JP3197747B2 - Reactor built-in recirculation pump top plug - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention provides for the installation and removal of a recirculation pump (hereinafter referred to as RIP) built in a reactor for circulating light water as a coolant for a reactor in a reactor pressure vessel during a periodic inspection. The present invention relates to a recirculation pump upper plug built into a nuclear reactor (hereinafter simply referred to as an upper plug).

[0002]

2. Description of the Related Art FIG. 4 schematically shows a longitudinal section of a boiling water reactor. A shroud 21 containing a reactor core 20 is provided in a reactor pressure vessel (hereinafter referred to as RPV) 15,
A control rod drive mechanism (hereinafter C)
RD) 42 is provided so as to pass through the RPV lower mirror 23. The RPV lower mirror 23 has a RIP 27,
The CRD 42 is circumferentially surrounded, and ten reactors of, for example, 1.35 million kW class are inserted at equal intervals through the RPV 15.

[0003] A coolant for cooling the core 20 flows in from a water supply sparger 41, and the RPV 15 and the shroud 21
, And is sent down into the reactor core 20 by the RIP 27.

FIG. 5 is an enlarged view of a portion V in FIG. As described above, the RIP 27 forcibly circulates the coolant in the RPV 15 and mainly includes the motor unit 30 and the pump unit 26 in a submerged state. Here, the pump unit 26 is attached to the upper part of the shaft 25 and guides the coolant from above to below.
4 and a diffuser 14 that is attached inside the RPV 15 and diffuses the coolant to be discharged.

On the other hand, the motor 32 is
The lower portion of the motor casing 17 is closed by a motor cover 31. Now, in general, a nuclear power plant is regularly inspected for exchanging fuel constituting the core 20 in the RPV 15 and inspecting various devices, and the RIP 27 is no exception. The parts of the RIP 27 are once removed from the RPV 15 for inspection, and are installed again after the inspection.

With reference to FIG. 6, a method of removing the RIP 27 will be described. To remove the RIP 27 at the time of the periodic inspection, first, the motor 32 is carried downward from the motor casing 17. Then, after closing the lower part of the motor casing 17 with a closing flange (not shown), the pump impeller 24 and the shaft 25 are hung by the gripping tool 50 and the auxiliary hoist (not shown) of the fuel exchanger 51 for use. Is moved to an impeller shaft storage rack 53 provided in the spent fuel pool 52. At the time of this operation, the motor casing 17 is in communication with the inside of the RPV 15 by removing the pump impeller 24 and the shaft 25 on the upper side. However, since the lower portion of the motor casing 17 is closed by a closing flange (not shown), the RPV
15 through the motor casing 17
It does not flow out of P27.

In order to inspect the RIP 27, the RIP 27
It is necessary to access the inside of the motor casing 17 from the lower part of the upper plug 1 shown in FIG.
3 is provided from the inside of the diffuser 14 so as to be in contact with the inner surface of the stretch tube 16 and the motor casing 1 is provided.
7 is closed from above. The handling of the upper plug 13 is performed by grasping the suspension rod 19 with a grasping tool.
This is performed by raising and lowering with an auxiliary hoist (not shown). The inside of the motor casing 17 closed by the upper plug 13 is filled with water supplied from a pipe provided in the motor casing 17 from an external water source having no radioactivity problem unlike the reactor water in the RPV 15. .

After the inspection of the RIP 27 has been completed, the procedure for re-installation is performed in the reverse order. That is, the upper plug 13 is pulled out and the pump impeller 2 is pulled out.
4 and the shaft 25 are installed from above, and then the closing flange 18 is removed and the motor 32 is housed in the motor casing 17.

[0009]

The lifting capacity of the auxiliary hoist of the refueling machine in handling the above-mentioned conventional RIP upper plug is the heaviest pump impeller, shaft (about 700 kg) and gripper (about 300 kg) among the RIP parts.
Since it is necessary to handle g), it is necessary to use about 1.5 tons. When the upper plug is fitted with a closing flange on the motor casing and water is injected into the motor casing and removed, the water pressure of the reactor water is not applied on the upper plug.
0Kg) and can be lifted easily and normally.

