JPS5823915B2 - Nuclear reactor control rod drive water piping - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a boiling water nuclear reactor, and particularly to drive water piping for driving control rods.

FIG. 3 shows a general piping system for the control rod drive mechanism of a nuclear reactor.

In the figure, 5 is a pressure regulating valve, 6 is a control rod driving water pump, 11 is a control rod housing, 12 is a water supply pipe for control rod insertion, 13 is a water supply pipe for control rod withdrawal, 14, 15, 16゜1
7 is a valve, 31 is a control rod drive water pipe, 32 is a cooling water pipe,
33 is the reactor scram piping, 34 is the driving water control device, 4
is the control rod driven water return pipe.

In this device, when moving the control rods up and down, high pressure water from the control rod drive water pump 6 is injected into the control rod housing 11.

When inserting a control rod, 1. The valve 14 is opened to inject water into the lower part of the housing 11, and at the same time, the valve 17 is opened to drain the water contained in the upper part of the housing, and the control rod is inserted by the differential pressure between the upper and lower parts of the housing.

Valve 14 and valve 17, which determine the position of the control rod, are closed to prevent drive water from being supplied.

After that, a small amount of cooling water is injected from the cooling water pipe 32, and the remaining amount of water is allowed to flow toward the control rod driving water return pipe 4.

Also, when scramming the reactor, the drive water control device 34
A larger amount of water is injected into the control rod housing 11 and the control rod is inserted.

Thereafter, water is supplied to the drive water control device 34 by the drive water pump 6.

At this time, since a large amount of water flows toward the drive water control device 34, the amount of water flowing through the drive water return pipe 4 decreases rapidly, sometimes reaching close to zero.

As described above, in this device, the driving water pump 6 is constantly operated to drive the control rods, inject cooling water, replenish scram water, etc., and the required flow rate for each operation, Since the required pressures differ, water is constantly allowed to flow through the driving water return pipe 4 while changing the pressure using the pressure regulating valve 5 in order to adjust the required pressure.

In order to effectively utilize the water flowing through the return pipe 4, the return pipe 4 is generally connected to the reactor pressure vessel.

FIG. 1 is a schematic diagram showing the connection of a conventional drive water return pipe, and details of each piping in FIG. 3 are omitted.

As seen in FIG. 1, conventionally, the drive water return pipe 4 was directly connected to the reactor pressure vessel 1.

In addition, in the figure, 2 is a control rod drive device, 3 is a control rod drive water pipe, 5 is a pressure regulating valve, 6 is a drive water pump, 7 is a water supply pipe, 8
9 is a reactor coolant purification system, and 9 is a containment vessel.

In the apparatus shown in FIG. 1, during normal operation, the driving water is at a low temperature, so the nozzle of the return pipe 4 is at a low temperature.

However, when the amount of water on the return pipe side suddenly decreases during a reactor scram, high-temperature water in the pressure vessel flows back to the return pipe nozzle side.

At this time, thermal stress acts on the return pipe nozzle due to the sudden temperature difference.

Since this operation is repeated for each reactor scram, there is a risk that cracks or the like may occur in the nozzle portion.

The object of the present invention is to connect a return pipe to other high-temperature water piping connected to the reactor pressure vessel, inject the low-temperature water in the return pipe into the high-temperature water, and directly supply low-temperature water to the pressure vessel nozzle. The purpose is to prevent nozzle cracking due to thermal stress by preventing contact.

The present invention will be explained in detail below.

In FIG. 2, the driving water return pipe 41 connected to the pressure regulating valve 5 is connected to the reactor coolant purification system 8, and the driving water return injected here is injected into the reactor via the water supply pipe 7. It looks like this.

According to this embodiment, the low-temperature water returned from the driving water is injected into the high-temperature water of the reactor coolant purification system, so the nozzle of the reactor pressure vessel 1 does not come into contact with the low-temperature water.

Therefore, the thermal stress caused by water return from the control rods is significantly reduced.

An example of temperature is as follows.

Reactor coolant purification system 225°C 145771”/h Control rod drive water return 40°C 3m”/h The average water temperature of this (225X145+40X3)÷148 =221°C becomes.

Since the water temperature in the reactor pressure vessel at this time is 285°C, 285-221=648C 285-40=245°C, and the temperature difference is reduced to about 1/4.

Note that on the reactor coolant purification system side, the temperature difference is slightly larger from 60°C to 64°C, but it is only about 7% and does not pose a problem.

FIG. 4 shows another embodiment of the present invention, and the difference from FIG. 2 is that the control rod drive water return pipe 42 is connected to the reactor coolant purification system on the population side of the regenerative heat exchanger 51. It is a point.

In this example, the reactor coolant purification system side is also at a low temperature (approximately 50
℃), the temperature difference between the control rod drive water return pipe and the control rod drive water return pipe is small, and thermal stress between the pipes can be avoided.

Note that since the combined water is heated in a regenerative heat exchanger and then injected into the reactor pressure vessel, the thermal effect on the pressure vessel nozzle is small.

In addition, according to the two embodiments described above, in either of them, it is possible to perform a pressure test and water filling of a nuclear reactor using a single-drive water pump.

Therefore, this system can be used not only during reactor operation but also when the reactor is shut down.

According to the present invention, the driving water return pipe is not connected directly to the pressure vessel, but is connected to another pipe connected to the pressure vessel, so the temperature of the water injected into the pressure vessel can be increased, and the water flowing into the pressure vessel nozzle can be increased. This has the effect of reducing thermal stress.

[Brief explanation of drawings]

Figure 1 is a route diagram showing the connection of a conventional control rod drive water return pipe, Figure 2 is a route diagram showing the connection of the control rod drive water return pipe according to the present invention, and Figure 3 is a route diagram of the control rod drive water system. , FIG. 4 is a route map showing another embodiment of the present invention. Explanation of symbols, 1... Reactor pressure vessel, 2...
...Control rod drive device, 3...Control rod drive water pipe, 4,41゜42...Control rod drive water return pipe, 5
...Pressure regulating valve, 6...Control rod drive water pump, 7...Water supply pipe, 8...Reactor coolant purification system, 51... ...Regenerative heat exchanger.

Claims (1)

[Claims] 1. Connect the return pipe for pressure adjustment water for driving the reactor control rods to another high-temperature water pipe connected to the reactor pressure vessel, and inject it into the reactor pressure vessel via the other high-temperature water pipe. Control rod drive water piping for a nuclear reactor, characterized by: