JP2012032276A - Corium cooling device and storage vessel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To supply nanoparticles into cooling water in a cooling flow passage in a corium cooling device without sedimentation or deposition.SOLUTION: A corium cooling device 7 has a deposition floor comprising a heat insulator 42 and a cooling flow passage top plate 93. An upper surface of the deposition floor is a deposition surface on which corium 41 is to be deposited. A cooling flow passage 43 is formed under the deposition floor. The side facing the cooling flow passage 43 of the deposition floor, namely, at least a part of the cooling flow passage top plate 93 is made of a porous material containing nanoparticles. When the corium 41 is dropped, the nanoparticles in pores of the porous material are discharged into the cooling water due to boiling on the cooling flow passage top plate 93.

Description

  The present invention relates to a core melt cooling device and a containment vessel.

  In water-cooled nuclear reactors, there is a possibility that the reactor water level sufficient for cooling cannot be maintained if the water supply to the reactor pressure vessel is stopped or the cooling water is lost due to piping abnormality. Assuming this situation, the reactor is automatically shut down due to a drop in water level, and the core is submerged and cooled by injecting coolant through the emergency core cooling system to prevent core melt accidents. .

  However, it is assumed that the emergency core cooling system and other water injection devices for the core cannot be used. In such a case, the fuel rod temperature rises due to decay heat that continues to occur even after the reactor is shut down, and may eventually lead to core melting.

  The hot core melt melts through the reactor pressure vessel lower mirror and falls onto the floor in the containment vessel. When the containment floor concrete becomes hot due to the core melt, a large amount of non-condensable gas is generated and the concrete is melted and eroded. The generated non-condensable gas increases the pressure in the containment vessel and may damage the reactor containment vessel. Moreover, the containment vessel boundary may be damaged by melting and erosion of concrete, and the containment vessel structure strength may be reduced. If this reaction continues, the containment vessel may be damaged, and radioactive substances in the containment vessel may be released to the external environment.

  In order to suppress the reaction between the core melt and the concrete, the core melt is cooled and the temperature of the contact surface with the concrete at the bottom of the corium is kept below the erosion temperature (under 1500K for general concrete), or the core melt It is necessary to prevent direct contact between concrete and concrete. A core catcher can be cited as a typical countermeasure facility when the core melt falls. This is a facility that receives the fallen core melt with a heat-resistant material and cools the core melt in combination with water injection means.

  Even if cooling water is poured onto the top surface of the core melt that has fallen to the reactor containment floor, if the amount of heat removal at the bottom of the core melt is small, the temperature at the bottom of the core melt will be maintained high due to decay heat. The concrete erosion of the containment floor cannot be stopped. Therefore, there is a method of cooling the core melt from the bottom surface.

  High cooling performance is required for the cooling water for cooling the core melt. In order to improve the cooling performance, for example, a technique for containing and dispersing solid particles such as metal in cooling water is known. By dispersing the particles in the cooling water in this manner, the thermal conductivity is increased as compared with the thermal conductivity of the medium itself that does not include the particles. In addition, it has been confirmed that by dispersing nano-scale fine particles as particles to be contained in the cooling water, the heat transfer coefficient and the critical heat flux are dramatically increased in a boiling test using the cooling water.

  A method for dispersing such fine particles in a medium has also been reported. Specifically, a method of dispersing the fine particles in the medium as they are, a method of more stably dispersing the particles in the medium by attaching a surfactant to the surface of the fine particles, and a dispersing agent in the fine particles and the medium. There is a method of stably dispersing by adding.

JP 2009-47637 A JP 2007-262302 A

  The heat from the core melt is transmitted to the water in the cooling water flow path provided below the core melt deposition floor through the heat-resistant material. The water in the cooling channel is heated and begins to boil, and the generated voids are quickly discharged from the cooling channel arranged radially, with the inclined surface. Steam bubbles generated by boiling flow upward in the cooling flow path, and finally flow out to the core melt upper surface pool. Boiling in the cooling channel results in natural circulation to the core melt top pool and to the cooling channel. Thereby, cooling continues and a debris is hold | maintained reliably.

