JP6100649B2 - Reactor core catcher - Google Patents

Description

  The present invention relates to a core catcher of a nuclear reactor installed in a nuclear reactor containment vessel.

  The function of the containment vessel of the nuclear power plant is that even if a serious accident (severe accident) occurs that the core melts, the radioactive material is released from the reactor pressure vessel. It is to prevent leakage around the power plant site by confining the reactor in the reactor containment vessel.

  FIG. 2 shows a longitudinal sectional view of a schematic structure of a reactor building of an improved boiling water reactor (ABWR). The reactor pressure vessel 1 is disposed in a reactor containment vessel 2, and a reactor building 3 is provided on the outer periphery of the reactor containment vessel 2. The reactor containment vessel 2 of the improved boiling water reactor ABWR is made of reinforced concrete lined with a steel liner, and has airtightness to prevent leakage of radioactive materials. The shape of the containment vessel 2 of the improved boiling water reactor is substantially cylindrical. The inside of the reactor containment vessel 2 includes a dry well 4 and a suppression chamber 5 that surround the reactor pressure vessel 1 and the like.

  The dry well 4 and the suppression chamber 5 are partitioned by a diaphragm floor 6 made of reinforced concrete and communicated with each other by a vent pipe 7. When a part of the reactor pressure vessel 1 or piping is damaged and steam is released into the containment vessel 2, the steam released into the dry well 4 passes through the vent pipe 7 and is submerged in the suppression chamber 5. Led to. By condensing the steam with the water in the suppression chamber 5, the pressure increase in the reactor containment vessel 2 is suppressed. In this figure, 8 is a drywell head, 9 is a reactor containment penetration, and 10 is a top slab.

  When a pipe connected to the reactor pressure vessel 1 is broken, cooling water is supplied to the core by starting an emergency core cooling device (not shown) and the core is cooled. However, although there is a very low probability, the reactor containment vessel is made up of concrete with a high-temperature core melt that melts the core due to decay heat due to inadequate core cooling due to failure to start up the emergency core cooling system, etc. 2 may fall onto the lower floor surface 11 of the second floor.

  Even if the core melt falls, if the water is appropriately injected from the upper part thereafter, the core melt is appropriately cooled from the upper surface side by the injected cooling water, and the accident converges. However, when the water injection is insufficient or when the water injection is delayed, the concrete on the floor 11 may be eroded.

  Therefore, a core catcher is one of the devices provided when the core melt falls on the lower floor surface 11 of the reactor containment vessel 2. The core catcher is a safety facility that is installed on the lower floor surface 11 of the reactor containment vessel and receives the core melt and cools it from the lower surface side.

  As prior art relating to the structure of the core catcher, there are Patent Documents 1 to 4. In these patent documents, a cooling water pipe inclined below the floor surface on which the core melt falling from the core accumulates in the event of a severe accident (severe accident) is provided. Means for more heat removal are described. Each of them has a structure in which a tray-like structure is provided below the cooling water pipe, the cooling water pipe is installed thereon, and the cooling water pipe is embedded.

  In the core catchers described in Patent Document 1, Patent Document 2, and Patent Document 3, the cooling water pipes viewed from the top surface are arranged radially, and in the core catcher described in Patent Document 4, the cooling water pipes viewed from the top surface are combed. It is arranged in a mold. In any of the cooling water pipes, the pipe near the outlet is bent in the vertical direction and opens to the lower part of the dry well 4 in the reactor containment vessel 2 to discharge the cooling water and steam. The discharged cooling water is stored on the lower surface 11 of the reactor containment vessel, and the steam remains in the reactor containment vessel 2. This steam is condensed by a containment spray or a containment cooling system, and is finally stored on the lower surface 11 of the reactor containment vessel.

  Moreover, in the core catcher of patent document 1-patent document 3, the exclusive return piping which returns the cooling water stored in the reactor containment vessel lower floor 11 to the core catcher is provided.

JP 2011-174790 A JP 2010-38571 A JP 2007-225356 A JP 2011-128142 A

  The core catcher cools the core melt from the lower surface side by cooling the core catcher itself as the cooling water flows through the cooling water piping inside. In this case, the cooling water is supplied to the core catcher when it is detected that the core melt has fallen into the reactor containment and the ambient temperature in the reactor containment has risen, or to the reactor containment. This is done by detecting that the fall of the core melt is inevitable. Cooling water to the core catcher is supplied from the outside of the containment vessel, supplied from a suppression chamber or a tank placed inside the containment vessel, or the steam in the containment vessel is condensed by a heat exchanger. For example, by supplying fresh water.

  As the above cooling water supply system, there is a system in which a plurality of cooling water pipes are connected to a common header pipe (cooling moisture pipe) or a common cooling water inlet reservoir. In such a system, when there is a bias in the heat load of each pipe, if the outlet of the cooling water pipe is submerged, the cooling water stored on the lower floor of the reactor containment vessel is stored in the upper part of the pipe with a low heat load. In some cases, a loop is formed that sucks in the water and supplies the cooling water to the piping having a high heat load through the cooling moisture piping or the cooling water inlet reservoir. When such a loop is formed, the flow rate of the cooling water supplied to the core catcher increases, and the cooling performance of the core catcher is improved.

  Also, in the core catcher equipped with a dedicated cooling water return pipe that returns the cooling water stored on the lower floor of the reactor containment vessel to the header pipe (cooling moisture pipe) of the core catcher or the cooling water inlet reservoir. As the opening is submerged, there is a flow in which the cooling water stored by the natural circulation force is returned to the cooling moisture pipe or the cooling water inlet reservoir. This can increase the flow rate of the cooling water supplied to the core catcher and improve the cooling performance of the core catcher.

  In any case, the driving force that sucks the stored cooling water and supplies it to the core catcher is a natural circulation force generated by steam generated in the cooling water pipe by the heat of the core melt. The higher the cooling water piping outlet is, the greater the natural circulation force, and the cooling capacity of the core catcher is improved by increasing the amount of cooling water supplied. Similarly, when the cooling water return pipe inlet is at a high place, the natural circulation force increases and the supply amount of cooling water increases.

