JPS5821198A - Internal pump - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a wet motor type internal pump for circulating nuclear reactor cooling water.

A conventional internal pump is a wet motor type pump installed at the bottom of a reactor pressure vessel 1 as shown in FIG. 6. Consists of a secondary seal 7, a motor rotor 8, a motor stator 9, and an auxiliary impeller 10 for motor cooling water. During reactor operation, reactor pressure vessel l
The internal water temperature reaches a high temperature of about 300C, but since the motor case 2 contains polymeric materials such as the winding insulation material of the motor stator 9 and the sealing rubber material of the secondary seal 7, the reactor pressure vessel It is necessary to reduce the amount of heat transmitted from motor case 1 to motor case 2 to maintain the water temperature inside motor case 2 at a low temperature of about 40 tZ'. Conventionally, impeller 3
As shown in FIG. Inject it into the motor case 2 from part A of the hole 6.
Gap B between shaft 5 and stretch tube 6 through a
and reached the D part.

As a result, the purge water also has the effect of cooling the motor case nozzle portion, thereby suppressing the heat transmitted from the reactor pressure vessel 1 to the motor case 2.

However, in the conventional structure, the gap between the stretch tube 6 and the motor case nozzle 2a is a gap with an axial length of nearly 1 m, and dead water accumulates there, causing the outer peripheral surface of the stretch tube 6 and the motor case nozzle 2a to There was a risk of damage due to crevice corrosion on the inner peripheral surface.

Furthermore, when the amount of purge water is increased to increase the cooling effect of the motor case nozzle part, the temperature difference between the stretch tube 6 and the motor case nozzle 2a becomes too large, and the axial thermal expansion of the two becomes different due to the temperature difference. Since high tensile thermal stress is generated in the tube 6, there is a structural upper limit to increasing the cooling effect of the motor case nozzle portion.

Therefore, there was a drawback that the heat transmitted from the reactor pressure vessel 1 to the motor case 2 could not be completely suppressed.

The purpose of the present invention is to improve the cooling effect of the motor case nozzle part using purge water, whose main purpose is to prevent the inflow of contaminant particles, more than ever before, and to reduce the heat transmitted from the reactor pressure vessel to the motor case in order to protect the motor insulation material, etc. It is an object of the present invention to provide a highly reliable internal pump for a nuclear reactor by reducing thermal stress in the stretch tube, preventing crevice corrosion in the gap between the stretch tube and the motor case nozzle, and reducing thermal stress in the stretch tube.

According to the present invention, the flow path of purge water that is injected into the motor case from the 11Ji section in the motor case and flows out from the lower part of the impeller into the reactor pressure vessel is not limited to the gap between the shaft and the stretch tube, but also between the stretch tube and the motor case. A corrugated plate is also provided in the gap between the nozzle and the stretch tube and the motor case nozzle.

An embodiment of the present invention will be described below with reference to FIGS. 3 and 4. In the internal pump embodying the present invention, as shown in FIG.
It flows not only through the gap B of the stretch tube 6, but also through the gap C between the stretch tube 6 and the motor case nozzle 2a, and reaches In.

Therefore, dead water does not accumulate in the gap C, and crevice corrosion on the outer circumferential surface of the stretch tube 6 and the inner circumferential surface of the motor case nozzle 2a can be prevented. to flow,
Even with the same amount of purge water as before, a greater cooling effect than before can be obtained.

In the internal pump embodying the present invention, as shown in FIGS. 3 and 4, a corrugated plate 11 is attached to the stretch tube 6 and the IVjll of the motor case nozzle 2a.
It is installed. In addition, motor case nozzle 2a
Since heat transfer occurs between the stretch tube 6 and the temperature difference between the two is small, generation of high tensile thermal stress in the stretch tube 6 can be prevented. By installing this corrugated plate 11, even with the same amount of purge water as in the past, a cooling effect greater than that in the past can be obtained. Furthermore, by increasing the amount of purge water, the cooling effect of the motor case nozzle section by the purge water can be further increased, and heat transfer from the reactor pressure vessel 1 to the motor case 2 can be completely suppressed.

The material for the corrugated plate 11 is most preferably a Ni-based alloy, which is known to have good thermal conductivity, high corrosion resistance, and high heat resistance, but the material is not limited thereto.

In addition to adopting this corrugated plate 11, if a circumferential groove is provided on the outer circumferential surface of the stretch tube 6, which serves as a flow path for purge water, the reactor pressure vessel 1 at the internal pump attachment part can be
The practical value of the present invention is extremely high because it is possible to reduce the delicate inclination that occurs because the internal pump is not symmetrical about the axis.

As explained above, according to the present invention, purge water, whose main purpose is to prevent the inflow of contaminant particles, can have a cooling effect on the motor case nozzle part that is more effective than before, and at the same time,
It is possible to obtain the effect of preventing crevice corrosion damage and the effect of preventing thermal stress damage to structural materials.

[Brief explanation of the drawing]

Fig. 1 is a longitudinal sectional view of a conventional internal pump, Fig. 2 is a longitudinal sectional view of a conventional motor case nozzle section, and Fig. 3 is a longitudinal sectional view of a conventional internal pump.
FIG. 4, a longitudinal cross-sectional view of the motor case nozzle portion according to the present invention, is a cross-sectional view taken along the line ■--■ in FIG. 3. l...Reactor pressure vessel, 2...Motor case, 2a
... Morph case nozzle, 3... Impeller, 4...
・Tiff user, deceased...Shaft, 6...Stretch tube, 8...Motor rotor, 9...Motor stator, A...Part A, B...Gap BXC...Gap C
XD... D section, E... Gap E0 Agent Patent attorney Toshiyuki Usuda'-'' ,...,, 1st flash

Claims (1)

[Claims] an impeller provided at the bottom of the reactor pressure vessel for circulating reactor cooling water; a diffuser disposed downstream of the impeller; and a motor attached to the bottom of the pressure vessel;
A gull internal pump includes a shaft enclosed in the motor and to which the impeller is fixed, and a stretch tube surrounding a part of the shaft and fixing the diffuser to the bottom of the reactor pressure vessel. A gap is provided between the cases, and a corrugated plate is installed in this gap so that purge water flows in the axial direction, thereby reducing the temperature difference between the stretch tube and the motor case. internal pump.