JP7092724B2 - Access hatch and access hatch protection system - Google Patents

Description

The present invention relates to the technology of the reactor containment vessel, and particularly to the access hatch and the access hatch protection system provided in the access tunnel for entering and exiting the inside of the reactor containment vessel.

A nuclear plant has a system in which an emergency generator operates when an external power source is lost due to an earthquake, wind and flood damage, fire, etc., and the emergency core cooling mechanism supplies sufficient cooling water to the core to prevent the core from melting. ..

However, in the unlikely event that the emergency core cooling mechanism does not function and a severe accident such as core meltdown occurs, the core melt (fuel debris) will fall to the bottom of the reactor pressure vessel, and the reactor pressure vessel will be further damaged. In some cases, fuel debris may fall into the lower dry well. Even in such a severe accident, it is necessary to prevent the diffusion of radioactive materials to the outside of the reactor containment vessel.

When fuel debris falls into the lower dry well, the reactor containment vessel is heated by heat radiation from the fuel debris. One of the parts of the reactor containment vessel that is relatively vulnerable to heat load is the access hatch provided in the access tunnel for entering and exiting the inside of the reactor containment vessel. When the access hatch is damaged (for example, thermal deformation) by a heat load, a gap is created in the flange surface, which can be a leak point for radioactive materials.

Therefore, various techniques for preventing damage due to the heat load of the access hatch have been studied. For example, Patent Document 1 (Japanese Patent Laid-Open No. 2013-7574) describes a reactor vessel containing a core, a reactor containment vessel containing the reactor vessel, and a reactor containment vessel below the reactor vessel and the reactor containment vessel. A nuclear plant having a radiant heat reflecting member arranged therein is disclosed. The radiant heat reflecting member is released from the molten core when the molten core in a state where the core is melted due to an accident flows out below the reactor vessel and is deposited in the lower part of the reactor containment vessel. It is said to block the radiant heat toward the side wall of the reactor containment vessel.

Japanese Unexamined Patent Publication No. 2013-7574

In the technique of Patent Document 1, it is expected that the heat load on the access hatch can be reduced by disposing the radiant heat reflecting member in the reactor containment vessel. However, since the state of the severe accident varies greatly depending on the event, the radiant heat reflecting member arranged in the reactor containment vessel may be damaged depending on the way / position of the fuel debris falling. If the radiant heat reflecting member is damaged, the action and effect of Patent Document 1 cannot be obtained, as a matter of course.

That is, it is required to maintain the soundness of the access hatch without being affected by the way / position of the fuel debris falling. Therefore, an object of the present invention is to provide an access hatch and an access hatch protection system that can maintain soundness without being affected by the way / position of the fuel debris fall even in the event of a severe accident. To provide.

(I) One aspect of the present invention is an access hatch provided in an access tunnel of the reactor containment vessel.
The access tunnel is a tunnel connecting the side wall of the reactor containment vessel and the lower dry well, and the access hatch heats to the side of the access hatch body facing the lower dry well when the access hatch is closed. A radiant reflection member is integrally arranged, and the end of the heat radiant reflection member is below the position of the flange surface of the access hatch body in the axial direction of the access tunnel when the access hatch is closed. It provides an access hatch characterized in that it is formed to project to the side of the drywell.

The present invention can be improved or modified as follows in the above-mentioned access hatch (I) according to the present invention.
(I) The access hatch is disposed at the end of the access tunnel on the side of the outer wall.
(Ii) The reflective surface of the heat radiation reflecting member is formed of an aluminum electrolytic polishing material, a silver-deposited material, or a hot-dip galvanizing material.
(Iii) In the access hatch, a flow path of a refrigerant is formed between the access hatch main body and the heat radiation reflection member.
(Iv) A refrigerant injection / discharge pipe for injecting the refrigerant into the flow path or discharging the refrigerant from the flow path is arranged so as to penetrate the access hatch main body.
(V) A refrigerant injection / discharge pipe for injecting the refrigerant into the flow path or discharging the refrigerant from the flow path is arranged so as to penetrate the heat radiation reflection member.