  On the other hand, if the cooling water pipe outlet or cooling water return pipe inlet is placed at a high place, the amount of cooling water that needs to be injected and the time required for water injection will increase before the water level is created above the inlet or outlet and the water is submerged. To do.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a core catcher for a nuclear reactor capable of improving the cooling performance of the core catcher, reducing the amount of cooling water necessary for improving the cooling performance, and reducing the time required for water injection. And

  In order to achieve the above object, the present invention is applied to a nuclear reactor in which a nuclear reactor core is supported by a dry well wall of a reactor containment vessel, and a core melt generated when the reactor core is melted is contained in the reactor containment vessel. A core catcher of a nuclear reactor installed on the floor of the reactor containment vessel so that the core catcher is received by the floor surface of the reactor containment vessel and the dry well wall at the bottom of the reactor core. A sacrificial layer installed at the bottom of the formed cylindrical space and receiving the core melt on the floor of the reactor containment vessel is arranged in a funnel shape. Cooling water provided at the bottom of the funnel-shaped sacrificial layer A first storage section, a plurality of cooling water pipes branched from the first storage section and arranged in the height direction along the funnel-shaped sacrificial layer and having an upper end opened, and provided on the upper part of the funnel-shaped sacrificial layer The second reservoir of hot cooling water and when the reactor core melts Means for supplying cooling water to the first reservoir of the reject water, and the plurality of cooling water pipes are positioned between the funnel-shaped sacrificial layer and the drywell wall at the rising portion of the funnel-shaped sacrificial layer, The upper position of the cooling water pipe is lower than the upper position of the funnel-shaped sacrificial layer, so that a second reservoir of cooling water is formed around the upper part of the rising portion of the funnel-shaped sacrificial layer. And

  In the present invention, the cooling water is stored in the upper part of the cooling water pipe outlet of the core catcher and in the upper part of the cooling water return pipe if there is a cooling water return pipe, so that the cooling water stored in the upper part is supplied to the core catcher. be able to. The core catcher is cooled more stably by increasing the flow rate of the supplied cooling water.

The conceptual diagram which expands and shows the peripheral part B of FIG. The figure which shows the longitudinal cross-section of the reactor building schematic structure of an improved boiling water reactor. The figure which shows the longitudinal cross-section of the reactor containment vessel lower part which installed the core catcher of Example 1. FIG. The figure which shows the detail of the B section of the core catcher of FIG. The figure which shows the detail of the A section of the core catcher of FIG. The figure which showed the comb-shaped arrangement | positioning example of the cooling water piping group of the core catcher of Example 1. FIG. The perspective view which showed the water pipe wall panel which manufactured the cooling water piping group and the cooling water piping with the water pipe wall. The perspective view of the part enclosed with the dashed-dotted line in FIG. The figure which shows the other division example of a water pipe wall. The figure which shows the longitudinal cross-section of the reactor containment vessel lower part which installed the core catcher of Example 2. FIG. The figure which showed the example of radial arrangement | positioning of the cooling water piping group of the core catcher of Example 3. FIG. The enlarged view which looked at the reactor containment vessel which installed the core catcher of Example 3 from the upper part. The figure which showed the branch radial type | mold arrangement example of the cooling water piping group of the core catcher of Example 4. FIG. FIG. 10 is a longitudinal sectional view of the vicinity of a cooling water pipe outlet of a core catcher according to a fifth embodiment. The enlarged view which looked at the reactor containment vessel which installed the core catcher of Example 5 from the upper part. The longitudinal cross-sectional view of the cooling water piping exit vicinity of the core catcher of Example 6. FIG. The figure which shows the modification of Example 6 of FIG. The enlarged view which looked at the reactor containment vessel which installed the core catcher of Example 7 from the upper part. The longitudinal cross-sectional view of the cooling water piping exit vicinity of the core catcher of Example 8. FIG.

  Details of the embodiment of the core catcher according to the present invention will be described below. In the embodiment, it is described as an example that it is installed in a boiling water reactor having a pressure suppression reactor containment vessel equipped with a suppression chamber, but the core catcher of the present invention can also be applied to other types of reactors. is there.

  A core catcher according to a first embodiment which is one of the preferred embodiments for achieving the above object will be described with reference to FIGS. 1 and 3 to 9.

  FIG. 3 is a longitudinal sectional view of the lower part of the reactor containment vessel 2 in which the core catcher 21 is installed. A core catcher 21 is installed on the lower surface 11 of the reactor containment vessel directly under the reactor pressure vessel 1. A stand 25 is installed in the lower space 19 on the lower floor surface 11 of the reactor containment vessel, and the core catcher 21 disposed thereon has a cooling water pipe 13, a cooling water tank (not shown) and cooling water at the center lower part. A core catcher water supply pipe 14 connected to the pipe 13, a cooling water pipe 12 group connected to the cooling water pipe 13, and a sacrificial layer 15 that receives the core melt 22.

  The sacrificial layer 15 is made of a heat-resistant material, so that erosion due to the core melt 22 can be minimized. However, since the sacrificial layer 15 is in contact with the cooling water pipe 12 and can be expected to be cooled by cooling water, the sacrificial layer 15 may be made of a metal material or concrete instead of a heat-resistant material. A core catcher cooling water inlet 27 is connected to the opposite end of the core catcher water supply pipe 14 connected to the cooling moisture pipe 13, and a core catcher water injection valve 16 is connected to the core catcher cooling water inlet 27. . A cooling water piping outlet 32 is provided in the cooling water piping 12 group of the core catcher. The arrows in the figure indicate the flow of cooling water in the cooling water flow path in the core catcher.

  According to the core catcher of the configuration of FIG. 3, the core melt 22 that falls from the core when a severe accident occurs (severe accident) is received by the sacrificial layer 15. At this time, the occurrence of a severe accident is detected, the core catcher water injection valve 16 installed at the core catcher cooling water inlet 27 is opened, and the cooling water in the upper cooling water tank (not shown) is supplied to the core catcher water supply descending pipe. 14A, led to the cooling moisture pipe 13 at the lower center of the reactor containment vessel through the core catcher water supply pipe 14. The piping path from the cooling water tank to the cooling water piping 13 may be a plurality of systems, but since it is necessary to introduce a large amount of cooling water as soon as possible, it is formed with a pipe that is thicker than the cooling water piping 12. ing. Further, the cooling moisture pipe 13 functions as a header.

