JPS644135B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a leak detection device for a bellows joint in a cooling system of a nuclear power plant.

The temperature of the heat medium handled in a nuclear power plant is
A fast breeder reactor has a high temperature of 500℃, and a high-temperature gas reactor has an extremely high temperature of approximately 1000℃. Therefore, piping that flows such a heat medium requires complicated piping routing to alleviate thermal stress caused by thermal expansion of the piping, which increases the length of the piping, increases the number of hangers and snaps, and increases the amount of insulation material. Instead, this increases the pressure loss within the piping, resulting in an increase in the capacity of the circulation pump or blower, which in turn leads to an increase in the amount of buildings, which is a factor leading to an increase in plant construction costs.

As a means to alleviate this increase in plant construction costs, attempts have been made to use bellows joints in the piping system to absorb thermal expansion and make the piping system more compact. In particular, in metal sodium cooled fast breeder reactors, although the temperature of the heat medium is high, the pressure is approximately 10
Since it is low at Kg/cm ² g or less, the use of bellows joints is considered promising. One of the bellows joints for this purpose is an angular displacement bellows joint that allows only bending deformation. This bellows joint will be explained with reference to FIG. 1. Two shells 1, 1' are connected by a boundary bellows 2 and a back-up bellows 3. Also, Ciel 1, 1' is
They are joined by a pin 5 via a connecting ring 4, and can rotate around the pin 5 even if bent due to thermal expansion of the piping. Since the pins 5 are provided in two orthogonal directions, the bellows joint can be bent in any direction. Reference numeral 6 designates a gas pipe connection port through which inert gas flows between the boundary bellows 2 and the backup bellows 3, and 7 designates a sleeve provided inside the boundary bellows 2. The pressure of the sodium flowing inside the boundary bellows 2 is higher than the inert gas pressure inside the boundary bellows 2 and the backup bellows 3, and the inert gas pressure is higher than atmospheric pressure.

By the way, the bellows joint 8 having such a structure is suitable for use in the piping system of a metal sodium cooled fast breeder reactor, for example, the second
As shown in the figure, the piping system of the secondary main cooling system, that is, the hot leg piping 12 that passes through the intermediate heat exchanger 9 and the partition wall 10 of the primary main cooling system and connects to the superheater 11 of the secondary main cooling system, and the superheater. 11 and the evaporator 13, a first cold leg pipe 16 that connects the evaporator 13 and the expansion tank 15, a second cold leg pipe 18 that connects the expansion tank 15 and the pump 17, and a middle leg pipe 14 that connects the evaporator 13 and the expansion tank 15. If it is installed at a location where thermal stress is applied in the middle of each piping, such as the third cold leg piping 19 connected to the heat exchanger 9, it will be subject to internal fluid pressure and frequent repeated bending displacements, resulting in structural strength weaknesses. If the boundary bellows 2 and back-up bellows 3 are damaged and the sodium flowing through the pipes leaks to the outside, it may cause a fire, and if the amount of leakage becomes large, it will lead to loss of coolant. In order to prevent sodium fires and loss of coolant, it is necessary to promptly detect leaks of sodium or argon gas between the boundary bellows 2 and back-up bellows 3, and discover damage to the boundary bellows 2 and back-up bellows 3. is necessary.

However, as seen in the piping system of the secondary main cooling system in FIG. 2, it is not easy to find a damaged bellows joint among a large number of bellows joints 8.

The present invention has been made to solve these problems, and is a bellows joint leak detection device that can quickly find a damaged bellows joint when a large number of bellows joints are provided in the cooling system of a nuclear power plant. We aim to provide the following.

