACS decay heat removal system described in Patent Document 1 has an air intake for directing air from the top of the reactor building into a concrete silo, forms downward and upward air paths in the space between the containment vessel and the concrete silo, and has a collector cylinder for receiving heat radiated from the containment vessel.

[0007] Residual decay heat generated from the reactor is transferred to the reactor vessel via the coolant, and then transferred from the reactor vessel to the containment vessel by thermal radiation. When the temperature of the containment vessel rises, heat is transferred to the collector cylinder by thermal radiation, and heat is also transferred to the air in the upward flow path from both sides of the containment vessel and the collector cylinder, and the heated air is released to the outside through an air exhaust port installed at the top of the reactor building.

[0008] According to the RVACS decay heat removal system described in Patent Document 1 mentioned above, air flows into the downward air flow path from the air intake, driven by the difference in air density with the upward air flow, and after flowing to the bottom of the concrete silo, it turns around and rises while being heated in the space between the containment vessel and the collector cylinder that forms the air flow path, and is released from the air exhaust.

[0009] The RVACS decay heat removal system, based on the principles described above, is a passive safety system that does not require power or manual operation. The air flow path is always open even during normal operation, and there is no equipment with complex structures such as heat exchangers, making it highly reliable.

[0010] However, in a fast reactor equipped with a RVACS decay heat removal system, if a double failure of the reactor vessel and containment vessel were to occur, which is a hypothetical event with an extremely low probability of occurring, the coolant stored in the reactor vessel could leak into the air flow path, blocking the space where the air reverses from the downward flow path to the upward flow path, causing the RVACS cooling function to be lost.

[0011] In addition, when a coolant that is highly reactive with air (such as liquid sodium) is used, there is a concern that a fire could occur if the coolant comes into contact with air.

[0012] As a measure to remove decay heat and enable cooling of the reactor even in the event of loss of the RVACS cooling function as described above, a configuration for removing decay heat described in Patent Document 2 has been proposed.

[0013] Patent Document 2 describes that as a cooling measure in the event of double rupture of the reactor vessel and the containment vessel, a liner tank for holding leaked liquid metal is provided inside a concrete silo, and an additional independent air cooling passage is provided, making it possible to remove decay heat even if the air passage in the RVACS is blocked due to double rupture of the reactor vessel and the containment vessel. [Prior art documents] [Patent documents]

[0014] [Patent Document 1] JP-A-6-174884 [Patent Document 2] Japanese Patent Application Publication No. 7-318678 Summary of the Invention [Problem to be solved by the invention]

[0015] The configuration for removing decay heat described in Patent Document 2, which takes measures to address the issues in Patent Document 1, provides a function for removing decay heat even if the air flow path of the RVACS is blocked. In addition, in order to prevent fires caused by contact between liquid metal and air, Patent Document 2 provides shutoff valves at the air intake and air exhaust of the RVACS, and closes the shutoff valves in the event of double damage to the reactor vessel and containment vessel.

[0016] However, the solution described in Patent Document 2 requires measures to prevent the shut-off valve from becoming stuck in the closed position due to rust or the like, and therefore there is a concern that the introduction of the shut-off valve may actually reduce the inherently high reliability of RVACS.

[0017] In addition, in the event of a large-scale fire caused by an aircraft crash into a reactor building, etc., there is a concern that alternative cooling methods that use outside air as the final heat sink may lose their cooling function at the same time as the RVACS due to the rise in outside air temperature.

[0018] The present invention has been made in consideration of the above-mentioned points, and an object of the present invention is to provide a reactor cooling system that can remove decay heat even when the RVACS air flow path is blocked or the outside air temperature rises, and can prevent air from coming into contact with liquid metal even in the event of a double failure of the reactor vessel and the containment vessel, thereby preventing the outbreak of a fire. [Means for solving the problem]

[0019] In order to achieve the above-mentioned object, the reactor cooling system of the present invention is a reactor cooling system equipped with a natural circulation flow path that introduces outside air to cool the heat of the reactor and exhausts high-temperature air, and is characterized by comprising a standby piping connected to the natural circulation flow path through a tubular member that forms an air flow path of the natural circulation flow path, and a system for supplying liquid nitrogen to the standby piping.