  The cooling water pipe 12 extending from the cooling water pipe 13 at the center lower part of the reactor containment vessel is composed of a plurality of pipes arranged without gaps on the lower surface of the sacrificial layer 15. It rises gradually toward the reactor containment vessel and forms a rising portion in the vertical direction around the reactor containment vessel. Thereby, it can be said that the plurality of cooling water pipes 12 are arranged in a so-called funnel shape.

  On the other hand, the sacrificial layer 15 that receives the core melt 22 that falls from the core is a top opening structure that is installed inside a funnel shape formed by the plurality of cooling water pipes 12, and is composed of a bottom surface and side surfaces. Yes. For this reason, the bottom face and the side face are cooled by the cooling water in the cooling water pipe 12. In the following description, the side surface of the sacrificial layer 15 is referred to as a cooling water pipe protection wall 31.

  In FIG. 3, the cooling water pipe outlet 32 is the upper end position of the cooling water pipe 12 that forms a rising portion in the vertical direction around the reactor containment vessel. On the other hand, the height of the cooling water pipe protective wall 31 which is the side surface of the sacrificial layer 15 installed inside the funnel-shaped cooling water pipe 12 is set to a position higher than the upper end position of the cooling water pipe outlet 32. Yes.

  In this way, the rising portion of the funnel-shaped cooling water pipe 12 is in contact with the dry well wall surface 30 on the outside and in contact with the cooling water pipe protection wall 31 on the inside. Further, the cooling water pipe outlet 32 is placed at a position lower than the cooling water pipe protective wall 31, so that a circumferential wall is formed in the upper space of the cooling water pipe 12 between the cooling water pipe protective wall 31 and the drywell wall surface 30. Part will be formed.

  FIG. 1 is an enlarged conceptual view of the peripheral portion B of FIG. In the plan view of FIG. 1, the height relationship of the piping and the like is such that the cooling water piping outlet 32 is positioned lower than the cooling water piping protection wall 31. In the top view in the lower part of FIG. 1, it can be understood that the eaves part 100 is configured in the upper space of the cooling water pipe 12 surrounded by the dry well wall surface 30 and the cooling water pipe protection wall 31. As a result, the cooling water branched from the cooling water pipe 13 at the center lower part and rising while cooling the lower surface and the side surface of the sacrificial layer 15 reaches the cooling water pipe outlet 32, gathers at the flange 100, and from the flange 100. The overflowing cooling water is poured into the core melt 22 in the sacrificial layer 15.

  FIG. 4 is a diagram showing details of the B part of the reactor containment vessel 2 in which the core catcher 21 of the present invention is installed, and FIG. 5 is a diagram showing details of the A part of the core catcher 21. As shown in these drawings, a cooling water pipe protection wall 31 is provided inside the vertical portion of the cooling water pipe 12 group, and the upper end of the cooling water pipe protection wall 31 is disposed above the cooling water pipe outlet 32. The cooling water 29 is stored in the cooling water pipe outlet 32 and between the cooling water pipe protection wall 31 and the dry well wall surface 30 in the cooling water outlet storage part 34 (the collar part 100). The cooling water pipe protective wall 31 is manufactured using a heat-resistant material, so that melt erosion can be prevented when the core melt 22 spreading in the lateral direction contacts the cooling water pipe protective wall 31. However, since the cooling water protection wall 31 is in contact with the cooling water pipe 12, it can be expected to be cooled by the cooling water 29, and therefore may be made of concrete instead of a heat-resistant material. Similarly, the wall surface may be made of a metal material such as stainless steel.

  FIG. 6 is a diagram showing an example of a comb arrangement of the cooling water pipe group of the core catcher according to the first embodiment of the present invention. When the cooling water pipe 12 is arranged, it is necessary to efficiently install the cooling water pipe 12 on the entire surface of the circular core catcher 21 when viewed from above and to lay out the cooling leakage portion. In the example of FIG. 6, a thick cooling water pipe 13 having a circular pipe is installed in the central vertical direction, and all the thin cooling water pipes 12 are connected to the cooling water pipe 13 and arranged in the horizontal direction. In the first embodiment, the cooling water pipes 12 are arranged in a comb shape. The cooling water pipe 12 extending in the lateral direction rises up to the peripheral edge and opens at the cooling water pipe outlet 32.

  As a result, the cooling water that has flowed from the cooling water distribution pipe 13 into the cooling water pipe 12 group flows out from the cooling water pipe outlet 32 provided at the outer periphery of the core catcher. In this embodiment, the cooling water pipe 12 group is constituted by a circular pipe, but it may be constituted by a rectangular pipe or a pipe having a cross-sectional shape.

  In the present invention, the cooling water piping 12 group and the cooling moisture piping 13 are manufactured with a water pipe wall, for example. A perspective view of the water tube wall panel 26 is shown in FIG. As shown in FIG. 7, the water pipe wall panel 26 has a panel shape. In the water pipe wall panel 26, a pipe part 17 through which cooling water passes and a wall part 18 connecting the pipe part 17 are integrated. By welding the water pipe wall panels 26 to each other, a structure having an arbitrary size having the cooling water pipe 12 and the cooling water pipe 13 can be created.

  The water tube wall panel 26 can be formed into an arbitrary shape and can also be formed into a curved shape, so that an arbitrary structure shape can be formed with the water tube wall panel 26. Also, the cooling water pipe 12 in the water pipe wall panel 26 can be arbitrarily arranged, and it is possible to adopt a structure in which the cooling water pipe 12 branches in the middle of one water pipe wall panel 26. It is possible to freely form a pipe flow path necessary for cooling.

  The water pipe wall is also used as a wall material for structures such as boilers that require cooling of the wall surface, and the water pipe wall alone has sufficient strength as a structural material. In order to prevent corrosion in the pipe portion, the water pipe wall 12 is generally made of stainless steel.

