JPH0943380A - Support sealing device for core superstructure and removal device for sodium etc. - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a support sealing device for a reactor superstructure and a removal device for sodium etc., which secures soundness of raising/lowering action of the core superstructure and causes less exposure of workers by providing a seal or a removal device for superiorly removing sodium, etc., in a hole part, which penetrates the upper lid, or a shaft part. SOLUTION: In a through hole 13 in a support 9, etc., for supporting a core superstructure which holds a control rod drive mechanism for driving a control rod which controls nuclear reaction in a core in the upper lid 5 of a reactor container including the core and sodium 3 for coolant in a fast breeder, a sealing means for preventing increase in sodium 3 provided in a sleeve 22 which supports the support 9 is formed from high-temperature resistant metal mesh seal 23.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a through hole provided in an upper lid of a nuclear reactor in a fast reactor, and relates to sealing sodium of liquid metal which is a reactor coolant, and particularly to a pillar of an upper core mechanism in the through hole. Or by a sealing means such as a plug,
The present invention relates to a support pillar sealing device for a core upper part mechanism and a sodium removing device.

[0002]

2. Description of the Related Art A reactor structure of a fast reactor in which the upper part of the reactor is simplified is shown in FIG. Along with the core 2, sodium 3 which is a high temperature liquid metal is contained as a coolant. Further, the cover gas 4 is sealed in the upper part and closed by an upper lid 5, and this upper lid 5 is cooled by a coolant in a separate cooling system in order to thermally protect the mounted equipment.

At the time of refueling, the control rod drive mechanism 6 expands and contracts and is pulled up, and along with this, the reactor core upper mechanism 7
Are pulled up via the columns 9 of the lifting drive device 8.
After that, the refueling machine 10 extends the telescopic variable arm 11 mounted and supported on the upper lid 5, extracts a predetermined fuel element in the core 2 with a gripper device and stores it, and then moves the whole refueling machine 10. Then, the fuel element is stored in the fuel relay tank 12.

The new fuel elements are loaded into the core 2 by the reverse route of the above-mentioned taking out of the old fuel elements. In this way, all the fuel elements in the core 2 can be transferred to the fuel relay tank 12. Therefore, at the time of operation, the penetrating portion of the column 9 that supports the core upper mechanism 7 in the upper lid 5 and the hole 13 that penetrates the upper lid 5 as shown in the longitudinal sectional view of FIG.
A shaft of a predetermined device such as the column 9 or a plug 14 is inserted and sealed by a seal 15, and the high temperature sodium 3 in the furnace is confined through a cover gas 4.

[0005]

The ascending / descending operation of the core upper part mechanism 7 is carried out through a plurality of columns 9 penetrating the cover gas 4 of the nuclear reactor. It is conceivable that the sodium 3 of the above will rise as high-temperature sodium vapor and will rise, and will be cooled in the annulus gap 17 of the hole 13 through which the support column 9 penetrates by the upper lid 5 and stick to it, hindering the vertical movement of the support column 9.

In addition, when checking the reactor, pull out the plug 14,
This can be reused or replaced with a new plug 14. In this case, as shown in the longitudinal sectional view of FIG. 14, a seal pipe 16 is previously installed on the upper lid 5 to cover the upper portion of the plug 14. Form a gas boundary.

After this, the plug 14 is pulled out upward, but when the droplet sodium 18 or 18 sodium 3 by sodium vapor is deposited in the annulus gap 17 of the plug 14 and the hole 13 of the upper lid 5, the plug 14 is pulled out or inserted. Interfere with. Therefore, the drop-shaped sodium 18 adhering to the portion of the plug 14 dipped in the sodium 3 does not enter the annulus gap 17 by a scraper 19 provided at the lower end of the hole 13 so as to mechanically remove the plug 14 from the outside. I try to scrape it.