[0020] Specifically, in order to achieve the above-mentioned object, the reactor cooling system of the present invention is characterized by comprising: a reactor core installed in a reactor vessel, reactor coolant filled in the reactor vessel, a containment vessel for storing the reactor vessel, a concrete silo for storing the containment vessel, a collector cylinder in a space between the containment vessel and the concrete silo, which forms an air ascending passage through which air heated by heat from the containment vessel ascends to cool the containment vessel, and an air descending passage that communicates with the air ascending passage and through which outside air descends and is led to the air ascending passage, a heat insulating material installed so as to be in contact with the radial outside of the collector cylinder, and a liquid nitrogen supply system installed on top of the concrete silo and which supplies liquid nitrogen to the air ascending passage and the air descending passage. Effect of the Invention

[0021] According to the present invention, decay heat can be removed even if the RVACS air flow path is blocked or the outside air temperature rises, and even in the event of a double failure of the reactor vessel and containment vessel, contact between air and liquid metal can be prevented, thereby preventing the outbreak of a fire. [Brief description of the drawings]

[0022] [Figure 1] 1 is a diagram showing an overall configuration of an example of a fast reactor nuclear power generation system to which a reactor cooling system of the present invention is applied. [Diagram 2] FIG. 1 is a diagram showing a first embodiment of a reactor cooling system according to the present invention. [Diagram 3] FIG. 3 is a diagram showing a state in which the reactor vessel and the containment vessel of the reactor cooling system shown in FIG. 2 are simultaneously damaged, causing the reactor coolant to leak into the air cooling passage. [Figure 4] FIG. 11 is a diagram showing a third embodiment of a reactor cooling system according to the present invention. [Diagram 5] FIG. 1 is a diagram showing a first embodiment of a reactor cooling system according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] The reactor cooling system of the present invention will be described below based on the illustrated embodiment. In each drawing, the same reference numerals are used for the same components. Furthermore, the structure, materials, and other specific configurations shown in the present invention are not limited to the embodiment and example taken up here, and can be appropriately combined or improved within the scope of not changing the gist of the present invention. Furthermore, elements that are not directly related to the present invention are omitted from the illustration.

[0024] First, before describing an embodiment of the reactor cooling system of the present invention, an example of a fast reactor nuclear power generation system to which the reactor cooling system is applied will be described.

[0025] FIG. 1 shows an overall configuration of an example of a fast reactor nuclear power generation system to which the reactor cooling system of the present invention is applied.

[0026] The fast reactor nuclear power generation system 1 shown in FIG. 1 includes a reactor vessel 2, a containment vessel 3, a reactor core 4, an intermediate heat exchanger 5, a primary cooling system main circulation pump 6, an upper reactor mechanism 19, secondary cooling system piping 7a, 7b, a secondary cooling system main circulation pump 8, and a steam generator 9, and further includes a high-pressure turbine 10a, a low-pressure turbine 10b, a generator 11, a condenser 12, a feedwater pump 13, and a feedwater heater 14.

[0027] Specifically, the reactor vessel 2 is housed in a containment vessel 3, and the space formed by the reactor vessel 2 and the containment vessel 3 is filled with an inert gas (eg, argon) 15.

[0028] Furthermore, the core 4 is contained within a reactor vessel 2, which is filled with reactor coolant (liquid metal, e.g., liquid sodium) 16, and the upper portion of the reactor vessel 2 is filled with a cover gas (e.g., argon) 17.

[0029] In addition, the steam generator 9 is connected to the intermediate heat exchanger 5 via secondary cooling system piping 7a and 7b, and a secondary cooling system main circulation pump 8 is installed in the middle of the secondary cooling system piping 7a. One end of this secondary cooling system piping 7a is connected to the intermediate heat exchanger 5, and the other end is connected to the steam generator 9.

[0030] The steam generated in the steam generator 9 is sent to the high-pressure turbine 10a and the low-pressure turbine 10b via the main steam system piping 20a. The high-pressure turbine 10a and the low-pressure turbine 10b are rotated by the steam sent from the steam generator 9, which rotates the generator 11 connected to the shaft of the low-pressure turbine 10b to generate electricity. Although not shown, the generator 11 is also connected to the shaft of the high-pressure turbine 10a.

[0031] The condenser 12 condenses the steam that has passed through the high-pressure turbine 10a and the low-pressure turbine 10b and returns it to water, and the feedwater system piping 20b returns the water condensed in the condenser 12 to the steam generator 9. A feedwater pump 13 and a feedwater heater 14 are installed in the feedwater system piping 20b downstream of the condenser 12.

[0032] The fast reactor nuclear power generation system 1 configured in this manner heats the secondary system coolant (e.g., liquid sodium) passing through the secondary cooling system piping 7a and 7b by passing the reactor coolant 16 heated in the reactor core 4 through the intermediate heat exchanger 5.

[0033] In addition, in the fast reactor nuclear power generation system 1, the secondary coolant after passing through the secondary cooling system piping 7a and 7b is sent to the steam generator 9 to generate steam, and this steam is guided via the main steam system piping 20a to the high-pressure turbine 10a and the low-pressure turbine 10b to rotate the turbines, which in turn rotate the generator 11 directly connected to the turbines, thereby generating electricity.

[0034] The steam used for power generation is condensed into water in a condenser 12, similar to a boiling water reactor (BWR) or pressurized water reactor (PWR) light water reactor nuclear power generation system, and then passes through feedwater system piping 20b, in which a feedwater pump 13 and a feedwater heater 14 are installed, where the water is heated and pressurized, and supplied to the steam generator 9.