  Further, the water pipe wall panel 26 can be manufactured in an arbitrary size. The cooling water flow path created on the water pipe wall is divided into sizes suitable for transportation and manufactured in advance at the factory, and at the installation site, the water pipe wall panels 26 are welded to reduce the man-hours for installation work at the site. It can be minimized, and on-site workability can be improved.

  An example of the division of the water pipe wall panel 26 will be described with reference to FIGS. A dotted line in FIG. 6 represents a divided portion of the water tube wall panel 26. In the embodiment of FIG. 6, for example, a panel is formed at a dotted line. The horizontal direction shown in the drawing is divided into three parts, that is, a left and right part composed only of the cooling water pipe 12 and a part including the central cooling water distribution pipe 13, and each part is divided into six parts in the vertical direction shown in the drawing. The core catcher 21 is made of an 18-divided panel which is constructed and manufactured by the wall panel 26 and welded and joined in the field.

  FIG. 8 is a perspective view of a portion surrounded by a one-dot chain line in FIG. By creating the cooling flow path with the water pipe wall, a structure in which the wall surface structure and the cooling water pipe are integrated can be obtained. The water pipe wall panel 26 is manufactured at the factory, and the water pipe wall is welded at the time of installation on site.

  FIG. 9 shows another example of dividing the water pipe wall. FIG. 9 is a diagram showing a case where the core catcher cooling water flow path is divided into 12 at the dotted line portion. The portion including the cooling water distribution pipe 13 at the center is divided into left and right parts and further divided into six parts in the vertical direction shown in the drawing, and each part is constituted by a water pipe wall panel 26 and joined. In this way, the number of panels and the panel shape can be arbitrarily designed, and it may be divided so as to have a division number and a size that improve workability comprehensively including on-site man-hours.

  When constructing the core catcher 21 on site, a plurality of water pipe wall panels 26 manufactured at the factory are arranged on a gantry 25 installed on the lower floor surface 11 of the reactor containment vessel. And the sacrificial layer 15 is disposed thereon.

  In this embodiment, the core catcher cooling water flow path is made of a water pipe wall from the viewpoint of workability, but the effect of the wall structure of the present invention can be expected even when the core catcher cooling water flow path is made by a conventional method of connecting pipes.

  The operation of the core catcher according to the present invention will be described again with reference to FIGS. In FIG. 3, when the core is melted in the reactor pressure vessel 1, the core melter 22 falls on the core catcher 21 by melting and penetrating the lower part of the reactor pressure vessel 1. The core melt 22 is deposited on the sacrificial layer 15 formed on the cooling water pipe 12 around the cooling water pipe 13.

  Water is poured into the cooling moisture pipe 13 by gravity dropping from a cooling water tank (not shown) located above the core catcher 21 through the core catcher water supply pipe 14. The core catcher water supply pipe 14 is provided with a melting valve as the core catcher water injection valve 16, and the core melt 22 falls on the lower floor 12 of the reactor containment vessel, and the increase in the ambient temperature in the reactor containment vessel 2 and Due to the radiant heat from the core melt 22, when the core catcher water injection valve 16 is heated, the partition of the water injection valve 16, which is a melting valve, is melted and water injection is started. In this embodiment, the core catcher water injection valve 16 is a melting valve, but may be another type of valve such as a blast valve.

  After the start of water injection, the cooling water flowing into the core catcher cooling water piping 12 group boils in the flow path to cool the core catcher 21 and becomes a two-phase flow of water and steam and is discharged from the cooling water piping outlet 32. The The discharged cooling water is stored in the cooling water outlet storage 34 (ie, the collar 100) formed at the upper part of the cooling water pipe outlet 32 and between the cooling water pipe protection wall 31 and the dry well wall 30. It flows onto the core melt 22 on the lower floor 12 of the reactor containment vessel, boils by the decay heat of the core melt 22, and cools the core melt 22 from its upper surface by its latent heat.

  The cooling water stored in the cooling water outlet storage 34 between the cooling water piping protective wall 31 and the dry well wall 30 is cooled with a low thermal load depending on the condition of the thermal load on the cooling water piping 12 by the core melt 22. The cooling water flow rate of the core catcher can be increased by being sucked from the water pipe 12 and supplied to the cooling water pipe 12 having a high heat load through the cooling moisture pipe 13.

  The phenomenon in which the cooling water is supplied from the low heat load pipe to the high pipe does not occur unless the cooling water pipe outlet 32 is submerged. Further, as this phenomenon, the higher the position of the cooling water piping outlet 32 is, the stronger the natural circulation force is, and the flow rate of the cooling water is increased.

  In the core catcher having the conventional structure, in order for the cooling water piping outlet 32 to be submerged, the entire lower space of the dry well 4 needs to be filled with cooling water, and the water surface needs to be formed above the cooling water piping outlet 32. Further, when the cooling water pipe outlet 32 is arranged at a high place with the aim of enhancing the cooling capacity, the amount of cooling water required for flooding and the time required for water injection are increased.

  However, in the core catcher of the present invention, the cooling water pipe protective wall 31 is provided, and the upper end of the wall surface is located above the cooling water pipe outlet, so that the cooling water is provided between the cooling water pipe protective wall 31 and the dry well wall surface 30. The outlet storage part 34 (the collar part 100) can be provided, and by having a structure in which the cooling water is stored in the space, the space below the dry well 4 is started before the suction of the water stored in the upper part of the cooling water pipe outlet 32 is started. It is not necessary to fill the whole with cooling water, and it is sufficient that water exists in the cooling water outlet storage 34. Moreover, since this cooling water outlet storage part 34 is significantly smaller than the dry well 4 space, the amount of cooling water required to form a water level in that part is small, and the time required for it is also greatly reduced. Therefore, the cooling capacity of the core catcher can be improved with a smaller cooling water injection amount and water injection time.

