JP2012176336A - Pipe washing method in nuclear power plant - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a washing method capable of reducing the amount of used pure water in a pipe washing process of a nuclear power plant.SOLUTION: The pipe washing method in a nuclear power plant has pipe washing equipment which supplies pure water supplied from a pure water producing device 1 to a washing object system 6 through a supply system 3, recovers washing water after washing the washing object system 6 to a recovery system 7 and further is branched into a water discharge 11 connected to water discharge processing equipment 12 and a circulation system 13 connected to the supply system 3. The pipe washing method in a nuclear power plant includes: a water filling process of filling pipe washing equipment and washing object system 6 with pure water; an extrusion washing process of discharging the pure water of an amount about one to two times the holding water amount of the pipe washing equipment and the washing object system 6 to the water discharge processing equipment 12 through the supply system 3, washing object system 6, recovery system 7 and water discharge 11; and a circulation washing process of circulating the pure water through the supply system 3, the washing object system 6, a circulation strainer 8 and a filtration filter 10 in the recovery system 7, and the circulation system 13.

Description

  The present invention relates to a pipe cleaning method, and more particularly to a pipe cleaning method during construction of a nuclear power plant.

  In the pipe cleaning process at the time of construction in a nuclear power plant, there is a problem that a water use plan is created and the work is carried out in consideration of pure water production capacity and water storage capacity while suppressing process delay potential. The background will be described below.

  There are three types of pipe cleaning work in nuclear power plants: water cleaning using pure water and filtered water, oil cleaning using oil, and gas cleaning using gas such as air and nitrogen, depending on the fluid used in each system. Most of the cleaning methods use pure water as a cleaning fluid.

  As shown in FIG. 3, the cleaning method using pure water is composed of five work steps of “water filling”, “extrusion cleaning”, “circulation cleaning”, “water quality determination”, and “drainage treatment”.

  S31 “water filling” is intended to dissolve and remove water-soluble impurities such as a pipe rust preventive agent adhering to the inner surface of the pipe in water, and fills the system to be cleaned and the pipe cleaning equipment with water.

  S32 “extrusion cleaning” discharges foreign matters such as water-soluble impurities dissolved during “water filling” in S31, fine dust (turbidity component) that does not precipitate and floats in the water, and welding dust from the system. For this purpose, a large volume of water about 4 to 5 times the amount of water held in the piping system consisting of the cleaning target system and the piping cleaning equipment to be cleaned is swept away all over the cleaning target system. The system to be cleaned and the pipe cleaning facility do not form a closed loop, and the water that has passed through the system to be cleaned is directly discharged to the drainage facility. S33 “Circulation cleaning” is a system that configures the system to be cleaned and the pipe cleaning equipment in a closed loop so that the water that has passed through the system to be cleaned returns to the system through a foreign matter trapping device such as a circulating strainer (filter). The purpose is to capture solid foreign substances other than the turbidity component remaining in the water after performing the “extrusion cleaning”.

  S34 “Water quality determination” confirms that the water quality (impurities and turbidity) of the cleaning water and the remaining foreign matter are below the specified values after the “circular cleaning” operation. In S35 “drainage treatment”, water quality treatment such as neutralization and sedimentation separation is performed so that the quality of the wastewater discharged from the system to be washed and the pipe washing equipment during the washing operation is not more than a specified value.

The nuclear power plant has a facility for water storage and production of water from the power generation method, the water storage amount The total water storage facilities for pure water and for filtration of water 4,000 m ³ approximately, pure water production capacity Is usually about 750 m ³ / day.

The pure water production apparatus has a continuous use restriction due to the maintainability of the production apparatus and the like, and the working day of a week is limited to about 6 days. Based on this, the pure water production is usually about 4,500 m ³ / week on a weekly basis and about 18,000 m ³ / month on a monthly basis.

In the conventional pipe cleaning method, when the amount of water used is considered on a monthly basis, a period requiring about 18,000 to 20,000 m ^{3 of} pure water continues for 2 to 3 months. Further, when considered on a weekly basis, in the peak period of pure water usage, cleaning operations that require a pure water usage exceeding 7,000 m ³ are almost continuous in half a month (2 weeks). For this reason, it is necessary to set a process in consideration of the pure water production capacity so that an interval between cleaning operations for each system can be made. Furthermore, unless a precise plan for pure water use is made, there is a possibility that the amount of water that can be stored will be exceeded due to the limited amount of water stored. In particular, in the construction of a continuous unit in the same plant, it is necessary to consider the amount of water used at the regular inspection of the existing units, which makes it very difficult to manage the amount of pure water used.

  In terms of process, if there is a margin that allows the process to be freely changed, it is possible to set the process so that the cleaning operation interval for each system can be increased. However, the pipe cleaning time will be the final stage of the pipe group installation period, and immediately after that, the trial run to be carried out on the entire system is refrained, so it is very difficult to extend the pipe cleaning work period and postponement of the execution time. This leads to a problem that affects the critical path of the entire plant construction process.

  The conventional method has the background described above, and pipe cleaning has a problem that it is necessary to carry out work by planning the water use while considering the pure water production capacity and possible storage capacity while suppressing the process delay potential. there were.

  Patent Documents 1 and 2 will be described below with reference to the process diagram of FIG. In Patent Document 1, the “extrusion cleaning” step is omitted, and immediately after “water filling” in S41, the process proceeds to “circulation cleaning” in S43. S44 “water quality determination” and S45 “drainage treatment” are performed in the same manner as in FIG.

  In S43 “circulation cleaning”, a relatively large foreign matter and a fine foreign matter are caught using a circulation strainer and a circulation filter. Therefore, although the problem of the amount of water used is solved, another problem arises by using a filtration device that removes suspended substances without carrying out the extrusion washing operation process. In Patent Document 1 in which extrusion cleaning is not performed, a very fine filter having a filtration accuracy of 100 μm or less is used as a circulation filter in order to capture suspended substances. At this time, most of the suspended solids discharged out of the system by extrusion cleaning remain in the closed loop, and all of them are passed through a filter with high filtration accuracy in the initial stage of circulating water. Clogging frequently occurs. Along with this, maintenance work for high-filtration precision circulation filters, such as increasing the number of filter backwashes and filter replacement, occurs during the cleaning work process, resulting in prolonged cleaning work process itself and affecting the critical process of the entire construction. A process delay potential is generated.

  Also in Patent Document 2, since a very fine filter having a pore diameter of about 2.5 μm is used, the filter is clogged frequently as in Patent Document 1, and a process delay potential associated with maintenance work of the circulation filter is generated. Become.

  Patent Document 3 limits the object to ultrapure water production and supply equipment, and is a special cleaning method using basic hydrogen peroxide water for the separation and dispersion of fine particles. The technical field is different from the pipe cleaning work, and the object to be cleaned is not targeted for water-soluble impurities, foreign matter such as welding dust, dust and the like.

  Patent Document 4 is intended for high-pressure jet cleaning of water cleaning as shown in the embodiment, and the equipment configuration is different from that shown in FIG. The fields are different.

JP-A-2003-88819 JP 2000-279906 A JP, 2006-297343, A JP-A-2004-255346

In the pipe cleaning work carried out at the time of construction of a nuclear power plant, the following problems are raised in the conventional method and known examples.
(1) In the circulation cleaning process, when the initial water flow is performed using a fine filter, the filter is clogged with the organic pipe anticorrosive agent and foreign matters such as dust and welding dust in the pipe. Due to the clogging of the fine filter, additional work such as backwashing and cleaning occurs, which causes an extension of the cleaning period.
(2) The construction of the nuclear project (construction process) planned in the future requires further process shortening than the current situation from the viewpoint of environmental impact and cost reduction. Since the effects of construction process delays due to (1) are very severe, drastic improvements are required.
(3) Pipe cleaning work at nuclear power plants requires a large amount of pure water to be used, so reducing the amount of water used is an issue.