  If the critical heat flux of the cooling channel is high, the safety margin can be increased. The critical heat flow rate can be improved by mixing the nanofluid into the cooling water. However, the nanofluid effect cannot be obtained unless the nanoparticles are dispersed in the cooling water by precipitation or deposition.

  Accordingly, an object of the present invention is to supply nanoparticles in cooling water in a cooling channel in a core melt cooling device so that precipitation and deposition do not occur.

  In order to achieve the above-mentioned object, the present invention provides a core melt cooling apparatus having a deposition bed provided below a reactor pressure vessel and separating an upward deposition surface and a cooling flow path below the deposition surface. In addition, at least a part of the side facing the cooling flow path of the deposition bed is formed of a porous material that holds the nanoparticles in the voids.

  In the core melt cooling apparatus, the present invention provides a deposition bed that is provided below the reactor pressure vessel and divides an upward deposition surface and a cooling channel below the deposition surface, and the cooling channel And a container containing nanoparticles, wherein when the container is immersed in cooling water, the nanoparticles in the container are released into the cooling water.

  Further, the present invention provides a core melt cooling apparatus, wherein a deposition bed provided below a reactor pressure vessel and separating an upward deposition surface and a cooling flow path below the deposition surface is disposed on the deposition surface. And a container containing nanoparticles.

  In the containment vessel, the present invention provides a pedestal floor, a pedestal side wall that rises from the pedestal floor and supports a reactor pressure vessel, a deposition surface that is provided on the pedestal floor, and an upper deposition surface below the deposition surface. A core melt cooling device comprising a deposition bed that partitions the cooling flow path, wherein at least a part of the side facing the cooling flow path of the deposition bed is formed of a porous material that holds nanoparticles in voids; It is characterized by having.

  In the containment vessel, the present invention provides a pedestal floor, a pedestal side wall that rises from the pedestal floor and supports the reactor pressure vessel, and is provided on the pedestal floor, and has an upward deposition surface and a lower surface of the deposition surface. A deposition bed that partitions the cooling flow path; and a container that is disposed in the cooling flow path and stores nanoparticles, and when the container is immersed in cooling water, the nanoparticles in the container are cooled in the cooling water. And a core melt cooling device to be discharged into the reactor.

  In the containment vessel, the present invention provides a pedestal floor, a pedestal side wall that rises from the pedestal floor and supports the reactor pressure vessel, and is provided on the pedestal floor, and has an upward deposition surface and a lower surface of the deposition surface. A core melt cooling device including a deposition bed that partitions the cooling flow path, and a container that is disposed on the deposition surface and stores nanoparticles.

  ADVANTAGE OF THE INVENTION According to this invention, a nanoparticle can be supplied so that precipitation and deposition may not arise in the cooling water of the cooling flow path in a core melt cooling device.

It is an elevational sectional view of the vicinity of the first embodiment of the core melt cooling device according to the present invention. It is an elevation sectional view of a containment vessel which stored a 1st embodiment of a core melt cooling device concerning the present invention. It is an elevational sectional view of the vicinity of the second embodiment of the core melt cooling device according to the present invention. It is a perspective view of the container which encloses the nano fluid in 2nd Embodiment of the core melt cooling device which concerns on this invention. It is a perspective view of the container which encloses nano fluid in one modification of a 2nd embodiment of a core melt cooling device concerning the present invention. It is an elevational sectional view near the third embodiment of the core melt cooling device according to the present invention. It is an elevational sectional view of the vicinity of the fourth embodiment of the core melt cooling device according to the present invention.

  An embodiment of a core melt cooling apparatus according to the present invention will be described with reference to the drawings. In addition, the same code | symbol is attached | subjected to the same or similar structure, and the overlapping description is abbreviate | omitted.

[First Embodiment]
FIG. 2 is an elevational sectional view of a containment vessel that accommodates the first embodiment of the core melt cooling device according to the present invention.