  The steam discharged from the cooling water pipe 12 group and the steam generated in the process of cooling the upper surface are cooled by a containment cooling system such as a static containment cooling system (not shown) above the reactor containment vessel 2. , Condensed and returned to the cooling water tank. The cooling water returned to the cooling water tank is again supplied to the core catcher 21 by gravity.

  The steam in the reactor containment vessel 2 may be condensed by a containment vessel spray system (not shown), and the condensed water in that case contributes to cooling by flowing onto the core melt 22.

  Thus, the cooling water is circulated, whereby the cooling of the core melt 22 is continued. As the sacrificial layer 15, which is also a heat resistance material, becomes thinner due to erosion by the core melt 22, the heat removal amount of the core catcher 21 increases, and therefore the sacrificial layer when the heat removal capability becomes greater than the heat generation amount of the core melt 22. 25 erosion is suppressed.

  Since the core melt 22 is held by the core catcher 21 and is cooled from the lower surface side, it is possible to prevent pressure breakage of the reactor containment vessel 2 and melting penetration of the reactor containment vessel lower floor 11. Radioactive materials released out of the containment vessel 2 are minimized.

  In the first embodiment, the cooling water source of the core catcher 21 is a cooling water tank disposed above the core catcher. However, the water in the suppression chamber 5 may be used as the cooling water source. By disposing the cooling water piping outlet 32 below the water surface of the suppression chamber 5, it is possible to inject cooling water into the core catcher 21 without using a dynamic device as in the case of the cooling water tank disposed at the top.

  Further, the water injection method into the cooling water pipe 12 in the core catcher 21 is not limited to the static water injection by gravity in the present embodiment, but a dynamic water injection facility such as a pump driven by electric power or a turbine (not shown). Water). Further, a facility (not shown) may be provided outside the storage container 2 and a facility capable of pouring water by connecting an emergency pump to the connection port may be provided.

  In addition, since it is not necessary to arrange the pipes without gaps by using the water pipe wall, only the pipes that pass through the center with a large amount of necessary heat removal are thickened, and the pipes that are arranged near the end where the amount of heat removal may be small are thin. It is also easy to arrange densely the pipes passing through the central part and roughly arrange the pipes arranged toward the ends, so that the cooling performance can be optimized. In FIG. 6, the cooling water pipe 12 is a straight pipe, but it may be formed as a tapered flow path with a narrow central portion and a thickened end to reduce pressure loss. By using the water pipe wall in this manner, the arrangement of the core catcher cooling water pipe 12 can be optimized, the cooling performance can be improved, and the core catcher 21 can be downsized.

  Since the existing core catcher requires a tray-like structure in addition to the cooling water pipe 12, the weight of the upper structure of the core catcher 21 is larger than the core catcher 21 of the present invention. Therefore, it is necessary to install a large mount 25 or to spread concrete under the cooling water pipe 12 group to support the cooling water pipe 12 group.

  However, since the water pipe wall has sufficient structural strength and functions as a structural material by itself, in the core catcher of the present invention, the water pipe wall panel 26 made of the water pipe wall is provided on the lower surface side of the cooling water pipe 12 group. Only the minimum structure to be fixed is required, and installation is easy. Also, since there is no need to fill the lower part with concrete, there is a core catcher lower space 19 as shown in FIG. 3, so that water is poured into this core catcher lower space 19 or overflowed cooling water flows into the lower part. Thus, the cooling water channel can be further cooled from the lower surface side, and the cooling performance can be improved.

  A core catcher 21 according to a second embodiment of the present invention will be described with reference to FIG. FIG. 10 is a cross-sectional view of the lower part of the containment vessel according to the second embodiment of the present invention. In this embodiment, since the water pipe wall can be easily formed into an arbitrary shape in the factory, the cooling water flow path is arranged with a curvature.

  When the core catcher cooling water flow path is manufactured as a straight pipe, a large bend can be made in the flow path such as a corner in the pipe connection portion as shown by A part in FIG. If there is such a large bend in the flow path, the local pressure loss may increase and the flow distribution may be uneven, or the heat removal performance may be uneven depending on the location. In particular, since the cooling water in the cooling water pipe 12 is a two-phase flow of steam and water, if the local pressure loss is large, the flow becomes unstable and the heat removal performance may fluctuate.

  By forming the cooling water flow path using the water pipe wall as in the second embodiment, a cooling water flow path having a smooth curvature with a small pressure loss as shown in FIG. Instability can be suppressed.

  Also in the case of the core catcher 21 having the structure of the second embodiment, the cooling water is stored in the cooling water outlet storing portion 34 between the cooling water piping protective wall 31 and the dry well wall 30 at the upper part of the cooling water piping outlet 32 according to the present invention. Provide. And by this structure, it is not necessary to fill the entire lower space of the dry well 4 with the cooling water until the start of the suction of the water stored in the upper part of the cooling water pipe outlet 32, and there is only water in the cooling water outlet reservoir 34. Then the suction of water starts.

  Since this cooling water outlet storage 34 is much smaller than the space below the dry well 4, the amount of cooling water required to form a water level in that portion is small, and the time required for it is also significantly less. The cooling capacity of the core catcher can be improved by the amount of water and water injection time. Further, when the cooling water pipe outlet 32 is arranged at a higher location and the cooling water flow rate is increased, the amount of water injection and the water injection time are not increased, so that the cooling water piping outlet 32 is arranged at a higher location. The cooling performance can be improved.

  A core catcher 21 according to a third embodiment of the present invention will be described with reference to FIGS. FIG. 11 is a top view of the cooling water pipe 12 group of the core catcher 21 according to the third embodiment of the present invention. Moreover, FIG. 12 is the enlarged view which looked at the reactor containment vessel 2 which installed the core catcher 21 in connection with Example 3 of this invention from the upper part.

  In Example 3, the cooling water inlet storage part 20 is installed in the center part, and the cooling water piping 12 group is drawn out from there radially, and a cooling water flow path is comprised. The cooling water pipes 12 can be densely arranged in the central portion where the core melt 22 that falls to the upper part is large by making it radial.