Hereinafter, one embodiment of the bellows joint leak detection device according to the present invention will be described with reference to FIG. 12
The group bellows joint 8 is a bellows joint in the middle leg piping 14 that connects the superheater 11 and the evaporator 13, and the group bellows joint 8 is the bellows joint in the middle leg that connects the evaporator 13 and the expansion tank 15. The bellows joint 8 of the group is a bellows joint for the first cold leg pipe 16, and the second cold leg pipe 18 connects the expansion tank 15 and the pump 17.
The bellows joint 8 of the group is a third bellows joint connected to the pump 17 and the intermediate heat exchanger 9.
This is a bellows joint for cold leg piping 19. An on-off valve 20 is provided in the space between the boundary bellows 2 and the back-up bellows 3 of each bellows joint 8.
The gas inlet pipe 21 and the gas discharge pipe 22 are connected to each other, and each bellows joint 8 of each leg pipe is connected.
The gas inlet pipe 21 and gas discharge pipe 22 are combined into one and connected in sequence. 1 on the hot leg piping 12 side
A gas sampling type sodium leak detector 2 is connected to the gas exhaust pipe 22' which is combined into a book and the gas inlet pipe 21' which is combined into one on the third cold leg side.
3. A flow meter 24, a gas circulator 25, and a flow meter 26 are interposed and connected to form a closed cycle. A flow rate difference alarm meter 2 is installed in the upstream and downstream flow meters of the gas circulation machine 25.
Connect 7. A gas supply device 28 is provided in the gas passage between the gas circulation machine 25 and the flow meter 24 on the upstream side thereof.
Connect. This gas supply device 28 includes a reservoir 30 equipped with a pressure controller 29, a gas tank 34 connected to the reservoir 30 via a gas pipe 33 having a pressure regulating valve 31 and an automatic valve 32, and a pressure regulating valve 35 provided in the reservoir 30. The pressure regulating valves 31 and 35 are opened and closed by a pressure controller 29. Gas introduction pipe 2
1' and the gas exhaust pipe 22' is provided with a gas pipe 36 that bypasses the bellows joint 8 of each leg piping,
In the middle of the gas pipe 36 are gas pipes 37, 38, 39, 4 that bypass the bellows joint 8 of each leg pipe.
0 is branched and connected to the joint between the gas exhaust pipe 22' and the gas inlet pipe 21' of the bellows joint 8 of each leg pipe, and the bellows joint of each leg pipe in the middle of the gas pipe 36 is bypassed. On-off valve 4 in the part where
1, 42, 43, 44, and 45 are provided. Therefore, a pressure indicator 46 is provided in the gas discharge pipe 22 of each bellows joint 8 in each leg piping, and a spark plug type sodium leak detection device is installed in the space between the boundary bellows 2 and back-up bellows 3 of each bellows joint 8. The vessels 47 are linked.

Next, the leak detection operation of the bellows joint leak detection device of the present invention configured as described above will be explained.

One of the bellows joints 8 provided in the middle of the hot leg piping 12, middle leg piping 14, first cold leg piping 16, second cold leg piping 18, and third cold leg piping 19 of the secondary main cooling system shown in FIG. When the boundary bellows 2 is damaged, liquid sodium, which is a coolant flowing through the pipe, leaks into the space between the boundary bellows 2 and the backup bellows 3.

To detect this leak, open the on-off valves 20 of the gas inlet pipes 21 and gas discharge pipes 22 of all bellows joints 8, and drive the gas circulation machine 25 to remove the boundary bellows 2 and back-up bellows of each bellows joint 8. An inert gas, such as argon gas, filled in the space between 3 and 3 is circulated. As a result, when argon gas flows into the gas sampling type sodium leak detector 23, sodium mixed in the argon gas is detected. Next, in order to detect which leg piping's bellows joint 8 is causing a sodium leak, argon gas is circulated in the space between the boundary bellows 2 and back-up bellows 3 of the bellows joint 8 of each leg piping. let That is, the on-off valves 20 of the gas introduction pipe 21 and the gas discharge pipe 22 in the bellows joint 8 of each leg pipe other than the third cold leg pipe 19 are closed, and the on-off valves 42, 43, 44, 45 of the gas pipe 36 bypassing these are closed. The argon gas in the space between the boundary bellows 2 and the backup bellows 3 of each bellows joint 8 of the third cold leg piping 19 is circulated, and whether or not sodium is mixed in the argon gas is detected using a gas sampling type sodium Detected by leak detector 23. When it is detected that liquid sodium is mixed in the argon gas, in order to detect which bellows joint 8 of the third cold leg piping 19 is leaking sodium, we sequentially check each bellows joint 8 of the third cold leg piping 19. The third
It is possible to discover in which bellows joint 8 of the cold leg piping 19 the boundary bellows 2 is damaged.