Further, the side surface 15a of the seal hole, which is in contact with the seal 15 such as the plug 14 which is important for the sealing function, may be accompanied by the radioactive corrosion product other than the sodium 3 together with the hole 13 after the plug 14 is removed. .

As shown in the longitudinal sectional view of FIG. 15, the removal of sodium 3 and radioactive corrosion products from the hole 13 and the side surface 15a of the seal hole is performed by the waste support rod 20 and the waste cloth 21 each time as shown in the longitudinal sectional view of FIG.
However, there is a risk that radioactive waste such as waste 21 will be generated and problems such as dropping waste 21 into the furnace may occur during this work, and there is a problem to reduce the exposure of workers. There is.

When the scraper 19 scrapes off sodium 3 and radioactive corrosion products attached to the plug 14 and the support 9, the scraper 19 may be damaged due to mechanical scraping of the plug 14 and the support 9. There was a risk of damage to the plug 14, and there was a hindrance to frequently replacing the scraper 19 with trouble.

An object of the present invention is to provide a seal or a removing device for satisfactorily removing sodium and the like in a hole portion or a shaft portion penetrating the upper lid to ensure the soundness of the ascending / descending operation of the core upper part mechanism and work. It is an object of the present invention to provide a pillar sealing device for a furnace upper mechanism and a device for removing sodium and the like, which is less exposed to personnel.

[0012]

In order to achieve the above object, a pillar sealing device for a reactor upper part mechanism according to the invention of claim 1 is provided in an upper lid of a reactor vessel containing a core and a coolant in a fast reactor. Prevent the rise of the coolant provided in the sleeve that supports the column at the penetrating part such as the column that supports the upper core mechanism that holds the control rod drive mechanism that drives the control rod that controls the nuclear reaction in the core The sealing means is a high temperature resistant metal mesh seal.

The metal mesh seal of the sealing means is formed between the sleeve and the column because it captures sodium vapor as a coolant mixed in the cover gas in the furnace and drops it as sodium droplets in the furnace. Prevents sodium from entering and adhering to the annulus gap. In addition, since the metallic mesh seal removes the dripping sodium adhering to the strut when pulling out the strut, sodium does not adhere to the seal part between the hole of the upper lid and the strut, and the soundness of the seal and the insertability of the strut are improved. Secured well.

According to a second aspect of the present invention, there is provided a strut sealing device for an upper furnace mechanism, wherein a sealing means provided on a sleeve for supporting the strut for preventing the coolant from rising is expanded at a low temperature and expanded at a high temperature. It is characterized in that it is a ring seal made of a shape memory alloy that shrinks. Since the shape memory alloy ring seal of the sealing means is reduced in diameter at high temperature during reactor operation,
The gap between the pillars becomes narrower and the sealing function is obtained. In addition, since the temperature is lowered during the operation of raising and lowering the support, the gap between the support and the support is sufficiently opened, and the operation of the support is facilitated.

According to a third aspect of the present invention, there is provided a strut sealing device for an upper furnace mechanism, wherein a sealing means provided on a sleeve for supporting the strut for preventing a coolant from rising is expanded at a low temperature and expanded at a high temperature. The feature is that the coil seal is made of a shape memory alloy that is reduced. The shape memory alloy coil seal of the sealing means obtains an excellent sealing function because its diameter is reduced at a high temperature during the operation of the nuclear reactor, the gap between the column and the column is narrowed, and there is no seam. In addition, since the temperature is lowered during the operation of raising and lowering the support, the gap between the support and the support is sufficiently opened, and the operation of the support is facilitated.

According to a fourth aspect of the present invention, there is provided a strut sealing device for an upper furnace mechanism in which a scraper for scraping the coolant is provided in parallel with a sealing means provided on a sleeve supporting the strut for preventing the coolant from rising. It is characterized by The coolant adhering to the support is first scraped off by the scraper and then blocked by the sealing means, so that the effect of preventing the coolant from rising is excellent.