  In this embodiment, the cooling water pipe 12 is a straight pipe, but it can also be formed as a tapered flow path having a narrow central portion and a thick end at the end in order to reduce pressure loss. In this case, the cooling performance can be optimized. Further, in the case of the radial cooling water pipe arrangement as shown in FIG. 11, it is easy to arrange the vertical portions of the cooling water pipe 12 densely compared to the comb arrangement, so that the cooling power in this portion can be increased. It becomes. In the case of the comb-shaped arrangement of FIGS. 4 and 6, the interval between the cooling water pipes 12 becomes sparse in the upper and lower parts in the height direction of FIG. Thus, all the intervals can be made uniform in the radial arrangement of the third embodiment. In the third embodiment, the cooling water pipe 12 group is constituted by a circular pipe, but may be constituted by a rectangular pipe or a pipe having another cross-sectional shape.

  A dotted line in FIG. 11 represents a divided portion of the water tube wall panel 26. In this embodiment, the core catcher 21 is divided by a line segment passing through the center, and is constituted by, for example, 12 divided panels. In this embodiment, the number of divisions is twelve. However, these can be set so that the number of divisions and the size are improved so that the workability is improved comprehensively including the man-hours at the site. The core catcher 21 of the third embodiment can have a cooling water flow path having a configuration as shown in the first or second embodiment.

  Also in the case of the core catcher 21 having the structure as in the third embodiment, the cooling water is stored in the cooling water outlet storage portion 34 above the cooling water pipe outlet 32 and between the cooling water pipe protection wall 31 and the dry well wall surface 30 according to the present invention. Provide structure. And by this structure, it is not necessary to fill the entire lower space of the dry well 4 with the cooling water until the start of the suction of the water stored in the upper part of the cooling water pipe outlet 32, and there is only water in the cooling water outlet reservoir 34. Then the suction of water starts. Since this cooling water outlet storage 34 is much smaller than the space below the dry well 4, the amount of cooling water required to form a water level in that portion is small, and the time required for it is also significantly less. The cooling capacity of the core catcher can be improved by the amount of water and water injection time. Further, when the cooling water pipe outlet 32 is arranged at a higher location and the cooling water flow rate is increased, the amount of water injection and the water injection time are not increased, so that the cooling water piping outlet 32 is arranged at a higher location. The cooling performance can be improved.

  A core catcher according to a fourth embodiment of the present invention will be described with reference to FIG. FIG. 13 is a top view of the cooling water pipe 12 group of the core catcher 21 according to the fourth embodiment of the present invention. The cooling water flow path of this embodiment has a shape in which the cooling water inlet storage section 20 is installed at the center, the cooling water piping 12 group is drawn out radially therefrom, and the cooling water flow path is divided into two branches on the way. .

  The cooling water piping 12 can be arranged densely by branching the cooling water piping 12 in the middle, and the cooling performance of the core catcher 21 is improved. The water pipe wall panel 26 of the cooling water flow path having such a branch is also easy to manufacture. In the fourth embodiment, one branch is branched into two, but it is possible to branch from one branch into three or more branches. Moreover, you may branch several times on a flow path. In this case, the cooling water pipes 12 can be arranged more densely.

  In the fourth embodiment, the cooling water pipe 12 group is constituted by a circular pipe, but may be constituted by a rectangular pipe or a pipe having another cross-sectional shape. Further, the core catcher 21 according to the fourth embodiment can have a cooling water flow path having a configuration as shown in the first or second embodiment.

  In the existing technology, when the cooling water pipes 12 are branched into a plurality of parts as described above, a complicated welding operation for the branched part is required on site. By manufacturing the water pipe wall panel 26 having the cooling water pipe 12 branched in advance using the water pipe wall, the water pipe wall panel 26 can be installed by simple welding at the time of installation work, and the workability is improved.

  A dotted line in FIG. 13 represents a divided portion of the water tube wall panel 26. In the present embodiment, the core catcher 21 is composed of a central portion and a water pipe wall panel 26 that is divided into six in the circumferential direction and divided into seven in total. These can be set so that the number of divisions and the size are improved so as to improve the workability comprehensively, including on-site man-hours.

  Also in the case of the core catcher 21 having the structure as in the fourth embodiment, the cooling water is stored in the cooling water outlet storage section 34 between the cooling water pipe outlet 32 and the cooling water pipe protection wall 31 and the dry well wall 30 according to the present invention. Provide structure. And by this structure, it is not necessary to fill the entire lower space of the dry well 4 with the cooling water until the start of the suction of the water stored in the upper part of the cooling water pipe outlet 32, and there is only water in the cooling water outlet reservoir 34. Then the suction of water starts. Since this cooling water outlet storage 34 is much smaller than the space below the dry well 4, the amount of cooling water required to form a water level in that portion is small, and the time required for it is also significantly less. The cooling capacity of the core catcher can be improved by the amount of water and water injection time. Further, when the cooling water pipe outlet 32 is arranged at a higher location and the cooling water flow rate is increased, the amount of water injection and the water injection time are not increased, so that the cooling water piping outlet 32 is arranged at a higher location. The cooling performance can be improved.

  A core catcher according to a sixth embodiment of the present invention will be described with reference to FIGS. 14 is a longitudinal sectional view of the vicinity of the cooling water pipe outlet 32 of the core catcher 21 according to the fifth embodiment of the present invention. FIG. 15 is a top view of the reactor containment vessel 2 in which the core catcher 21 according to the fifth embodiment of the present invention is installed. It is an enlarged view.

  The core catcher 21 of the present embodiment can have a cooling water flow path configured as shown in the first or second embodiment. Here, the flow path unique to Example 5 added to the configuration shown in Example 1 or Example 2 will be described. In the core catcher 21 of the fifth embodiment, the cooling water return pipe 35 is installed, so that the core catcher 21 is stored in the cooling water outlet storage section 34 above the cooling water pipe outlet 32 and between the cooling water pipe protection wall 31 and the drywell wall surface 30. A structure in which the cooling water 29 is sucked and returned to the cooling water pipe 13 of the core catcher or the cooling water inlet reservoir 20 is added to the cooling water flow path of the core catcher 21 described in the first to fourth embodiments. .