[0035] In this embodiment, a tank-type fast reactor will be described as an example, but the present invention is not limited to this and can also be applied to a loop-type fast reactor in which the reactor vessel 2, the primary cooling system main circulation pump 6, and the intermediate heat exchanger 5 are housed in a tank separate from the reactor vessel 2. EXAMPLES

[0036] Next, an embodiment of a reactor cooling system that is applied to the above-mentioned fast reactor nuclear power generation system will be described.

[0037] A first embodiment of the reactor cooling system of the present invention is shown in Fig. 2. Note that in the reactor cooling system of Fig. 2, the secondary cooling system and the main steam system are omitted.

[0038] The reactor cooling system 21 of this embodiment shown in Fig. 2 is disposed outside the containment vessel 3 of the fast reactor shown in Fig. 1. In Fig. 2, the reactor cooling system 21 exists underground below the ground surface 37, but it may be installed above ground.

[0039] 2, the reactor cooling system 21 of this embodiment is roughly composed of a concrete silo 27 that houses the containment vessel 3, a collector cylinder 24 that is a cylindrical member that forms the air descending passage 22 and the air ascending passage 23 that are natural circulation passages and receives heat radiated from the containment vessel 3, an air inlet 29 for taking in air 36 into the air descending passage 22, and an air outlet 28 for discharging the high-temperature air 36. The arrows indicate the flow of air (outside air) 36 (this also applies to each embodiment described below).

[0040] The reactor cooling system 21 of this embodiment can remove decay heat by transferring heat generated from the reactor core 4 to the air 36 in the air ascending passage 23 and releasing the air 36 to the outside through the air exhaust port 28.

[0041] Further, the collector cylinder 24 is provided with a heat insulator 25, which is a cylindrical member that insulates the air descending passage 22 and the air ascending passage 23 to suppress a decrease in cooling capacity.

[0042] Furthermore, in the unlikely event of double damage to the reactor vessel 2 and the containment vessel 3, causing reactor coolant (liquid metal, for example liquid sodium) 16 to leak into the air ascending passage 23 and the air descending passage 22, a stainless steel liner 26 is installed on the surface of the concrete silo 27 facing the containment vessel 3 to prevent the reactor coolant 16 from coming into contact with the concrete and to stably hold the reactor coolant 16.

[0043] In addition, in the reactor cooling system 21 of this embodiment, a liquid nitrogen supply system 32 is installed on the upper part of the concrete silo 27 .

[0044] This liquid nitrogen supply system 32 is composed of a double container 31 with excellent insulation properties for storing liquid nitrogen 30, a liquid nitrogen valve 34 for controlling the supply of liquid nitrogen 30, a first liquid nitrogen supply pipe 33a which is a backup pipe connected from the liquid nitrogen valve 34 through the insulation material 25 to the air downward flow path 22, a second liquid nitrogen supply pipe 33b which is a backup pipe connected from the liquid nitrogen valve 34 through the insulation material 25 to the air upward flow path 23, and a connection part 35 for supplying liquid nitrogen 30 to the double container 31 from the outside.

[0045] In FIG. 2, the liquid nitrogen supply system 32 is installed underground except for the connection part 35, but it can also be installed above ground.

[0046] FIG. 3 shows a state in which the reactor vessel 2 and the containment vessel 3 of the reactor cooling system 21 shown in FIG. 2 are simultaneously damaged, and the reactor coolant 16 leaks into the air cooling passages (the air downflow passage 22 and the air upflow passage 23).

[0047] As shown in Fig. 3, when the reactor coolant 16 leaks, the air descending passage 22 and the air ascending passage 23 are completely isolated, so that it is not possible to expect decay heat removal by air 36. Furthermore, if the air 36 comes into contact with the reactor coolant 16, for example, when liquid sodium, which is a liquid metal, is used as the reactor coolant 16, there is a concern that a violent chemical reaction may occur, causing a fire.

[0048] Even in such a situation, in the reactor cooling system 21 of this embodiment, liquid nitrogen 30 is supplied to the air ascending passage 23 and the air descending passage 22 from the double container 31 storing the liquid nitrogen 30 via the first and second liquid nitrogen supply pipes 33a and 33b, and the reactor coolant 16 leaked into the air ascending passage 23 and the air descending passage 22 is cooled, thereby forming a solidified layer 38 in the middle of the air ascending passage 23 and the air descending passage 22.

[0049] The formation of this solidified layer 38 prevents the scattering of compounds resulting from the reaction between the reactor coolant (liquid metal, for example, liquid sodium) 16 and air 36, and furthermore, the liquid nitrogen 30 evaporates and becomes nitrogen gas 39, thereby displacing the air and preventing contact between the reactor coolant (liquid metal, for example, liquid sodium) 16 and the air 36.

[0050] In addition, by continuously supplying liquid nitrogen 30, it is possible to cool the reactor coolant 16 and the containment vessel 3 and remove decay heat. The high-temperature nitrogen gas 39 is discharged from the air intake 29 and the air exhaust .

