JP2014025785A - Core melt holding device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a core melt holding device capable of holding a core melt for a predetermined period of time in spite of heat and chemical reaction of the core melt and being put into a practical use, and being arranged even in the existing reactor.SOLUTION: A core melt holding device is provided below a reactor pressure vessel. The holding device is composed of a metal member including at least one metal material such as tungsten, molybdenum, tantalum and niobium.

Description

  Embodiments described herein relate generally to a core melt holding device.

  In a water-cooled nuclear reactor, if cooling water is no longer supplied into the reactor pressure vessel due to a stoppage of cooling water supply or pipe breakage, the reactor water level falls and the core is exposed, and cooling of this core is not possible. It may be enough. In such a case, the reactor is automatically shut down in response to a signal indicating a drop in water level, and the core is submerged and cooled by injecting coolant through the emergency core cooling system (ECCS), causing a core melting accident. It is designed to prevent it.

  However, it takes a certain amount of time to charge the coolant, and although there is a very low probability, there is a possibility that the emergency core cooling device does not operate and the water injection device to other cores cannot be used. obtain. In such a case, the water level in the reactor pressure vessel remains lowered, and the exposed core is not sufficiently cooled, so the fuel rod temperature rises due to decay heat that continues to occur after the reactor shuts down. In the end, however, it is thought that the core melts.

  When such a situation occurs, the hot core melt (corium) melts down into the lower part of the reactor pressure vessel, and further melts through the lower part of the reactor pressure vessel and falls onto the floor in the containment vessel. . The core melt heats the concrete stretched on the containment floor, reacts with the concrete when the contact surface becomes hot, generates a large amount of noncondensable gases such as carbon dioxide and hydrogen, and melts and erodes the concrete.

  The generated non-condensable gas can be reduced in pressure by cooling in the suppression pool to some extent, but if the amount of generated gas is large, the pressure cannot be reduced sufficiently even by the suppression pool. As a result, the pressure in the containment vessel may be increased, the reactor containment vessel may be damaged, and the containment vessel boundary may be damaged by melting and erosion of concrete. That is, a reaction between the core melt and concrete occurs, and when this reaction continues for a predetermined time, the containment vessel is damaged, and there is a possibility that radioactive substances in the containment vessel are released to the external environment.

  From this point of view, in order to suppress the reaction between the core melt and concrete, the core melt is cooled and the temperature of the contact surface with the concrete at the bottom of the core melt is below the erosion temperature (1500 K for general concrete). (1227 ° C. or lower) or cooling so that the core melt and the concrete do not come into direct contact with each other. As a representative of the latter means, there is a so-called core melt holding device (core catcher). This core melt holding device is a facility for receiving the core melt that has fallen with a heat-resistant material and cooling the core melt in combination with water injection means.

  However, it may take about 10 minutes until the cooling water is supplied from the water injection means. During this time, the core melt must be held only by the core melt holding device. Therefore, extremely high heat resistance is required for the core melt holding device.

  Conventional attempts to construct a core melt holding device using concrete composed mainly of calcium oxide and silicon oxide, or to construct a core melt holding device using tiles of high melting point materials, etc. Has been made. However, when holding the core melt, the temperature of the core melt holding device suddenly rises from room temperature to 2000 ° C., and there is a problem of damage due to thermal stress generated at that time, or the core melt falls. Various damage factors, such as mechanical impacts, are combined.

  In addition, the water-cooled nuclear reactor already installed several decades ago may not be provided with the core melt holding device as described above, and even in such an existing nuclear reactor, the above-mentioned holding is performed from the viewpoint of safety. It is required to incorporate the device. However, since there is not enough work space in the existing nuclear reactor, it has been difficult to assemble the core melt holding device with the tiles as described above.

Japanese Patent Application Laid-Open No. 5-5795 JP-A-6-300880

  The problem to be solved by the present invention is that the core melt can be held for a predetermined time by the heat and chemical reaction of the core melt and can be put to practical use. An object of the present invention is to provide a core melt holding device that can be installed.

  One aspect of the present invention is a core melt holding device provided below a reactor pressure vessel, the holding device including a metal member containing at least one metal material of tungsten, molybdenum, tantalum, and niobium. It is characterized by.

