JP3000335B2 - Plant construction method and reactor pipe cleaning method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for constructing a plant and a method for cleaning a reactor pipe constituting a nuclear power plant, that is, a main steam pipe and a water supply pipe.
The present invention relates to a method for cleaning a reactor pipe for shortening a nuclear power plant construction process.

[0002]

2. Description of the Related Art Foreign matter or impurities such as welding debris and dust may be mixed in a pipe of a nuclear power plant during a manufacturing process or during installation of a pipe. In the case of a nuclear power plant, if foreign matter or impurities remain in the piping system, these substances are activated during operation of the plant, which may cause an increase in dose rate.

Therefore, foreign substances and impurities are removed by washing, the inside of the piping system is kept clean, and the reactor core, valve body and other equipment are not damaged.

In the case of nuclear power plants, in principle, the air system is cleaned by air blowing, the oil system is cleaned by oil flushing, and the water / steam system is cleaned by water flushing or steam blowing. Since the nuclear reactor piping targeted by the present invention belongs to a water / steam system, cleaning by water flushing, cleaning using a surfactant, alkali cleaning, and the like are generally performed.

[0005] In the conventional method of cleaning reactor piping, a temporary pipe is used in the main steam system and the water supply system with one spool to be connected to the reactor pressure vessel side of each pipe, ie, a final spool, removed. By connecting each pipe, the reactor pressure vessel was bypassed, and the reactor pipe was cleaned. Therefore, all reactor piping except for the reactor pressure vessel was to be cleaned.
Note that the flow direction of the cleaning fluid when cleaning the reactor piping is, in principle, the same direction as during normal operation.

[0006]

SUMMARY OF THE INVENTION A containment vessel (RC)
The inside of the CV) is a site where a large amount of piping including the reactor piping is arranged, and the amount of installation work is large.

[0007] In order to carry out the conventional method of cleaning the reactor piping, the reactor pressure vessel is carried into the reactor building in order to bypass the piping in the reactor containment vessel with the reactor pressure vessel installed. The installation of the reactor pressure vessel, its surrounding reactor piping and valves must be completed during a limited period from the start to the start of the so-called pre-operation.

In order to clean the reactor pipe by the conventional method, a temporary cleaning pipe is set while the final spools of the main steam system and the water supply system are not connected to the reactor pressure vessel joint. The work sequence was to bypass the furnace pressure vessel, complete the water flushing cleaning, remove the temporary piping, set the final spool, weld, and complete the installation.

In the method of cleaning a reactor pipe according to such a method, the cleaning of the reactor pipe and the operation of connecting the final spools of the main steam system and the water supply system to the reactor pressure vessel joint are in a tandem relationship. For this reason, this part has become a critical path in the nuclear power plant construction process, and has been a factor that prolongs the entire plant construction period.

An object of the present invention is to provide a plant construction method and a reactor pipe cleaning method capable of shortening the construction process of a nuclear power plant.

[0011]

The present invention achieves the above object.
In order to achieve this, the connection work between the reactor pressure vessel and the final spool of the main steam system piping and the water supply system piping inside the reactor containment vessel, and the connection between the main steam system piping and the water supply system piping outside the reactor containment vessel A method of constructing a plant is proposed in which a washing operation is carried out in parallel with a washing operation in which washing is carried out by bypass connection of temporary piping and passing water through each piping for washing .

[0012] The present invention also provides the above object.
In the method of cleaning reactor piping including main steam piping and water supply piping at the time of nuclear power plant construction,
By-pass connection of the valve outside the reactor containment vessel of the main steam system piping and the valve outside the reactor containment vessel of the water supply system piping by temporary piping to clean only the reactor piping outside the reactor containment vessel, The inside of the reactor piping that is disposed inside the reactor containment vessel and that is excluded from the cleaning is subjected to rust-prevention treatment with a rust inhibitor in advance, and when the reactor pressure vessel is filled with water, the protection inside the reactor piping that is excluded from the cleaning is prevented. We propose a method of cleaning reactor piping to remove rust agent and foreign matter .

[0013]

In the plant construction method of the present invention, the operation of connecting the reactor pressure vessel to the final spool of the reactor piping inside the reactor containment vessel and the operation of cleaning the reactor piping outside the reactor containment vessel are performed. Since the process proceeds independently, the operation of cleaning the reactor piping and the operation of connecting the reactor piping to the reactor pressure vessel do not interfere with each other, and the plant construction process can be shortened.