[0051] Furthermore, the liquid nitrogen supply system 32 is capable of continuously supplying liquid nitrogen 30 from the outside to the double container 31 via a connection part 35 .

[0052] Furthermore, by installing multiple liquid metal leak detectors 40 in the space between the reactor vessel 2 and the containment vessel 3 and in the space between the concrete silo 27 and the containment vessel 3, and operating the liquid nitrogen valve 34 of the liquid nitrogen supply system 32 so as to automatically open if the liquid metal leak detector 40 detects a leak of the reactor coolant 16, liquid nitrogen 30 can be supplied quickly in the event of double damage to the reactor vessel 2 and the containment vessel 3.

[0053] In addition, the liquid nitrogen supply system 32 can be simplified by omitting the connection part 35 and arranging the liquid nitrogen valve 34 on the ground.

[0054] When supplying liquid nitrogen 30, a portable liquid nitrogen storage container can be connected to the liquid nitrogen valve 34, thereby enabling the supply of liquid nitrogen 30.

[0055] As described above, according to this embodiment, even if hypothetical events occur, such as the double failure of the reactor vessel 2 and containment vessel 3 of a fast reactor having RVACS, or an event that reduces the functionality of the RVACS, such as a large-scale fire caused by an aircraft crashing into a reactor building, etc., a reactor cooling system 21 for removing decay heat is provided, and contact between the leaked reactor coolant (liquid metal, for example, liquid sodium) 16 and the air can be blocked without installing a closing device at the air inlet and outlet of the RVACS.

[0056] That is, according to this embodiment, even if the RVACS air flow path becomes blocked or the outside air temperature rises, decay heat can be removed, and even in the event of double damage to the reactor vessel 2 and the containment vessel 3, contact between the air and the reactor coolant (liquid metal, for example, liquid sodium) 16 can be prevented, thereby preventing the outbreak of a fire. EXAMPLES

[0057] FIG. 4 shows a second embodiment of the reactor cooling system of the present invention.

[0058] The reactor cooling system 21 of the first embodiment shown in FIG. 2 is equipped with only a liquid nitrogen supply system 32, whereas the reactor cooling system 41 of the present embodiment shown in FIG. 4 is different in configuration from the reactor cooling system 21 of the first embodiment in that it is equipped with a high-pressure nitrogen gas supply system 42, which is a nitrogen gas supply system, in addition to the liquid nitrogen supply system 32 of the first embodiment.

[0059] The high-pressure nitrogen gas supply system 42 of this embodiment is roughly composed of a high-pressure nitrogen gas tank 44 filled with high-pressure nitrogen gas 43, a plurality of high-pressure nitrogen valves 45 for controlling the supply of the high-pressure nitrogen gas 43, a first high-pressure nitrogen gas supply pipe 46a connected from the high-pressure nitrogen valve 45 through the heat insulating material 25 to the air descending flow path 22, and a second high-pressure nitrogen gas supply pipe 46b connected from the high-pressure nitrogen valve 45 through the heat insulating material 25 to the air ascending flow path 23. The other configurations are similar to those of the reactor cooling system 21 of the first embodiment.

[0060] The high-pressure nitrogen gas supply system 42 of this embodiment may supply the high-pressure nitrogen gas 43 by a high-pressure nitrogen gas tank 44, an evaporator, and a compressor.

[0061] In the reactor cooling system 41 of this embodiment, prior to the supply of liquid nitrogen by the liquid nitrogen supply system 32 in the event of a leak of the reactor coolant (liquid metal, for example liquid sodium) 16, the high-pressure nitrogen gas supply system 42 supplies high-pressure nitrogen gas 43 to the air ascending passage 23 and the air descending passage 22 via first and second high-pressure nitrogen gas supply pipes 46a and 46b, thereby replacing air with nitrogen gas and suppressing condensation of moisture contained in the air 36 when the liquid nitrogen 30 is supplied.

[0062] This makes it possible to suppress chemical reactions that may occur when the leaked reactor coolant (liquid metal, for example, liquid sodium) 16 comes into contact with the condensed water.

[0063] In the reactor cooling system 41 shown in FIG. 4, the high-pressure nitrogen gas tank 44 is placed above ground, but it may also be placed underground.

[0064] In addition, a connection part for supplying high-pressure nitrogen gas 43 from the outside may be added to the high-pressure nitrogen gas tank 44, or multiple high-pressure nitrogen gas tanks 44 may be prepared and the high-pressure nitrogen valves 45 may be replaced to enable a continuous supply of high-pressure nitrogen gas 43.

[0065] Furthermore, the high-pressure nitrogen gas tank 44 may be portable, and the high-pressure nitrogen gas 43 may be supplied from a large tank vehicle via a high-pressure nitrogen valve 45, for example.