  The cooling water return pipe 35 sucks the cooling water 29 stored above the cooling water return pipe inlet 36 and returns it to the cooling water pipe 13 of the core catcher 21 or the cooling water inlet reservoir 20 to cool the core catcher 21. The flow rate of the cooling water 29 flowing through the water pipe 12 group can be increased, and the cooling performance of the core catcher 21 can be improved. Further, the cooling water pipe outlet 32 and the cooling water return pipe inlet 36 are sucked in more cooling water 29 due to an increase in natural circulation power when arranged at a high place, so that the cooling water pipe 13 or the cooling water inlet storage section is sucked. 20 can be supplied.

  As shown in FIG. 15, the cooling water pipe outlet 32 and the cooling water return pipe inlet 36 open outside the cooling water pipe protection wall 31 and inside the dry well wall surface 30. Further, as shown in FIG. 14, the cooling water pipe outlet wall 32 and the cooling water return pipe according to the present invention are arranged by arranging the upper end of the cooling water pipe protection wall 31 above the cooling water pipe outlet 32 and the cooling water return pipe inlet 36. The cooling water is stored in the cooling water outlet reservoir 34 between the cooling water pipe protection wall 31 and the dry well wall 30 above the inlet 36.

  With this structure, it is not necessary to fill the entire lower space of the dry well 4 with the cooling water before the suction of the water stored in the upper part of the cooling water pipe outlet 32 and the cooling water return pipe inlet 36 is started, and this cooling water outlet storage part 34 If water is present in the water, suction of cooling water is started.

  The cooling water outlet storage 34 is much smaller than the space below the dry well 4, so that the amount of cooling water required to form a water level in that portion is small and the time required for it is much less. The cooling capacity of the core catcher can be improved by the amount and time of water injection. Further, when the cooling water pipe outlet 32 and the cooling water return pipe inlet 36 are arranged at a higher location and the cooling water flow rate is increased, the water injection amount and the water injection time are not increased. The cooling performance can be improved by arranging the water return pipe inlet 36 at a higher position.

  The structure having the cooling water return pipe 36 can be applied to the core catcher having the cooling water flow path obtained by combining the first to fourth embodiments and the fourth embodiment.

  A core catcher according to a sixth embodiment of the present invention will be described with reference to FIGS. FIG. 16 is a longitudinal sectional view of the vicinity of the cooling water pipe outlet 32 of the core catcher 21 according to the sixth embodiment of the present invention, and FIG. 17 shows a modification of the sixth embodiment of the present invention.

  The core catcher 21 of the sixth embodiment can have a cooling water flow path having a configuration as shown in the first, second, or fifth embodiment. Here, the flow path unique to Example 6 added to the configuration of Example 1, Example 2, or Example 5 will be described.

  The core catcher 21 according to the sixth embodiment has a structure in which the cooling water is stored in the cooling water outlet storage portion 34 above the cooling water pipe outlet 32 and between the cooling water pipe protective wall 31 and the dry well wall surface 30. A cooling water outlet storage part water injection pipe 33 capable of direct water injection is connected to the storage part 34. 16 and 17, the cooling water return pipe 35 is not illustrated, but a system including the cooling water return pipe 35 may be used.

  The cooling water pipe 12 group may be a comb-like arrangement as in the first embodiment or a radial arrangement as in the third or fourth embodiment.

  By pouring water from the cooling water outlet storage portion water injection pipe 33 to the cooling water pipe storage portion 34, the cooling water pipe outlet 32 and / or the cooling water return pipe inlet 36 can be quickly flooded. The water supply source used for water injection from the cooling water outlet reservoir water injection pipe 33 may use the water in the suppression chamber 5 in addition to the cooling water tank disposed above the cooling water outlet reservoir 34. In this case, the surface of the suppression chamber 5 needs to be higher than the cooling water outlet reservoir 34. In addition to static water injection by gravity, water may be injected by dynamic water injection equipment (not shown) such as a pump driven by electric power or turbine drive. Further, a facility (not shown) may be provided outside the storage container 2 and a facility capable of pouring water by connecting an emergency pump to the connection port may be provided. Further, as shown in FIG. 15, the cooling water outlet storage portion water injection pipe 33 and the cooling water outlet storage portion 34 are not directly connected, and the cooling water from the cooling water outlet storage portion water injection pipe 33 flows into the cooling water outlet storage portion 34. Also good.

  A core catcher according to a seventh embodiment of the present invention will be described with reference to FIG. FIG. 18 is an enlarged view of the reactor containment vessel 2 provided with the core catcher 21 according to the seventh embodiment of the present invention as viewed from above.

  In the core catcher 21 of the present embodiment, a space is also provided between the cooling water piping protective wall 31 and the dry well wall surface 30 and between the cooling water piping 12 below the cooling water piping outlet 32, so that the cooling water is provided in this region. The structure will flow in. With this structure, the time until the cooling water pipe outlet 32 is submerged slightly increases. However, since the cooling water pipe protective wall 31 can be cooled from the back, lateral erosion caused by the core melt 22 is further reduced. Can be prevented. This structure can also be used in the core catcher 21 of the first to sixth embodiments.

  A core catcher according to an eighth embodiment of the present invention will be described with reference to FIG. FIG. 19 is a longitudinal sectional view of the vicinity of the cooling water pipe outlet of the core catcher according to the eighth embodiment of the present invention.

  In the core catcher 21 of the present embodiment, the cooling water piping protective wall 31 is divided in the height direction, and the cooling water piping protective wall is provided only in the vicinity of the cooling water piping outlet 32 and in the range where it may come into contact with the core melt 22. 31 is arranged. When the core catcher 21 is installed, the space volume of the dry well 4 is reduced. The core catcher 21 of the present embodiment can suppress the decrease in the space volume of the dry well 4. This structure can also be used in the core catcher 21 of the first to seventh embodiments.

  Through the embodiments described above, in the present invention, when there is a cooling water pipe outlet upper part of the core catcher, and when there is a cooling water return pipe, the cooling water is stored in the upper part of the cooling water return pipe inlet so that the cooling water is stored in the upper part. Water can be supplied to the core catcher. The core catcher is cooled more stably by increasing the flow rate of the supplied cooling water.

