JPH0425518B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a wet motor type pump used for circulating coolant in a nuclear reactor, and particularly to its water leakage prevention structure.

[Technical background of the invention]

First, a conventional wet motor type pump will be explained with reference to FIG.

In FIG. 1, a vertical boss 2 is formed at the lower end of a reactor pressure vessel 1 to communicate the inside and outside of the pressure vessel 1. At the lower end of this boss 2, a motor of a wet motor pump 3 is formed. A plurality of casings 5 of the section 4 are vertically installed. A stator and a rotor (not shown) are disposed within the motor section 4, and a pump shaft 6 integrated with the rotor extends vertically from the casing 5 to reach the inside of the reactor pressure vessel 1. ing. The pump shaft 6 is supported by journal bearings 7 and 8 at the upper and lower ends of the casing 5, and a thrust disk 9 protruding from the lower end is supported by a pair of thrust bearings 10 and 11. It is supported by.

A pump impeller 12 for circulating coolant within the reactor pressure vessel 1 is protruded from the upper end of the pump shaft 6 . Also, this impeller 1
A diff user 13 for rectifying the coolant is protruded on the outer peripheral side of the sleeve 14 of the diff user 13.
By engaging the engaging portion 7 at the upper end of the stretch tube 16 installed in the boss 2,
The differential user 13 is seated and supported on the upper end surface of the boss 2. Further, the motor casing 5 is connected to primary cooling system pipes 18 and 19 that cool the inside of the motor section 3, and furthermore, the upper end of the motor casing 5 is connected to the temperature inside the reactor pressure vessel 1. When the temperature is higher than the temperature inside the motor section 3, this high temperature is transferred from the reactor pressure vessel 1 to the motor section 3.
Purge water system piping 2 to prevent movement to
0 is connected.

[Problems with background technology]

By the way, since there is no sealing function between the pump shaft 6 penetrating the inside of the boss 2 and the stretch tube 16 installed inside the boss 2, there is usually no seal between the inside of the reactor pressure vessel 1 and the inside of the motor section 3. The pressures are equal. If water leaks from the primary cooling system piping 18 or 19 while the inside of the reactor pressure vessel 1 is at high temperature and pressure of 100°C or higher,
The pressure inside the motor section 4 becomes low, and a large amount of high-temperature, high-pressure water flows from the reactor pressure vessel 1 into the motor section 3 via the stretch tube 16 and the pump shaft 6. At that time, purge system piping 2
The cooling capacity from 0 was exceeded, and therefore the motor section 4 reached a high temperature, and there was a risk that the insulation function of the motor coil, which was designed at room temperature, would be destroyed. As a result, the motor becomes unusable, and high-temperature steam gushes out from the water leaking point, causing an accident in which humans cannot approach the reactor pressure vessel 1 until the high-temperature, high-pressure water in the reactor pressure vessel 1 is exhausted. There was a possibility that this could become a problem.

[Purpose of the invention]

In view of these points, the present invention provides a wet motor type pump that can shut off between the motor section and the reactor pressure vessel when the pressure inside the motor section falls below the pressure inside the reactor pressure vessel. The purpose is to

[Summary of the invention]

In order to achieve the above-mentioned object, a wet motor type pump according to the present invention includes a motor section located outside the reactor pressure vessel, and an impeller extending from the motor section into the reactor pressure vessel and protruding from the tip thereof. A pump shaft, a diff user located on the outer peripheral side of the impeller, a stretch tube that fixes the diff user to the reactor pressure vessel, a thrust bearing that supports the pump shaft, and a cooling device that supplies cooling water into the motor section. a spring member that biases the thrust bearing in a direction in which the pump shaft protrudes into the reactor pressure vessel; and a sealing device that engages with each other to prevent liquid from flowing when the device is in the position.

[Embodiments of the invention]

The present invention will be explained below with reference to embodiments shown in the drawings. Note that the same components as those of the conventional device described above are denoted by the same reference numerals in the drawings, and the explanation thereof will be omitted.

In FIGS. 2 to 5, the lower thrust bearing 11 of the thrust bearings 10 and 11 supporting the thrust disk 9 of the pump shaft 6 is biased upward by a coil spring 21, as shown in FIG. has been done.

On the other hand, the upper end surface 22 of the engaging portion 17 of the stretch tube 16 is a substantially trapezoidal sealing surface that is smoothly curved into a somewhat circular arc. It is surrounded. The enlarged portion 23 has a sealing surface 24 at its lower portion that engages with the sealing surface 22 to prevent liquid from flowing when the coil spring 21 is bent. This sealing surface 24 complements the sealing surface 22 of the stretch tube 16.

Note that the primary cooling type pipes 18 and 19 are connected to a heat exchanger 25 that cools the cooling water, forming a closed cooling water circulation cycle.

Next, the operation of the above-described embodiment will be explained with reference to FIG.