[0066] In addition, at least one liquid metal leak detector 40 is installed in the space between the concrete silo 27 and the containment vessel 3, and when this liquid metal leak detector 40 detects a leak of the reactor coolant 16, the high-pressure nitrogen valve 45 of the high-pressure nitrogen gas supply system 42 is automatically opened.Furthermore, a dew point meter 47 is installed in the air ascending passage 23 and the air descending passage 22, and the liquid nitrogen valve 34 of the liquid nitrogen supply system 32 is automatically opened on the condition that the moisture in the air has been sufficiently removed by this dew point meter 47.In this way, high-pressure nitrogen gas 43 and liquid nitrogen 30 can be rapidly supplied in the event of double damage to the reactor vessel 2 and the containment vessel 3.

[0067] Furthermore, by arranging the liquid nitrogen valve 34 of the liquid nitrogen supply system 32, the double container 31 and its connection part 35, the high-pressure nitrogen valve 45 of the high-pressure nitrogen gas supply system 42, and the high-pressure nitrogen gas tank 44 at a sufficiently far radial distance from the reactor vessel 2, liquid nitrogen 30 and high-pressure nitrogen gas 43 can be continuously supplied from the outside, even in the event of a widespread fire caused by an aircraft crash into a reactor building, etc.

[0068] Of course, with this configuration of the present embodiment, the same effects as those of embodiment 1 can be obtained, and prior to the supply of liquid nitrogen 30 by the liquid nitrogen supply system 32 when the reactor coolant 16 leaks, the high-pressure nitrogen gas 43 is supplied by the high-pressure nitrogen gas supply system 42 to the air ascending passage 23 and the air descending passage 22 via the first and second high-pressure nitrogen gas supply pipes 46a and 46b, thereby replacing the air with nitrogen gas and suppressing the condensation of moisture contained in the air 36 when the liquid nitrogen 30 is supplied, thereby suppressing chemical reactions caused by contact between the leaked reactor coolant (liquid metal, for example liquid sodium) 16 and the condensed moisture. EXAMPLES

[0069] FIG. 5 shows a third embodiment of the reactor cooling system of the present invention.

[0070] The reactor cooling system 41 of the second embodiment shown in FIG. 4 has a high-pressure nitrogen gas supply system 42 including a high-pressure nitrogen gas tank 44 and one system of supply piping (first and second high-pressure nitrogen gas supply piping 46a and 46b), whereas the reactor cooling system 48 of the present embodiment shown in FIG. 5 differs in that the high-pressure nitrogen gas supply system 42 includes a high-pressure nitrogen gas tank 44 and two or more systems of supply piping.

[0071] That is, the reactor cooling system 48 of this embodiment shown in Figure 5 includes, in addition to the high-pressure nitrogen gas supply system 42 having a high-pressure nitrogen gas tank 44 and its supply piping (first and second high-pressure nitrogen gas supply piping 46a and 46b), a high-pressure nitrogen gas supply system 42a having a high-pressure nitrogen gas tank 44a and its supply piping (third and fourth high-pressure nitrogen gas supply piping 46c and 46d).

[0072] That is, the third and fourth high-pressure nitrogen gas supply pipes 46c and 46d of the high-pressure nitrogen gas supply system 42a shown in Figure 5 penetrate the concrete silo 27, pass through the insulation material 25, and are installed at a different height than the first and second high-pressure nitrogen gas supply pipes 46a and 46b (the height of the outlet portions of the third and fourth high-pressure nitrogen gas supply pipes 46c and 46d is lower than the height of the outlet portions of the first and second high-pressure nitrogen gas supply pipes 46a and 46b) so as to supply high-pressure nitrogen gas 43a to the air ascending flow path 23 and the air descending flow path 22.

[0073] In this embodiment, the penetration portions of the third and fourth high-pressure nitrogen gas supply pipes 46c and 46d into the concrete silo 27 are located higher than the liquid level of the reactor coolant 16 that is expected in the event of a leakage of the reactor coolant 16.

[0074] In addition, the third and fourth high-pressure nitrogen gas pipes 46c and 46d pass through a position higher than the liquid level of the leaked reactor coolant 16 that is expected in the event of double failure of the reactor vessel 2 and the containment vessel 3, and descend through the insulation 25, thereby preventing any impact on the reliability of the concrete silo 27's function of retaining the reactor coolant 16.

[0075] With this configuration of the present embodiment, it goes without saying that the same effects as those of the first embodiment can be obtained, and in the case where the degree of double damage to the reactor vessel 2 and the containment vessel 3 is minor and the amount of leakage of the reactor coolant 16 is small, the air below the concrete silo 27 can be effectively replaced with nitrogen gas.

[0076] To summarize the present embodiment described above, the reactor cooling systems 21, 41 and 48 of the present embodiment are reactor cooling systems in which the air descending passage 22 and the air ascending passage 23 are formed by the collector cylinder 24 and the heat insulating material 25 in the space between the containment vessel 3 and the concrete silo 27, and the containment vessel 3 can be cooled by air driven by natural circulation.

