JPH10268078A - In-pile lower part structure of pressurized water reactor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable maintaining melt in the reactor vessel at the step before the progression of a core meltdown accident to a large scale by providing a multitude of ceramic member on the upper surface of lower head in the form without any adverse effects due to coolant flow in the lower plenum. SOLUTION: At the tip end of a lower core support column 31 extended downward from a lower core support plate 11, a lower connection plate 33 practically having no flow hole is horizontally supported. The surface shape of the lower connection plate 33 is circle and the outer edge is close to the inner surface of the lower head part 1a of the reactor vessel main body 1 with a narrow gap. In the space between the lower connection plate 33 and the upper surface of the lower head 1a, a ceramic form 35 is charged. The shape of the ceramic form 35 can be like particle, saddle or cylinder and the material is desired to have high temperature resistivity not to melt out at the coolant temperature during reactor operation. As the ceramic form 35 receives molten core, the lower head 1a is thermally protected and its melting penetration is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a nuclear reactor, and more particularly to a lower structure in a reactor having a function of holding a melt of core components in an accident.

[0002]

2. Description of the Related Art FIGS. 8 and 9 show an example of a conventional structure of a pressurized water reactor. In the figure, the reactor vessel main body 1
The upper opening is closed by a detachable upper lid 3, from which the core vessel 5 is supported by hanging. A horizontal lower core plate 7 is supported below the core tank 5, and a number of fuel assemblies 9 constituting the core are arranged thereon. A lower core support plate 11 is provided below the lower core plate 7 and is horizontally supported from the inner surface of the reactor vessel main body 1. A lower core support column 13 connected to a lower surface of the lower core support plate 11 is provided below the lower core support plate 11. It is connected to the connecting plate 15 and the drop buffer plate 17. Further, a plurality of in-core instrumentation guide tubes 19 connected to the lower core support plate 15 and extending in the vertical direction are aligned with the in-core instrumentation conduits connected and opened to the lower end plate portion of the reactor vessel main body 1. These are connected to each other by an upper connecting plate 21 at an intermediate portion.
The planar shape of the lower connecting plate 15 and the upper connecting plate 21 is designed to form a considerable internal space, as shown in particular in FIG. 9, so that there is no substantial resistance to the coolant flowing therethrough. It has become. During operation of the reactor, the coolant flows into the reactor vessel through the inlet nozzle 23, flows down the annular descending space 25, reverses the flow direction in the lower plenum 27, and Then, it passes through the lower core plate 7 and enters the core, rises while being heated while being in contact with the fuel assembly 9, flows laterally in the upper plenum 28, and flows out through the outlet nozzle 29.

[0003]

In the above-mentioned pressurized water reactor, at the time of a serious accident, the nuclear reaction heat of the reactor core may not be sufficiently removed and a part of the reactor may melt and fall. According to the conventional design concept, a molten core receiving facility called a core catcher is provided directly below the reactor vessel, and when the molten core melts down the reactor vessel and falls through, the vessel is cooled in response thereto. In this way, even if a core melting accident occurs, the core is finally cooled by the core catcher to ensure safety, but lacks the function of preventing the penetration of the reactor vessel by the molten core and preventing the progress of the accident. I hate it. Accordingly, it is an object of the present invention to provide a reactor internal lower structure of a pressurized water reactor capable of holding a melt in a reactor vessel at a stage where a core melting accident does not proceed on a large scale.

[0004]

According to the present invention, in order to solve the above problems, according to the present invention, a reactor vessel body having an upper opening closed by an openable / closable upper lid, and a reactor vessel body having an upper opening formed therein. A core vessel that is suspended and defines an annular descent space for the coolant in cooperation with the reactor vessel body, a lower core plate that is extended and supported below the core vessel, and formed on the lower core plate; A lower core support plate which is located below the core and the lower core plate and is connected to and supported by a lower end portion of the core vessel, between a lower head portion of the reactor vessel body and the lower core support plate; In a pressurized water reactor defining a lower plenum communicating with the annular descending space, the lower structure in the reactor has a plurality of upper surfaces on a lower end plate portion in a manner not adversely affected by a flow of coolant in the lower plenum. That the ceramic member was provided And butterflies. Preferably, a disk that covers the upper surface of the ceramic member and is isolated from the coolant flow in the lower plenum is suspended from the lower core support plate, or the outer peripheral edge is connected to the upper inner peripheral surface of the lower head plate portion. A fixed partition disk is provided, and a number of ceramic members are filled between the lower end plate portion and the partition disk. In the former preferred embodiment, in a nuclear reactor in which an in-core instrumentation conduit is connected to a lower head portion of the reactor vessel, an inner extension of the conduit extends between the ceramic members and faces the lower surface of the disk. It is configured to open.