[0014] Further, the connection operation between the reactor pressure vessel and the final spool of the main steam system piping and the water supply system piping inside the reactor containment vessel, and the connection between the main steam system piping and the water supply system piping outside the reactor containment vessel. The cleaning work for cleaning the reactor pipes by passing them through the temporary pipes and passing the water through each pipe is performed in parallel.The procedure for cleaning the reactor pipes and connecting the reactor pipes to the reactor pressure vessel Are changed from the conventional tandem relationship to the parallel relationship, which can be performed simultaneously, and the plant construction process can be shortened.

In the method of cleaning a reactor pipe according to the present invention, a valve outside the reactor containment vessel of the main steam system pipe and a valve outside the reactor containment vessel of the water supply system pipe are bypass-connected by a temporary pipe, and the main steam system is bypassed. Independent of the work of connecting the final spools of the system and water supply system to the reactor pressure vessel joint,
Since only the reactor piping outside the containment vessel is cleaned,
Cleaning work of reactor piping can be excluded from the critical path in the nuclear power plant construction process.

The inside of the reactor piping, which is disposed inside the reactor containment vessel and excluded from the cleaning, is subjected to a rust-preventive treatment with a rust-preventive agent in advance. Remove the rust inhibitor and foreign substances in the excluded reactor piping.

Therefore, according to the method for cleaning a reactor pipe of the present invention, the entire plant construction process can be shortened.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIGS. 1 to 9, an improved boiling water nuclear power plant, that is, an ABWR will be described as an example.
A method for cleaning a reactor pipe according to the present invention will be described.

FIG. 5 is a diagram showing an example of a system configuration of a nuclear power plant to which the method for cleaning a reactor pipe according to the present invention is applied. In the case of ABWR, the main steam system piping 21
The reactor pressure vessel (RPV) 1 and the steam turbine equipment are connected through a reinforced concrete structure serving as a containment vessel, that is, RCCV2. The steam turbine equipment includes a high-pressure turbine 3 and a low-pressure turbine 4 for rotating a generator. The steam generated in the reactor pressure vessel 1
The main steam pipe 21 guides the high-pressure turbine 3 via the main steam header 5 to rotate the high-pressure turbine 3. The steam leaving the high-pressure turbine 3 is supplied to a moisture separation heater 16.
Through the low-pressure turbine 4
To rotate. The steam used in the steam turbine facilities 3 and 4 is condensed in the condenser 6, and is supplied again to the reactor pressure vessel 1 through a condenser pipe 22 and a water supply pipe 23. In addition, the arrow 91 in FIG. 5 has shown the water flow direction at the time of normal operation.

When cleaning the reactor piping, generally, in addition to the main steam piping 21, the condensing piping 22, and the water supply piping 23, the condensing water circulation piping 24 and the water supply circulation piping 25 attached thereto are also cleaned at the same time. I do.

FIG. 6 is a diagram showing an example of the configuration of a cleaning facility 70 used for cleaning the reactor piping when constructing a nuclear power plant. The water used for cleaning is pure water.
The pure water is supplied to a pure water tank 74 installed near the construction site.
Is taken from The pure water is mixed with hot water supplied from the house boiler equipment 75 in the heating device 76 to be heated, and sent out to the system to be cleaned by the temporary cleaning pump 71. The cleaning water is sent to the condensate piping 22 by a temporary pipe via a check valve 45 corresponding to the outlet side of the low-pressure condensate pump 7, sent from the water supply pipe 23 to the main steam pipe 21 by a temporary pipe, and stopped by the main steam. It is circulated from the valve 46 through the temporary piping to return to the temporary cleaning equipment 70.
The cleaning water polluted by the cleaning is sent to a wastewater treatment facility 78. In addition, if necessary, chemical injection equipment 7
Cleaning chemicals are injected from 7.

FIG. 7 is a diagram showing an example of a system configuration for cleaning a reactor pipe by a conventional cleaning method. In order to clarify the features of the present invention, before describing embodiments of the present invention, the overall configuration of a cleaning system in this conventional method of cleaning a reactor pipe will be described.

