JP4926924B2 - Water purification device in the suppression chamber - Google Patents

Description

  The present invention relates to a purification device and a purification method for water stored in a suppression chamber provided surrounding a nuclear reactor containment vessel.

  In general, the boiling water nuclear power plant 50 has a structure as shown in FIG. 1, and is generally composed of a reactor building 51 and a turbine building 57. The reactor building 51 communicates with a boiling water reactor (BWR) 53, a dry well 54 containing the nuclear reactor 53, and the dry well 54 and a vent pipe 56, and surrounds the dry well 54. Thus, a nuclear reactor containment vessel 52 including a suppression chamber 55 provided below is installed. A top view of the reactor containment vessel 52 is as shown in FIG. 1B, and the suppression chamber 55 has an annular shape when viewed from above.

  A large amount of water W is stored inside the suppression chamber 55, and a mixture of steam and water released into the dry well 54 in the event of a breakage of the nuclear reactor 53 or the like (suppression chamber 55 The water W has a function of suppressing the pressure rise in the dry well 54 by condensing the steam into the water W, and the stored water W is sprayed to cool the reactor 53 It also plays a role as irrigation water. In addition, the suppression chamber 55 may be called a pressure control chamber from the functional side, and may be called a torus from the external side of having a torus shape.

  Further, the water W in the suppression chamber is water quality controlled by setting a predetermined reference value (for example, pH 5.4 to 7.5) from the viewpoint of preventing damage to the suppression chamber 55. In the reactor 53, radioactive iodine is generated by fission of uranium fuel. The water W in the suppression chamber has a role of absorbing this radioactive iodine so that it is not released to the outside in the event of an accident. From the viewpoint of improving the absorption rate of radioactive iodine, the water quality is controlled based on the reference value so that the pH of the water W in the suppression chamber does not become too low.

  The suppression chamber 55 is generally made of stainless steel or the like, and a coating is applied to the inner wall to prevent corrosion due to water W (for example, Patent Document 1). Since such paint deteriorates with age, repainting is performed periodically (for example, once every 10 years).

  By the way, the paint contains, for example, butyl acetate as a component, and since acetic acid is eluted from the paint, the water W in the suppression chamber becomes acidic and the pH becomes lower than the reference value. There is a problem of end. Therefore, conventionally, consideration has been given to maintaining the pH of the water W in the suppression chamber in a suitable state by using the following various methods.

JP 2000-314795 A

  One technique for maintaining the pH of the water W in the suppression chamber in a suitable state is to replace all the water W. However, due to the fact that there is a large amount of water W stored in the suppression chamber, there is a problem that this method is very time-consuming and expensive.

  In addition, a method using an ion exchange resin can be considered. However, since the ion exchange resin absorbs a larger amount of carbonic acid contained in the water than acetic acid, this method has a problem that acetic acid cannot be efficiently removed.

  In addition, there is a method of neutralizing water by mixing chemicals, but it is also harmful. For example, when sodium hydroxide is mixed, acetic acid can be neutralized, but sodium may damage the paint and the suppression chamber 55.

  Therefore, the present invention provides a suppression that can easily and surely remove acetic acid present in the water W stored in the suppression chamber provided in the reactor containment vessel and adjust the water quality to a suitable state. It is an object of the present invention to provide a purification device and a purification method for water in a chamber.

The apparatus for purifying water in a suppression chamber according to the present invention elutes from the paint applied to the inner wall of the suppression chamber provided in the reactor containment vessel, and removes acetic acid present in the water stored in the suppression chamber. In order to remove the water, a flow path for extracting the water from the suppression chamber and then returning the water to the suppression chamber is provided with an activated carbon filter for filtering the water, and in the water upstream of the activated carbon filter in the flow path. A contaminant removing filter for removing contaminants present, wherein the channel includes a first channel for returning water filtered through the contaminant removing filter to the suppression chamber, and the activated carbon filter. And further branched to a second flow path that returns to the suppression chamber. Flow rate of each flow path, if the pH of the water has been recovered to within the range of the reference value, characterized in that it is adjusted so as to gradually reduce the flow rate of the second flow path.