  The core 10 is housed inside the reactor pressure vessel 1. The reactor pressure vessel 1 is provided inside the containment vessel 2. The containment vessel 2 has a pedestal floor 15 and a cylindrical pedestal side wall 16 extending upward from the pedestal floor 15.

  The reactor pressure vessel 1 is supported on the pedestal side wall 16. A space surrounded by the pedestal floor 15 and the pedestal side wall 16 below the reactor pressure vessel 1 is called a lower dry well 13. That is, the reactor pressure vessel 1 is provided above the lower dry well 13. In addition, a pressure suppression pool 4 is formed inside the storage container 2 so as to surround the outer peripheral surface of the pedestal side wall 16. A core melt cooler (core catcher) 7 is provided in the lower dry well 13 below the reactor pressure vessel 1.

  Further, the storage container 2 has a water tank 5. A water injection pipe 8 extends from the water tank 5 to the core melt cooling device 7. An injection valve 40 is provided in the middle of the water injection pipe 8. Further, the storage container 2 has a storage container cooler 6. The containment vessel cooler 6 has a pipe extending from the end opened to the dry well to the water tank 5 through a heat exchanger submerged in water. The containment vessel cooler 6 is a static containment vessel cooling facility, a dry well cooler, or the like.

  FIG. 1 is an elevational sectional view of the vicinity of the core melt cooling device in the present embodiment. FIG. 1 shows a state in which the core melt 41 falls through the lower head 3 of the reactor pressure vessel 1 and falls into the core melt cooling device 7 and is supplied with cooling water.

  The core melt cooling device 7 is installed on the pedestal floor 15. The core melt cooling device 7 includes a support base 91, a cooling channel bottom plate 92, a cooling channel top plate 93, and a heat insulating material 42. The upper surface of the support base 91 is formed in a conical shape opened upward. A cylindrical gap is formed at the center of the support base 91. A gap at the center of the support base 91 is a water supply container 44.

  The cooling flow path bottom plate 92 is formed in a conical shape opened upward, and is placed on the upper surface of the support base 91. The outer edge of the cooling channel bottom plate 92 rises in the vertical direction.

  The cooling flow path top plate 93 is formed in a conical shape opened upward, and is arranged with a space from the cooling flow path bottom plate 92. The outer edge of the cooling channel top plate 93 rises in the vertical direction. Between the cooling flow path bottom plate 92 and the cooling flow path top plate 93 is a cooling flow path 43 extending from the water supply container 44 to the outlet opening 81 opened upward. The cooling channel top plate 93 is a holding container opened upward as a whole, and a heat insulating material 42 is laid on the inner surface thereof.

  At least a part of the cooling channel top plate 93 is formed of a porous material. The part formed of the porous material of the cooling flow path top plate 93 contains nanoparticles in the holes communicating with the surface. A nanoparticle is a solid particle such as a metal having a nanoscale, that is, a size of about several nanometers.

  The nanoparticles are held in the porous voids as the nanoparticles themselves or as a fluid (nanofluid) containing the nanoparticles. The fluid containing the nanoparticles is water or ionic fluid. Even in a normal case where there is no cooling water in the cooling channel 43, the nanofluid is held by the capillary force of the pores of the porous material, and the nanofluid does not fall from the porous. Moreover, when an ionic liquid is used as a fluid containing nanoparticles, the evaporation of the fluid is suppressed.

  The portion rising at the outer edge of the cooling flow path bottom plate 92 is provided across the gap between the inner surface of the pedestal side wall 16 and the gap. Between the portion rising at the outer edge of the cooling channel bottom plate 92 and the inner surface of the pedestal side wall 16 is a water supply channel vertical portion 46 extending downward from the inlet opening 82. A water supply channel horizontal part 47 extends from the lower end of the water supply channel vertical part 46 to the water supply container 44. The cooling flow path bottom plate 92 and the cooling flow path top plate 93 can be formed, for example, by closely arranging hollow structures having a fan-shaped shape projected in the vertical direction around the water supply container 44.

