JPS638828B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for cleaning a piping system equipped with a pump.

For example, in plants such as nuclear power plants, various types of equipment, piping, and electrical instrumentation are installed in a mixed manner, making the plant construction process generally very complicated.

Among these, piping installation work is performed by sequentially welding and joining short pipes called spools, but in order to maintain the health and safety of the plant, the inside of the piping is removed once the piping work has been completed to a certain extent. The pipes are cleaned to remove foreign matter and oil from inside the pipes.

Figure 1 shows an example of a reactor residual heat removal system (hereinafter referred to as RHR system) installed as part of the emergency core cooling system in a nuclear power plant.
Cooling water 3 stored in a suppression chamber 2 provided at the bottom of the reactor containment vessel 1 is supplied to a penetration chamber 4a, an isolation valve 5a and a strainer 6.
The water is sucked up by the RHR pump 7, passes through a pipe 10 equipped with a flange 8 and a check valve 9, and is introduced into the pressure vessel 11 through the isolation valve 5b and penetration 4b again.

Note that the pipe 10a is a pipe that supplies cooling water to the spray 2a disposed within the spray chamber 2, 5c represents a check valve, and 4c represents a penetration. Further, in the figure, 9b indicates a check valve, and 5d indicates an isolation valve.

In the RHR system as described above, a conventional cleaning method performed during construction work will be described below with reference to FIG. That is, first, the strainer 6 provided on the inflow side piping of the RHR pump 7 and the check valve 9 provided on the RHR pump discharge side piping are removed, and a temporary bypass pipe 12 is installed between them.
The isolation valve 5 provided in the RHR system is closed.

Further, a pair of flanges 8 used when disassembling the pump are provided facing each other on the discharge side piping of the RHR pump 7, and a blind cover 13 is inserted in advance between the pair of flanges.

Next, a temporary water supply pipe 14 is provided downstream of the isolation valve 5, and one end of this pipe is connected to the cleaning equipment 15.

The cleaning water sent out from this cleaning equipment 15 passes through the temporary water supply pipe 14, enters the piping downstream of the isolation valve 5a, passes through the temporary bypass pipe 12, and enters the piping 10.
flow inside.

The cleaning water that has flowed into the piping 10 in this way is contaminated by the cleaning inside the piping, so the piping at the connection to the reactor pressure vessel 11, which is the final spool, is removed and a temporary drain is installed in advance. The waste is discharged outdoors from route 16.

The reason why the temporary bypass pipe 12 is provided in advance to bypass the RHR pump 7 for cleaning is that the RHR pump is a large joint type pump.
This is because the impeller is long and the pit is deep, so when dirty cleaning water is poured into the pit, dirt accumulates, making subsequent cleaning difficult.

In addition to this cleaning problem, if you run cleaning water through the pump internals after they are assembled, it will not give good results to the pump, so please be careful when running cleaning water inside the pump. The pump internal must be disassembled and removed in advance.

In addition, in such a conventional cleaning method, the check valve 9
Since it is necessary to disassemble the equipment, this disassembly work and the restoration work are difficult, which is a very negative point from a process standpoint.

Especially in recent nuclear power plants,
There is a strong demand to shorten the construction period, and the construction process for such emergency core cooling systems is also becoming more difficult.

The present invention has been made with attention to this point,
The present invention attempts to provide a piping cleaning method in which a removable flanged short pipe is inserted in advance on the discharge side piping of an RHR pump, and the piping is cleaned using this flanged short pipe.

The details of the present invention will be explained below with reference to an embodiment shown in FIGS. 3 and 4. Note that in FIGS. 3 and 4, parts common to those in FIG. 1 are indicated by the same reference numerals.

In the piping cleaning method of the present invention, as shown in FIG. 3, a flanged short pipe 17 is used which is removably inserted in advance onto the discharge side piping of the RHR pump 7 and has flanges formed at both ends.