[0077] In addition, the reactor cooling systems 21, 41 and 48 of this embodiment are reactor cooling systems having a liquid nitrogen supply system 32 installed on the top of the concrete silo 27, a first liquid nitrogen supply pipe 33a connected to the air downflow passage 22 from the liquid nitrogen supply system 32 through an insulating material 25 installed radially outside the collector cylinder 24, and a second liquid nitrogen supply pipe 33b connected to the air upflow passage 23 from the liquid nitrogen supply system 32 through an insulating material 25 installed radially outside the collector cylinder 24.

[0078] Furthermore, according to the configuration of the reactor cooling systems 21, 41 and 48 of this embodiment, even if a double failure of the reactor vessel 2 and the containment vessel 3 is assumed, the liquid nitrogen 30 supplied from the liquid nitrogen supply system 32 passes through the first and second liquid nitrogen supply pipes 33a and 33b installed in the insulation 25, and is supplied to the air downward flow path 22 and the air upward flow path 23, thereby cooling and solidifying the surface of the leaked reactor coolant (liquid metal, for example liquid sodium) 16, thereby preventing the reactor coolant 16 from scattering.

[0079] In addition, by providing separate piping for supplying liquid nitrogen 30 to the air downflow passage 22 and the air upflow passage 23, liquid nitrogen 30 can be supplied to both the air downflow passage 22 and the air upflow passage 23, which become isolated spaces in the event of a leak of reactor coolant 16.

[0080] Furthermore, the liquid nitrogen 30 evaporates and the surrounding atmosphere is replaced with nitrogen gas, and contact between the reactor coolant 16 and the air is cut off. At this time, as the liquid nitrogen 30 evaporates and the temperature of the nitrogen gas rises, heat is absorbed from the reactor coolant 16 and the containment vessel 3, and the heated nitrogen gas is discharged into the air from the air intake 29 and the air exhaust 28 located above the air ascending passage 23 and the air descending passage 22, respectively, and the decay heat generated in the reactor core can be removed.

[0081] In addition, in the configuration of the reactor cooling system 41 described above, in addition to the liquid nitrogen supply system 32, a high-pressure nitrogen gas supply system 42 and first and second high-pressure nitrogen gas supply pipes 46a and 46b connected from the high-pressure nitrogen gas supply system 42 to the air downward flow path 22 and the air upward flow path 23 through the insulation 25 are provided. In the event of double damage to the reactor vessel 2 and the containment vessel 3, high-pressure nitrogen gas 43 is supplied to the air upward flow path 23 and the air downward flow path 22 prior to the supply of liquid nitrogen 30, thereby replacing the air in the air upward flow path 23 and the air downward flow path 22 with nitrogen gas, and preventing condensation of moisture in the air when liquid nitrogen 30 is supplied.

[0082] Furthermore, in the above-mentioned reactor cooling systems 21, 41 and 48, a plurality of liquid metal leak detectors 40 are installed in the space between the reactor vessel 2 and the containment vessel 3, and in the space between the containment vessel 3 and the concrete silo 27, and when any of the liquid metal leak detectors 40 detects a leak of the reactor coolant 16, nitrogen gas and liquid nitrogen 30 are automatically supplied, thereby more effectively preventing contact between the reactor coolant (liquid metal, for example liquid sodium) 16 and the air.

[0083] In addition, in the above-mentioned reactor cooling systems 41 and 48, by installing multiple high-pressure nitrogen gas supply pipes connected to the high-pressure nitrogen gas supply system 42 and configuring a structure capable of supplying nitrogen gas to multiple heights of the air ascending passage 23 and the air descending passage 22, it is expected that the air in the air ascending passage 23 and the air descending passage 22 can be replaced with nitrogen gas regardless of the amount of leakage of the reactor coolant 16.

[0084] In addition, in the above-mentioned reactor cooling systems 41 and 48, one end of the first and second liquid nitrogen supply pipes 33a and 33b connected to the liquid nitrogen supply system 32 is positioned at a position higher than the liquid level of the reactor coolant 16 formed in the air ascending passage 23 and the air descending passage 22 when it is assumed that all of the reactor coolant 16 in the reactor vessel 2 has leaked outside the containment vessel 3, thereby making it possible to expect a cooling effect for the reactor coolant 16 and the containment vessel 3 and an effect of preventing contact between the reactor coolant 16 (liquid metal, for example, liquid sodium) and the air, regardless of the amount of leakage of the reactor coolant 16.

[0085] In addition, in the above-mentioned reactor cooling systems 21, 41 and 48, the liquid nitrogen supply system 32 and the high-pressure nitrogen gas supply system 42 can be temporary facilities such as tank cars, and the effects of this embodiment can be expected even when the liquid nitrogen supply system 32 and the high-pressure nitrogen gas supply system 42 are connected to piping installed in advance in the event of double damage to the reactor vessel 2 and the containment vessel 2.