  The present invention supplies pure water supplied from a pure water production apparatus to a system to be cleaned via a supply system having a cleaning pump, and the cleaning water after cleaning the system to be cleaned is supplied with a circulation strainer and a filtration filter. In a pipe cleaning method for a nuclear power plant having a pipe cleaning facility for branching into a drainage system connected to a wastewater treatment facility and a circulation system connected to the supply system, The water filling process for filling the pipe cleaning equipment and the system to be cleaned with pure water, and the supply system, the system to be cleaned, the recovery system, and the drainage of pure water about 1 to 2 times the amount of water held in the pipe cleaning equipment and the system to be cleaned An extrusion cleaning process for draining the wastewater treatment facility via a system, and the circulating strainer and the filtration filter in the supply system, the system to be cleaned, and the recovery system. Terpolymer, and having a circulation cleaning process of circulating through the circulation system.

  Further, in the pipe cleaning method for a nuclear power plant, the system to be cleaned is a pipe system at the time of construction of the nuclear power plant.

  In the pipe cleaning method of a nuclear power plant, the filtration accuracy of the filtration filter is finer than the filtration accuracy of the circulation strainer, and is a size that captures fine foreign matters floating in water.

  In the pipe cleaning method for a nuclear power plant, the filtration accuracy of the filtration filter is 0.1 to 100 microns, and the filtration accuracy of the circulation strainer is 60 to 120 mesh.

  The pipe cleaning method for a nuclear power plant further includes a water quality determination step for confirming that the quality of pure water after cleaning the system to be cleaned is below a specified value.

  Further, in the pipe cleaning method for a nuclear power plant, the pipe cleaning equipment includes a water storage tank for storing pure water produced by the pure water production apparatus.

  The present invention drastically reduces the amount of water used, which was a problem of the conventional method, by performing extrusion cleaning using water that is about 1 to 2 times the amount of water retained in the system, and is dissolved in water by water filling work. It is possible to prevent the remaining impurities from being discharged out of the system.

  In addition, by carrying out cyclic cleaning in the equipment configuration including the filtration filter, it captures residual fine foreign matter that accompanies the adoption of extrusion cleaning with reduced water consumption, and fine foreign matter that accumulates in the filter as the capture time increases As a result, most of the water can be discharged by performing extrusion cleaning in advance with low water consumption, reducing the number of clogging of the filter, and reducing additional work such as backwashing and cleaning. .

The schematic diagram which shows the piping washing equipment concerning the Example of this invention. The process drawing concerning the Example of this invention. Process drawing which shows the conventional piping washing method. Process drawing which shows the other conventional piping washing process.

  1 and 2, examples of the embodiment according to the present invention will be described in detail. FIG. 1 shows an outline of the equipment configuration according to the present invention, and a feature from the conventional example is that it has a filtration filter for capturing fine foreign matters (turbidity components) floating in water.

  In the pipe cleaning facility shown in FIG. 1, pure water produced by the pure water production apparatus 1 is stored in a water storage tank 2. Reference numeral 3 denotes a supply system having a cleaning pump 4 and a plurality of switching valves 5, and supplies pure water to a cleaning target system 6 composed of plant piping or the like at the time of cleaning. Here, the system to be cleaned prepares a piping system in a state in which equipment that may cause water retention is removed. By doing in this way, smooth washing with an appropriate amount of water becomes possible.

  Reference numeral 7 denotes a collection system for collecting pure water after washing, and includes a circulation strainer 8, a water quality determination device 9, a filtration filter 10, and a plurality of switching valves 5. Washing water (purified water after washing) that has passed through the recovery system 7 is drained to the wastewater treatment facility 13 via the drainage system 11 or supplied again to the supply system 3 via the circulation system 12. . Each device of the pipe cleaning equipment is connected to a control device (not shown) and is operated according to a work process in a certain sequence.

