JPS60247087A - Internal pump for nuclear reactor - Google Patents

Abstract

PURPOSE:To improve the cooling effect at the nozzle section while to reduce thermal stress of tube by providing a plurality of axial grooves in a portion of the outercircumference of stretch tube and passing purge cooling water to the gap between the tube and a motor case nozzle. CONSTITUTION:Plural grooves 11 are made in the outercircumference of a stretch tube 6 to pass the purge cooling water positively to a gap F reaching to section D near a diffuser 4 thus to prevent the inter-gap corrosion at the gap F which had been a dead water region conventionally. Since the motor case nozzle 2a is simultaneously cooled by the purge cooling water passing through the gap F, the differential thermal expansion against said tube 6 is reduced considerably thus to reduce the thermal stress of said tube 6 resulting in a highly reliable internal pump for nuclear reactor.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to a wet motor type internal pump for a nuclear reactor that circulates reactor cooling water.

[Prior art and its problems]

A conventional internal pump is a wet motor type pump installed at the bottom of a nuclear reactor pressure vessel 1 shown in FIG. 1, and an impeller 3.
Diffuser 4. and a shaft 5 inside the motor case 2. It consists of a stretch tube 6, a secondary seal 7, a motor rotor, a motor 8 for motor/stator, and an auxiliary impeller lO for motor cooling water. During reactor operation, the water temperature inside the reactor pressure vessel 1 reaches a high temperature of about 300°C, but inside the motor case 2 there are
Since the secondary seal 7 contains a polymeric material such as a seal rubber material, it reduces the amount of heat transferred from the reactor pressure vessel 1 to the motor case 2 and lowers the water temperature inside the motor case 2 to 40℃8.
It is necessary to maintain the temperature at a low temperature.

Conventionally, the motor was
Purge water, whose main purpose is to prevent contaminated fluid in the reactor pressure vessel 1 from flowing into the motor case 2, is pumped into the motor case 2 from part A in the middle of the motor case 2, as shown in Figure 2. The liquid was injected into the hole 6a between the shaft 5 and the stretch tube 6 [B], and then flowed out into the D section. This also has the effect of cooling the purge water ζ and the motor case nozzle part, and suppresses the heat transmitted from the reactor pressure vessel 1 to the motor case 2.

However, in the conventional structure, the gap between the motor case nozzle 2a with the stretch tube 6 is a gap with an axial length of nearly 1 m, and dead water accumulates there, causing the stretch tube 6 to form on the outer circumferential surface and the motor case nozzle 2a on the inner circumference. There was a risk of damage due to crevice corrosion on the 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 too large, and the axial thermal expansion of the two becomes different due to the temperature difference. However, since high tensile thermal stress occurs in the Stretch Chee-Pro, there is an upper limit to the structure in order to increase the cooling effect of the motor case nozzle.

Therefore, the disadvantage is that the heat transmitted from the reactor pressure vessel l to the motor case 2a cannot be completely suppressed.
had.

In order to solve this problem, Japanese Patent Application Laid-open No. 58-21198, in which a corrugated plate was provided between the stretch tube and the motor case, also proposed a stretch chain pro and a motor case nozzle 2a.
The gap between the parts will not be completely eliminated, and there is a risk that the temperature gradient will be large and high thermal stress will occur in the part where the purge cooling water does not flow. Further, the structure is complicated because it is necessary to install a large number of purge water circulation holes in the stretch tube or to use a corrugated plate.

[Purpose of the invention]

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 the thermal stress of the stretch tube and preventing crevice corrosion in the gap between the stretch tube and the motor case nozzle.

[Summary of the invention]

The present invention relates to a wet motor type internal reactor pump for circulating reactor cooling water provided at the bottom of a reactor pressure vessel, in which a plurality of axial grooves are provided in a portion of the outer circumference of a stretch tube. The feature is that purge cooling water flows through almost all parts of the gap between the motor case nozzle and the motor case nozzle.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings.

Figure @3, similar to Figure 2, is a diagram explaining the area around the stretch tube 6, where conventional purge cooling water flows only into gap B. In the present invention, a plurality of grooves 11 are provided on the outer periphery of the stretch tube 6, and the purge cooling water is actively circulated from the purge water inlet A section to the gap F extending to the D section near the diffuser 4. It used to be a dead area.・Completely prevents crevice corrosion in gap F.

In addition, in the present invention, the grooves are only provided in the stretch tube 6, and there is no need to process any relatively large structures around the stretch tube 6, and there is no need to add any unnecessary parts, making it extremely easy to carry out the invention. It's easy.

Furthermore, since the motor case nozzle 2a is simultaneously cooled by the purge cooling water passing through the gap Fi, the difference in thermal expansion between the stretch tube and the stretch tube is much smaller than before, making it an extremely reliable reactor internal. You will get a pump.

FIG. 4 is a cross-sectional view taken along line II in FIG. 3, in which a groove 11 is provided on the outer periphery of the stretch tube. Of course, the number, shape, etc. of these grooves can be arbitrarily designed in order to adjust the amount of purge water passing through the gap F.

〔Effect of the invention〕

According to the present invention, even when the temperature difference between the stretch tube and the motor case nozzle is significantly reduced compared to the conventional method, there is virtually no dead area, so crevice corrosion is prevented and extremely A highly reliable internal pump for nuclear reactors can be obtained.

[Brief explanation of the drawing]

Figure 1, No. 21311! ! 3 is a longitudinal sectional view of a conventional internal pump for a nuclear reactor, FIG. 3 is a sectional view showing a part of the internal pump for a nuclear reactor according to the present invention, and FIG. FIG. 1... Reactor pressure vessel, 2... Motor case, 2a
... Motor case nozzle, 3... Impeller, 4...
Diffuser, 5...Shaft, 6...Stretch tube, 8...Motor, 11...Groove, B, F...
gap.

Claims (1)

[Scope of Claims] An impeller for circulating reactor cooling water provided at the bottom of the reactor pressure vessel, a diffuser disposed downstream of the impeller, and a motor attached to the bottom of the pressure vessel. An internal pump comprising a shaft contained 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, the outer periphery of the stretch tube An internal pump for a nuclear reactor, characterized in that an axial groove is cut in a portion of the tube, and cooling water is passed between the stretch tube and a motor case nozzle.