[0005]

Embodiments of the present invention will be described below with reference to the accompanying drawings. The same reference numerals are given to the same parts throughout all the drawings including FIGS. 8 and 9 to facilitate understanding of the contents of the invention. Referring to FIG. 1, an upper opening of a reactor vessel main body 1 is closed by a detachable upper lid 3, from which a reactor core vessel 5 is supported by hanging. Usually, two to four inlet nozzles 23 are integrally formed on the upper side of the reactor vessel main body 1, and the same number of outlet nozzles 29 are also integrally formed. An annular descending space 25 is provided between the core tank 5 and the inner surface of the reactor vessel main body 1.
And an inlet nozzle 23 is open to it. Further, a horizontal lower core plate 7 is supported at a lower portion of the core tank 5, and a number of fuel assemblies 9 (only one is shown) constituting the core are arranged and loaded thereon. A lower core support plate 11 is provided below the lower core plate 7 and connected to a lower end portion of the core tank 5, and these are horizontally supported from the inner surface of the reactor vessel main body 1. On the other hand, the upper end of the fuel assembly 9 is pressed by the upper core plate 8, and the upper core support plate 12 supports the upper core plate 8.

Further, the characteristic portion of the present invention will be further described. A plurality of lower core support columns 31 extend downward from the lower core support plate 11, and a disk having substantially no flow hole at the tip thereof, that is, a disk having no flow hole. The lower connecting plate 33 is supported horizontally. The planar shape of the lower connecting plate 33 is circular as shown in FIG. 2, and the outer peripheral edge thereof is close to the inner peripheral surface of the lower end plate 1 a of the reactor vessel main body 1 at a narrow interval. And
In a segment space between the lower connecting plate 33 and the upper surface of the lower end plate portion 1a, a ceramic molded body 35 is spread and filled. The shape of the ceramic molded body 35 may be an appropriate one such as a granular shape, a saddle shape, a cylindrical shape, and the material may be any material as long as it has high-temperature heat resistance so as not to elute at a coolant temperature during operation of the reactor. A mixture of materials may be used. The upper connecting plate 37 has a substantially annular shape as shown in FIG.

In the pressurized water reactor having the above-described core structure, during normal operation, the coolant flows into the reactor vessel main body 1 through the inlet nozzle 23, flows down the annular descending space 25, and falls in the lower plenum 27. The flow direction is reversed, passes through the lower core support plate 11 and the lower core plate 7 and enters the core,
The fuel flows upward while being heated in contact with the fuel assembly 9, flows laterally in the upper plenum 28, and flows out through the outlet nozzle 29. The coolant flowing into the lower plenum 27 from the annular descending space 25 collides with the upper surface of the lower lower connecting plate 33 and changes its direction.
Since the top surface of the layer is substantially covered,
There is no adverse effect from the coolant flow. When a part of the fuel assembly 9 is melted due to an accident, the fuel assembly 9 falls through the holes of the lower core plate 7 and the lower core support plate 11 due to gravity, but is received by the ceramic molded body 35, 1, the heat transfer to the lower end plate 1a is reduced,
The soundness is maintained for a long time or until the next safety operation is performed.

Depending on the type of the reactor, an in-core instrumentation conduit for guiding an in-reactor detector for detecting a neutron flux of the core may be connected to the lower head 1a of the reactor vessel body 1. In order to apply the present invention to a reactor of this type, the embodiment shown in FIGS. To explain this, a lower connecting plate 43 is horizontally supported at a lower end of a lower core support column 41 extending downward from the lower core support plate 11 in FIG. The plan shape of the lower connecting plate 43 is shown in FIG. 5, but the lower connecting plate 31 shown in FIG.
Is different in that an in-furnace instrumentation guide tube is attached as described later. In other words, the upper end of the in-core instrumentation conduit 48 that penetrates the lower end plate portion 1a of the reactor vessel body 1 in a water-tight manner extends to near the lower surface of the lower connecting plate 43, and opens to the corresponding hole. The lower end of the in-furnace instrumentation guide tube 49 is fixed to the lower connecting plate 43 in line with the in-furnace instrumentation conduit 48. On the other hand, the upper end of the in-core instrumentation guide tube 49 is fixed to the lower surface of the lower core support plate 11, and the upper connecting plate 47 located above the lower connecting plate 43 connects the plurality of in-core instrumentation guide tubes 49 to each other. ing. FIG. 6 shows a plan shape of the upper connecting plate 47. Then, a ceramic molded body 45 similar to that of the above-described embodiment is filled between the lower connecting plate 43 and the lower end plate portion 1a. As described above, only the changed part has been described. However, since the configuration other than the above is the same as that of the first embodiment, the same effects as those of the above-described embodiment can be obtained in this embodiment.