  Next, in the cleaning operation process shown in FIG. 2, in S21 “water filling”, pure water in the water storage tank 2 is supplied to fill the system to be cleaned and the pipe cleaning equipment to a full state, and water-soluble impurities such as pipe rust preventives are removed. Dissolve in pure water. Next, in S22 “push-out cleaning”, the supply system 3, the cleaning target system 6, the recovery system 7, It flows out to the waste water treatment facility 12 via the drainage system 11, and discharges water-soluble impurities and fine foreign matters. Next, in S23 “circulation cleaning”, a closed loop composed of the supply system 3, the system 6 to be cleaned, the recovery system 7, and the circulation system 12 is configured, and a relatively large foreign matter is captured by the circulation strainer 8, and the washing water is collected by the filtration filter 10. To capture fine foreign matter. When the filtration accuracy of the circulation strainer 8 is 60 to 120 mesh and the filtration accuracy of the filtration filter 10 is about 0.1 to 100 microns, the foreign matter can be appropriately removed.

  Thereafter, in S24 “water quality determination”, it is confirmed that the quality of the washing water and the remaining foreign matter are not more than specified values, and the water quality treatment is performed in S25 “drainage treatment”.

  In the present embodiment, in the extrusion cleaning process, water that is about 1 to 2 times the amount of water retained in the system is used, and the extrusion cleaning is performed in which most of the water-soluble impurities and fine foreign matters are discharged out of the system. Thereafter, in the circulation cleaning step, circulation cleaning is performed by a closed loop of the pipe cleaning equipment including the circulation strainer 8 and the filtration filter 10 shown in FIG. 1 to capture a part of the remaining fine foreign matters and a relatively large foreign matter. . In addition, about a water filling process, a water quality determination process, and a waste water treatment process, work is implemented like a conventional construction method and a well-known example.

  In this way, the amount of water required is about 1 to 2 times that of the conventional water to be cleaned and 4 to 5 times the amount of pure water retained by the pipe cleaning equipment. Washing is possible with a water amount of 20 to 40%, and the water amount can be significantly reduced.

1: Pure water production device 3: Supply system 4: Cleaning pump 6: Cleaning target system 8: Circulation strainer 7: Recovery system 9: Water quality determination device 10: Filtration filter 11: Drainage system 12: Wastewater treatment facility 13: Circulation system

Claims (6)

Purified water supplied from the pure water production device is supplied to the system to be cleaned via a supply system having a cleaning pump, and the cleaning water after cleaning the system to be cleaned is circulated with a strainer, a filtration filter, and a water quality determination device. In a pipe cleaning method for a nuclear power plant having a pipe cleaning facility for branching into a drainage system connected to a wastewater treatment facility and a circulation system connected to the supply system,
A water filling step for filling the pipe cleaning equipment and the system to be cleaned with pure water, and the supply system, the system to be cleaned, the recovery system for pure water that is about 1 to 2 times the amount of water held in the pipe cleaning equipment and the system to be cleaned; Extrusion cleaning process for draining to the wastewater treatment facility via a drainage system, and circulation for circulating pure water via the supply system, the system to be cleaned, the circulation strainer and the filtration filter in the recovery system, and the circulation system A piping cleaning method for a nuclear power plant, characterized by comprising a cleaning step.   2. The nuclear power plant pipe cleaning method according to claim 1, wherein the system to be cleaned is a piping system at the time of construction of the nuclear power plant.   3. The method of cleaning a pipe of a nuclear power plant according to claim 1 or 2, wherein the filtration accuracy of the filtration filter is finer than the filtration accuracy of the circulation strainer, and is a size that captures fine foreign matters floating in water. A method for cleaning pipes of nuclear power plants.   4. The method of cleaning a pipe of a nuclear power plant according to claim 3, wherein the filtration accuracy of the filtration filter is 0.1 to 100 microns, and the filtration accuracy of the circulation strainer is 60 to 120 mesh. How to clean piping for nuclear power plants.   The pipe cleaning method for a nuclear power plant according to any one of claims 1 to 4, further comprising a water quality determination step for confirming that the quality of pure water after cleaning the system to be cleaned is below a specified value. A method for cleaning piping of a nuclear power plant.   6. The nuclear power plant pipe cleaning method according to claim 1, wherein the pipe cleaning equipment includes a water storage tank for storing pure water produced by the pure water production apparatus. How to clean a power plant piping.

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