JP3597644B2 - Water quality maintenance equipment for nuclear power plants - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a water quality maintenance device for a nuclear power plant that decomposes and removes TOC (Total Organic Carbon) in storage water in a condensate storage tank installed in the nuclear power plant to maintain the purity of the storage water. .
[0002]
[Prior art]
FIG. 2 illustrates a primary system of a conventional boiling water nuclear power plant, FIG. 3 illustrates a means for maintaining purity of stored water in a condensate storage tank, and FIG. 4 illustrates a relationship between TOC in reactor water and conductivity. Will be described.
[0003]
In FIG. 2, steam generated in a reactor 1 is sent to a turbine 3 via a main steam pipe 2, and a generator 4 is rotated to generate power. The steam that has driven the turbine 3 is condensed by the condenser 5 to be condensed.
[0004]
This condensate is pressurized by a low-pressure condensate pump 6, passes through an air extractor 7 and a ground steam condenser 8, and is contaminated by a condensate filtration device 9 and a condensate desalination device 10 installed in the condensate purification system. Removed. The condensate purified by the condensate desalination device 10 is further pressurized by a high-pressure condensate pump 11 and sent to a low-pressure feedwater heater 12 to be heated.
[0005]
Then, the pressure is further increased by the water supply pump 13, heated by passing through the high pressure water heater 14, and supplied into the reactor 1 through the water supply pipe 15. In addition, hydrogen is injected for the soundness of structural equipment in the nuclear reactor 1, and the injection of hydrogen is performed at a hydrogen injection point 16 between the condensate desalination device 10 and the high-pressure condensate pump 11.
[0006]
In the boiling water nuclear power plant, a condensate storage tank 17 shown in FIG. 3 is connected between the condensate desalination unit 10 and the high-pressure condensate pump 11 via a branch pipe. FIG. 3 shows a basic system diagram for storing pure water obtained by purifying raw water from a water source 18 by a pure water producing apparatus 19 in a condensate storage tank 17.
[0007]
In FIG. 3, raw water normally pumped from a water source 1 such as seawater or river water is purified by a pure water producing apparatus 19, stored as it is in a condensate storage tank 17 through a pure water supply pipe 20, and then supplied to a condensate supply pump 21. , And is transferred to each device 22 in the nuclear power plant. The plant surplus water from each device 22 is returned to the condensate storage tank 17 by a feedback pipe 23.
[0008]
In the boiling water nuclear power plant shown in FIG. 2, after the periodic inspection of the plant is completed, the condensate stored in the condensate storage tank 17 shown in FIG. 3 is filled with water through the condensate supply pump. . The purification before starting the plant is performed by the condensate filtration device 9 and the condensate desalination device 10 of the condensate purification system.
[0009]
In this purification, when the TOC of the condensate storage tank 17 is high, it may be difficult for the condensate filtration device 9 and the condensate desalination device 10 to completely remove the TOC component. For this reason, the TOC concentration is checked before filling the plant. If the TOC concentration is high, the total amount of water (about 2000 to 3000 m ³ ) in the condensate storage tank 17 is blown and stored again from the pure water production apparatus 19 to reduce the TOC. After confirming, refill the plant. The flow of water after the completion of the purification before the start of the plant and the start of the plant is as described in FIG.
[0010]
[Problems to be solved by the invention]
A conventional pure water production apparatus is configured by combining filtration and desalination. That is, as shown in FIG. 3, pure water is produced from pure water by the pure water production apparatus 19 , and supplied to the condensate storage tank 17 through the pure water supply pipe 20 for storage. The pure water production apparatus 19 is filled with an ion exchange resin, and the desalination treatment of the raw water is performed using the ion exchange resin.
[0011]
This ion-exchange resin elutes organic impurities from the resin matrix due to aging deterioration and the like. This organic impurity is called TOC (Total Organic Carbon). When the TOC generated by the ion exchange resin is decomposed, sulfate and nitrate ions are generated, which has an adverse effect such as corrosion of plant constituent materials.