[0086] Furthermore, in the above-mentioned reactor cooling systems 21, 41 and 48, the connection positions of the liquid nitrogen supply system 32 and the high-pressure nitrogen gas supply system 42 and their supply piping are located, for example, about 100 m horizontally away from the reactor vessel 2, and the piping from the connection position of the supply piping to the reactor vessel 2 is buried underground, so that the effects of this embodiment can be expected even when the RVACS cooling function is temporarily lost during a large-scale fire caused by an aircraft crash into a reactor building, etc.

[0087] The present invention is not limited to the above-described embodiments, and includes various modified examples. For example, the above-described embodiments have been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to those including all of the configurations described. In addition, it is possible to replace a part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. In addition, it is possible to add, delete, or replace a part of the configuration of each embodiment with another configuration. [Explanation of symbols]

[0088] 1...fast reactor nuclear power generation system, 2...reactor vessel, 3...containment vessel, 4...core, 5...intermediate heat exchanger, 6...primary cooling system main circulation pump, 7a, 7b...secondary cooling system piping, 8...secondary cooling system main circulation pump, 9...steam generator, 10a...high pressure turbine, 10b...low pressure turbine, 11...generator, 12...condenser, 13...feed water pump, 14...feed water heater, 15...inert gas, 16...reactor coolant, 17...cover gas, 19...upper reactor mechanism, 20a...main steam system piping, 20b...feed water system piping, 21, 41, 48...reactor cooling system, 22...air downflow path, 23...air upflow path, 24...collector cylinder, 25...insulation material, 26...liner, 27...concrete sump Iro, 28...air outlet, 29...air intake, 30...liquid nitrogen, 31...double container, 32...liquid nitrogen supply system, 33a...first liquid nitrogen supply pipe, 33b...second liquid nitrogen supply pipe, 34...liquid nitrogen valve, 35...connection, 36...air, 37...ground surface, 38...solidified layer, 39...nitrogen gas, 40...liquid metal leak detector, 42, 42a...high pressure nitrogen gas supply system, 43, 43a...high pressure nitrogen gas, 44, 44a...high pressure nitrogen gas tank, 45...high pressure nitrogen valve, 46a...first high pressure nitrogen gas supply pipe, 46b...second high pressure nitrogen gas supply pipe, 46c...third high pressure nitrogen gas supply pipe, 46d...fourth high pressure nitrogen gas supply pipe, 47...dew point meter.

Claims

1. A reactor cooling system having a natural circulation flow path that introduces outside air to cool the heat of a reactor and exhausts high-temperature air, 1. A reactor cooling system comprising: a standby pipe connected to the natural circulation flow path through a cylindrical member that forms an air flow path of the natural circulation flow path; and a system for supplying liquid nitrogen to the standby pipe.

2. 2. The reactor cooling system of claim 1, The natural circulation flow path is formed around a containment vessel that contains a reactor vessel that contains a reactor core, and includes an air ascending flow path through which air that has become hot due to heat from the containment vessel ascends and passes, and an air descending flow path that communicates with the air ascending flow path and through which the outside air descends and is led to the air ascending flow path, the cylindrical member is provided between the air descending passage and the air ascending passage and includes a collector cylinder for receiving heat radiated from the containment vessel, and a heat insulating material provided around the collector cylinder for insulating the air descending passage and the air ascending passage from each other to suppress a decrease in cooling capacity, The auxiliary piping includes a first liquid nitrogen supply piping connected to the air descending flow path through the insulating material from a liquid nitrogen valve that controls the supply of liquid nitrogen from a container that stores the liquid nitrogen, and a second liquid nitrogen supply piping connected to the air ascending flow path through the insulating material from the liquid nitrogen valve, 2. A reactor cooling system comprising: a liquid nitrogen supply system installed on an upper portion of a concrete silo that houses the containment vessel;

3. 3. A reactor cooling system according to claim 2, comprising: A reactor cooling system characterized in that the liquid nitrogen supply system comprises the container for storing the liquid nitrogen, the liquid nitrogen valve for controlling the supply of the liquid nitrogen, the first liquid nitrogen supply piping connected to the air downward flow path from the liquid nitrogen valve through the insulation, the second liquid nitrogen supply piping connected to the air upward flow path from the liquid nitrogen valve through the insulation, and a connection portion for supplying the liquid nitrogen to the container from the outside.

4. 1. A reactor cooling system comprising: a reactor core installed in a reactor vessel; reactor coolant filled in the reactor vessel; a containment vessel for storing the reactor vessel; a concrete silo for storing the containment vessel; a collector cylinder in a space between the containment vessel and the concrete silo, the collector cylinder forming an air ascending passage through which air heated by heat from the containment vessel ascends to cool the containment vessel and an air descending passage that communicates with the air ascending passage and through which outside air descends and leads to the air ascending passage; a heat insulating material installed so as to be in contact with the radial outside of the collector cylinder; and a liquid nitrogen supply system installed above the concrete silo for supplying liquid nitrogen to the air ascending passage and the air descending passage.