Basically, the nuclear power plant shown in FIG. 5 has a system configuration in which a washing facility shown in FIG. 6 is added. In FIG. 7, the pipe indicated by a broken line is a temporary pipe used for cleaning. Regarding the main steam system pipe 21 and the water supply system pipe 23, one final spool 30 to be connected to the reactor pressure vessel 1 is not installed, and the reactor pressure vessel 1 is A temporary pipe 27 to be bypassed is set to be a bypass route for washing water. Note that an arrow 92 shown in FIG. 7 indicates the flow direction of the cleaning water at the time of cleaning. In this case, the reactor containment vessel 2
The cleaning water flows through the associated steam as well as the main steam system piping 21 and the water supply system piping 23 of the reactor inside.

In the conventional cleaning method employing such a system configuration, since the piping in the reactor containment vessel 2 is bypassed with the reactor pressure vessel 1 installed, the reactor pressure vessel 1 is connected to the reactor building. The installation of the reactor pressure vessel 1, the reactor piping around the reactor vessel, valves, and the like must be completed during a limited period from the time when the reactor is carried into the so-called pre-operation.

In order to clean the reactor piping by the conventional method, the final spools 30 of the main steam system and the water supply system are used.
Is not connected to the connection section of the reactor pressure vessel 1, the temporary cleaning pipe 27 is set to bypass the reactor pressure vessel 1, cleaning by water flushing is completed, and the temporary pipe 27 is removed. , The final spool 30 was set, welded, and the installation was completed.

On the other hand, FIG. 1 is a diagram showing an example of a system configuration in a case where a reactor pipe is cleaned by the reactor pipe cleaning method of the present invention. In FIG. 1, pipes indicated by broken lines are temporary pipes used for cleaning. In the method of cleaning a reactor pipe according to the present invention, the main steam isolation valve 42 outside the reactor containment vessel 2 belonging to the main steam pipe 21 and the check valve 43 outside the reactor containment vessel 2 belonging to the water supply pipe 23 are provided. Is bypassed using the temporary piping 28. Therefore, water is not passed through the main steam system pipe 31 inside the reactor containment vessel 2, the water supply system pipe 32 inside the reactor containment vessel 2, and each valve, and is not subject to cleaning. In addition, the basic configuration of the cleaning equipment is the same as that of the conventionally known method of cleaning a nuclear reactor. Note that the direction of the arrow 92 in FIG. 1 indicates the flow direction of the cleaning water at the time of cleaning.

In the present embodiment, when the cleaning by water flooding, the cleaning using a surfactant, and the cleaning using alkaline water are performed on the piping system except for the bypass area in the containment vessel 2, The cleaning fluid is circulated in the flow direction during normal operation, but may be circulated in the opposite direction for cleaning.

A method of connecting the temporary cleaning pipe 28 to bypass the pipe in the containment vessel 2 according to the present invention will be described. Temporary piping 28 bypassing PCV 2
Is connected to the main steam isolation valve 42 and the check valve 43 by a flange. In places where cleaning water must be closed,
Attach the closing plate as needed.

FIG. 2 is a view showing a state in which the temporary cleaning pipe 28 is connected to the water supply system check valve 43. In order to connect the temporary pipe 28 to the water supply system check valve 43, first, the bonnet (not shown) of the water supply system check valve 43 is removed, and the valve body 47 is taken out. Next, the temporary pipe 28 that bypasses the reactor containment vessel 2 is connected to the flange portion 65 of the check valve 43 from which the bonnet has been removed, and fixed with bolts 66. The gate valve 44 (FIG. 1) disposed in the reactor containment vessel 2 is kept closed so that the washing water does not flow into the reactor pressure vessel 1. After the cleaning is completed, the hypothetical pipe 28 that bypasses the reactor containment vessel 2 is removed, and the valve body 47 is returned to the original state.

FIG. 3 is a view showing a state where the temporary pipe 28 is connected to the main steam isolation valve 42 outside the containment vessel 2. To connect the main steam isolation valve 42 outside the containment vessel 2 and the temporary cleaning pipe 28, first, the main steam isolation valve 42
Here, the bonnet (not shown) is removed, and the valve body is taken out. Next, in order to prevent the cleaning water from leaking to the reactor pressure vessel 1 side, a closing plate 61 for preventing leakage is attached to the main steam isolation valve 42 on the reactor pressure vessel 1 side. A temporary pipe is connected to the flange portion 62 of the main steam isolation valve 42 from which the bonnet has been removed, and fixed with bolts 66. After the cleaning is completed, the temporary pipe 28 bypassing the reactor containment vessel 2 and the leakage prevention closing plate 61 used at the time of cleaning are removed, and the valve body 47 is returned to the original state.