[0012]
FIG. 4 shows the relationship between the TOC concentration of the condensate and the reactor water conductivity and time. In FIG. 4, the vertical axis is the TOC concentration on the left side, the electrical conductivity is on the right side, the horizontal axis is the date and time, the symbol a is reactor water electrical conductivity (TOC high), b is reactor water electrical conductivity (TOC low), and c is TOC. The concentration (high) and d indicate the TOC concentration (low). The condensed water is stored water in the condensed water storage tank 17, and the reactor water is cooling water supplied to the reactor 1.
[0013]
As is clear from FIG. 4, when the TOC concentration (high) c of the condensed water is about 150 ppb, the reactor water conductivity TOC (high) a becomes high immediately after the start of the plant. In the case of the TOC concentration (low) d of the condensate, it becomes low like the reactor water conductivity TOC (low) b.
[0014]
Generally, a nuclear power plant has a condensate storage tank 17 for storing water used as make-up water at the time of plant startup or the like. For this reason, when water is filled at the time of starting the plant with make-up water having a large amount of TOC components, an event that the water quality at the time of starting is deteriorated occurs, and reducing the TOC has been a problem.
[0015]
In the condensate storage tank 17, surplus water from each device 22 of the plant is collected. There is a possibility that TOC components such as rust preventives and oils used at the time of the periodic inspection may be introduced into the surplus water and may flow into the surplus water. Therefore, the establishment of a method for reducing the TOC by using the condensate storage tank water alone has become an issue. .
[0016]
The present invention has been made to solve the above-mentioned problem, and it is possible to decompose and remove the TOC component of the storage water in the condensate storage tank to maintain the quality of the storage water in the condensate storage tank high. An object of the present invention is to provide a water quality maintenance device for a nuclear power plant that can effectively use hydrogen generated during decomposition.
[0017]
[Means for Solving the Problems]
The invention according to claim 1 is a pure water producing apparatus for purifying raw water, a pure water supply pipe connected to the pure water production apparatus, and a condensate desalination of a nuclear power plant connected downstream of the pure water supply pipe. A condensate storage tank connected via a branch pipe between the apparatus and the high-pressure condensate pump, and a total organic carbon decomposition apparatus connected to the pure water supply pipe , A hollow fiber membrane filter connected to the pure water supply pipe; a desalination tower connected to the hollow fiber membrane filter and filled with an ion exchange resin; and an ozone generator. The outlet of the salt tower is connected via a desalinated water supply pipe, and the ozone outlet of the ozone generator is connected to a pure water supply pipe on the inlet side of the condensate storage tank by an ozone injection pipe . Generated by the plant for water supply to nuclear power plants Characterized by being adapted to enter.
[0018]
According to the present invention, the ozone generator by water decompose TOC of the pure water supplied to the condensate storage tank is decomposed by the ozone, it is possible to maintain a high quality of condensate storage tank, generated from the ozone generator Can be supplied to the condensate purification system, so that TOC decomposition can be performed during the purification operation before starting the plant. Further, it is possible to supply hydrogen that is effective for maintaining the integrity of the equipment in the reactor .
[0020]
Further , according to the present invention, the purity of purified water purified by the pure water production apparatus can be further increased by the hollow fiber membrane filter and the desalination tower, the TOC decomposition efficiency by ozone is increased, and the condensate storage tank is improved. Water quality can be maintained.
[0021]
The invention of claim 2 is characterized in that a circulation pipe is provided for connecting the condensate storage tank and a pure water supply pipe between the pure water producing apparatus and the total organic carbon decomposing apparatus. According to the present invention, since the storage water containing the TOC component decomposed by ozone can be fed back through the circulation pipe and removed by the hollow fiber membrane filter and the desalination tower, the water quality of the condensate storage tank can be further improved. Can be maintained.