According to a fifth aspect of the present invention, there is provided a strut sealing device for an upper furnace mechanism, wherein a sleeve for supporting the strut is provided with a sealing means, and a blow gas down pipe is connected to a gap between the strut and the sleeve. Characterize. Gas blow from the blow gas down pipe into the gap between the support and the sleeve,
In addition to blocking the coolant of the sealing means, the rise of the coolant is prevented by gas blowing.

According to a sixth aspect of the present invention, there is provided a strut sealing device for an upper furnace mechanism, wherein the strut is provided with a sealing means for preventing the coolant from rising. When the sealing means is provided on the column, the function of preventing the coolant from rising is the same as that of the one mounted on the sleeve, but the sealing means can be easily inspected when the column is pulled out, and maintenance is easy.

According to a seventh aspect of the present invention, there is provided a strut sealing device for an upper furnace mechanism, wherein the strut is provided with a sealing means for preventing the coolant from rising, and the tip of the sleeve is provided in the furnace with the liquid surface of the coolant. It is characterized by being located in the vicinity or in the coolant. The sleeve reduces contact between the stanchion and the cover gas, thus reducing the amount the sodium vapor is raised to the sealing means.

According to an eighth aspect of the present invention, there is provided a strut sealing device for a reactor upper part mechanism, which irradiates a penetrating portion such as an upper lid of a nuclear reactor vessel with a hole side of the penetrating portion and a periphery of a plug inserted into the penetrating portion. A laser emitter and a laser oscillator connected to the laser emitter are provided. At the time of pulling out the plug, the laser light is emitted from the laser light emitting device to the sodium or the radioactive corrosion product attached to the plug to evaporate by the laser energy. The evaporated sodium and the like are returned to the furnace by a separate gas blow.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described with reference to the drawings. It should be noted that the same components as those of the above-described conventional technique are designated by the same reference numerals and detailed description thereof will be omitted. The first embodiment relates to claim 1, and a sleeve 22 is attached to a hole 13 penetrating the upper lid 5 as shown in the longitudinal sectional view of FIG. In
An annulus gap 17 is formed between the column 9 that moves up and down and the sleeve 22.

Below the sleeve 22, there is a sealing means for preventing the rise of sodium vapor or sodium vapor mist mixed in the cover gas 4 in the furnace (hereinafter, both are collectively referred to as sodium vapor). A high temperature resistant metal mesh seal 23 that fills the gap 17 is attached and configured. For example, the metal mesh seal 23
For example, there is one in which circular knitting of stainless steel fine wires is also made into a core by gathering circularly knitting of stainless steel fine fibers, and further double knitting is performed with monel wire and stainless steel.

Next, the operation of the above configuration will be described. The metal mesh seal 23 withstands use in a high-temperature sodium vapor atmosphere, but does not have airtight sealing performance like a normal rubber seal.

Therefore, some gas breathing occurs between the cover gas 4 and the annulus gap 17 formed above the metal mesh seal 23. However, due to the high temperature, the sodium vapor mixed in the cover gas 4 and rising,
It adheres to the metal mesh seal 23 and becomes a droplet of sodium 18, which is prevented from rising.

When the support column 9 is moved up and down during refueling, the temperature at the metal mesh seal 23 is radiated from the liquid surface 3a of the sodium 3 which is the reactor coolant, and due to heat conduction.
Since the temperature is maintained at about 30 to 170 ° C., the sodium vapor adhering to the metal mesh seal 23 does not solidify and drops as sodium droplets 18.

Therefore, the operation of the sodium 3 as a sealing means is performed soundly. Further, when the support column 9 moves up and down, the range of the cover gas 4 on the support column 9 and the dripping sodium 18 adhering to the area below the cover gas 4 are removed by the metal mesh seal 23. It does not hinder.