Next, in the method for cleaning a reactor pipe according to the present invention, a procedure for ensuring cleanliness of water will be described. In the present invention, as compared with the conventional cleaning method, for a range that is newly excluded from cleaning by water flushing cleaning, alkaline water cleaning, or the like, foreign matter that has entered inside prior to installation on the site. Check for any foreign matter, and if foreign matter has entered, remove it before installing. As a specific method for removing foreign matters, a method of cleaning the inside using means such as hand wiping cleaning and vacuum cleaning can be considered.

The inside of the reactor piping arranged inside the reactor containment vessel 2 and excluded from the cleaning is subjected to a rust proof treatment with a water-soluble or volatile rust preventive agent in advance, and the reactor pressure vessel 1 is filled with water. At this time, water is passed through the reactor piping excluded from the cleaning to remove rust preventives and foreign substances. In addition,
For parts of piping components such as valves that have been subjected to rust-preventive treatment with rust-preventive oil and parts that require removal of foreign substances, remove the rust-preventive oil and foreign substances before assembling the piping system. Keep it. For the inner surface of the valve where an oil-based rust preventive is used, residual oil is removed by hand wiping or the like. More specifically, the main steam isolation valve 41 on the main steam system side, the air pressure check valve 48 on the water supply system side, the check valve 49 on the water supply system, and the like, all of which are disposed inside the reactor containment vessel 2, perform this work. Subject to.

At the time of pre-operation of safety system, etc., the reactor pressure vessel 1
When water is passed through the piping when filling the water, the water-soluble or volatile rust inhibitor is removed. Therefore, the reactor piping disposed in the reactor containment vessel 2 is particularly washed with alkaline water. It is not necessary to perform cleaning such as.

That is, for the range of the piping system excluded from the objects of cleaning such as water flushing cleaning and alkaline water cleaning, which is included in the reactor containment vessel 2, the rust prevention treatment inside the piping system is entirely water-soluble or If a rust preventive treatment is performed with a volatile rust preventive agent, the reactor pressure vessel 1 can be used during the operation test of the core cooling system, the water filling test of the reactor pressure vessel, the pre-operation, etc. performed after the installation of the piping belonging to the reactor. When water is passed through the pipes when the water is filled with water, the water-soluble or volatile rust inhibitor enclosed for the purpose of protecting the inner surface of the pipes is removed, and drainage is performed from the drain pipes provided in the system. The waste water is discharged to the pot 18 and finally discharged
Is discharged.

With respect to inspection and confirmation after installation of the piping system excluded from cleaning processes such as water flushing cleaning and alkaline water cleaning, work is performed from the portion where the final spool 30 connected to the reactor pressure vessel 1 is connected. A person enters the inside of the pipe and visually inspects it, or inspects the inner surface of the piping system using an endoscope or the like. As a result, if there is a residue inside, the residue may be removed by suction or discharge using a vacuum cleaner, or by wiping with hand.

FIG. 4 is a view showing a situation in which a dummy ring 63 is set at a pipe portion from which a flange type orifice has been removed. In the method for cleaning a reactor pipe according to the present invention, equipment that may be damaged during passage of water is removed or bypassed with a temporary pipe or the like. As shown in FIG. 1, the pump equipment belonging to the system in the range to be washed is bypassed using a temporary pipe or a temporary pressure-resistant hose 29 in order to avoid damage due to foreign matter or contaminants during water flow. For example, instrumentation equipment such as the flow meter 55, which may be damaged when it comes into contact with contaminants during cleaning, is to be mounted with a flange, removed during cleaning, and replaced with a temporary dummy ring 63 without a throttle. Attach and wash water.

Here, the effect of shortening the construction process of a nuclear power plant by applying the present invention will be described.
FIG. 8 is a diagram showing the operation procedure of a conventional method of cleaning a reactor pipe. The connection of the main steam system pipe 21 and the water supply system pipe 23 carried into the reactor containment vessel 2 is completed except for one final spool 30 connected to the reactor pressure vessel 1. In this state, using the temporary pipe 27, cleaning preparation work such as connecting the water supply pipe 23 and the main steam pipe 21 in the containment vessel 2 is performed. After the cleaning is completed, the temporary pipe 27 is removed and carried out. Next, the final spool 30 connected to the reactor pressure vessel 1 is connected to a state where a system test can be performed. In this case, the operation inside the reactor containment vessel 2 is a tandem operation procedure, and cannot be performed in parallel in time.