  When a core melting accident occurs and the core melt 41 penetrates the lower head 3 of the reactor pressure vessel 1, it falls onto the heat insulating material 42 of the core melt cooling device 7. That is, in the core melt cooling apparatus 7 of the present embodiment, the upper surface of the heat insulating material 42 is a deposition surface provided below the reactor pressure vessel 1 and on which the core melt 41 is deposited. When the core melt falls, the injection valve 40 is opened by a signal for detecting breakage of the lower head 3 of the reactor pressure vessel. The signal for detecting the breakage of the lower head 3 is, for example, a signal indicating the lower head temperature and the pedestal atmosphere temperature.

  As a result, cooling water is supplied from the water tank 5 to the core melt cooling device 7 through the water injection pipe 8. The cooling water supplied to the core melt cooling device 7 flows out from the water injection pipe outlet hole 83 opened in the pedestal side wall 16. The cooling water that has flowed out from the water injection pipe outlet hole 83 is supplied to the water supply container 44 through the water supply flow path horizontal portion 47. Further, the cooling water is distributed from the water supply container 44 to the cooling flow path 43.

  The heat of the high temperature core melt 41 is transmitted to the heat insulating material 42 and further transmitted to the cooling water through the wall of the cooling channel 43. As the heat of the core melt 41 is transmitted, the cooling water flowing through the cooling flow path 43 will eventually boil.

  The cooling water supplied from the water supply container 44 rises through the cooling flow path 43 and overflows from the outlet opening 81 located on the outer periphery. Most of the cooling water overflowing from the outlet opening 81 flows into the holding container that holds the core melt 41 of the core melt cooling device 7. The cooling water exiting the cooling flow path 43 from the outlet opening 81 overflows on the heat insulating material 42 and forms a water pool 45 on the core melt. The cooling water forming the water pool 45 boils on the surface of the core melt 41 and cools the core melt 41. Thus, the core melt 41 is cooled by both boiling in the cooling flow path 43 and boiling of the surface of the core melt 41.

  The initial water supply to the water supply container 44 is performed through the water injection pipe 8 by gravity dropping the water stored in the water tank 5 installed above the core melt cooling device 7. When the initial water injection is completed, the core melt cooling device 7 is submerged. The cooling water flooded in the core melt cooling device 7 is supplied to the water supply container 44 via the water supply flow paths 46 and 47 by natural circulation caused by boiling in the cooling flow path 43.

  The steam generated by cooling the core melt is condensed by the containment vessel cooler 6 at the upper part of the containment vessel 2 and returned to the water tank 5. The cooling water obtained by condensing the steam returned to the water tank 5 is again used for cooling the core melt 41, and the cooling of the core melt 41 is continued by natural circulation of the water.

  The upper surface of the cooling channel 43, that is, the heat transfer surface is inclined. For this reason, the vapor bubbles generated by the boiling in the cooling flow path 43 are easily separated from the heat transfer surface by buoyancy. As a result, a good heat transfer coefficient can be obtained.

Since the melting point of the heat insulating material 42 is, for example, about 2400 ° C. when ZrO ₂ is used, it is higher than the temperature of the core melt 41 (average of about 2200 ° C.) and is less likely to melt. Further, by disposing the heat insulating material 42, the core melt 41 does not directly contact the wall of the structure forming the cooling flow path 43, and the heat flux is suppressed by the heat resistance of the heat insulating material 42. There is little possibility that the wall of the structure forming the cooling channel 43 will be damaged.

  As described above, the core melt cooling device 7 of the present embodiment can effectively lower the temperature of the core melt, and the core melt is stably held inside the core melt cooling device 7. .