The second embodiment relates to claim 2 and is shown in FIG.
As shown in the perspective view of FIG. 2 and the cross-sectional view of the mating portion of FIG. 2B, instead of the metal mesh seal 23 in the first embodiment, a shape memory alloy ring seal is used as the sealing means.
24 is attached below the sleeve 22. In addition,
The ring seal 24 made of the shape memory alloy has the mating portion 25 formed therein, and has a characteristic that it shrinks at a high temperature and expands at a low temperature.

The operation of the above construction is that at the temperature during the operation of the reactor (the temperature of the coolant during normal operation is about 550 ° C.), the mating portion 25 of the shape memory alloy ring seal 24 is closed and To prevent the sodium vapor and the sodium 3 from entering the annulus gap 17. In addition, since the coolant temperature is normally maintained at about 200 ° C. during refueling, the shape memory alloy ring seal 24 is memorized so that the gap 25 is opened at this refueling temperature.

As a result, the lifting and lowering operation of the column 9 associated with the operation of the core upper part mechanism 7 is not hindered. Further, since there is almost no vapor generation from the sodium 3 during the fuel exchange, there is no need to worry that the sodium 3 due to the sodium vapor and the droplet-shaped sodium 18 adheres to the support column 9 or the like.

The third embodiment relates to claim 3, and as shown in the front view of FIG. 3, the shape memory alloy coil seal 26 of the sealing means attached below the sleeve 22 is coil-shaped and has a diameter of
Similar to the shape memory alloy ring seal 24 of the second embodiment, it is configured to be stored so as to shrink at high temperature and expand at low temperature.

Similar to the second embodiment, the function of the above construction is that when the reactor is in operation, the inner diameter of the shape memory alloy coil seal 26 makes the gap between the support 9 and the column 9 extremely small, so that sodium vapor and sodium 3 The annulus gap
Prevent entry into 17.

However, at the time of refueling, the surrounding temperature is widened so that the vertical movement of the column 9 is not hindered. The operation is the same as that of the second embodiment, but since there is no joint like the abutment portion 25 due to the coil shape and more multiplexing is performed, a further excellent sealing effect can be obtained. .

The fourth embodiment relates to claim 4, and as shown in the longitudinal sectional view of FIG. 4, below the sleeve 22 supporting the support column 9, the metal mesh seal 2 shown in the first to third embodiments.
3, any one of the shape memory alloy seal ring 24 and the shape memory alloy seal coil 26, and the scraper 24 for scraping off the droplet-shaped sodium 18 adhering to the support column 9 are provided side by side. Note that, for convenience of description, the metal mesh seal 23 will be representatively illustrated and described below.

As the operation of the above-mentioned constitution, the metal mesh seal 23 and the like prevent the invasion of sodium vapor into the annulus gap 17, and the scraper 24 scrapes the cooler to enhance the invasion prevention function. Furthermore, since the scraper 24 removes the sodium droplets 18 adhering to the support 9 when the support 9 is pulled out, the soundness of the lifting operation of the support 9 is further ensured. Further, from this, the frequency of maintenance of the metal mesh seal 23, the seal coil 26, etc. can be reduced.

The fifth embodiment relates to claim 5, and as shown in the longitudinal sectional view of FIG. 5, in the sleeve 22 for supporting the support 9, the metal mesh seal 23 shown in the first to third embodiments is provided below. Etc. Further, a blow gas down pipe 28 is connected to the annulus gap 17 through the sleeve 22.

The function of the above construction is to prevent sodium vapor from entering the annulus gap 17 by the metal mesh seal 23 shown in the first to third embodiments. In addition to this intrusion prevention function, blow gas down piping
By blowing down the backup gas from 28 to the annulus gap 17, the intrusion prevention function is further improved.

Even if the function of preventing the intrusion of the metal mesh seal 23 and the like is deteriorated, the backup gas is blown down so that the sodium vapor is covered by the cover gas 4.
Can be prevented from entering from. Therefore, it is not necessary to immediately perform maintenance, and the operation can be performed for a longer period without trouble. Needless to say, the intrusion prevention function by this blowdown can be used in combination with other than those shown in the first to third embodiments.

