JPH03124996A - Recirculating pump for atomic reactor - Google Patents

Abstract

PURPOSE:To easily perform disassembly and replacement even if galling occurs on sleeves and replace only the sleeves by adding removable sleeve structures between a pump shaft and a casing cover. CONSTITUTION:Two-stage sleeves of a shaft sleeve 28 and a cover sleeve 29 are provided between a shaft 7 and a casing cover 4 so that the shaft 7 and both sleeves 28 and 29 can be easily replaced without replacing the casing cover 4. The sleeve tip of the shaft sleeve 28 on the pump chamber side serving as a purge water outlet section has the shape of an impeller 30, the cover sleeve 29 is fitted to the casing cover 4, the high-temperature reactor water flows in from the intermediate position between a mechanical seal chamber an a pump chamber, and it is returned to the pump chamber via a eat exchanger mechanism at the lower section on the pump chamber side. Disassembly and replacement can be easily performed even if galling occurs on both sleeves 28 and 29.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field] The present invention relates to a reactor recirculation pump for a boiling water nuclear reactor.

[Conventional technology]

A conventional technique will be explained with reference to FIGS. 1 and 2.

The reactor recirculation pump has a welded structure in which the suction and discharge ports of the pump are connected to piping, and the pump casing 1 is configured as part of the flow path.

A suction port 2 is formed on the lower side of the pump casing 1, and an opening 3 for inserting an internal structure is provided on the opposite side to form a single-stage overhang, single-suction, volute pump. cover 4
The opening 3 is sealed and is divided into a sealed part 5 exposed to high temperature reactor water and a shaft sealing chamber wall 6. A cover penetrating wall 9 through which the main shaft passes is located at this border, and has a small operating clearance 8 between it and the shaft. The main shaft 7 and the cover penetrating wall 9 on both sides of the operating gap 8 have a labyrinth structure. The lower side of this operating clearance 8 is inside the pump 1
3, and the upper side is a shaft sealing chamber 10.

The shaft sealing chamber 10 is divided into two parts. Inside the pump 13
The one closest to is the lower seal chamber 11, and the upper seal chamber 1 is above it.
2 are configured. The lower seal chamber 11 is inside the pump 1
3, and the upper seal chamber 12 is configured to have half the pressure of the lower seal chamber 11. Each seal chamber is provided with a set of mechanical seals of the same type. The lower mechanical seal 14 seals the differential pressure between the lower seal chamber 11 and the upper seal chamber 12, and the upper mechanical seal 15 seals the differential pressure between the upper seal chamber 12 and the upper seal chamber 12. Seal pressure differential. That is, it has a two-stage tandem seal structure composed of two mechanical seals.

In order to prevent the reactor water 16 containing radioactive substances inside the pump 13 from entering the shaft sealing chamber 10 and flowing out to the outside, and to prevent the temperature of the shaft sealing chamber 10 from rising due to high temperature reactor water, a purge is made from the outside to the lower sealing chamber 11. Inject water 17. A portion of the purge water becomes net purge water 18 which is forced through the operating gap 8 into the pump interior 13. The other part becomes bleed-off water 19 which is depressurized and extracted to the outside of the shaft sealing chamber.

The purpose of the bleed-off water pressure reduction mechanism is to control the pressure in the lower seal chamber 11 and the upper seal chamber 12, and water in the lower seal chamber 11 passes through the lower pressure reduction mechanism 20 and enters the upper seal chamber 12.

Furthermore, it passes through the upper pressure reducing mechanism 21 from the upper seal chamber 12 and is extracted to the outside of the pump.

The shaft seal portion 10 is cooled in order to maintain stable function of the mechanical seal for a long period of time. Two series of cooling devices are provided to maintain the temperature of the shaft sealing chamber 1o below an allowable temperature. One series is a cooling system in which a jacket 22 provided on the outside of the operating gap 8 and a jacket 23 provided on the outer periphery of the shaft seal wall 6 are connected in series. By flowing low-pressure cooling water here, heat is removed from the entire shaft sealing chamber 10.