FIG. 9 is a diagram showing the operation procedure of the method for cleaning a reactor pipe according to the present invention. According to the present invention, the connection work between the reactor pressure vessel 1 and the final spool 30 in the reactor containment vessel 2 can be started immediately after the reactor pressure vessel 1 is carried into the reactor building. On the other hand, the operation after cleaning the outside of the containment vessel 2 is also completed by removing the temporary cleaning pipe 28 connected to the valve by a flange and returning the valve body 47 removed at the time of cleaning. That is,
Operations in the reactor containment vessel 2 such as connection work between the reactor pressure vessel 1 and the final spool 30 include cleaning preparation such as connection of the temporary pipe 28, cleaning, removal of the temporary pipe 28, and unloading of the temporary pipe 28. Since the process can proceed independently of the series of cleaning operations, it is possible to shorten the operation steps in the containment vessel 1.

[0039]

According to the plant construction method of the present invention, a connection operation between the reactor pressure vessel and the final spool of the reactor piping in the reactor containment vessel, and a cleaning of the reactor pipe outside the reactor containment vessel. Since the work and progress independently
The cleaning of the reactor piping and the connection of the reactor piping to the reactor pressure vessel do not interfere with each other, and the plant construction process can be shortened.

Further, the connection work between the reactor pressure vessel and the final spools of the main steam system piping and the water supply system piping inside the reactor containment vessel, and the connection between the main steam system piping and the water supply system piping outside the reactor containment vessel. The cleaning work for cleaning the reactor pipes by passing them through the temporary pipes and passing the water through each pipe is performed in parallel.The procedure for cleaning the reactor pipes and connecting the reactor pipes to the reactor pressure vessel Are changed from the conventional tandem relationship to the parallel relationship, which can be performed simultaneously, and the plant construction process can be shortened.

According to the method for cleaning a reactor pipe of the present invention,
By-pass connection of the valve outside the reactor containment vessel of the main steam system piping and the valve outside the reactor containment vessel of the water supply system piping by temporary piping, and connecting the final spools of the main steam system and the water supply system to the reactor pressure vessel Since only the reactor piping outside the reactor containment vessel is cleaned independently of the work of connecting to the reactor section, the cleaning work of the reactor piping can be excluded from the critical path in the nuclear power plant construction process.

On the other hand, the inside of the reactor piping, which is disposed inside the reactor containment vessel and excluded from the cleaning, is subjected to a rust-preventive treatment in advance with a rust preventive agent, and is excluded from the cleaning when the reactor pressure vessel is filled with water. Rust preventive agent and foreign matter in the reactor pipe.

Therefore, according to the method for cleaning a reactor pipe of the present invention, the entire plant construction process can be shortened.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of a system configuration in a case where a reactor pipe is cleaned by a method for cleaning a reactor pipe of the present invention.

FIG. 2 is a view showing a state in which a temporary pipe is connected to a water supply system check valve prior to cleaning the reactor pipe according to the present invention.

FIG. 3 is a diagram showing a state in which a temporary pipe is connected to a main steam isolation valve prior to cleaning a reactor pipe according to the present invention.

FIG. 4 is a diagram showing a state in which a dummy ring is connected to a pipe portion from which an orifice has been removed before cleaning a reactor pipe according to the present invention.

FIG. 5 is a diagram showing an example of a system configuration of a nuclear power plant to which the method for cleaning a reactor pipe according to the present invention is applied.

FIG. 6 is a diagram showing an example of a configuration of a cleaning facility used for cleaning a reactor pipe when constructing a nuclear power plant.

FIG. 7 is a diagram showing an example of a system configuration when a reactor pipe is cleaned by a conventional cleaning method.

FIG. 8 is a diagram showing an operation procedure of a conventional method of cleaning a reactor pipe.

FIG. 9 is a diagram showing an operation procedure of a method for cleaning a reactor pipe according to the present invention.