The sixth embodiment relates to claim 6 and, as shown in the enlarged cross-sectional view of FIG. 6, is constructed by providing the metal mesh seal 23 and the like used in the first to third embodiments on the support 9 side. In addition, the metal mesh seal 23, as shown in FIG.
It is inserted into and is screwed to the column 9 by the column tip 9a, and the column tip 9a is provided with a loosening stopper 29.

Since the metal mesh seal 23 and the like come out above the upper surface of the upper lid 5 when the support column 9 is pulled out, the operation of the above-described structure can easily perform maintenance on the metal mesh seal 23 and the like.

The seventh embodiment relates to claim 7, and as shown in the sectional view of FIG. 7, the tip of the sleeve 30 which is attached to the upper lid 5 and supports the support 9 is located near the sodium surface 3a or in sodium. And a breathing port 31 opening to the cover gas 4 is provided between the metal mesh seal 23 and the sodium liquid surface 3a.

The function of the above construction is that when the sleeve 30 is placed in the sodium 3, the portion of the support column 9 located in the cover gas 4 is covered by the sleeve 30, and the gap between the support column 9 and the sleeve 30 is reduced. Since it is narrow, the convection behavior of the support column 9 with the cover gas 4 is significantly suppressed. This reduces the amount of sodium vapor that enters the metal mesh seal 23 and the like.

The breathing port 31 provided in the sleeve 30 prevents the sodium 3 and the sodium vapor in the sleeve 30 from being pushed up into the annulus gap 17 due to the pressure increase of the cover gas 4 outside the sleeve 30. ing. Also, when the tip of the sleeve 30 is positioned near the sodium liquid surface 3a, the same action and effect as described above can be obtained, and the breathing port 31 may be opened depending on the separation distance between the tip of the sleeve 30 and the sodium liquid surface 3a. do not need.

The eighth embodiment relates to claim 8 and, as shown in the longitudinal sectional view of FIG. 8, on the upper surface of the upper lid 5 and on the upper portion of the plug 14,
Seal pipe 16 to secure the cover gas boundary
Is installed. In addition, 1 is on the side of this seal pipe 16.
One or more airtight windows 32 are provided. Furthermore, this airtight window 32
A laser light emitting device 33 is arranged so as to face it, and a laser oscillator 35 is connected through an optical fiber 34. Also, the seal pipe 16
Is connected to a blow gas down pipe 28.

Next, the operation of the above configuration will be described. When the plug 14 is pulled out from the hole 13 of the upper lid 5, a seal gas 16 is previously attached to the upper surface of the upper lid 5 to secure a cover gas boundary, and a backup gas is supplied from the blowdown gas pipe 28 to the seal pipe 16. Blow down.

When the plug 14 is pulled up while rotating, the radioactive decay products formed in the furnace together with the sodium droplets 18 and the sodium 3 adhering to the plug 14 are scraped off by the scraper 19 and flowed by gas blow. . For the remaining droplets of sodium 18, etc., the pull-up status of the plug 14 is monitored by the airtight window 32 of the seal pipe 16, and when the remaining droplets of sodium 18 etc. are observed in the airtight window 32, laser light is emitted by the laser emitter 33. Irradiate.

As a result, the droplets of sodium 18 or the like attached to the plug 14 are evaporated by the laser energy, flown by gas blow and returned to the furnace, and the droplets of sodium 18 or the like attached to the surface of the plug 14 are removed. To be done. On the other hand, in the hole 13 of the upper lid 5, especially the seal hole side 15a to which the seal 15 closely adheres
As for the removal of sodium, as shown in the longitudinal sectional view of FIG. 9, a seal pipe 16 to which a blowdown gas pipe 28 is connected is attached around the plug 14 on the upper surface of the upper lid 5.