Further, water purification device of the suppression in the chamber according to the present invention, eluted from coated on the inner wall of the suppression chamber provided in the containment vessel paint, present in the water stored in the suppression in the chamber In order to remove acetic acid, a flow path for extracting the water from the suppression chamber and then returning the water to the suppression chamber is provided with an activated carbon filter for filtering the water, and the water is upstream of the activated carbon filter in the flow path. A contaminant removing filter for removing contaminants present therein, wherein the channel is a first channel for returning water filtered through the contaminant removing filter to the suppression chamber; and the activated carbon. Further filtered through a filter and then branched to a second flow path returning to the suppression chamber, and The flow rate of each flow path is determined by stopping the flow to the first flow path when the pH of the water is to be quickly restored within the range of the reference value. It is adjusted so that it may flow through a flow path .

According to the purification equipment for water suppression in chamber configured as described above, it is possible to efficiently remove the acetic acid by the activated charcoal filter. And if it is an activated carbon filter, it can be easily disposed of by, for example, incineration, and the amount of waste can be reduced.

In addition, after the water is filtered through the filter for removing impurities to remove the impurities present in the water, the activated carbon filter is used for filtration. That is, impurities are removed before the water is filtered by the activated carbon filter, and water from which impurities are removed is supplied to the latter activated carbon filter, so that the activated carbon filter can remove acetic acid more efficiently. it can. Note that the contaminant is, for example, water scale called a clad.
Moreover, according to the state of the water in a suppression chamber and the capability of an activated carbon filter, the quantity which filters the extracted water with an activated carbon filter can be adjusted. For example, when the pH of water has recovered within the range of the reference value, it is desired to gradually adjust the flow rate of the second flow path to decrease, or to quickly recover the pH of the water within the range of the reference value. In this case, the flow to the first flow path is stopped and the entire amount of the water is adjusted to flow to the second flow path.

Moreover, according to this invention, the structure which arrange | positions the means to measure said pH in said 2nd flow path can also be selected.

Further, according to the present invention, each of the first and second flow paths is provided with a valve, and each valve opening is adjusted based on the measured pH value obtained by the pH measuring means. It is also possible to adopt a configuration that adjusts the flow rate of the flow path.

As described above, the present according to the purification equipment for water suppression the chamber according to the invention, the acid present in the water stored in suppression the chamber provided in the reactor containment vessel inexpensive and readily and reliably By removing, the water quality can be adjusted to a suitable state.

  Hereinafter, embodiments of a water purification device and a purification method for water in a suppression chamber according to the present invention will be described with reference to the drawings.

  First, as described above, the boiling water nuclear power plant 50 has a structure as shown in FIG. 1, and a large amount of water W is stored in the reactor containment vessel 52 installed in the reactor building 51. A suppression chamber 55 is provided.

  The water purification device and the purification method in the suppression chamber according to the present embodiment are used to purify the water W stored in the suppression chamber 55, and the water purification device in the suppression chamber ( Hereinafter, it may be simply referred to as a “purification device” (1) has a schematic configuration as shown in FIG.

  Specifically, the purifying apparatus 1 is for removing impurities from the pump P that extracts (i.e., pumps) water W from the suppression chamber 55 and removes impurities present in the water extracted by the pump P. The filter 10 includes an acetic acid removing activated carbon filter (also called a charcoal filter) 20 that removes acetic acid present in the water from which the contaminants have been removed by the contaminant removing filter 10. That is, the contaminant removal filter 10 is disposed upstream of the activated carbon filter 20 for acetic acid.

  The foreign matter removing filter 10 is provided to remove foreign matters such as water scale called a clad. The foreign matter removing filter 10 is a filter housing in which a filter material called a bobbin filter is mounted in a filter housing made of stainless steel, for example. Further, the contaminant removal filter 10 is constituted by a plurality of filters having different sizes of contaminants that allow passage. Specifically, the contaminant removal filter 10 includes two types of filters 11 and 12, the upstream first filter 11 has a filtration accuracy of 1.0 μm, and the downstream second filter 12 has a filtration accuracy of 0. .5μ is set. The first filter 11 and the second filter 12 are arranged side by side in the flow path 30 through which the water pumped up by the pump P flows. In addition, as a material of the filter material of the bobbin filter, for example, polypropylene, polyphenylene sulfide, cotton or the like is used. Further, the contaminant removal filter 10 is not limited to such a spool filter, and may use activated carbon as in the activated carbon filter 20.

  The activated carbon filter 20 is suitable for removing organic impurities, and is provided to remove acetic acid. The activated carbon filter 20 is a filter housing made of activated carbon having a fibrous or granular shape in a stainless steel filter housing, for example. The activated carbon filter 20 is a filter that is normally used for removing chlorine. Specifically, water containing 2 ppm of free residual chlorine is allowed to flow at 23 ° C. for 40 tons at a flow rate of 10 liters / minute. The chlorine removal efficiency at that time is 80%.