  In the present embodiment, the heat insulating material 42 and the cooling flow channel are used as a deposition bed that partitions the upper surface of the heat insulating material 42 on which the core melt 41 is deposited and the cooling flow channel 43 provided therebelow. A top plate 93 is provided. The side facing the cooling flow path 43 of the deposition bed, that is, at least a part of the cooling flow path top plate 93 is formed of a porous material containing nanoparticles. For this reason, when such an accident occurs, if boiling occurs due to the heat of the core melt 41 on the heat transfer surface of the cooling channel 43, the nanoparticles contained in the porous material of the cooling channel top plate 93 are It is discharged from the porous material together with the boiling steam. As a result, the nanoparticles are uniformly mixed in the cooling water of the cooling flow path 43. As described above, the nanofluid can be supplied into the cooling water with the fall of the core melt 41 without the operation of the power source or the operator during the severe accident.

  Nanofluids containing nanoscale particles improve the critical heat flux. That is, the cooling performance of the core melt 41 in the core melt cooling device 7 is improved. The nanofluid is arranged in the vicinity of the heat transfer surface in advance. For this reason, nanoparticles can be supplied in the cooling water of the cooling flow path 43 in the core melt cooling device 7 so that precipitation and deposition do not occur. That is, it is possible to prevent a reduction in the effect of the nanofluid due to precipitation and adhesion of nanoparticles in the nanofluid supply path.

[Second Embodiment]
FIG. 3 is an elevational sectional view of the vicinity of the second embodiment of the core melt cooling apparatus according to the present invention.

  The core melt cooling device 7 of the present embodiment has a nanoparticle holding container 52 in which a nanofluid 51 is enclosed. One or a plurality of nanoparticle holding containers 52 enclosing the nanofluid 51 are arranged in the water supply container 44. Instead of the nanofluid 51, the nanoparticles themselves may be enclosed in the nanoparticle holding container 52.

  FIG. 4 is a perspective view of a container enclosing a nanofluid in the present embodiment.

The nanoparticle holding container 52 is provided with a lid 53 that is lighter than water on the upper surface. Therefore, when the nanoparticle holding container 52 is immersed, the lid 53 is opened by buoyancy, and the internal nanofluid 51 is released into the cooling water. The lid 53 is made of, for example, polypropylene having a density of 0.90 to 0.91 g / cm ² . Even when only nanoparticles are encapsulated in the nanoparticle holding container 52, the lid 53 is opened by buoyancy, and when water enters the nanoparticle holding container 52, the nanoparticles are dispersed in the water. , And released to the outside of the nanoparticle holding container 52.

  FIG. 5 is a perspective view of a container that encloses a nanofluid in a modification of the present embodiment.

  In this modification, a float 54 is attached to a lid 53 of a nanoparticle holding container 52 enclosing the nanofluid 51. The float 54 is formed in a hollow shape, for example. As a result, the density of the lid 53 as a whole is smaller than that of water.

  Even when the nanofluid 51 is sealed in such a nanoparticle holding container 52, when the nanoparticle holding container 52 is immersed in water, the lid 53 is opened by buoyancy, and the internal nanofluid 51 is placed in the cooling water. Released.

  Also in the present embodiment, when an accident occurs, the cooling water is supplied from the water tank that supplies the cooling water to the core melt cooling device 7, and when water is injected, the fluid containing the nanoparticles, or the nanoparticles are in the hands of humans. It is mixed in the cooling water without borrowing anything or using an electrical signal.

  The nanofluid is disposed in the water supply container 44. For this reason, nanoparticles can be supplied in the cooling water of the cooling flow path 43 extending from the water supply container 44 so that precipitation and deposition do not occur. That is, it is possible to prevent a reduction in the effect of the nanofluid due to precipitation and adhesion of nanoparticles in the nanofluid supply path. Further, by holding the nanofluid or nanoparticles in the nanoparticle holding container 52, it is possible to prevent the nanofluid 51 or nanoparticles from being deteriorated and scattered due to environmental conditions during normal operation. In addition, when there is no deterioration due to environmental conditions and there is no air flow that scatters, the nanoparticles can be directly arranged in the cooling flow path 43 of the core melt cooling device 7 without being held in the container. .