  According to the present invention, the core melt can be held for a predetermined time by the heat and chemical reaction of the core melt and can be put to practical use, and can also be disposed in an existing nuclear reactor. it can.

It is sectional drawing which shows schematic structure of the water-cooled nuclear reactor in 1st Embodiment. It is sectional drawing which expands and shows schematic structure of the core melt holding | maintenance apparatus of the water-cooled nuclear reactor shown in FIG. It is sectional drawing which expands and shows schematic structure of the core melt holding | maintenance apparatus in 2nd Embodiment. It is sectional drawing which expands and shows schematic structure of the other core melt holding | maintenance apparatus in 2nd Embodiment. It is sectional drawing which shows schematic structure of the water-cooled nuclear reactor in 3rd Embodiment. It is sectional drawing which expands and shows schematic structure of the other core melt holding | maintenance apparatus in 4th Embodiment.

  Hereinafter, details of the present invention and other features and advantages will be described based on embodiments with reference to the drawings.

(First embodiment)
1 is a cross-sectional view showing a schematic configuration of a water-cooled nuclear reactor in the present embodiment, and FIG. 2 is an enlarged cross-sectional view showing a schematic configuration of a core melt holding device of the water-cooled nuclear reactor shown in FIG. It is.

  As shown in FIG. 1, the water-cooled nuclear reactor 10 of the present embodiment includes a reactor containment vessel 11. The reactor containment vessel 11 has an outer wall 111 that is a containment wall for defining the outer shell thereof, and a pair of opposing plate-like fixing members 112 that are provided on the inner side of the outer wall 111 and are erected in the vertical direction. In the internal space S defined by the pair of fixing members 112, the reactor pressure vessel 12 is fixed to the pair of fixing members 112 by the fixing jig 113. Further, the reactor containment vessel 11 has a sump floor 14 below the reactor pressure vessel 12 via a lower dry well 13, and below the sump floor 14 on the bottom (bottom surface) of the outer wall 111. A core melt holding device 15 is provided.

  The lower dry well 13 and the sump floor 14 are not essential constituent elements of the present embodiment, and can be omitted as necessary.

  In addition, a cooling water generator 16 for generating, for example, cooling water by cooling the water vapor generated in the reactor pressure vessel 12 by the cooler 161 is provided in the upper left part of the reactor containment vessel 11. The generated cooling water 16A is sent from the cooling water generator 16 through the pipe 162 to the cooling water storage tank 17 provided below the cooling water generator 16, and stored as cooling water 17A. The cooling water 17 </ b> A is supplied to the cooling water passage of the core melt holding device 15 through the pipe 171. Further, a suppression pool 18 is provided so as to be defined by the outer wall 111 of the storage container 11 and the pair of members 112, and cooling water 18A is stored.

  As shown in FIG. 2, the core melt holding device 15 is formed so as to form a cooling water channel 155 in cooperation with the bottom (bottom) of the outer wall 111 of the reactor containment vessel 11 and the triangular prism-shaped jig 115. A metal member 151 of the mold is included. Note that the jig 115 is also a constituent element of the reactor containment vessel 11, but the jig 115 is provided as an auxiliary to form the cooling water channel 155 in the present embodiment. Is not a mandatory configuration requirement.

  However, by providing the jig 115, the cooling water can be efficiently brought into contact with the cooling surface 151B of the core melt holding device 15, and, as will be described later, is dropped and held on the holding surface 151A. The core melt can be cooled efficiently.

  In the present embodiment, the metal member 151 constituting the core melt holding device 15 needs to be made of at least one metal material of tungsten, molybdenum, tantalum, and niobium. These metals have extremely high melting points at 1 atm of 3422 ° C., 2623 ° C., 3027 ° C. and 2415 ° C., respectively.

  On the other hand, an emergency core cooling system (ECCS) (not shown) does not function sufficiently and a core melting accident occurs, and the core melt generated when the fuel rod temperature rises due to decay heat and core melting occurs. When the lower part of the reactor pressure vessel 12 is melted and dropped, the core melt is held by the holding surface 151 A of the metal member 151 constituting the core melt holding device 15.