Another embodiment will be described. FIG.
Only the portions different from the above-described first and second embodiments will be described with reference to FIG. 6. There is no lower connecting plate or upper connecting plate below the lower core support plate 11, and the dish-shaped partitioning disk 53 is a lower head plate. The partition disk 5 is fixed in close contact with the upper inner peripheral surface of the portion 1a.
A ceramic molded body 55 similar to that described above is filled between the lower end plate 3 and the lower end plate portion 1a. Even in such a lower structure inside the reactor, since the lower plenum 51 communicates with the annular descending space 25, there is no large difference in the flow of the coolant during the normal operation. The effect of the present invention of protecting the lower end plate portion 1a from melting and penetration can be obtained.

[0010]

As described above, according to the present invention,
Since the ceramic molded body spread over the upper surface of the lower head portion of the reactor vessel main body receives the molten core, the lower head portion can be thermally protected and its penetration through the melt can be prevented. Furthermore, according to the present invention, if the above-mentioned ceramic molded body is separated from the coolant flow by a disk such as a lower connecting plate or a partition disk and retains its function for a long time, and the molten core falls, By receiving this as described above, it is possible to prevent melt penetration of the reactor vessel.

[Brief description of the drawings]

FIG. 1 is an elevational sectional view showing an embodiment of the present invention.

FIG. 2 is a plan sectional view taken along the line II-II in FIG.

FIG. 3 is a plan sectional view taken along the line III-III of FIG. 1;

FIG. 4 is an elevational sectional view showing another embodiment of the present invention.

FIG. 5 is a plan sectional view taken along the line VV of FIG. 4;

6 is a plan sectional view taken along the line VI-VI in FIG. 4;

FIG. 7 is an elevational sectional view showing still another embodiment of the present invention.

FIG. 8 is a vertical sectional view showing an example of the internal structure of a conventional pressurized water reactor.

FIG. 9 is a plan sectional view taken along line IX-IX of FIG. 8;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Reactor vessel main body 1a Lower head plate part 3 Upper lid 5 Core tank 7 Lower core plate 8 Upper core plate 9 Fuel assembly 11 Lower core support plate 12 Upper core support plate 23 Inlet nozzle 25 Annular descending space 27 Lower plenum 28 Upper plenum 29 Outlet nozzle 31 Lower core support column 33 Lower connecting plate 35 Ceramic molded body 37 Upper connecting plate 41 Lower core supporting column 43 Lower connecting plate 45 Ceramic molded body 47 Upper connecting plate 48 In-core instrumentation conduit 49 In-core instrumentation guide tube 51 Lower plenum 53 Partition disk 55 Ceramic molded body

Claims (4)

[Claims] 1. A reactor vessel body whose upper opening is closed by an openable and closable upper lid. The reactor vessel body is suspended from the upper opening in the reactor vessel body, and the coolant is cooperated with the reactor vessel body. A core tank defining an annular descending space, a lower core plate extended and supported below the core tank, a core formed on the lower core plate, and the core tank positioned below the lower core plate Having a lower core support plate connected and supported at the lower end of the
In a pressurized water reactor having a lower plenum communicating with the annular descending space between a lower head plate portion of the reactor vessel body and the lower core support plate, a large number of ceramics are formed on an upper surface of the lower head plate portion. Lower part structure of a pressurized water reactor, characterized by laying down members. 2. A disk supporting an upper surface of said ceramic member and separating from a coolant flow in said lower plenum is supported by said lower core support plate.
The lower inside structure of the pressurized water reactor described in the above. 3. An in-core extension of an in-core instrumentation conduit connected to a lower head portion of the reactor vessel main body extends between the ceramic members and opens to a lower surface of the disk. The lower part structure of the pressurized water reactor according to claim 2. 4. A reactor vessel body whose upper opening is closed by an openable and closable upper lid, the reactor vessel body is suspended from the upper opening in the reactor vessel body, and the coolant is cooperated with the reactor vessel body. A core tank defining an annular descending space, a lower core plate extended and supported below the core tank, a core formed on the lower core plate, and the core tank positioned below the lower core plate Having a lower core support plate connected and supported at the lower end of the
In a pressurized water reactor having a lower plenum communicating with the annular descending space between a lower head portion of the reactor vessel body and the lower core support plate, an upper inner peripheral surface of the lower head portion is provided. Provide a partition disk whose outer peripheral edge is connected and fixed,
A lower inside structure of a pressurized water reactor, wherein a plurality of ceramic members are filled between the lower end plate portion and the partition disk.