Each bellows joint 8 of the third cold leg piping 19
If sodium is not mixed in the argon gas in , there is no damage to the boundary bellows, so the on-off valves 20 of the gas inlet pipe 21 and the gas discharge pipe 22 at the bellows joint 8 of each leg pipe other than the second cold leg pipe 18 On-off valves 41, 43, 4 of the gas pipe 36 that close the gas pipes and bypass these
4 and 45 to circulate the argon gas in the space between the boundary bellows 2 and the backup bellows 3 of each bellows joint 8 of the second cold leg piping 18, and check whether sodium is mixed in the argon gas. Detected by gas sampling type sodium leak detector 23. When it is detected that sodium is mixed in the argon gas, in order to detect which bellows joint 8 of the second cold leg piping 18 is leaking liquid sodium, each bellows joint 8 is sequentially opened. By opening and closing the on-off valves 20 of the gas inlet pipe 21 and the gas discharge pipe 22, the second cold leg pipe 1
It can be discovered in which bellows joint 8 of 8 the boundary bellows 2 is damaged.

Each bellows joint 8 of the second cold leg piping 18
If there is no sodium mixed in the argon gas, the boundary bellows 2 will not be damaged, so from now on, follow the steps described above to install cold leg piping 1, middle leg piping 14, and hot leg piping 1 in this order.
Boundary bellows 2 of bellows joint 8 at any position in the piping system of the secondary main cooling system can be detected by detecting whether sodium is mixed in the argon gas at bellows joint 8 of
You can find out if it is damaged.

On the other hand, as a backup of the gas sampling type sodium leak detection method, a spark type sodium detector 47 detects whether liquid sodium has accumulated in the lower part of the space between the boundary bellows 2 and the backup bellows 3. You can discover if there is a sodium leak.

Furthermore, if the backup bellows 3 of any of the bellows joints 8 provided in the middle of each leg piping is damaged, the argon gas filled in the space between the backup bellows 3 and the boundary bellows 2 will leak. To detect this leak, open the on-off valves 20 of the gas inlet pipes 21 and gas discharge pipes 22 of all bellows joints 8, drive the gas circulation machine 25, and close the boundary bellows 2 and back-up bellows of each bellows joint 8. 3. Circulate argon gas between the two. As a result, the flow rate of argon gas flowing into the gas circulator 25 is measured by the flow meter 24, the flow rate of argon gas fed from the gas circulator 25 is measured by the flow meter 26,
The measured flow rate of both flowmeters 24 and 26 is the flow rate difference alarm meter 2.
7, and an alarm is issued due to the flow rate difference between the measured flow rates, indicating that the flow rate of argon gas on the upstream side of the gas circulator 25 is low, that is, argon gas is A gas leak is detected. Next, in order to detect which leg pipe's bellows joint 8 is leaking argon gas, the on-off valves of the inflow and outflow pipes 21 and 22 of all the bellows joints are closed, and the argon gas is leaked to the bellows joint. The inflow and outflow are shut off, and the change in argon gas pressure between the boundary bellows and the backup bellows is measured using a pressure indicator.

When the back-up bellows breaks, the argon gas between the boundary bellows and the back-up bellows leaks into the atmosphere, so as time passes, the pressure indicated by the pressure indicator approaches atmospheric pressure. .