(II) Another aspect of the present invention is a system for protecting an access hatch provided in an access tunnel of a reactor containment vessel.
The access hatch is a kind of the access hatch according to the present invention, and includes a refrigerant flow pipe through which the refrigerant flows, and one end of the refrigerant flow pipe is connected to the refrigerant injection / discharge pipe. It provides an access hatch protection system characterized in that the other end is connected to the pressure suppression pool of the reactor containment vessel.

(III) Yet another aspect of the present invention is a system for protecting an access hatch provided in an access tunnel of a reactor containment vessel.
The access hatch is a kind of the access hatch according to the present invention, and includes a refrigerant transport pump for transporting a refrigerant and a refrigerant distribution pipe through which the refrigerant flows, and the refrigerant flow pipe is the access. The present invention provides an access hatch protection system characterized in that the refrigerant is circulated on the side surface of the side wall of the hatch main body.

(IV) Yet another aspect of the present invention is a system for protecting an access hatch provided in an access tunnel of a reactor containment vessel.
The access hatch is a kind of the access hatch according to the present invention, and includes a refrigerant transport pump for transporting the refrigerant and a refrigerant flow pipe through which the refrigerant flows, and the refrigerant flow pipe is the refrigerant. It provides an access hatch protection system characterized by being connected to an injection / discharge pipe.

The present invention can be improved or modified as follows in the above-mentioned access hatch protection systems (III) and (IV) according to the present invention.
(Vi) A normally closed isolation valve that can be opened remotely or statically is interposed between the refrigerant flow pipe and the refrigerant injection / discharge pipe.
(Vii) The refrigerant transport pump is configured to be connectable to a movable emergency power source.

INDUSTRIAL APPLICABILITY According to the present invention, there is provided an access hatch and an access hatch protection system capable of maintaining soundness without being affected by the way / position of dropping fuel debris even in the event of a severe accident. be able to.

It is sectional drawing which shows the schematic structure of the reactor containment vessel which has the access hatch which concerns on this invention. It is sectional drawing which shows the example of the reactor containment vessel when a severe accident occurs. It is sectional drawing which shows one Embodiment of the access hatch and the access hatch protection system which concerns on this invention. It is sectional drawing which shows the access hatch and another embodiment of the access hatch protection system which concerns on this invention. It is sectional drawing which shows the access hatch and another embodiment of the access hatch protection system which concerns on this invention. It is sectional drawing which shows the access hatch and another embodiment of the access hatch protection system which concerns on this invention.

Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings. The present invention is not limited to the embodiments taken up here, and can be appropriately combined with a known technique or improved based on the known technique without departing from the technical idea of the invention. .. The same reference numerals may be given to members and parts having the same meaning (including cases where the difference is small).

[Rough configuration of reactor containment vessel]
FIG. 1 is a schematic cross-sectional view showing a schematic configuration of a reactor containment vessel having an access hatch according to the present invention. The reactor containment vessel of FIG. 1 shows an example of the reactor containment vessel of an advanced boiling water reactor (ABWR).

The core 10 is housed in the reactor pressure vessel 20, and the reactor pressure vessel 20 is housed in the reactor containment vessel 30. The reactor containment vessel 30 is divided into a dry well 31 for accommodating the reactor pressure vessel 20 and a suppression chamber 32. Inside the suppression chamber 32, there is a pressure suppression pool 32a (also called a wet well) that stores cooling water.

The reactor pressure vessel 20 is supported by a support leg 35 supported by a cylindrical pedestal 34. The drywell 31 is referred to as the upper drywell 31a above the support leg 34 and below the support leg 35 and inside the pedestal 34 as the lower drywell 31b. The suppression chamber 32 forms a ring so as to surround the lower dry well 31b.

The upper dry well 31a and the suppression chamber 32 are connected by a vent pipe 33, and are configured to guide steam into the cooling water of the pressure suppression pool 32a when the pressure in the dry well 31 rises.