The ninth embodiment relates to claim 8, wherein the sodium removing plug 36 has substantially the same outer shape as the plug 14,
A laser emitter 33 is embedded in a hole opened at the lower periphery.
A laser oscillator 35 is connected to the laser emitter 33 via an optical fiber 34.

The operation of the above construction is that the sodium removal plug 36 is inserted into the hole 13 after the plug 14 is removed while rotating, and the blowdown gas pipe 28 to the seal pipe 16 are inserted.
While the backup gas is blown down inside, the seal laser side 33a and the hole 13 are irradiated with the optical laser from the laser emitter 33. As a result, the droplet-shaped sodium 18 and the like attached by the laser energy are evaporated, and the evaporated sodium gas and the like are made to flow by the blow gas and return to the inside of the furnace.

The tenth embodiment relates to claim 8, and as shown in the longitudinal sectional view of FIG. 10, a hole 13 for inserting the plug 14 in the upper lid 5.
The laser emitter 33 is embedded in the hole opened at the bottom of the. A laser oscillator 35 is connected to the laser emitter 33 via an optical fiber 34.

The operation of the above structure is that the surface of the plug 14 is irradiated with laser light from the light emitter 33 when the plug 14 is pulled out while being rotated. This allows plug 14
Droplet-like sodium 18 and the like adhering to the surface of the laser are vaporized by laser energy when they reach the position of the laser emitter 33. Evaporated sodium gas or the like is caused to flow by blow-down of the blowdown gas and returns to the inside of the furnace, whereby the droplet-shaped sodium 18 or the like adhering to the surface of the plug 14 is removed.

According to the eighth to tenth embodiments, since the sodium 3 and the like adhering to the shaft or the hole is not mechanically removed, there is no fear of damaging the equipment. Further, it is easy to apply it to a place where a general device penetrates the lid without a troublesome replacement work of the scraper 19.

[0052]

As described above, according to the present invention, since it is possible to prevent sodium vapor from entering the annulus gap between the column and the sleeve in the upper lid of the fast reactor, it is possible to improve the reliability of the lifting and lowering operation of the core upper part mechanism. The facility operation rate of the fast reactor plant can be improved and maintenance can be simplified.

Further, since the attached sodium and radioactive corrosion products are easily removed without the operator directly approaching the seal portion of the column of the upper lid, the operator is less exposed to radiation. Further, radioactive waste such as waste cloth and waste cloth support is not generated, and disposal thereof is unnecessary, which is economical. In addition, there is no need to worry about the waste cloth or waste cloth support falling, and safe work can be performed.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of a strut sealing device according to a first embodiment of the present invention.

FIG. 2 is a seal ring of a second embodiment according to the present invention,
(A) is a perspective view and (b) is a cross-sectional view of the abutment portion.

FIG. 3 is a front view of a seal coil according to a third embodiment of the present invention.

FIG. 4 is a vertical cross-sectional view of a strut sealing device according to a fourth embodiment of the present invention.

FIG. 5 is a vertical sectional view of a strut sealing device according to a fifth embodiment of the present invention.

FIG. 6 is an enlarged sectional view of a seal portion of a sixth embodiment according to the present invention.

FIG. 7 is a vertical sectional view of a strut sealing device according to a seventh embodiment of the present invention.

FIG. 8 is a vertical sectional view of an apparatus for removing sodium and the like according to an eighth embodiment of the present invention.

FIG. 9 is a vertical cross-sectional view of a device for removing sodium and the like according to a ninth embodiment of the present invention.

FIG. 10 is a vertical sectional view of a device for removing sodium and the like according to a tenth embodiment of the present invention.

FIG. 11 is a vertical sectional view of a fast reactor in which the upper part of the furnace is simplified.

FIG. 12 is a vertical cross-sectional view showing a fuel exchange in a fast reactor.