  Further, the nanoparticle holding container 52 enclosing the nanoparticles may be formed of a water-soluble material. Even in this case, when the nanoparticle holding container 52 is immersed in the cooling water, the nanoparticle holding container 52 is dissolved in the cooling water, whereby the internal nanoparticles are released to the outside.

[Third Embodiment]
FIG. 6 is an elevational sectional view of the vicinity of the third embodiment of the core melt cooling apparatus according to the present invention.

  The core melt cooling device 7 of the present embodiment has a water tank 62 in which a nanofluid 51 is enclosed. One or a plurality of water tanks 62 enclosing the nanofluid 51 are disposed on the heat insulating material 42. Instead of the nanofluid 51, the nanoparticles themselves may be enclosed in the water tank 62. The water tank 62 in which the nanofluid 51 is sealed is formed of plastic, low melting point metal or resin. Here, the low melting point metal is a metal whose melting point is lower than the temperature of the core melt 41 (see FIG. 1). This water tank 62 is arranged without a gap as a unit divided into a plurality on the upper surface of the heat insulating material 42.

  Also in the present embodiment, when an accident occurs, the cooling water is supplied from the water tank that supplies the cooling water to the core melt cooling device 7. When the core melt 41 falls on the core melt cooling device 7, the water tank 62 in which the nanofluid 51 is sealed melts by conduction heat or radiation heat. Along with this, the nanoparticles encapsulated in the water tank 62 are released to the outside of the water tank 62. In other words, when an accident occurs, the nanoparticles are mixed into the cooling water without any human hand or using an electrical signal. The cooling water mixed with the nanoparticles flows into the water supply channels 46 and 47 from the inlet opening 82 by natural circulation, and flows into the cooling channel 43 through the water supply container 44.

  In the present embodiment, since the nanofluid 51 is disposed on the core melt cooling device 7, it is possible to prevent the nanofluid effect from being reduced due to the precipitation and adhesion of nanoparticles in the nanofluid supply path. In addition, by arranging the water tank 62 filled with the nanofluid 51 as a plurality of divided units without gaps, the heat insulating material 42 is protected from jet erosion when the core melt 41 falls, and manufacturing and construction are easy. It becomes.

[Fourth Embodiment]
FIG. 7 is an elevational sectional view of the vicinity of the fourth embodiment of the core melt cooling apparatus according to the present invention.

  The core melt cooling apparatus 7 of the present embodiment has a nanoparticle holding container 71 in which a nanofluid 51 is enclosed. The nanoparticle holding container 71 is disposed on the upper surface of the heat insulating material 42. The nanoparticle holding container 71 is provided with a lid 72 that is opened when the internal pressure exceeds a predetermined value.

  The nanoparticle holding container 71 enclosing the nanofluid 51 includes a partition provided at an interval above the upper surface of the heat insulating material 42, for example, and the nanofluid 51 is interposed between the partition and the heat insulating material 42. It is a space to enclose. A lid 72 is provided between the outer edge portion of the partition and the heat insulating material 42.

  Also in the present embodiment, when an accident occurs, the cooling water is supplied from the water tank that supplies the cooling water to the core melt cooling device 7. Moreover, the fallen core melt 41 (see FIG. 1) is received in a container 71 in which a nanofluid 51 is enclosed. When the internal pressure of the nanoparticle holding container 71 rises due to an impact when the core melt 41 falls or due to heat transferred from the core melt 41, the lid 72 on the outer periphery of the nanoparticle holding container 71 is opened. As a result, the fluid containing the nanoparticles inside the nanoparticle holding container 71 is ejected without any human hand or without using an electric signal, and is mixed into the cooling water. The cooling water mixed with the nanoparticles flows into the water supply channels 46 and 47 from the inlet opening 82 by natural circulation, and flows into the cooling channel 43 through the water supply container 44.

  In the present embodiment, since the nanofluid 51 is disposed on the core melt cooling device 7, it is possible to prevent the nanofluid effect from being reduced due to the precipitation and adhesion of nanoparticles in the nanofluid supply path. Further, by receiving the core melt 41 by the fluid layer, the impact of the core melt drop can be reduced.