In the reactor containment vessel 30, an access tunnel 36 for entering and exiting from the side wall 30a penetrates the pressure suppression pool 32a of the suppression chamber 32 and leads to the lower dry well 31b. An access hatch 37 is attached to the access tunnel 36, and the access hatch 37 is closed during normal operation of the nuclear power plant. The access hatch 37 is opened during periodic inspections of the nuclear plant, allowing workers to enter and exit the lower drywell 31b. At the bottom of the lower drywell 31b, a gantry 40 used for periodic inspections may be installed.

(Severe accident)
FIG. 2 is a schematic cross-sectional view showing an example of a reactor containment vessel in the event of a severe accident. As shown in FIG. 2, if core meltdown occurs as a severe accident, it is conceivable that fuel debris 11 penetrates the bottom of the reactor pressure vessel 10 and accumulates on the gantry 40. Then, if the access hatch 37 continues to receive strong heat radiation from the fuel debris 11, there is a concern that the access hatch 37 will be heated and cause thermal deformation (leakage of radioactive materials due to this).

[First Embodiment]
FIG. 3 is a schematic cross-sectional view showing an embodiment of an access hatch and an access hatch protection system according to the present invention. As shown in FIG. 3, the access hatch 37 is composed of an access hatch main body 37a and a heat radiation reflection member 37b, and faces one side of the access hatch main body 37a (when the access hatch 37 is closed, it faces the lower dry well 31b). The heat radiation reflection member 37b is integrally arranged on the side).

Also, when the access hatch 37 is closed, the end of the heat radiation reflection member 37b protrudes toward the lower drywell 31b from the position of the flange surface 37c of the access hatch main body 37a in the axial direction of the access tunnel 36. It is preferably configured. By providing such a heat radiation reflecting member 37b, the amount of heat input to the access hatch main body 37a (the temperature rise due to it) is suppressed, and the heat deformation (particularly the flange surface 37c) of the access hatch main body 37a (particularly the flange surface 37c) is caused by the radioactive material. Leakage) can be prevented.

The access hatch body 37a is usually made of stainless steel. The heat radiation reflecting member 37b is particularly limited to the material as long as it can effectively reflect heat radiation (for example, the reflectance in the infrared region is preferably 70% or more, more preferably 80% or more, still more preferably 90% or more). There is no. For example, a material obtained by laminating an aluminum electrolytic abrasive, a silver-deposited material, or a hot-dip galvanized material on a base material of a stainless steel plate as a reflective surface can be preferably used. From the viewpoint of protecting the reflective surface, a protective layer (for example, a transparent silica layer or a transparent alumina layer) may be further formed on the surface of the reflective surface.

However, since the reflectance of the heat radiation reflecting member 37b is not 100%, a part of the incident heat radiation is absorbed by the heat radiation reflecting member 37b. Here, in the access hatch 37 of the present embodiment, since the heat radiation reflection member 37b is directly lined on the access hatch main body 37a, the heat absorbed by the heat radiation reflection member 37b is immediately conducted to the access hatch main body 37a. ..

Since the access hatch main body 37a has a sufficiently large heat capacity as compared with the heat radiation reflecting member 37b, the temperature of the access hatch main body 37a does not rise immediately. Further, since the other surface of the access hatch main body 37a (the surface on the side wall 30a side of the reactor containment vessel 30 when the access hatch 37 is closed) is open, the heat conducted to the access hatch main body 37a is the other surface. Heat is dissipated sequentially from the surface (open surface).

The access hatch 37 may be basically arranged at any position in the axial direction of the access tunnel 36, but is stored in the reactor from the viewpoint of reducing the amount of heat radiation (reducing the viewing angle from the heat source). It is preferably closer to the side wall 30a of the vessel 30, and more preferably disposed at the end of the access tunnel 36 on the side wall 30a (see FIG. 1).

The access hatch protection system of the present embodiment includes a refrigerant transport pump 50 for transporting the refrigerant and a refrigerant flow pipe 51 through which the refrigerant flows, and the refrigerant flow pipe is the other surface of the access hatch main body 36a. The structure is such that the refrigerant is circulated on the (open surface). The access hatch protection system of the present embodiment is not an indispensable system, but it is desirable to prepare it from the viewpoint of efficiently dissipating the heat conducted to the access hatch main body 37a.