  Since the core melt is, for example, a mixture of uranium dioxide, which is a fuel, and zirconium oxide, which is an oxide of a fuel cladding tube, the temperature is about 2500 ° C. Further, in the present embodiment, since the sump bed 14 is provided above the core melt holding device 15, when the mixture penetrates the sump bed 14 and reaches the core melt holding device 15, It reacts with silicon or the like of the concrete constituting the sump floor 14, and the temperature becomes about 1600 to 1700 ° C.

  Therefore, even when the core melt falls on the metal member 151 of the core melt holding device 15, the temperature is sufficiently lower than the melting point of the metal material constituting the metal member 151. As a result, the core melt can be held by the metal member 151, and the core melt penetrates the bottom (bottom surface) of the outer wall 111 of the reactor containment vessel 11, leading to damage to the containment vessel 11. It is possible to avoid a situation in which the radioactive material inside is released to the outside environment.

The thermal conductivity of tungsten, molybdenum, tantalum and niobium constituting the metal member 151 is 174 W / m · K, 138 W / m · K, 57 W / m · K and 53.7 W / m · K, respectively. High value. Therefore, the heat of the core melt held by the holding surface 151A of the metal member 151 is efficiently propagated appropriately from the holding surface 151A toward the cooling surface 151B, and is absorbed by the cooling water flowing through the cooling water channel 155. . Therefore, the temperature of the core melt held on the holding surface 151 </ b> A of the metal member 151 decreases rapidly, and is held more stably on the holding surface 151 </ b> A of the metal member 151.

  Note that alumina, zirconia, and the like constituting conventional ceramic tiles and ceramic blocks exhibit melting points of 2054 ° C. and 2715 ° C. equivalent to the above-described metal materials at 1 atmosphere, but have a thermal conductivity of 30 W / m · K and It is extremely low at 2.7 W / m · K. Therefore, since cooling with cooling water cannot be performed efficiently, in order to maintain the core melt for a relatively long time, it is necessary to make the tiles and blocks into a multilayer structure and to improve the heat resistance strength of these ceramic structures themselves. There is.

  Therefore, the number of ceramic members to be used increases, the size of the core melt holding device increases, and an operator enters an existing nuclear reactor to combine a number of ceramic members to produce a holding device. It is extremely difficult from the viewpoint of the space in the furnace.

  On the other hand, in the present embodiment, the metal member 151 has a high melting point and is made of a metal material having a sufficiently high thermal conductivity as compared with the ceramic member described above. In view of the cooling effect from the cooling surface 151B by water, the thickness of the metal member 151 can be made sufficiently small and downsized. For example, the thickness of the core melt holding device using the conventional ceramic member is about 100 cm, but according to the present embodiment, the thickness can be reduced to about 20 cm.

  Further, the metal member 151 is lighter than the ceramic member described above, and is excellent in workability. Therefore, the holding device 15 can be manufactured relatively easily by entering an existing nuclear reactor.

  Even when the sump bed 14 is not provided as in the present embodiment, the temperature of the core melt is about 2500 ° C., and considering the cooling effect by the cooling water from the cooling surface 151B, the above-described tungsten or the like is used. The core melt can be sufficiently held by the metal member 151 of the holding device 15.

(Second Embodiment)
FIG. 3 is an enlarged cross-sectional view showing a schematic configuration of the core melt holding device of the water-cooled nuclear reactor in the present embodiment. In addition, the same code | symbol is used about the same or the same component as the component shown in FIG.1 and FIG.2. Further, in the present embodiment, as shown in FIG. 3, other configurations, that is, other configurations of the water-cooled nuclear reactor 10 including the reactor containment vessel 11, except that the configuration of the core melt holding device 15 is different. Since this is the same as the configuration shown in FIG. 1, the description thereof is omitted in this embodiment.

  The core melt holding device 25 shown in FIG. 3 cooperates with the bottom (bottom surface) of the outer wall 111 of the reactor containment vessel 11 and the triangular prism-like jig 115 in the same manner as the core melt holding device 15 shown in FIG. In addition, a bowl-shaped metal member 151 that forms a cooling water channel 155 is formed, and a film body 152 formed of a predetermined oxidizing agent is further formed on the metal member 151. 2, the jig 115 is also a constituent element of the reactor containment vessel 11, but the jig 115 is an auxiliary element for forming the cooling water channel 155 in this embodiment. Provided, and is not an essential component of the reactor containment vessel 11.