[0023]
The invention of claim 3 is characterized in that the total organic carbon decomposition apparatus is connected to a heat source in a nuclear power plant by piping. ADVANTAGE OF THE INVENTION According to this invention, the hydrogen generated from an ozone generator can be burned, and the thermal energy can be utilized for the heat source of a nuclear power plant.
[0024]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of a water quality maintenance device for a nuclear power plant according to the present invention will be described with reference to FIG. 1, the same parts as those in FIG. 3 are denoted by the same reference numerals, and the description of the overlapping parts will be omitted.
[0025]
The embodiment of the present invention is different from the conventional example shown in FIG. 3 in that a TOC decomposing device 24 is provided in a pure water supply pipe 20 for connecting a pure water producing device 19 and a condensate storage tank 17 to a condensate storage tank. By decomposing the TOC in the pure water flowing into the condensate storage tank 17, the TOC concentration of the storage water in the condensate storage tank 17 is reduced and the water quality is maintained at high purity. Maintain high purity.
[0026]
The TOC decomposing device 20 includes a hollow fiber membrane filter 25 and a desalting tower 26 connected in series to a pure water supply pipe 20 downstream of the pure water producing device 19. A bypass pipe 28 having a bypass valve 27 is provided on the inlet side of the hollow fiber membrane filter 25 and on the outlet side of the desalination tower 26. A desalinated water supply pipe 29 is connected to the outlet side of the desalination tower 26, and an ozone generator 30 is connected to the desalinated water supply pipe 29.
[0027]
The ozone outlet side of the ozone generator 30 and the downstream side of the bypass pipe 28 on the desalination tower 26 side are connected by an ozone injection pipe 31. A hydrogen gas outlet pipe 32 is connected to the ozone generator 30. A circulation pipe 34 having a condensate circulation pump 33 is provided between the condensate storage tank 17 and the pure water production apparatus 19.
[0028]
Next, the operation of the present embodiment will be described.
As shown in FIG. 1, raw water pumped from a water source 18 such as seawater or river water is purified by a pure water production device 19, stored in a condensate storage tank 17 as it is, and then passed through a condensate replenishment pump 21 to the plant. In this embodiment, in order to reduce the TOC concentration, an ozone generator 30 by water decomposition, a hollow fiber membrane filter 25, This is provided with a TOC decomposing device 24 including a salt tower 26.
[0029]
FIG. 1 shows a system in which the TOC decomposer 24 is implemented, in which the water in the condensate storage tank 17 is circulated between the TOC decomposer 24 and the condensate storage tank 17 using a condensate circulation pipe 34. Thus, even when the TOC concentration of the condensed water already stored is high, the circulation operation is performed via the condensate circulation pump 33. At the same time, ozone generated from the ozone generator 30 is injected from the ozone injection pipe 31 and returned to the condensate storage tank 17, where TOC is decomposed by the decomposition action of ozone.
[0030]
The TOC is decomposed by passing through the hollow fiber membrane filter 25 and the desalting tower 26 by the circulation operation, and the generated ionic impurities such as sulfate ions and nitrate ions are removed. Thereby, the water quality of the condensate storage tank 17 can be maintained at high purity. This circulation operation can be performed by the condensate storage tank 17 alone. In this circulation operation, the hollow fiber membrane filter 25 and the desalination tower 26 can be bypassed by the bypass pipe 28, and ozone alone can be injected.
[0031]
Further, the TOC decomposition device 24 can be provided in a condensate purification system of a nuclear power plant. That is, by directly supplying the ozone generated from the ozone generator 30 to the downstream of the condensate desalination device 10 in the plant, it is possible to perform the TOC decomposition during the purification operation before starting the plant.
[0032]
Further, the TOC decomposer 24 can be connected to a heat source in the nuclear power plant and a hydrogen source at the time of injecting hydrogen into feed water. That is, the ozone generator 30 by water decomposition generates hydrogen at the same time as ozone is generated. It is possible to utilize the thermal energy obtained by burning the hydrogen as heat supply in the place.