5. 5. A reactor cooling system according to claim 4, comprising: A reactor cooling system characterized in that the liquid nitrogen supply system comprises a container for storing the liquid nitrogen, a liquid nitrogen valve for controlling the supply of the liquid nitrogen, a first liquid nitrogen supply pipe connected to the air downward flow path from the liquid nitrogen valve through the insulation, a second liquid nitrogen supply pipe connected to the air upward flow path from the liquid nitrogen valve through the insulation, and a connection portion for supplying the liquid nitrogen to the container from the outside.

6. 6. A reactor cooling system according to claim 5, comprising: A reactor cooling system characterized in that the liquid nitrogen is supplied from the container to the air ascending passage and the air descending passage via the first and second liquid nitrogen supply pipes, and the reactor coolant leaked into the air ascending passage and the air descending passage is cooled, thereby forming a solidified layer in the middle of the air ascending passage and the air descending passage.

7. 6. A reactor cooling system according to claim 5, comprising: A reactor cooling system comprising: a liner installed on a surface of the concrete silo facing the containment vessel.

8. 6. A reactor cooling system according to claim 5, comprising: A reactor cooling system characterized in that liquid metal leak detectors are installed in the space between the reactor vessel and the containment vessel and in the space between the concrete silo and the containment vessel, and when the liquid metal leak detector detects a leak of the reactor coolant, the liquid nitrogen valve of the liquid nitrogen supply system automatically opens to supply the liquid nitrogen.

9. 6. A reactor cooling system according to claim 5, comprising: A reactor cooling system comprising: a nitrogen gas supply system for supplying nitrogen gas to the air ascending passage and the air descending passage in addition to the liquid nitrogen supply system.

10. 10. The reactor cooling system of claim 9, A reactor cooling system characterized in that the nitrogen gas supply system comprises a nitrogen gas tank filled with nitrogen gas, a plurality of nitrogen valves for controlling the supply of the nitrogen gas, a first nitrogen gas supply pipe connected from the nitrogen valve through the insulation to the air downward flow path, and a second nitrogen gas supply pipe connected from the nitrogen valve through the insulation to the air upward flow path.

11. 11. The reactor cooling system of claim 10, A reactor cooling system characterized in that, prior to the supply of liquid nitrogen by the liquid nitrogen supply system in the event of a leak of the reactor coolant, the nitrogen gas is supplied to the air ascending passage and the air descending passage via the first and second nitrogen gas supply pipes by the nitrogen gas supply system.

12. 12. The reactor cooling system of claim 11, at least one liquid metal leak detector is installed in a space between the concrete silo and the containment vessel, and when the liquid metal leak detector detects a leak of the reactor coolant, the nitrogen valve of the nitrogen gas supply system is automatically opened; A reactor cooling system comprising: a dew point meter installed in the air ascending passage and the air descending passage; and a nitrogen valve of the liquid nitrogen supply system automatically opened when moisture in the air has been sufficiently removed by the dew point meter.

13. 11. The reactor cooling system of claim 10, A reactor cooling system comprising, in addition to the nitrogen gas supply system, a nitrogen gas supply system separate from the nitrogen gas supply system that supplies nitrogen gas to the air ascending passage and the air descending passage.

14. 14. The reactor cooling system of claim 13, A reactor cooling system characterized in that the other nitrogen gas supply system comprises: another nitrogen gas tank filled with another nitrogen gas other than the nitrogen gas, a plurality of other nitrogen valves for controlling the supply of the other nitrogen gas, a third nitrogen gas supply pipe connected from the other nitrogen valve through the insulation to the air downward flow path, and a fourth nitrogen gas supply pipe connected from the other nitrogen valve through the insulation to the air upward flow path.

15. 15. The reactor cooling system of claim 14, The third and fourth nitrogen gas supply pipes are installed so as to penetrate the concrete silo, pass through the insulation, and supply the other nitrogen gas to the air upflow passage and the air downflow passage at a height different from that of the first and second nitrogen gas supply pipes.

16. 16. A reactor cooling system as recited in claim 15, comprising: A reactor cooling system, wherein the height of the outlets of the third and fourth nitrogen gas supply pipes is lower than the height of the outlets of the first and second nitrogen gas supply pipes.

17. 17. The reactor cooling system of claim 16, a second nitrogen gas supply pipe for supplying nitrogen gas to said second silo through said second nitrogen gas supply pipe; a second nitrogen gas supply pipe for supplying nitrogen gas to said second silo through said second nitrogen gas supply pipe;

18. 17. The reactor cooling system of claim 16, the third and fourth nitrogen gas supply pipes penetrate a position higher than a liquid level of the leaked reactor coolant assumed in the event of a double failure of the reactor vessel and the containment vessel, and descend through the insulation.

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