  However, by providing the jig 115, the cooling water can be efficiently brought into contact with the cooling surface 151B of the core melt holding device 25 and, as will be described later, is dropped and held on the holding surface 151A. The core melt can be cooled efficiently.

  In the present embodiment, the metal member 151 constituting the core melt holding device 15 is made of tungsten, molybdenum, which is a refractory metal material, considering its heat resistance, similarly to the core melt holding device 15 shown in FIG. It is necessary to consist of at least one metal material of tantalum and niobium.

  The core melt produced by the core melting accident caused by the core melting accident due to the core melting accident due to the core melting accident without the emergency core cooling system (ECCS) (not shown) functioning sufficiently When the lower part of the reactor pressure vessel 12 is melted and dropped, the core melt is held by the core melt holding device 25.

  The core melt may contain, for example, stainless steel, that is, iron, chromium, nickel, etc., which is a structure in the reactor, in addition to uranium dioxide which is a fuel and zirconium oxide which is an oxide of a fuel cladding tube. When such a core melt falls directly onto the metal member 151 made of the refractory metal material as described above, the metal component of the core melt and the refractory metal material constituting the metal member 151 are retained. May form a low melting point alloy or a low melting point eutectic, and it may be difficult to hold the high temperature core melt with the metal member 151 alone.

  However, in this embodiment, the film body 152 made of a predetermined oxidant is formed on the metal member 151. Therefore, the core melt comes into contact with the film body 152 before coming into contact with the metal member 151, and the metal component in the core melt becomes a predetermined metal oxide by the film body 152, that is, the oxidizing agent. The metal oxide thus formed does not alloy or eutectic with the refractory metal material constituting the metal member 151. For this reason, the metal member 151 can hold | maintain a high temperature core melt stably, without impairing the original characteristic of the high melting point metal material which is the constituent material. Specifically, the holding surface 151A and the residue that is not subjected to oxidation of the film body 152 are held.

  The metal component of the core melt reacts with the metal member 151 of the core melt holding device 25 to form a low melting point alloy or eutectic, and the metal component of the core melt is oxidized to form a metal oxide. Thus, the phenomenon that the metal member 151 does not react and does not generate the low melting point alloy and the eutectic as described above has been found based on an enormous experiment by the present inventors. Naturally, the discovery of the phenomenon should also be considered as an invention in this embodiment.

  Therefore, in this embodiment, even when the core melt contains a metal component, the core melt is retained when it falls onto the metal member 151 of the core melt holding device 25. The surface 151A can sufficiently hold the core melt, and the core melt penetrates the bottom (bottom surface) of the outer wall 111 of the reactor containment vessel 11 and the containment vessel 11 is damaged. Can be avoided.

  The oxidant constituting the film body 152 preferably has an oxide standard formation energy larger than the oxide standard formation energy of the metal material component constituting the core melt. For example, the metal member 151 is formed as described above. When composed of a refractory metal material, examples include copper oxide (cuprous oxide, cupric oxide, etc.), iron oxide (ferrous oxide, ferric oxide, etc.), alumina, silica, and manganese oxide. be able to. In particular, when copper oxide is used, the metal component in the core melt can be sufficiently oxidized, and the above-described effects can be sufficiently achieved.

  Note that, as in the first embodiment, the refractory metal material such as tungsten constituting the metal member 151 has a relatively high thermal conductivity, and therefore the heat of the core melt held on the holding surface 151A of the metal member 151. Is efficiently transmitted from the holding surface 151A to the cooling surface 151B as appropriate, and is absorbed by the cooling water flowing through the cooling water channel 155. Therefore, the temperature of the core melt held on the holding surface 151 </ b> A of the metal member 151 decreases rapidly, and is held more stably on the holding surface 151 </ b> A of the metal member 151.

  Further, when compared with a conventional ceramic member, its thermal conductivity is extremely high, lightweight and excellent in workability, so that an operator can enter the existing reactor and relatively easily hold the holding device 25. Can be produced.

  The thickness of the film body 152 depends on the type of oxidant constituting the film body 152, but can be, for example, 50 mm to 200 mm. Therefore, even when the core melt holding device 25 has such a film body 152, there is no obstacle to the production of the holding device 25 by the operator in the existing nuclear reactor.