If the purge water 17 is not injected, high-temperature water passes through the operating gap 8 and rises into the shaft sealing chamber 10, where it mixes with the water inside.

The jacket 22 around the running gap 8 also has the effect that the hot water is cooled while rising through the running gap 8 .

The other series is a high-pressure water conduit that takes out a part of the purge water 24 from the lower end of the lower sealing chamber 11 to the outside of the pump, coils around the outside of the shaft sealing chamber wall 6, and enters the upper part of the shaft sealing chamber 10. form. The coil 25 passes through a cooling chamber 26 provided in an annular shape concentrically with the shaft sealing chamber 1o, is cooled from the outside, and enters the lower sealing chamber 11 above the shaft sealing chamber 10 again. A part of the purge water 24 is sent into the coil by a circulation vane 27 provided on the lower side of the lower seal chamber 10, and is circulated and cooled. These two cooling systems keep the shaft sealing chamber 1o at a permissible temperature or lower.

[Problem to be solved by the invention]

The above conventional technology has a structure in which the low-temperature purge water passes through the flow path between the main shaft and the casing cover and then mixes with the high-temperature reactor water in the pump room at the outlet, and the temperature of the purge water is low near the outlet. Local thermal deformation of the main shaft and casing cover occurs due to the sudden rise in temperature. If the purge water flow path is narrow, there is a possibility that the main shaft and the casing cover may come into contact with each other due to this local thermal deformation or deformation due to vibration, and may become jammed. In addition, in the unlikely event that the two were sewn together, the main shaft and casing cover would have to be completely replaced.

An object of the present invention is to have a structure that allows restarting operation with a minimum number of parts, without replacing the main shaft and casing cover, even if the main shaft and casing cover become jammed. An object of the present invention is to provide a nuclear reactor recirculation pump in which the replacement part is provided with a mechanism for raising the temperature of purge water in order to reduce local thermal deformation.

Another object of the present invention is to reduce the amount of radiation that workers are exposed to by providing a structure that allows the reactor recirculation pump to be easily disassembled and replaced.

[Means to solve the problem]

The above purpose is to provide removable sleeves on the surface of the main shaft and the surface of the casing cover in the casing cover penetration part of the main shaft, and to enable heat exchange between the high temperature reactor water in the casing and the purge water in this sleeve. This is achieved by providing a structure that allows this.

[Effect]

The sleeves attached to the main shaft and the casing cover of the penetrating portion are fixed to the main shaft and the casing cover with bolts or the like, and can be easily removed. Therefore, in the event that the main shaft sleeve and casing cover sleeve come into contact and become jammed, you can remove the bolts, etc. that fix the main shaft sleeve and casing cover sleeve, and the main shaft and the jammed main shaft sleeve can be removed without removing the casing cover. And the casing cover sleeve can be easily disassembled. Therefore, the machine can be restarted by replacing only the main shaft sleeve and casing cover sleeve.

In addition, one or both of the main shaft sleeve and casing cover sleeve is provided with a flow path through which high-temperature reactor water in the pump room flows, and by promoting heat exchange with the low-temperature purge water flowing between both sleeves, the flow path is It is possible to raise the temperature of the purge water and make the temperature gradient gentler. As a result, local thermal deformation of both sleeves is reduced, and galling of both sleeves due to this can be prevented.

Note that the jacket cooling holes for cooling the purge water provided in conventional models are provided as a countermeasure when the purge water stops.If the purge water does not stop, jacket cooling holes are provided. There's no need.

The radiation dose for workers during disassembly and replacement is the same as with conventional models during normal inspections, but in the unlikely event that the main shaft sleeve and casing cover sleeve become galled and disassembled or replaced,
As mentioned above, since it can be easily disassembled, it is possible to significantly reduce the amount of radiation exposure.