  If the cooling water pipe outlet or the cooling water return pipe inlet or both of them are arranged at a higher place, the natural circulation force increases, so that the flow rate for sucking water stored in the upper portion increases. Therefore, when the cooling water pipe outlet and / or the cooling water return pipe inlet is arranged at a higher location, the flow rate of the cooling water supplied to the core catcher increases, so that the core catcher is cooled more stably.

  However, due to the high location, the amount of water required until the cooling water pipe outlet and / or the cooling water return pipe inlet, or both, is submerged by the water injection, and the time required for water injection also increases. Therefore, in the present invention, a wall surface is provided on the inner side from the cooling water pipe outlet, and the end of the wall surface is provided above the cooling water pipe outlet and, if there is a cooling water return pipe, provided above the cooling water return pipe inlet. The cooling water is stored in a limited region between the inner wall surface and the outer dry well wall surface.

  If the core melt falls, the cooling water is stored in that area prior to the dry well lower space, so that if there is a cooling water pipe outlet and a cooling water return pipe, return the cooling water. The pipe inlet is faster than the conventional structure and can be submerged with a small amount of water injection. Thus, the cooling water return pipe inlet and the cooling water return pipe inlet can be arranged at a high place when there is a cooling water pipe outlet and a cooling water return pipe without sacrificing the water injection amount and the time required for water injection.

  As described above, according to the present invention, the cooling performance of the core catcher can be improved, the amount of water required for water injection to the core catcher and the time required for water injection can be reduced, and the soundness of the reactor containment vessel in the event of a severe accident can be reduced. The safety of the nuclear power plant can be improved by maintaining the characteristics.

1: Reactor pressure vessel, 2: Reactor containment vessel, 3: Reactor building, 4: Dry well, 5: Suppression chamber, 6: Diaphragm floor, 7: Vent pipe, 8: Dry well head, 9: Reactor containment penetration part, 10: Top slab, 11: Reactor containment lower floor, 12: Cooling water piping, 13: Cooling water piping, 14: Core catcher water supply piping, 15: Sacrificial layer, 16: Core catcher Water injection valve, 17: pipe part, 18: wall part, 19: lower space, 20: cooling water inlet reservoir, 21: core catcher, 22: core melt, 25: mount, 26: water pipe wall panel, 27: Core catcher cooling water inlet part, 29: cooling water, 30: drywell wall surface, 31: cooling water pipe protective wall, 32: cooling water pipe outlet, 33: cooling water outlet reservoir injection pipe, 34: cooling water outlet reservoir 3 : The return cooling water pipe, 36: cooling water return pipe inlet

Claims (9)

The reactor core is applied to a nuclear reactor that is supported by a dry well wall of a containment vessel, and the nuclear melt generated when the reactor core is melted is received on the floor surface of the containment vessel. A core catcher for a nuclear reactor installed on the floor of a containment vessel,
A core catcher is installed at the bottom of the reactor core, at the bottom of a cylindrical space formed by the floor surface of the reactor containment vessel and the drywell wall, and the core melt is placed on the floor surface of the reactor containment vessel. The sacrificial layer for receiving is arranged in a funnel shape,
A funnel-shaped sacrificial layer is disposed around the height direction of the funnel-shaped sacrificial layer, is branched from a first reservoir of cooling water provided at the bottom of the funnel-shaped sacrificial layer, and is disposed in the height direction along the funnel-shaped sacrificial layer. A cooling water pipe group composed of a plurality of cooling water pipes having an opening is disposed in contact with the dry well wall;
The upper end position of the funnel-shaped sacrificial layer is higher than the upper end position of the cooling water pipe group constituted by the plurality of cooling water pipes, so that the cooling between the funnel-shaped sacrificial layer and the dry well wall is performed. A second reservoir of cooling water is formed in the upper part of the water pipe group, and the cooling water is supplied to the first reservoir of the cooling water through a coolant supply means when the reactor core melts. Reactor core catcher. A reactor core catcher according to claim 1,
The core catcher for a nuclear reactor according to claim 1, wherein the cooling water pipe group is composed of water tank wall panels in which hook parts and wall parts are alternately arranged. A reactor core catcher according to claim 1 or claim 2,
The core catcher of a nuclear reactor, wherein the first reservoir of the cooling water is arranged in a straight line, and is arranged in a comb shape having a plurality of cooling water pipes connected to the left and right thereof. A reactor core catcher according to claim 1 or claim 2,
The core catcher for a nuclear reactor, wherein the first reservoir of the cooling water is arranged in a central portion and is arranged in a radial shape in which a plurality of cooling water pipes are connected radially from the central portion. A core catcher for a nuclear reactor according to claim 4,
The core catcher of a nuclear reactor, wherein the plurality of cooling water pipes arranged in the radial shape are branched into a plurality of pipes on the way to the opening portion. A core catcher for a nuclear reactor according to any one of claims 1 to 5,
A core catcher for a nuclear reactor, wherein a return pipe is installed in the cooling water pipe group between the first storage part of the cooling water and the second storage part of the cooling water . A reactor core catcher according to claim 6,
The core catcher of a nuclear reactor, wherein the return pipe is disposed in a path away from the funnel-shaped sacrificial layer. A core catcher for a nuclear reactor according to any one of claims 1 to 7,
A core catcher for a nuclear reactor, comprising means for injecting cooling water into the lower part of the reactor core through the dry well wall. A core catcher for a nuclear reactor according to any one of claims 1 to 8,
The plurality of cooling water pipes are positioned between the funnel-like sacrificial layer and the dry well wall at the rising portion of the funnel-like sacrificial layer, and the upper position of the plurality of cooling water pipes is the upper position of the funnel-shaped sacrificial layer. By forming a lower position than the upper portion of the rising portion of the funnel-shaped sacrificial layer, the second reservoir of the cooling water is formed,
In a part of the rising portion of the funnel-shaped sacrificial layer, a part of the cooling water pipe is not covered with the funnel-shaped sacrificial layer and is in contact with the lower space of the reactor core. Core catcher.

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