  Further, in FIG. 3, the film body 152 is formed on the entire surface of the metal member 151. However, the film body 152 may be formed only in the central portion of the holding device 25 from which the core melt falls. Good.

  The film body 152 can be formed by a thermal spraying method using a raw material in which a powder of an oxidant as described above is dispersed in a predetermined solvent. It can also be formed by a method such as painting and solidifying.

  FIG. 4 is an enlarged cross-sectional view showing a schematic configuration of another core melt holding device of the water-cooled nuclear reactor according to the present embodiment. In addition, the same code | symbol is used about the same or the same component as the component shown in FIGS. In the present embodiment, as shown in FIG. 4, except for the configuration of the core melt holding device 35, other configurations, that is, other configurations of the water-cooled nuclear reactor 10 including the reactor containment vessel 11 are provided. Since this is the same as the configuration shown in FIG. 1, the description thereof is omitted in this embodiment.

  The core melt holding device 35 shown in FIG. 4 is provided with a plurality of block bodies 153 made of an oxidizing agent instead of the film body 152 made of an oxidizing agent in the core melt holding device 25 shown in FIG. The other configurations are the same as those of the core melt holding device 25 shown in FIG.

  In the core melt holding device 35 shown in FIG. 4 as well, an emergency core cooling device (ECCS) (not shown) does not function sufficiently and a core melting accident occurs, and the fuel rod temperature rises due to decay heat. Then, the core melt generated by melting the core falls through the lower part of the reactor pressure vessel 12 by melting, and the core melt is oxidized by, for example, uranium dioxide as a fuel and an oxide of a fuel cladding tube. In the case of containing stainless steel as an internal structure in addition to zirconium, that is, iron, chromium, nickel, etc., the core melt comes into contact with the plurality of block bodies 153 before coming into contact with the metal member 151, and the core melt The metal component therein becomes a predetermined metal oxide by the block body 153, that is, the oxidizing agent.

  The metal oxide thus formed does not alloy or eutectic with the refractory metal material constituting the metal member 151. For this reason, the metal member 151 can stably hold the core melt at a high temperature without impairing the original characteristics of the refractory metal material that is the constituent material thereof. The original function can be performed.

  Therefore, in the present embodiment, even when the core melt contains a metal component, it is sufficient when the core melt falls on the metal member 151 of the core melt holding device 25. A situation in which the core melt penetrates the bottom (bottom surface) of the outer wall 111 of the reactor containment vessel 11 and the containment vessel 11 is damaged, causing radioactive substances in the containment vessel 11 to be released to the external environment. Can be avoided.

  As the oxidant constituting the block body 153, the same oxidant as that constituting the film body 152 can be used, and copper oxide is particularly preferable as in the case of the film body 152.

  As in the case of the core melt holding device 25 shown in FIG. 3, the refractory metal material such as tungsten constituting the metal member 151 has a relatively high thermal conductivity, so that the holding surface 151A of the metal member 151 The heat of the held core melt is efficiently propagated from the holding surface 151 </ b> A toward the cooling surface 151 </ b> B as appropriate, and is absorbed by the cooling water flowing through the cooling water channel 155. Therefore, the temperature of the core melt held on the holding surface 151 </ b> A of the metal member 151 decreases rapidly, and is held more stably on the holding surface 151 </ b> A of the metal member 151.

  In addition, when compared with a conventional ceramic member, its thermal conductivity is extremely high, lightweight and excellent in workability, so that an operator can enter the existing reactor and relatively easily hold the device 35. Can be produced.

  The plurality of block bodies 153 depends on the type of oxidant constituting the plurality of block bodies 153, but can have a size of, for example, 200 mm × 200 mm × 5 tmm. The same effects as the body 152 are produced.

  Further, the block body 153 can be configured as a molded body obtained by compressing a powder of an oxidizing agent as a raw material, or can be configured as a sintered body obtained by sintering the molded body.

(Third embodiment)
FIG. 5 is a diagram showing a schematic configuration of a water-cooled nuclear reactor in the present embodiment. In addition, the same code | symbol is used regarding the same or the same component as the component shown in FIGS. Further, in the present embodiment, as shown in FIG. 5, the oxidizing agent described in the second embodiment is disposed outside the bottom portion (bottom surface) of the reactor pressure vessel 12 fixed and held in the reactor containment vessel 11. Since the other configuration, that is, the other configuration of the water-cooled nuclear reactor 10 including the reactor containment vessel 11 is the same as the configuration shown in FIG. Then, explanation is omitted.