Therefore, when performing cleaning work, first
The inlet strainer 6 and flanged short pipe 17 of the RHR pump 7 are removed, and a temporary bypass pipe 18 of the RHR pump 7 is installed between them as shown in FIG.

Then, a temporary water supply pipe 14 is provided downstream of the isolation valve 5 as in the conventional case, and one end thereof is connected to the cleaning equipment 15.

Next, cleaning water is sent from the cleaning equipment 15 into the piping 10 through the temporary water supply pipe 14 and the temporary bypass pipe 18 through the check valve 9, thereby cleaning the inside of the piping 10.

Note that the cleaning water that has reached the final end of the pipe 10 is
As in the conventional method, the final spool of the pipe 10 is removed and the temporary drain 1 connected instead
6 and is discharged outdoors.

As described above, according to the method of the present invention, the RHR pump 7 can be easily separated from the cleaning water flow path by using the flanged short pipe 17, and the check valve 9 on the discharge side of the RHR pump 7 can be easily separated from the flow path of the cleaning water. Since there is no need to disassemble the product, cleaning can be done safely and easily.

Furthermore, the length of the temporary bypass pipe 18 can be made shorter than in the conventional method, resulting in overall cost reduction.

Figure 5 shows a comparison of the processes according to the conventional method and the method of the present invention, with (A) showing the conventional method and (B) the process diagram according to the method of the present invention plotted over time on the horizontal axis. .

In the figure, 19 is piping installation work, 20 is check valve disassembly work, 21 is strainer removal work, 22 is pump discharge side blind cover installation work, 23 is temporary bypass pipe installation work, 24 is cleaning work, 25 26 is temporary bypass pipe removal work, 26 is check valve restoration work, 2
7 shows the strainer restoration work, 28 shows the removal of the blind cover on the pump discharge side, 29 shows the piping system pressure test, and 30 shows the pump trial run.

These series of steps are subcritical steps in the construction of a nuclear power plant and are extremely difficult, but as is clear from Figure 5, when cleaning is carried out using the method of the present invention, disassembly of the check valve and The restoration works 20 and 26 are no longer necessary, and the construction period indicated by 31 can be shortened.

As described above, according to the method of the present invention, it is possible to safely reduce costs, and furthermore, it is possible to shorten the construction period.

[Brief explanation of the drawing]

Figure 1 is a piping system diagram showing a conventional RHR system, Figure 2 is a partial piping system diagram of an RHR system used to explain the conventional cleaning method, and Figure 3 is a diagram explaining the cleaning method of the present invention. Fig. 4 is a piping system diagram of a part of the RHR system used to demonstrate the cleaning method of the present invention, and Fig. 5 is a diagram of the piping system around the pump of the RHR system used for the cleaning method of the present invention. FIG. 1...Reactor containment vessel, 2...Suppression chamber, 3...Cooling water, 4a, 4b, 4c...
Penetration, 5a, 5b, 5c, 5d...
Isolation valve, 6...Strainer, 7...Reactor residual heat removal system pump (RHR pump), 8...Flange,
9... Check valve, 10... Piping, 11... Reactor pressure vessel, 12... Temporary bypass pipe, 13... Blind lid, 14... Temporary water supply pipe, 15... Cleaning equipment, 1
6...Temporary drainage channel, 17...Short pipe with flange, 1
8...Temporary bypass pipe.

Claims (1)

[Claims] 1. A method for cleaning a piping system including a pump and a strainer inserted upstream of the pump, in which a removable flanged short pipe is inserted in advance downstream of the pump, and the strainer is inserted upstream of the pump. When cleaning the piping system, the strainer and the flanged short pipe are removed, a temporary bypass pipe for bypassing the pump is provided between them, and cleaning water is flowed into the piping system through the temporary bypass pipe. How to clean piping. 2. The piping cleaning method according to claim 1, wherein the piping system is a nuclear reactor residual heat removal system.