[0033]
In the case of nuclear power plants, hydrogen injection has recently been confirmed to be effective for maintaining the integrity of in-furnace equipment, and some plants have begun to apply them to actual equipment. Hydrogen generated from the ozone generator 30 can be used as the hydrogen source.
[0034]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the TOC which flows into a condensate storage tank is decomposed | disassembled by ozone by the TOC decomposer which can produce pure water combined with the ozone generation part by water decomposition, and the TOC concentration of the storage water of a condensate storage tank is reduced. I do. Further, it is possible to perform performs TOC degradation during purification of operation before the plant starts, the hydrogen supply for maintaining sound reactor equipment.
[0035]
In addition, a TOC decomposer, which combines a purifier consisting of a hollow fiber membrane and an ion exchange resin and an ozone generator by water splitting, is installed downstream of the pure water production unit to decompose TOC flowing into the condensate storage tank. By doing so, the quality of the stored water in the condensate storage tank can be maintained at high purity, and the water quality of the reactor water can be maintained at high purity.
[Brief description of the drawings]
FIG. 1 is a system diagram showing an embodiment of a water quality maintenance device for a nuclear power plant according to the present invention.
FIG. 2 is a system diagram showing a primary system of a conventional boiling water nuclear power plant.
FIG. 3 is a basic system diagram for storing pure water in a condensate storage tank provided on the downstream side of the condensate desalination apparatus of the plant of FIG. 2;
FIG. 4 is a characteristic diagram showing a relationship between TOC in reactor water and electrical conductivity in FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Reactor, 2 ... Main steam pipe, 3 ... Turbine, 4 ... Generator, 5 ... Condenser , 6 ... Low-pressure condensate pump, 7 ... Air extractor, 8 ... Ground steam condenser, 9 ... Condenser Water filtration device, 10… condensate desalination device, 11… high pressure condensate pump, 12… low pressure feedwater heater, 13… feedwater pump, 14… high pressure feedwater heater, 15… water supply pipe, 16… hydrogen injection point, 17 ... condensate storage tank, 18 ... water source, 19 ... pure water production equipment, 20 ... water supply supply pipe, 21 ... condensate supply pump, 22 ... each equipment, 23 ... feedback pipe, 24 ... TOC decomposition equipment, 25 ... hollow fiber Membrane filter, 26 ... desalination tower, 27 ... bypass valve, 28 ... bypass pipe, 29 ... desalination tower supply pipe, 30 ... ozone generator, 31 ... ozone injection pipe, 32 ... hydrogen gas outlet pipe, 33 ... return Water circulation pump, 34… circulation piping.

Claims (3)

A pure water production device for purifying raw water, a pure water supply pipe connected to the pure water production device, and a condensate desalination device and a high pressure condensate pump of a nuclear power plant connected downstream of the pure water supply piping A condensate storage tank connected via a branch pipe between the apparatus, and a total organic carbon decomposition apparatus connected to the pure water supply pipe, wherein the total organic carbon decomposition apparatus is connected to the pure water supply pipe. A hollow fiber membrane filter, a desalination tower connected to the hollow fiber membrane filter and filled with an ion exchange resin, and an ozone generator, wherein the ozone generator is removed to the outlet side of the desalination tower. The ozone outlet side of the ozone generator is connected to a pure water supply pipe on the inlet side of the condensate storage tank by an ozone injection pipe, and hydrogen generated by the ozone generator is connected to a nuclear power plant. Injected into plant water supply DOO quality maintenance system of a nuclear power plant, characterized in. 2. The nuclear power plant according to claim 1, wherein a circulation pipe is provided via a circulation pump to a pure water supply pipe between the condensate storage tank and the pure water production apparatus and the total organic carbon decomposition apparatus. Water quality maintenance equipment for power plants. The water quality maintenance device for a nuclear power plant according to claim 1, wherein the total organic carbon decomposition device is connected to a heat source in the nuclear power plant by piping.

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