[Explanation of symbols]

 1 Reactor Pressure Vessel (RPV) 2 Reactor Containment Vessel (RCCV) 3 High Pressure Turbine 4 Low Pressure Turbine 5 Main Steam Header 6 Condenser 7 Low Pressure Condensate Pump 8 High Pressure Condensate Pump 9 Condensate Filtration Device 10 Condensate Desalination Device 11 Air extraction device 12 Ground steam condenser 13 Feed water heater 14 Turbine driven reactor feed pump 15 Electric driven reactor feed water pump 16 Moisture separation heater 18 Drain pot 19 Sixth feed water heater Drain cooler 21 Main steam System piping 22 Condensing system piping 23 Water supply system piping 24 Condensing water circulation piping 25 Water supply circulation piping 27 Temporary piping bypassing the reactor pressure vessel 28 Temporary piping bypassing the reactor containment vessel 29 Temporary piping or temporary hose other than the temporary piping 28 30 Final spool for connection with reactor pressure vessel 31 Main steam system piping inside reactor containment vessel 32 Reactor grade Water supply piping in the storage container 41 Main steam isolation valve (inside the reactor containment vessel) 42 Main steam isolation valve (outside the reactor containment vessel) 43 Water supply system (outside the reactor containment vessel) 44 Water supply system gate valve (reactor containment) (Inside of container) 45 Check valve corresponding to outlet side of low pressure condensate pump 46 Main steam stop valve 47 Valve element 48 Air pressure check valve on water supply system side 49 Check valve of water supply system corresponding to inside of reactor containment vessel 50 Turbine bypass valve 51 Globe Valve 52 Gate valve 53 Check valve 54 Orifice 55 Flow meter 61 Leak prevention closing plate 62 Flange part of main steam isolation valve 63 Temporary dummy ring without throttle 64 Closure of cleaning pipe 65 Flange part of check valve 66 Bolt 70 Temporary cleaning equipment 71 Temporary cleaning pump 72 Water supply auxiliary pump 73 Temporary strainer 74 Pure water tank 75 Houseboy Facilities 76 water passing direction of the heating device 77 the chemical injection equipment 78 wastewater treatment 設槽 91 plants normal wash water during water passing direction 92 cleaning during operation

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Naoto Yoshida 3-1-1 Kochi-cho, Hitachi-shi, Ibaraki Hitachi, Ltd. Inside the Hitachi Plant (72) Ryohei Miyahara 3-1-1 Kochi-cho, Hitachi-shi, Ibaraki No. 1 Hitachi, Ltd., Hitachi Plant (72) Inventor Hiroshi Takano 3-1-1, Sachimachi, Hitachi City, Ibaraki Prefecture Inside Hitachi, Ltd. Hitachi Plant (72) Inventor Kazuto Tadodo, Sachimachi, Hitachi City, Ibaraki Prefecture 3-1-1, Hitachi, Ltd.Hitachi Plant Hitachi Plant (72) Inventor Tatsuo Makita 1-1-1 Uchikanda, Chiyoda-ku, Tokyo Inside Hitachi Plant Construction Co., Ltd. (72) Inventor Keiya Sato Chiyoda-ku, Tokyo 1-1-14 Uchikanda Inside Hitachi Plant Construction Co., Ltd. (58) Field surveyed (Int. Cl. ⁷ , DB name) G21C 19/02 G21C 13/00 G21D 1/00

Claims (2)

(57) [Claims] 1. A connection operation between a reactor pressure vessel and a final spool of a main steam system piping and a water supply system piping in a reactor containment vessel, and the main steam system piping and the water supply system piping outside the reactor containment vessel. A plant construction method in which a washing operation for washing by washing by passing water through each of the above-mentioned pipes is connected in parallel with a temporary pipe. 2. A method for cleaning a reactor pipe including a main steam pipe and a water supply pipe at the time of construction of a nuclear power plant, comprising: a valve outside the reactor containment vessel of the main steam pipe and the atom of the water feed pipe. By-pass connection with a valve outside the reactor containment vessel by a temporary pipe, while cleaning only the reactor pipe outside the reactor containment vessel, and reactor pipe arranged inside the reactor containment vessel and excluded from the cleaning A reactor pipe characterized in that the inside of the reactor pipe is preliminarily treated with a rust inhibitor to remove the rust inhibitor and foreign matter in the reactor pipe excluded from the cleaning when the reactor pressure vessel is filled with water. Cleaning method.