  In FIG. 5, instead of the film body 151 made of the oxidant formed on the metal member 151 of the core melt holding device 25 of the second embodiment, the film body 121 made of the same oxidant is replaced with the reactor containment vessel. 11 is formed outside the bottom (bottom) of the reactor pressure vessel 12.

  Therefore, an emergency core cooling system (ECCS) (not shown) does not function sufficiently and a core melting accident occurs. The temperature of the fuel rods rises due to decay heat, and the core melt generated by melting the core melts. In the case of containing, for example, uranium dioxide, which is a fuel, and zirconium oxide, which is an oxide of a fuel cladding tube, stainless steel which is an internal structure of the reactor, that is, iron, chromium, nickel, etc. Before reaching the core melt holding device 15 through the bottom (bottom) of the pressure vessel 12, the metal component contained therein reacts in advance with the oxidant formed outside the bottom (bottom) of the reactor pressure vessel 12. Thus, a predetermined metal oxide is obtained.

  Therefore, even when the core melt passes through the bottom (bottom surface) of the reactor pressure vessel 12 and reaches the core melt holding device 15 having the metal member 151 made of a refractory metal material such as tungsten. The metal oxide formed as described above does not alloy or eutectic with the refractory metal material constituting the metal member 151. For this reason, the metal member 151 can stably hold the core melt at a high temperature without impairing the original characteristics of the refractory metal material that is the constituent material thereof. The original function can be performed.

  Therefore, in the present embodiment, even when the core melt contains a metal component, it is sufficient when the core melt falls on the metal member 151 of the core melt holding device 15. A situation in which the core melt penetrates the bottom (bottom surface) of the outer wall 111 of the reactor containment vessel 11 and the containment vessel 11 is damaged, causing radioactive substances in the containment vessel 11 to be released to the external environment. Can be avoided.

  The oxidant to be formed outside the bottom portion (bottom surface) of the reactor pressure vessel 12 may be formed by laying a block body made of the same oxidant instead of the film body 121 as described above. . Also in this case, the same effect as described above can be obtained.

  Further, the size of the film body 121, the size of the block body, and the like can be the same as those in the second embodiment.

  Further, in this embodiment, the core melt holding device shown in the first embodiment is used, and the film body 121 made of an oxidant is formed only outside the bottom (bottom surface) of the reactor pressure vessel 12. However, the core melt holding device shown in the second embodiment is used, and the film body 121 made of an oxidant is provided outside the bottom (bottom surface) of the reactor pressure vessel 12, and the core melt holding device 25 is provided. , 35, a film body 152 made of a similar oxidizing agent may be formed on the metal member 151, and the block body 153 may be laid.

  In this case, the metal component in the core melt can be more reliably converted to the metal oxide, and the core melt can be more reliably held in the core melt holding devices 25 and 35.

  Other features and functions and effects are the same as those in the first embodiment, and a description thereof will be omitted.

  It should be noted that the oxidizing agent having the above-described effects is not the outside of the bottom (bottom surface) of the reactor pressure vessel 12 as in this embodiment, but the generation location of the core melt, the core melt holding device 15, and the like. It can also be provided at any location between. For example, a film body or a block body can be laid on the sump floor 14, or a separate structural material can be formed and formed on the structural material as a film body or a block body.

(Fourth embodiment)
FIG. 6 is an enlarged cross-sectional view showing a schematic configuration of the core melt holding device of the water-cooled nuclear reactor in the present embodiment. In addition, the same code | symbol is used about the same or the same component as the component shown in FIGS. Further, in the present embodiment, as shown in FIG. 6, other than the configuration of the core melt holding device 45 is different, that is, the other configuration of the water-cooled nuclear reactor 10 including the reactor containment vessel 11. Since this is the same as the configuration shown in FIG. 1, the description thereof is omitted in this embodiment.