[Other embodiments]
The above-described embodiments are merely examples, and the present invention is not limited to these. Moreover, it can also implement combining the characteristic of each embodiment.

DESCRIPTION OF SYMBOLS 1 ... Reactor pressure vessel, 2 ... Containment vessel, 3 ... Lower head, 4 ... Pressure suppression pool, 5 ... Water tank, 6 ... Containment vessel cooler, 7 ... Core melt cooling device, 8 ... Injection pipe, 10 ... Core , 13 ... Lower dry well, 15 ... Pedestal bed, 16 ... Pedestal side wall, 40 ... Injection valve, 41 ... Core melt, 42 ... Insulation, 43 ... Cooling channel, 44 ... Water supply container, 45 ... Water pool, 46 DESCRIPTION OF SYMBOLS ... Water supply flow path vertical part, 47 ... Water supply flow path horizontal part, 51 ... Nanofluid, 52 ... Nanoparticle holding container, 53 ... Lid, 54 ... Floating, 62 ... Water tank, 71 ... Nanoparticle holding container, 72 ... Lid 81 ... outlet opening, 82 ... inlet opening, 83 ... water injection pipe outlet hole, 91 ... support base, 92 ... cooling channel bottom plate, 93 ... cooling channel top plate

Claims (11)

  A deposition bed that is provided below the reactor pressure vessel and divides an upward deposition surface and a cooling channel below the deposition surface, and at least a part of the side of the deposition bed facing the cooling channel is A core melt cooling device, characterized in that it is made of a porous material that holds nanoparticles in voids. A deposition bed provided below the reactor pressure vessel and separating the upward deposition surface and a cooling flow path below the deposition surface;
A nanoparticle holding container that is disposed in the cooling flow path and contains nanoparticles;
The core melt cooling device is characterized in that when the nanoparticle holding container is immersed in cooling water, the nanoparticles in the container are released into the cooling water.   The core melt cooling device according to claim 2, wherein the nanoparticle holding container is formed of a water-soluble material.   The core melt cooling apparatus according to claim 2, wherein the nanoparticle holding container includes a lid that is opened by buoyancy when immersed in cooling water. A deposition bed provided below the reactor pressure vessel and separating the upward deposition surface and a cooling flow path below the deposition surface;
A nanoparticle holding container disposed on the deposition surface and containing nanoparticles;
A core melt cooling device characterized by comprising:   6. The core melt cooling device according to claim 5, wherein the nanoparticle holding container is formed of any one of plastic, low melting point metal and resin.   The core melt cooling device according to claim 6, wherein a plurality of the nanoparticle holding containers are arranged without gaps.   The core melt cooling device according to any one of claims 5 to 7, wherein the nanoparticle holding container includes a lid that is opened when an internal pressure exceeds a predetermined value. With a pedestal floor,
A pedestal sidewall that rises from the pedestal floor and supports the reactor pressure vessel;
A deposition bed provided on the pedestal floor and partitioning an upward deposition surface and a cooling channel below the deposition surface, wherein at least a part of the side of the deposition bed facing the cooling channel is nano A core melt cooling device formed of a porous material that holds the particles in voids;
A containment vessel. With a pedestal floor,
A pedestal sidewall that rises from the pedestal floor and supports the reactor pressure vessel;
A deposition bed provided on the pedestal floor and partitioning the deposition surface facing upward and a cooling channel below the deposition surface; a nanoparticle holding container disposed in the cooling channel and containing nanoparticles; A core melt cooling device in which the nanoparticles in the container are released into the cooling water when the nanoparticle holding container is immersed in the cooling water,
A containment vessel. With a pedestal floor,
A pedestal sidewall that rises from the pedestal floor and supports the reactor pressure vessel;
A deposition bed that is provided on the pedestal floor and divides an upward deposition surface and a cooling flow path below the deposition surface; and a nanoparticle holding container that is disposed on the deposition surface and stores nanoparticles. A reactor core melt cooling device,
A containment vessel.

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