If the flange is not mounted, the water pressure of the reactor water on the upper surface of the upper plug is about 2.
Although 5 kg / cm ² is acting, the weight is about 1.1 tons even considering the weight and this water load, and the auxiliary hoist capacity is smaller than 1.5 tons. Is possible. However, if the upper plug is pulled out before the mounting of the closing flange or after removing the closing flange, a large amount of reactor water may flow out to the lower part of the RIP via the inside of the motor casing.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object that the closing flange is not yet attached when the upper plug is removed by mistake, or the upper plug has already been removed. The present invention provides an upper plug capable of preventing the outflow of reactor water generated due to the presence of the upper plug.

[0012]

In order to achieve the above-mentioned object, in the upper plug of the present invention, the invention described in claim 1 is used for removal and attachment at the time of periodic inspection of the RIP, and a disk-shaped upper part is provided. A vertical rib having a hollow cylindrical shape having a load receiver, and a body provided with an inverted conical portion at the lower end thereof, which is substantially bullet-shaped and has a cylindrical communication passage therein and a sealing material on the outer peripheral surface. An upper plug that is provided so as to come into contact with the inner surface of the stretch tube from the inside of the diffuser after removing the pump impeller and the shaft of the RIP and that closes the inside of the motor casing from the upper part. An emergency suspension rod having a cylindrical vertical hole drilled a predetermined length in the axial direction at the upper end and inserted into a circular hole drilled in the load receiver provided at the lower end. Is inserted into a cylindrical vertical hole, the lower is fixed to the emergency suspension rod by the lower fixing pins,
A break pin having a cross section partially formed so as to be broken by a predetermined load, and a cylindrical vertical hole inserted through an upper portion of the break pin, and a normal time suspension in which the upper portion of the break pin is fixed by an upper fixing pin. It has a lower rod.

According to a second aspect of the present invention, there is provided a seal plate provided at a lower end of the longitudinal rib and provided with the cylindrical communication passage in the center, instead of the main body according to the first aspect, and the seal plate and the stretch plate. 2. The upper plug according to claim 1, further comprising an annular sealing material provided in a gap with an upper end surface of the tube.

According to a third aspect of the present invention, there is provided the upper plug according to the first or second aspect, further comprising an emergency suspension rod having a grip portion on an upper portion. The invention described in claim 4 is
The normal suspension rod is provided so as to accommodate the emergency suspension rod with the cylindrical guide portion as the lower portion, and the outer peripheral surface of the guide portion is cylindrically formed on the load receiving upper surface so as to be inserted into the inner surface. 3. The upper plug according to claim 1, further comprising a lateral displacement prevention guide provided. According to a fifth aspect of the present invention, there is provided the upper plug according to the fourth aspect, further comprising a suspending member provided on an outer surface of the lateral displacement prevention guide.

[0015]

In the upper plug having the above-mentioned structure, when a predetermined load is applied, the upper plug is inserted into the vertical holes formed in the normal suspension rod and the emergency suspension rod, and the upper and lower fixing pins and the lower fixing rod, respectively. The break pin fixed by the pin breaks and the upper plug is left without being pulled out together with the emergency suspension rod, so the sealing function is not impaired,
Therefore, the reactor water in the RPV does not flow out.

[0016]

FIG. 1 shows a first embodiment of an upper plug according to the present invention. In FIG. 1, an upper plug 60 has a vertical rib 11 having a hollow cylindrical shape, a main body 12 which is continuous with a lower end thereof, has an inverted conical portion, is substantially bullet-shaped, and has a cylindrical communication passage 61 therein. Having. The body 12 is provided with a double sealing material 10 made of an elastic material such as synthetic rubber in the circumferential direction. A load receiver 9 is provided on the upper surface of the vertical rib 11, and a hollow cylindrical lateral displacement prevention guide 6 is installed on the load receiver 9. A circular hole 62 is formed in the center of the load receiver 9, and the emergency suspension rod 2 having the internal plug 8 at the lower end is inserted into the circular hole 62. A cylindrical vertical hole 63 having a predetermined length is formed at the upper end of the emergency suspension rod 2. The breaking pin 3 is inserted into the vertical hole 63. A part of the cross section of the breaking pin 3 is formed to have a smaller area than the cross sectional area of the other part so as to break under a predetermined load.