〔Example〕

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

A two-stage sleeve consisting of a shaft sleeve 28 and a cover sleeve 29 is provided between the shaft 7 and the casing cover 4 of the reactor recirculation pump, so that the shaft and both sleeves can be easily replaced without removing the casing cover 4. .

The shaft sleeve 28 has an impeller 30 shape at the end of the sleeve on the pump chamber side, which serves as a purge water outlet. The cover sleeve 29 is attached to the casing cover 4, allows high temperature reactor water to flow in from an intermediate position between the mechanical seal chamber and the pump chamber, and returns it to the pump chamber via a cylindrical heat exchanger mechanism in the lower part on the pump chamber side.

According to this embodiment, the seal purge water exchanges heat with the high-temperature reactor water to make the temperature gradient gentle, thereby preventing local thermal deformation and forming a flow path that makes it difficult for the high-temperature reactor water to flow into the mechanical seal chamber.

Fig. 4 shows an example of application of Fig. 3.

Between the reactor recirculation pump shaft 7 and the casing cover 4, a shaft sleeve 31 and a cover sleeve 32 are provided.
The shaft 7, the shaft sleeve 31, and the cover sleeve 32 can be easily replaced without removing the casing cover 4.

The shaft sleeve 31 has a purge water inlet near the casing cover 4, and has a two-stage structure to raise the temperature of the purge water.

The cover sleeve 32 is attached to the casing cover 4 to allow high temperature reactor water to flow in from an intermediate portion between the mechanical seal chamber and the pump chamber and return to the pump chamber.

According to the present invention, the flow path through which low-temperature seal purge water exchanges heat with high-temperature reactor water becomes longer, the temperature gradient becomes gentler, 1 local thermal deformation can be prevented, and high-temperature process fluid flows into the mechanical seal chamber. This creates a difficult flow path.

FIG. 5 shows an example of application of FIG. 4.

This structure is a one-stage version of the two-stage type shown in FIG.

According to the present invention, an effect similar to that shown in FIG. 4 can be obtained.

FIG. 6 shows an example of application of FIG. 1.

Between the shaft 7 and the casing cover 4 of the reactor recirculation pump, a shaft sleeve 35 and a cover sleeve 36 are provided.
This figure shows a structure with .

The shaft sleeve 35 has a simple shape, but the cover sleeve 36 has a spiral-shaped flow path that allows high-temperature reactor water to pass near the mechanical seal chamber side, and allows seal purge water to rise from the mechanical seal chamber side. It has a warming structure.

Further, a cylindrical groove is provided on the inner ring side of the cover sleeve 36 to make it difficult for high temperature reactor water to flow in from the pump chamber.

According to the present invention, the temperature gradient of the purge water can be made gentle, and local thermal deformation can be prevented.

Furthermore, by using the sleeve method of this structure, maintenance and inspection are easy and the structure becomes replaceable.

FIG. 7 shows an example of application of FIG. 6.

According to the present invention, a puffer 39 using purge water for cooling the mechanical seal chamber is installed in the vicinity of the mechanical seal chamber between the cover sleeve 38 and the shaft sleeve 37 in the structure shown in FIG. The temperature increase in the mechanical seal chamber can also be reduced, and furthermore, the temperature of the purge water is raised by the blower 39, thereby preventing local thermal deformation.

In FIG. 8, the tips of the shaft sleeve 40 and the cover sleeve 41 on the pump chamber side are made into a dry structure 42 so that a low temperature can be generated in the mixing section.

Further, grooves are provided in both the inner ring and the outer ring of the cover sleeve 41 from the vicinity of the mechanical seal chamber, and the purge water is heated from the vicinity of the mechanical seal chamber by high-temperature reactor water to make the temperature gradient of the purge water gentle.

Furthermore, cooling holes 43 are provided in the casing cover 4 to maintain the low temperature of the mechanical seal chamber.

According to the present invention, high-temperature reactor water can be prevented from flowing into the mechanical seal chamber by placing low-temperature water in the lower part of the mixing section of purge water and high-temperature reactor water.