FIG. 13 is a vertical sectional view of a conventional plug portion.

FIG. 14 is a vertical cross-sectional view of sodium removal in a conventional plug part.

FIG. 15 is a vertical cross-sectional view of sodium removal in a conventional seal part.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Reactor vessel, 2 ... Reactor core, 3 ... Sodium (liquid metal), 3a ... Sodium liquid level, 4 ... Cover gas, 5 ... Upper lid, 6 ... Control rod drive mechanism, 7 ... Core upper mechanism, 8 ... Drive device, 9 ... Support, 9a ... Lower support, 10 ... Fuel exchanger, 11 ... Variable arm, 12 ... Fuel relay tank, 13 ... Hole, 14 ... Plug, 15 ... Seal, 15a ... Seal hole side, 16 ... Seal pipe , 17… annular gap, 18… droplet sodium, 1
9, 27… scraper, 20… waste support, 21… waste, 2
2, 30 ... Sleeve, 23 ... Metal mesh seal, 24 ... Seal ring, 25 ... Mating part, 26 ... Seal coil, 28 ... Blowdown gas piping, 29 ... Loose stop, 31 ... Breathing port, 32 ... Airtight window, 33 ... Laser emitter, 34 ... Optical fiber, 35 ... Laser oscillator, 36 ... Sodium removal plug.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Koji Matsumoto 2-4 Suehiro-cho, Tsurumi-ku, Yokohama-shi, Kanagawa Toshiba Keihin Plant (72) Inventor Aya Hasegawa, 8 Shinsita-cho, Isogo-ku, Yokohama-shi, Kanagawa In-house company Toshiba Yokohama office (72) Inventor Kenichi Kubota 8 Shinsita-cho, Isogo-ku, Yokohama-shi, Kanagawa Stock company In-house Toshiba Yokohama office (72) Inoue Hiroaki Inokakura Komukai-shi, Kawasaki-shi, Kanagawa Incorporated company Toshiba Research and Development Center

Claims (8)

[Claims] 1. A column for supporting a core upper mechanism holding a control rod drive mechanism for driving a control rod for controlling a nuclear reaction in the reactor core with an upper lid of a reactor vessel containing a core and a coolant in a fast reactor. In a penetrating portion such as, the sealing means for preventing the coolant from rising in the sleeve supporting the strut is a high temperature resistant metal mesh seal, and a strut sealing device for a core upper part mechanism. 2. A shape memory alloy ring seal, the diameter of which expands at a low temperature and shrinks at a high temperature, is used as a sealing means for preventing the coolant from rising in the sleeve supporting the support column. The pillar sealing device for the core upper part mechanism according to claim 1. 3. The shape memory alloy coil seal, the diameter of which expands at a low temperature and shrinks at a high temperature, is used as a sealing means for preventing the coolant from rising in the sleeve supporting the support column. The pillar sealing device for the core upper part mechanism according to claim 1. 4. The core according to claim 1, further comprising a scraper for scraping off the coolant, which is provided in parallel with a sealing means provided on a sleeve for supporting the support column to prevent the coolant from rising. Supporting device for upper mechanism. 5. The support of the upper core mechanism according to claim 1, wherein the sleeve supporting the support is provided with sealing means, and a blow gas down pipe is connected to a gap between the support and the sleeve. apparatus. 6. The pillar sealing device for a core upper part mechanism according to claim 1, wherein a sealing means for preventing the coolant from rising is provided on the shaft side. 7. The column is provided with a sealing means for preventing the coolant from rising, and the tip of the sleeve is located in the furnace near the liquid surface of the coolant or in the coolant. A pillar sealing device for an upper core mechanism according to claim 1 or claim 6. 8. A laser light emitter for irradiating the hole side of the through-hole and the periphery of a plug inserted into the through-hole and a laser oscillator connected thereto are provided in the through-hole such as the upper lid of the reactor vessel. A device for removing sodium, etc.