A normal suspension rod 1 having a cylindrical guide portion 64 for accommodating the emergency suspension rod 2 is provided inside the hollow cylindrical lateral displacement prevention guide 6. . A cylindrical vertical hole 65 is also drilled in the normal suspension rod 1, and the upper portion of the break pin 3 inserted in the emergency suspension rod 2 is inserted into the vertical hole 65. The upper part of 3 is fixed by an upper fixing pin 4 provided in the suspending rod 1 in a normal state, and the lower part is fixed to a lower fixing pin 5 provided in the suspending rod 2 in an emergency.
Therefore, when the suspension rod 1 is pulled up in the normal state, the breaking pin 3
, The emergency suspension rod 2 is simultaneously pulled up.

Incidentally, the lateral displacement prevention guide 6 is provided with a hanging metal fitting 7 for when the upper plug 60 cannot be lifted using the normal hanging rod 1 or the emergency hanging rod 2.

The operation of the upper plug 60 thus configured will be described with reference to FIG. In FIG. 2, a closing flange 18 is attached to the bottom of the motor casing 17, and the inside of the motor casing 17 is supplied with water from the outside, not the reactor water, and the inside of the RPV 15 and the inside of the motor casing 17 are hydraulically driven. There is no differential pressure. In this state, only the weight of the upper plug 60 is applied to the upper plug 60, and the upper plug 60 can be pulled up without breaking the breaking pin 3. At this time, even if the upper plug 60 is pulled up, the reactor water in the RPV 15 does not flow out because the closing flange 18 is provided at the bottom of the motor casing 17.

On the other hand, the handling procedure is erroneously
In the case where 8 has not yet been attached or has been removed, the upper plug 60 is added to its own weight,
A water load of about 2.5 kg / cm ² in the RPV 15 is applied. In such a case, if the upper plug 60 is to be pulled out, the breaking pin 3 is broken, and the normal hanging rod 1 is pulled up by the grip 50 together with the guide portion 64 and the upper part of the breaking pin 3. Therefore,
The lower portion of the breaking pin 3 is left on the upper plug 60 side together with the emergency suspension rod 2, and the sealing material 10 is not lifted, so that the sealing function is not impaired at all. That is, the reactor water in the RPV 15 does not flow out. After the breaking pin 3 breaks, the closing flange 18
After taking necessary measures such as installing the emergency suspension rod 2
The upper plug 6 is used for lifting the
0 can be removed. If the emergency hanging rod 2 cannot lift the upper plug 60, the hanging plug 7 may be used to lift the upper plug 60.

In order to ensure that only a vertical load is applied to the breaking pin 3 so as to obtain a reliable breaking load, the suspension rod 1 is normally provided so as to be movable only in the vertical direction by the lateral displacement prevention guide 6. ing.

Next, a second embodiment of the upper plug of the present invention will be described with reference to FIG. 3, the same components as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. In the upper plug 66 of the second embodiment, a disk-shaped seal plate 33 is used instead of the main body 12 of the first embodiment.
The inner plug 8 is brought into contact with the inner surface of the motor casing 17, and a sealing member 34 is interposed between the sealing plate 33 and the stretch tube 16 to close the motor casing 17 from above. Same as the example. Therefore,
The second embodiment having such a configuration also has the same operation and effect as the first embodiment.

[0023]

As described above, in the upper plug of the recirculation pump with a built-in reactor according to the present invention, if the motor casing is provided with a closing flange, it can be pulled out and the closing flange is provided. If not, the breaking pin breaks and cannot be pulled out, so that the sealing function is not impaired. Therefore, it is possible to improve the safety of RIP inspection without water in the RPV containing radioactivity flowing out of the motor casing to the outside.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a first embodiment of an upper plug according to the present invention.