Furthermore, by providing cooling holes in the casing cover, the mechanical seal chamber can be maintained at a low temperature.

Furthermore, by heating the seal purge water, the temperature gradient can be made gentler, and local thermal deformation can be prevented.

In addition, if galling occurs, the shaft and sleeve can be easily replaced by using this sleeve method without removing the casing cover.

〔Effect of the invention〕

According to the present invention, there are the following effects.

1) By adding a removable sleeve structure between the pump shaft and casing cover, even if both sleeves become jammed, it can be easily disassembled and replaced, and only the sleeve can be replaced. be able to.

Furthermore, since the range of one disassembly becomes smaller and the time for disassembly and replacement can be shortened, it is possible to reduce the amount of radiation that disassembly workers receive from inside the pump casing.

2) The temperature gradient of the purge water caused by changing the flow of the purge water and high-temperature process fluid can be made gentler, making it possible to reduce local deformation of the shaft sleeve and casing cover sleeve, thereby reducing galling. can be prevented.

[Brief explanation of drawings]

FIG. 1 is an overall longitudinal sectional view of a high temperature pump according to the prior art, FIG. 2 is a detailed view of the shaft seal shown in FIG. 1, and FIG. 3 is a detailed view of the shaft seal according to an embodiment of the present invention. Figures 4 to 8 are diagrams of examples of application from Figure 3 onwards. 1...Pump casing, 2...Suction port, 3-way opening. 4... Cover (casing cover), 5... Sealed part,
6... Shaft sealing chamber wall, 7... Main shaft (shaft), 8...
・Operating clearance, 9...Cover penetration wall, 10...Shaft sealing chamber, 11...Lower seal chamber, 12...Upper seal chamber, 13...Pump inside, 14...Lower mechanical seal , 15... Upper mechanical seal, 16... Reactor water, 17... Purge water, 18... Net purge water, 1
9... Bleed-off water, 20... Lower pressure reducing mechanism, 2
1... Upper pressure reducing mechanism, 22... Jacket, 23...
...Jacket, 24...Part of purge water, 25...
- Coil, 26... Cooling chamber, 27... Circulation vane, 28... Shaft sleeve, 29... Cover sleeve, 30...
・Impeller, 31...Shaft sleeve, 32...Cover sleeve, 33...Shaft sleeve, 34...
・Cover sleeve, 35...Shaft sleeve, 36
...Cover sleeve, 37...Shaft sleeve,
38...Cover sleeve, 39...Battu fur, 4
0...Shaft sleeve, 41...Cover sleeve, 42...Lock-like structure, 43...Figure 4 Figure 8 Figure 8

Claims (1)

[Claims] 1. A main shaft that transmits power from the motor, an impeller attached to the main shaft, a spiral casing that covers the impeller, a mechanical seal to prevent fluid from leaking into the motor, and a cooling device inside. The main shaft, the casing, and the casing cover constitute a pump chamber, and seal purge water flows through the gap between the casing cover and the main shaft to mechanically pump high-temperature reactor water. A nuclear reactor recirculation pump with a structure that prevents leakage into the seal. 2. The reactor recirculation pump according to claim 1, characterized in that one or more removable sleeves are provided on the main shaft of the penetrating portion and on the surface of the casing cover. pump. 3. In the reactor recirculation pump according to claim 1, the main shaft of the penetrating portion and the surface of the casing cover are removably provided, and a heat source is provided between the high-temperature reactor water in the pump chamber and the purge water. A nuclear reactor recirculation pump characterized by having a sleeve having a replaceable structure. 4. In the nuclear reactor recirculation pump according to claim 1, one or more stages of sleeves are provided on the surface of the main shaft of the penetrating portion and are removable and have circulation vanes at the purge water outlet, and A nuclear reactor recirculation pump characterized by having one or several removable sleeves on the surface of a casing cover.