  The core melt holding device 45 shown in FIG. 6 cooperates with the bottom (bottom surface) of the outer wall 111 of the reactor containment vessel 11 and the triangular prism-shaped jig 115 in the same manner as the core melt holding device 15 shown in FIG. And a corrugated metal member 151 that forms a cooling water channel 155, and further has a corrosion-resistant layer 154 formed below the metal member 151.

  In the core melt holding device 45 of the present embodiment, the cooling surface in contact with the cooling water corresponds to the lower surface 154B of the corrosion resistant layer 154. In general, deionized water via ion-exchange resin is used as the cooling water, but in the event that a core melting accident occurs because the emergency core cooling system (ECCS) (not shown) does not function sufficiently , Seawater may be mixed in the cooling water.

  On the other hand, the metal member 151 constituting the core melt holding device 45 is made of at least one metal material of tungsten, molybdenum, tantalum and niobium which are refractory metal materials, and these refractory metal materials have much corrosion resistance. Is not expensive. Therefore, the metal member 151 may be corroded and deteriorated while the core melt holding device 45 is being used, and the core melt falling from the reactor pressure vessel may not be sufficiently held.

  However, in this embodiment, a corrosion-resistant layer 154 is provided below the metal member 151, and this layer is brought into contact with cooling water. Therefore, even when seawater or the like is mixed into the cooling water as described above, the corrosion of the metal member 151 can be prevented by the presence of the corrosion-resistant layer 154, and thus the above-described problems can be avoided. .

  In addition, as a material which comprises the corrosion-resistant layer 154, organic materials, such as a fluororesin, an eboxy resin, a modified eboxy resin, a polyurethane resin, and an acrylic silicon resin, austenitic stainless steel, a duplex stainless steel, titanium, etc. The metal-based material can be used. Moreover, the thickness of the corrosion-resistant layer 154 can be set to 0.1 mm to 3 mm, for example.

  The corrosion-resistant layer 154 is formed over the entire surface where the metal member 151 contacts the cooling water. The corrosion-resistant layer 154 can be formed using, for example, a general-purpose coating technique or lining technique.

  Moreover, in this embodiment, although the corrosion-resistant layer 154 was provided with respect to the core melt holding | maintenance apparatus 15 of 1st Embodiment regarding FIG. 2, it consists of an oxidizing agent as shown in FIG.3 and FIG.4. The present invention can also be applied to the core melt holding devices 25 and 35 having the film body 152 and the block body 153.

  Other features and functions and effects are the same as those in the first embodiment, and a description thereof will be omitted.

  As mentioned above, although several embodiment of this invention was described, these embodiment was posted as an example and is not intending limiting the range of invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 10 Water-cooled nuclear reactor 11 Reactor containment vessel 12 Reactor pressure vessel 13 Lower dry well 14 Sump bed 15, 25, 35, 45 Core melt holding device 151 Metal member 152 Film body 153 (Oxidizing agent) Block body 154 Corrosion resistant layer 155 Cooling water channel 16 Cooling water generator 17 Cooling water storage tank 18 Suppression pool

Claims (7)

A core melt holding device provided below a reactor pressure vessel,
The holding device for a core melt is characterized by comprising a metal member containing at least one metal material of tungsten, molybdenum, tantalum and niobium.   The core melt holding device according to claim 1, wherein an oxidizing agent is provided on a holding surface of the core melt facing the nuclear pressure vessel of the holding device.   The core melt holding device according to claim 2, wherein the oxide standard generation energy of the oxidant is larger than the oxide standard generation energy of the metal material component constituting the core melt.   4. The core melt holding device according to claim 3, wherein the oxidizing agent is copper oxide.   The core melt holding device according to any one of claims 1 to 4, wherein a corrosion resistant layer is provided on a cooling surface of the holding device in contact with cooling water. A reactor containment vessel for containing a reactor pressure vessel,
A containment wall for defining the outer shell of the reactor containment vessel;
A pair of opposing fixing members provided inside the storage wall and erected in the vertical direction;
A reactor pressure vessel fixed and arranged with respect to the pair of fixing members via a predetermined fixing jig in an internal space defined by the pair of fixing members;
In the internal space, the core melt holding device according to any one of claims 1 to 5, which is provided below the reactor pressure vessel,
A reactor containment vessel characterized by comprising:   The reactor containment vessel according to claim 6, wherein an oxidizing agent is provided on a bottom surface of the reactor pressure vessel.

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