The refrigerant is not particularly limited as long as it does not ignite or ignite and has a high cooling capacity, but it is more preferable that the refrigerant can be easily prepared from the viewpoint of ease of maintenance (that is, cost), for example, water. Seawater, air, etc. can be preferably used.

Further, since the access hatch protection system of the present invention is a system that can respond even when a severe accident occurs, the refrigerant transport pump 50 can be connected to a movable emergency power source (not shown, for example, a power supply vehicle). It is preferable that it is.

[Second Embodiment]
FIG. 4 is a schematic cross-sectional view showing another embodiment of the access hatch and the access hatch protection system according to the present invention. As shown in FIG. 4, the access hatch 37'of the second embodiment has a point in which a refrigerant flow path 37d is formed between the access hatch main body 37a and the heat radiation reflection member 37b, and a flow path 37d. Unlike the access hatch 37 of the first embodiment, the refrigerant injection / discharge pipe 37e for injecting the refrigerant or discharging the refrigerant from the flow path 37d is arranged so as to penetrate the access hatch main body 37a, and is the same as the others. It is something to do.

Since the access hatch 37'of the present embodiment has a refrigerant flow path 37d between the access hatch main body 37a and the heat radiation reflection member 37b, the heat absorbed by the heat radiation reflection member 37b is dissipated more directly. can do.

Although it is not an essential configuration, from the viewpoint of shape stability of the heat radiation reflection member 37b, it is preferable that the heat radiation reflection member 37b and the access hatch main body 37a are connected by a flow path column 37f. Further, from the viewpoint of heat transfer from the heat radiation reflection member 37b to the refrigerant, it is preferable that an uneven structure (not shown) is formed inside the flow path 37d. However, the flow path column 37f and the uneven structure are not essential configurations.

The access hatch protection system of the present embodiment includes a refrigerant transport pump 50 and a refrigerant flow pipe 51, and the refrigerant flow pipe 51 is connected to the refrigerant injection / discharge pipe 37e. From the viewpoint of maintenance of the access hatch protection system, it is preferable that a normally closed isolation valve 52 that can be remotely or statically opened is interposed between the refrigerant flow pipe 51 and the refrigerant injection / discharge pipe 37e.

Although not shown in the figure, it is preferable that a part of the refrigerant injection / discharge pipe 37e and / or the refrigerant flow pipe 51 is a flexible pipe from the viewpoint of easy opening / closing of the access hatch 37'.

[Third Embodiment]
FIG. 5 is a schematic cross-sectional view showing another embodiment of the access hatch and the access hatch protection system according to the present invention. As shown in FIG. 5, the access hatch 37 ”of the third embodiment is the access hatch of the second embodiment in that the refrigerant injection / discharge pipe 37e'is arranged so as to penetrate the heat radiation reflection member 37b. Unlike 37', the others are the same.

The access hatch protection system of the present embodiment includes a refrigerant transport pump 50 and a refrigerant flow pipe 51, one end of which is connected to the refrigerant injection / discharge pipe 37e'and the other end of the refrigerant flow pipe 51. Is connected to the pressure suppression pool 32a of the reactor containment vessel 30, which is different from the access hatch protection system of the second embodiment and is the same as the others.

Since the refrigerant flow pipe 51 is connected to the pressure suppression pool 32a of the reactor containment vessel 20, there is an advantage that it is not necessary to separately prepare a refrigerant supply source. Others show the same action and effect as the second embodiment.

[Fourth Embodiment]
FIG. 6 is a schematic cross-sectional view showing another embodiment of the access hatch and the access hatch protection system according to the present invention. As shown in FIG. 6, the access hatch protection system of the fourth embodiment is different from the access hatch protection system of the third embodiment in that it does not include the refrigerant transport pump 50, and is the same as the others.

Since the refrigerant transport pump 50 is not provided, there is an advantage that it is not necessary to separately prepare a power source for operating the refrigerant transport pump 50. Others show the same action and effect as in the third embodiment.

