JPH0493696A - Internal pump - Google Patents

Abstract

PURPOSE:To prevent reactor cooling water containing a clad from penetrating into a pump and a motor by installing plural pieces of plate projections, heading for an outer circumference, on the lower end face of an impeller boss, and thereby forming a small pump there. CONSTITUTION:A vane 21 made up of a plate projection is installed in the lower end face of an impeller boss 14 being opposed to the upper end face of an inner cylinder 10 of a diffuser 11. Cooling water containing a clad is accelerated and fed, under pressure, by a pump shaft 3, the impeller boss 14 and an impeller 9 rotated and driven by a motor 6, and carried downward. In this case, part of a flow of the cooling water contained with the clad tries to penetrate into the inner part through a clearance 19, but it is repelled away to the outside by means of pumping action of the vane 21, no entering into a clearance 17 or 18. Accordingly, any possible penetration of the clad into a motor part is thus preventable. In this connection, the vane 21 may be installed in the inner cylinder of the diffuser.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an internal pump for a nuclear reactor, and more particularly to a wet motor type internal pump for recirculating reactor cooling water.

[Conventional technology]

The conventional internal pump is disclosed in Japanese Patent Application Laid-Open No. 1-245195.
As described in the publication, it is as shown in Figure 5. In FIG. 5, reference numeral 1 denotes a reactor pressure vessel, and a motor casing 2 is attached to the outside of the bottom of the vessel. A motor 6 consisting of a motor rotor 4 and a stator 5 is housed within the motor casing 2.
A pump shaft 3 is attached above the pump shaft 3, and a pump impeller 9 for circulating reactor cooling water is fixed to the uppermost end of the pump shaft 3. A diffuser 11 having an inner cylinder 10 surrounding the pump shaft 3 is installed downstream of the impeller 9. The upper end 16 of the inner cylinder 10 is formed into a cylindrical shape with only the inner peripheral side protruding, and the boss part 14 of the impeller 9 has a covering part 1 so as to cover the upper end 16 of the inner cylinder 10.
5 is provided. The motor casing 2 is provided with a purge water inlet 13, and the purge water injected into the motor casing 2 from the purge water inlet 13 passes through the gap around the pump shaft 3, and further flows between the pump shaft 3 and the diffuser 11. The crud in the pressure vessel 1 can be prevented from entering the motor casing 2 through the passage B formed between the inner cylinder 10 and the inner cylinder 10. .

When the pump is operated, the crud in the cooling water moves violently with the water flow and tries to enter the passage B through the gap between the boss 14 of the impeller 9 and the upper end 16 of the inner cylinder 10 of the diffuser 11. Since the covering part 15 acts as a lid, it is possible to prevent cruts from entering.

[Problem to be solved by the invention]

By the way, in the above-mentioned conventional technology, the passage resistance of the gap between the boss 14 of the impeller 9 and the upper end 16 of the inner cylinder 10 of the diffuser 11 is increased to prevent the crud from entering. As for the size of the gap in the direction, it is necessary to lower the pump shaft 3 downward during maintenance and inspection to form a seal on the upper end surface of the trench tube 12, so a large gap of about 1 is required. For this reason, the passage resistance increases to a certain extent, but it is inevitably limited, and in addition, when the pump is operating, the water flow fluctuates violently and irregularly, so crud in the water flow will not penetrate depending on the size of the passage resistance. However, there is a possibility that some of them will invade. If the crud enters the interior and falls onto the motor section 6 passing through the gap around the pump shaft 3, workers will be exposed to radiation during maintenance and inspection of the motor section 6.

An object of the present invention is to provide an internal pump that can prevent crud in reactor cooling water from entering the pump or motor, and can prevent workers from being exposed to radiation during maintenance inspections such as motor inspections. be.

[Means to solve the problem]

In order to achieve the above object, the present invention provides a plate-shaped protrusion extending from the inner periphery to the outer periphery on either or both of the upper end surface of the inner cylinder of the diffuser and the lower end surface of the impeller boss opposing thereto. A small pump was formed through which water was released into the pressure vessel.

[Effect]

In the present invention, a small pump is formed in the axial gap between the upper end surface of the inner cylinder of the diffuser and the lower end surface of the impeller boss facing the inner cylinder, so that the air is discharged from the inside to the outer periphery. At the same time as the outflow of the purge water is accelerated, the water that enters the inside from the pressure vessel side is splashed away. Therefore, the cooling water in the pressure vessel and the crud in the cooling water do not fall into the gap around the pump shaft or enter the motor section below the gap.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

Reference numeral 2 denotes a motor casing of an internal pump. A motor 6 consisting of a motor rotor 4 and a motor stator 5 is housed inside the casing 2. A pump shaft 3 driven by the motor is attached to the upper part of the motor rotor 4. ing. The upper end of this pump shaft 3 protrudes into the pressure vessel 1 through the bottom opening 8 of the pressure vessel 1, and an impeller 9 for circulating cooling water in the pressure vessel 1 is installed at the upper end of this protrusion. An upright impeller boss 14 is attached. A pump shaft 3 is located downstream of this impeller 9.
A diffuser 11 having an inner cylinder 10 surrounding the pressure vessel 1 is fitted with a bottom opening 8 in the pressure vessel 1, and a stretch tube 12 is inserted through the lower end of the diffuser 1. Screw (not shown)
The diffuser 12 is crimped to the bottom opening 8 of the pressure vessel 1 with tightening.

