JPS6151753B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is used to maintain a reactor coolant recirculation pump to prevent leakage of cooling water in a reactor pressure vessel during disassembly and assembly of a water immersion motor that drives the pump. Regarding water sealing device.

As shown in the drawing, the reactor coolant recirculation pump consists of a diffuser 2 and an impeller 3 located above the lower bottom wall 1 of the reactor pressure vessel, and the drive shaft 4 of the impeller 3 vertically penetrates the bottom wall 1. It is integrally connected to the drive shaft of the motor 5. The motor 5 is a water immersion motor, and is built into a motor case 6 attached to the lower surface of the bottom wall 1. 7 is a bearing. A cylindrical gap is provided around the drive 4, and the inside of the container and the inside of the motor case 6 communicate with each other by using this as a flow path 8, and the coolant flows therethrough.

With the above configuration, when the motor case 6 is opened for maintenance and the motor 5 is pulled out or inserted, a water sealing device is required because the coolant inside the container leaks. Conventionally, two water sealing devices have been used, as shown in FIG. One is a water sealing device that uses contact between metal surfaces, which connects the lower surface 9a of the boss 9 of the pump impeller 3 and the nozzle 10 on the bottom wall 1 opposite thereto.
By contacting the upper surface 10a, a portion 8a of the flow path 8 is closed. Furthermore, as a back-up water seal device, a rubber tube (water seal ring) 1 is installed around the drive shaft 4.
1 is provided and pressurized by the pressurizing device 12 when necessary, thereby bringing the inner surface of the rubber tube 11 into close contact with the drive shaft 4 and filling the flow path 8. This prevents coolant from leaking downward.

In all of the above conventional methods, functional deterioration due to aging is expected. In water sealing devices that use metal surfaces in contact, the sealing surface becomes rough and the performance deteriorates as the pump is used, and in water sealing devices that use rubber tubes, the lifespan of the rubber is currently expected to be several years. Requires regular replacement.

In order to solve the above-mentioned problems, the present invention provides a maintenance water sealing device for a reactor cooling water recirculation pump, which uses a freezing method to perform water sealing more reliably.

Hereinafter, embodiments of the present invention will be described with reference to FIG.

Components that are the same as those shown in FIG. 1 are designated by the same reference numerals, and their explanations will be omitted.

In FIG. 2, a freezing pipe 13 is installed in the upper part of the motor case 6 near the outlet of the flow path 8 so as to surround the drive shaft 4 in a coiled manner. Freezer tube 13
A gap is provided between the drive shaft 4 and the flow path 8.
Make sure not to block it. Both ends of the freezing tube 13 pass through the motor case 6 and are connected to a refrigerant inlet 14 and a refrigerant outlet 1.
Connected to 5. These inlets and outlets 14 and 15 are connected to a heat exchanger of a refrigerator 16 via on-off valves 17 and 18, forming a closed cycle. The refrigerant may be of a type that evaporates in the freezing tube 13 and takes away the heat of evaporation, or a low freezing point liquid cooled to below zero degree C may be used.

During maintenance, the refrigerator 16 is operated and the on-off valves 17,1
8 is opened to circulate and supply refrigerant into the freezing tube 13.
The coolant existing around the freezing tube 13 freezes and eventually completely blocks the flow path 8. Even if the motor case 6 is opened, the coolant will not leak out. The motor 5 is pulled out, inspected or repaired, and kept frozen until it is reinserted and the motor case 6 is closed. When the maintenance is completed, the refrigerator 16 is stopped and the supply of refrigerant is stopped, and the frozen coolant will eventually thaw.

Water sealing by freezing is sufficient even when installed alone, but more accurate water sealing can be achieved if used in combination with the water sealing device by metal surface contact described above.
It goes without saying that the shape of the freezing tube is not limited to that shown in the figure and may be placed anywhere in the flow path.

As described above, the maintenance water sealing device for a reactor coolant recirculation pump of the present invention has a freezing pipe arranged in the pump section penetrating the lower bottom wall of the reactor vessel and the flow path to the water immersion motor. This system freezes the cooling water in the flow path by introducing a refrigerant into the flow path, creating a water seal effect. It is a unique device that can always be expected to provide a reliable water seal, protect workers from radiation exposure, allow them to work with peace of mind, and greatly improve the maintainability of recirculation pumps.

Further, in the apparatus according to the present invention, since the freezing tube is disposed inside the flow path, the cooling water receives resistance near the freezing tube and increases the heat transfer coefficient, making it easier to freeze.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of a reactor cooling water recirculation pump equipped with a conventional water sealing device, and FIG. 2 is a longitudinal sectional view of a reactor cooling water recirculation pump having an embodiment of the water sealing device of the present invention. It is. DESCRIPTION OF SYMBOLS 1... Reactor pressure vessel bottom wall, 2... Defuser, 3... Impeller, 4... Drive shaft, 5... Motor, 6... Motor case, 8... Channel, 13...
Freezer tube, 16... Freezer.

Claims (1)

[Claims] 1 A drive shaft that penetrates the bottom of the reactor pressure vessel integrates the recirculation pump installed inside the reactor pressure vessel and the water immersion motor installed outside the reactor pressure vessel, and the reactor In a reactor cooling water recirculation pump that forms a cooling water flow path that passes through the pressure vessel and the motor case, a freezing tube is arranged in a coil around the drive shaft inside the flow path. An atom characterized in that both ends are connected to a refrigerator heat exchanger, a refrigerant is circulated and supplied to the freezing tube during maintenance, and the flow path is blocked by freezing the cooling water around the freezing tube. Water sealing device for maintenance of reactor cooling water recirculation pump.