The above-described embodiments have been described for the purpose of assisting the understanding of the present invention, and the present invention is not limited to the specific configurations described. For example, it is possible to replace a part of the configuration of the embodiment with the configuration of the common general technical knowledge of those skilled in the art, and it is also possible to add the configuration of the common general technical knowledge of the person skilled in the art to the configuration of the embodiment. That is, the present invention can delete, replace, or add another configuration to a part of the configuration of the embodiment of the present specification without departing from the technical idea of the invention. ..

10 ... Core, 11 ... Fuel debris, 20 ... Reactor pressure vessel, 30 ... Reactor containment vessel, 30a ... Side wall,
31… Drywell, 31a… Upper Drywell, 31b Lower Drywell,
32 ... suppression chamber, 32a ... pressure suppression pool, 33 ... vent tube,
34 ... pedestal, 35 ... support legs, 36 ... access tunnel,
37, 37', 37 "... Access hatch,
37a ... Access hatch body, 37b ... Thermal radiation reflecting member, 37c ... Flange surface,
37d ... Distribution, 37e, 37e'... Refrigerant injection / discharge piping, 37f ... Channel support,
40 ... gantry,
50 ... Refrigerant transport pump, 51 ... Refrigerant flow piping, 52 ... Isolation valve.

Claims (11)

An access hatch installed in the access tunnel of the reactor containment vessel.
The access tunnel is a tunnel connecting the side wall of the reactor containment vessel and the lower dry well.
The access hatch is integrally provided with a heat radiation reflection member on the side of the access hatch body facing the lower dry well when the access hatch is closed.
The heat radiation reflecting member is formed so that its end portion protrudes toward the lower drywell in the axial direction of the access tunnel from the position of the flange surface of the access hatch body when the access hatch is closed. ing,
An access hatch that features that. In the access hatch according to claim 1,
The access hatch is disposed at the end of the access tunnel on the side of the side wall.
An access hatch that features that. In the access hatch according to claim 1 or 2.
The reflective surface of the heat radiation reflecting member is formed of an aluminum electrolytic polishing material, a silver-deposited material, or a hot-dip galvanizing material.
An access hatch that features that. In the access hatch according to any one of claims 1 to 3.
In the access hatch, a flow path of a refrigerant is formed between the access hatch main body and the heat radiation reflection member.
An access hatch that features that. In the access hatch according to claim 4,
A refrigerant injection / discharge pipe for injecting the refrigerant into the flow path or discharging the refrigerant from the flow path is arranged so as to penetrate the access hatch main body.
An access hatch that features that. In the access hatch according to claim 4,
A refrigerant injection / discharge pipe for injecting the refrigerant into the flow path or discharging the refrigerant from the flow path is arranged so as to penetrate the heat radiation reflection member.
An access hatch that features that. A system that protects the access hatch installed in the access tunnel of the reactor containment vessel.
The access hatch is the access hatch according to claim 6.
A refrigerant distribution pipe through which the refrigerant flows is provided.
One end of the refrigerant flow pipe is connected to the refrigerant injection / discharge pipe, and the other end is connected to the pressure suppression pool of the reactor containment vessel.
An access hatch protection system that features that. A system that protects the access hatch installed in the access tunnel of the reactor containment vessel.
The access hatch is the access hatch according to any one of claims 1 to 3.
A refrigerant transport pump for transporting the refrigerant and a refrigerant flow pipe through which the refrigerant flows are provided.
The refrigerant flow pipe is configured to circulate the refrigerant on the side surface of the side wall of the access hatch main body.
An access hatch protection system that features that. A system that protects the access hatch installed in the access tunnel of the reactor containment vessel.
The access hatch is the access hatch according to claim 5 or 6.
A refrigerant transport pump for transporting the refrigerant and a refrigerant flow pipe through which the refrigerant flows are provided.
The refrigerant flow pipe is connected to the refrigerant injection / discharge pipe.
An access hatch protection system that features that. In the access hatch protection system according to claim 9,
A normally closed isolation valve that can be opened remotely or statically is interposed between the refrigerant flow pipe and the refrigerant injection / discharge pipe.
An access hatch protection system that features that. In the access hatch protection system according to any one of claims 8 to 10.
The refrigerant transport pump is configured to be connectable to a movable emergency power source.
An access hatch protection system that features that.

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