Therefore, when the pressure on the pressure indicator is at the initial set pressure, there is no leakage of argon gas, and when it becomes lower than the set pressure, it is found that argon gas is leaking. Thus, in which bellows joint 8 of which leg piping, back up bellows 3
You can find out if it is damaged.

Although the sodium leak detection operation and the argon gas leak detection operation have been explained separately above, both detection operations are not performed separately.Sodium leak detection and argon gas leak detection can be performed in a single detection operation. It is something that is done together.

When the circulating flow rate decreases due to a leak of argon gas due to damage to the backup bellows 3, argon gas is supplied from the gas supply device 28. That is, the reservoir 30 is located upstream of the gas circulator 25.
Argon gas is supplied from the reservoir 30, a decrease in argon gas in the reservoir 30 is detected by the pressure controller 29, the pressure regulating valve 31 is opened, and the automatic valve 32 is opened in advance.
The gas is supplied from the open gas tank 34. When the pressure of the argon gas in the reservoir 30 reaches a certain value or higher, the pressure controller 29 closes the pressure regulating valve 31, opens the pressure regulating valve 35, and partially returns the argon gas.

As can be seen from the above explanation, according to the bellows joint leak detection device according to the present invention, when a large number of bellows joints are provided in the cooling system of a nuclear power plant, sodium and inert gases can be detected at any bellows joint at any position in any piping. It is possible to easily and quickly detect whether a leak is occurring and discover damage to the boundary bellows and back-up bellows of the bellows joint.If sodium and inert gas leaks are continuously detected, sodium leaks can be detected in advance. This has extremely great effects on nuclear power plants, such as being able to prevent leaks to the outside, preventing plant accidents due to major damage, and increasing the reliability of the entire plant.

[Brief explanation of the drawing]

Figure 1 is a perspective view of a bellows joint, Figure 2 is a diagram showing the piping system of the secondary main cooling system of a fast breeder reactor employing the bellows joint, and Figure 3 is a diagram showing the piping system of the secondary main cooling system of a nuclear power plant according to the present invention. It is a figure showing the leak detection device of a bellows joint. 2... Boundary bellows, 3... Back up bellows, 8... Bellows joint, 12... Hot leg piping, 14... Middle leg piping, 16...
1st cold leg piping, 18... 2nd cold leg piping, 19... 3rd cold leg piping, 20...
...Opening/closing valve, 21, 21'...Gas introduction pipe, 22,
22'... Gas exhaust pipe, 23... Gas sampling type sodium leak detector, 24, 26... Flow meter, 25... Gas circulator, 27... Flow rate difference alarm meter, 28... Gas supply device, 36 ,37,38,
39,40...Gas pipe, 41,42,43,4
4, 45...Opening/closing valve, 46...Pressure indicator, 47
...Spark plug type sodium leak detector.

Claims (1)

[Claims] 1 Connecting a gas inlet pipe and a gas exhaust pipe each equipped with an on-off valve to the space between the boundary bellows and back-up bellows of a plurality of bellows joints provided in each of a plurality of leg pipes in a cooling system of a nuclear power plant. Connect each gas inlet pipe and gas exhaust pipe of the bellows joint of the leg piping together in sequence, and connect the gas exhaust pipe of the bellows joint of the first leg piping and the gas inlet pipe of the bellows joint of the last leg piping. A gas sampling type sodium leak detector, a flow meter, a gas circulator, and a flow meter are interposed and connected to form a closed cycle, and a flow rate difference alarm meter is linked to the flow meters upstream and downstream of the gas circulator. A gas supply device is connected between the gas circulation machine and the flow meter on its upstream side, and gas pipes with on-off valves are provided to bypass the bellows joints to one gas inlet pipe and one gas discharge pipe to the bellows joints of each leg piping. A leak detection device for a bellows joint in a cooling system of a nuclear energy plant, comprising: a spark plug-type sodium leak detector installed at the bellows joint of each leg piping; and a pressure indicator installed at the gas discharge pipe of the bellows joint. .