13 is a purge water supply port for injecting purge water into the motor casing, 17 is a gap between the pump shaft 3 and the stretch tube 12, and 18 is a gap between the pump shaft 3 and the inner cylinder 10 of the diffuser 11. There is a gap in between. 19
721 is a gap formed between the upper end surface of the inner cylinder 10 of the diffuser 11 and the lower end surface of the impeller boss 14 facing the ○. When the vane 21 rotates, it acts as a pump to discharge water from the inner circumference to the outer circumference.

The internal pump configured in this way operates as follows. Cooling water containing cladding flowing in from above the impeller 9 of the pump is rotated by the pump shaft 3 driven by the motor 6. It is accelerated and pumped by the impeller boss 14 and the impeller 9, and is swept downstream. In this case, a part of the flow of the cooling water containing the cruts is directed towards the axial clearance 19 and attempts to enter the interior, but due to the pumping action of the vane 21, the water flows from the inner circumference to the outer circumference of the lower end surface of the impeller boss 14. Since the cooling water containing the crud cannot enter the inside of the pump, that is, the gaps 17 and 18, the crud can also be prevented from entering. On the other hand, the purge water injected into the motor casing 2 from the purge water supply port 13 flows through the gaps 17 and 18 around the pump shaft 3.
The purge water then flows out into the pressure vessel 1 through the axial clearance 19. In this case, the pumping action of the vane 21 on the lower end surface of the impeller boss 14 accelerates the outflow of the purge water into the pressure vessel 1. The cooling water containing crat flows from the axial clearance 19 to the clearances 17 and 18 around the pump shaft 3.
can't get into it. Therefore, intrusion of crud can also be prevented.

According to this embodiment, there is a great effect in preventing the cladding from entering the motor section.

FIG. 3 shows a second embodiment in which vanes 22 are provided on the upper end surface 20 of the inner cylinder 10. In this case, internal information 10
Due to the rotation of the impeller boss 14 facing the upper end surface 20, it passes through the gaps 17 and 18 around the pump shaft 3,
The purge water exiting from the axial gap 19 into the pressure vessel l is guided along the vanes 22 and is discharged at an accelerated rate.

For this reason, the intrusion of cooling water into the interior from the pressure vessel 1 side is also inhibited. In this case, since the vane 22 does not rotate, the effect of preventing the intrusion of the cladding is lower than that in the first embodiment, but since it is a stationary vane, it has the advantage of being easier to install.

〔Effect of the invention〕

According to the present invention, it is possible to prevent the cooling water in the furnace containing the cladding from entering the motor section through the gap around the pump shaft at the inlet section thereof.

Therefore, radioactive cladding does not fall or enter the gap around the pump shaft or the motor section located below it, and radioactive contamination can also be prevented. Therefore, there is no problem of radiation exposure to workers during maintenance and inspection of the motor section, etc.

[Brief explanation of drawings]

FIG. 1 is a vertical cross-sectional view of a main part of an internal pump showing one embodiment of the present invention, FIG. 2 is a view taken along the ■-■ arrow in FIG. 1,
FIG. 3 is a vertical cross-sectional view of main parts showing another embodiment, and FIG.
The IV-TV arrow direction view in the figure and FIG. S are longitudinal cross-sectional views of a conventional internal pump. 1... Reactor pressure vessel, 3 Pump shaft, 9... Impeller, 10... Inner cylinder, 11... Diffuser, 14... Figure A, Figure, Figure

Claims (1)

[Claims] 1. A wet motor housed in a motor casing vertically installed in an opening at the bottom of the reactor pressure vessel, a pump shaft coupled to the upper end of the shaft of the wet motor, and a pump shaft coupled to the upper end of the pump. a combined impeller boss, an impeller installed on the outer surface of the impeller boss for circulating reactor cooling water, a diffuser having an inner cylinder surrounding the pump shaft on the downstream side of the impeller, and the pump shaft. In the internal pump, the internal pump has a gap as a passage for purge water to flow toward the pressure vessel between the diffuser inner cylinder and the inner cylinder, and a plurality of plates facing the outer periphery are arranged on the lower end surface of the impeller boss facing the upper end surface of the diffuser inner cylinder. An internal pump characterized in that a small pump is formed by providing a plate-like protrusion. 2. The internal pump according to claim 1, wherein the small pump is formed by providing a plurality of plate-shaped protrusions extending toward the outer circumference on the upper end surface of the inner cylinder of the diffuser.