First, when the wet motor pump 3 is stopped in a normal state with no water leakage, the pressure inside the reactor pressure vessel 1 and the pressure inside the motor casing 5 are equal, so the impeller 12 and the pump shaft 6 are affected by their own weight (W ₁ ) is supported by a coil spring 21 via a lower thrust bearing 11. At this time, the stretch tube 16 and the seal surfaces 22, 24 of the pump shaft 6 are separated. This situation is shown in position in FIG.

When the motor moves, an upward thrust (F) is generated on the impeller 12, and as shown in the position in _FIG .
It floats up due to the larger thrust force (F), comes into contact with the upper thrust bearing 10, and is supported.
At this time, the lower thrust bearing 11 is urged upward. The coil spring 21 is fully extended, and a gap is created between the thrust disk 9 and the lower thrust bearing 11.

Furthermore, the motor section 4 or the primary cooling system piping 1
8, 19 and the heat exchanger 9, when the inside of the reactor pressure vessel 10 is at high temperature and high pressure of 100°C or higher, the pressure inside the motor casing 5 becomes lower than that inside the reactor pressure vessel 10, Since the pump shaft 6 has its own weight (W ₁ ) and a load (P) caused by the pressure difference acting in the same direction as its own weight, a load of W ₁ +P acts on the lower thrust bearing 11. , the deflection of the coil spring 21 becomes larger than when only the dead weight (W ₁ ) of the pump shaft 6 acts, and the pump shaft 6 moves downward by the increased deflection amount of the spring 21. In the process of deflection of the spring 21, the sealing surface 24 of the pump shaft 6 is moved toward the sealing surface 24 of the stretch tube 16, as shown in FIG.
2 and prevents high-temperature, high-pressure water from flowing from the reactor pressure vessel 1 side to the pump casing 5 side.

According to the embodiment described above, when a water leak occurs on the motor side, high-temperature, high-pressure water on the reactor pressure vessel side flows into the motor side due to contact between the sealing surface 24 of the pump shaft 6 and the stretch tube 22. The insulation performance of the motor coils will not be destroyed and the motor will be in a healthy condition.Moreover, the water on the reactor pressure vessel 1 side will not leak, so the pressure vessel 1
The equipment inside can be maintained in good condition.

In addition, when the pump is normally stopped and there is no water leakage on the motor side, the seal surfaces 22 and 24 are not in contact with each other, so when the pump 3 is started, there is little frictional resistance and smooth startup is possible.

Furthermore, during pump operation, the pump shaft 6 floats due to the thrust of the impeller 12, is supported by the upper thrust bearing 10, and is separated from the lower thrust bearing 11, thereby reducing frictional resistance and improving motor efficiency.

Incidentally, as shown in FIG. 7, the sealing surfaces 22 and 24 may each be provided with annular projections and depressions to ensure watertightness.

〔Effect of the invention〕

As explained above, the wet motor type pump according to the present invention includes a spring member that biases the thrust bearing in the direction in which the pump shaft projects into the reactor pressure vessel, and a spring member that is provided on the pump shaft and the stretch tube so that the pump shaft The sealing device engages with each other to prevent the flow of liquid when the motor is in the retracted position, so even if the pressure inside the motor decreases, the flow of liquid between the reactor pressure vessel and the motor is prevented. has the excellent effect of being blocked.

[Brief explanation of drawings]

FIG. 1 is a vertical sectional view showing a conventional wet motor type pump, FIG. 2 is a vertical sectional view showing an embodiment of the wet motor type pump according to the present invention, and FIGS. Enlarged view of part B, No. 5
The figure is an enlarged view of the area near the upper end of the stretch tube.
FIG. 6 is an explanatory view showing the operation of the embodiment shown in FIGS. 2 to 5, and FIG. 7 is a front view showing a modification of FIG. 5. DESCRIPTION OF SYMBOLS 1... Pressure vessel, 2... Boss, 3... Wet motor type pump, 4... Motor section, 5... Motor casing, 10, 11... Thrust bearing, 12
... Impeller, 13 ... Deaf user, 16 ...
Stretch tube, 18, 19...Primary cooling system piping, 21...Coil spring, 22, 24...Sealing surface.

Claims (1)

[Scope of Claims] 1. A motor section located outside the reactor pressure vessel, a pump shaft extending from the motor section into the reactor pressure vessel and having an impeller protruding from its tip, and a pump shaft located on the outer peripheral side of the impeller. In the wet motor type pump, the wet motor type pump has a diff user for fixing the diff user to the reactor pressure vessel, a stretch tube for fixing the diff user to the reactor pressure vessel, a thrust bearing for supporting the pump shaft, and a cooling water pipe for supplying cooling water into the motor section. a spring member that biases the thrust bearing in a direction in which the pump shaft protrudes into the reactor pressure vessel; and a spring member provided on the pump shaft and the stretch tube that engages with each other when the pump shaft is in the retracted position. A wet motor type pump further comprising a sealing device for preventing liquid from flowing through the wet motor type pump. 2. A wet motor pump according to claim 1, wherein said sealing device includes opposing sealing surfaces on the pump shaft and stretch tube that are generally trapezoidal in shape. 3. The wet motor type pump according to claim 1, wherein the sealing device has a sealing surface having annular irregularities.