FIG. 2 is a vertical cross-sectional view showing a mounted state of an upper plug according to the first embodiment.

FIG. 3 is a longitudinal sectional view showing a second embodiment of the upper plug according to the present invention.

FIG. 4 is a longitudinal sectional view showing the structure of a nuclear reactor.

FIG. 5 is an enlarged longitudinal sectional view showing a portion V in FIG. 4;

FIG. 6 is a schematic view for explaining a method of disassembling and inspecting the RIP.

FIG. 7 is a longitudinal sectional view showing a conventional example of an upper plug.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Normal suspension rod 2 ... Emergency suspension rod 3 ... Breaking pin 4 ... Upper fixing pin 5 ... Lower fixing pin 6 ... Side slip prevention guide 7 ... Suspension metal fitting 8 ... Internal plug 9 ... Load receiving 10 ... Sealing material 11 ... vertical rib 12 ... body 13 ... upper plug 14 ... diffuser 15 ... reactor pressure vessel (RPV) 16 ... stretch tube 17 ... motor casing 18 ... closing flange 19 ... hanging rod 20 ... core 21 ... shroud 22 ... RIP nozzle 23 ... RPV lower mirror 24 ... Pump impeller 25 ... Shaft 26 ... Pump unit 27 ... Reactor built-in recirculation pump (RIP) 30 ... Motor unit 31 ... Motor cover 32 ... Motor 33 ... Seal plate 34 ... Seal material 41 ... Water supply sparger 42: Control rod drive mechanism (CRD) 50: Gripping tool 51: Refueling machine 52: Spent fuel pool 53: A Pella shaft storage rack 60 ... upper plug 61 ... communicating passage 62 ... hole 63 ... vertical hole 64 ... guide portion 65 ... vertical hole 66 ... upper plug

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G21C 15/243 520 F04D 7/08 G21C 19/02

Claims (5)

(57) [Claims] 1. A hollow cylindrical vertical rib having a disk-shaped load receiver at an upper portion thereof, which is used at the time of removal and attachment at the time of a periodic inspection of a built-in recirculation pump of a nuclear reactor, and is continuously inverted at a lower end thereof. It has a conical portion and a cylindrical communication passage inside and a main body with a sealing material on the outer peripheral surface, and after removing the pump impeller and shaft of the reactor built-in type recirculation pump, the stretch tube from the inside of the diffuser is removed. An upper plug, which is provided so as to be in contact with the inner surface and closes the inside of the motor casing from above, is provided with an internal plug closing the communication passage at a lower end portion, is inserted into a circular hole formed in the load receiver, and An emergency suspension rod having a cylindrical vertical hole drilled a predetermined length in the axial direction, and an emergency suspension rod inserted through the cylindrical vertical hole, and a lower portion fixed to the emergency suspension rod by a lower fixing pin. It has a breaking pin, a part of which is shaped so as to be broken by a predetermined load, and a cylindrical vertical hole that penetrates the upper part of the breaking pin, and fixes the upper part of the breaking pin with an upper fixing pin. An upper plug for a recirculation pump incorporated in a nuclear reactor, comprising a normal suspension rod. 2. A seal plate provided at a lower end of the longitudinal rib and provided with the cylindrical communication passage in the center instead of the main body according to claim 1, and a gap between the seal plate and an upper end surface of the stretch tube. 2. The upper plug of a recirculation pump incorporated in a nuclear reactor according to claim 1, further comprising: an annular sealing member provided in the reactor. 3. An emergency suspension rod having a grasping portion at an upper portion thereof.
Reactor built-in recirculation pump top plug as described. 4. The normal-time suspension rod is provided so as to receive the emergency suspension rod with a cylindrical guide portion as a lower portion, and has a cylindrical shape such that an outer peripheral surface of the guide portion is inserted into an inner surface. 3. The upper plug of a recirculation pump with a built-in reactor according to claim 1, further comprising a side slip prevention guide provided on the load receiving upper surface. 5. The upper plug of a recirculation pump built in a nuclear reactor according to claim 4, further comprising a suspension metal fitting provided on an outer surface of said lateral displacement prevention guide.