The channel 30 (specifically, the second filter 12) contaminant removal filter 10 branched into two flow passages 31, 32 downstream of the. The first flow path 32 reaches the suppression chamber 55, and the water that has flowed into the first flow path 32 is returned to the suppression chamber 55 as it is. The activated carbon filter 20 for acetic acid is disposed in the second flow path 31, and the water flowing into the second flow path 31 is filtered by the activated carbon filter 20 and then returned to the suppression chamber 55 .

Further, the flow rates of the branched flow paths 31 and 32 are configured to be adjustable. Specifically, valves 41 and 42 are provided in the flow paths 31 and 32, respectively, and the flow rates of the flow paths 31 and 32 are adjusted by adjusting the opening degree of the valves 41 and 42. The opening degree of the valves 41 and 42 may be adjusted manually or automatically. As a configuration in which the opening degree is automatically adjusted, pH measuring means for measuring the pH of the water flowing through the second flow path 31 and the valve 41 based on the measured value of pH input from the pH measuring means. , 42 is incorporated in the purifier 1 and, for example, the pH value and the valve opening are associated in advance, and the valve opening is adjusted in accordance with the measured pH value. Conceivable.

  The water purification apparatus 1 in the suppression chamber having the above-described configuration is used by the following method.

  First, at the start of the purification operation, for example, the purification device can extract and return water W from an opening (usually closed by grating or the like) formed at a predetermined location on the upper portion of the suppression chamber 55. 1 is installed in the vicinity of the opening. Preferably, two purification devices 1 as described above are used in the purification operation, and the two purification devices 1 and 1 have a suppression chamber having an annular shape in top view so as to purify the water W as far away as possible. In 55, it arrange | positions in two places as far apart as possible (for example, two places on the circumference of a point symmetrical about the center point of a circle).

In the purification process, first, the water P in the suppression chamber 55 is pumped up by the pump P. The pumped water is introduced into the first filter 11 and filtered. Next, the entire amount of the water filtered by the first filter 11 is introduced into the second filter 12 and filtered. Since the second filter 12 has higher filtration accuracy than the first filter 11, finer impurities are removed. The water filtered by the second filter 12 is then branched into two flow paths 31 and 32. First, the water introduced into the first flow passage 3 2 is directly returned to the suppression chamber 55. Meanwhile, the water introduced into the second flow path 3 1 is filtered is introduced into the activated carbon filter 20, then returned to the suppression chamber 55.

In a normal use state, water is set to flow through both the flow paths 31 and 32, and only a part of the extracted water is filtered by the activated carbon filter 20. However, since the flow rates of the respective flow paths 31 and 32 can be adjusted as appropriate, for example, when the pH recovers within the range of the reference value during a series of purification operations, the flow rate of the second flow path 31 is gradually increased. The usage method is to reduce (or completely eliminate) the flow rate. However, for example, when it is desired to restore the pH of the water W within the range of the reference value as quickly as possible, the total amount of the water pumped up in the state where no water is allowed to flow in the first flow path 32 is set to the second level . It may be used such that it flows through the flow path 31 and is filtered through the activated carbon filter 20.

  As a result of purifying the water W in the suppression chamber by such a method, the nature of the water was that the pH was 4.8 before purification and the concentration of acetic acid was 1500 ppb. It was confirmed that the concentration of acetic acid was improved to about 1200 ppb within the range of values.

  By the way, the purification apparatus 1 and the purification method of the water in the suppression chamber can be appropriately used when necessary. For example, it can be used at the time of periodic inspection of the facilities constituting the nuclear power plant 50, or can be used constantly while operating the nuclear power plant 50. However, since the most elution of acetic acid occurs immediately after the coating is applied to the inner wall of the suppression chamber 55, it is efficient to use it once a year during regular inspection for several years after the coating is applied. It is.

  As described above, according to the water purification device and the purification method in the suppression chamber according to the present embodiment, acetic acid present in the water stored in the suppression chamber provided in the reactor containment vessel can be easily and inexpensively obtained. And it can remove reliably and can adjust the water quality of the water to a suitable state. That is, acetic acid can be efficiently removed by the activated carbon filter. And if it is an activated carbon filter, it can be easily disposed of by, for example, incineration, and the amount of waste can be reduced.

  In addition, contaminants are removed before the water is filtered by the activated carbon filter, and water from which contaminants are removed is supplied to the latter activated carbon filter, so that the activated carbon filter can more efficiently remove acetic acid. it can.

  Furthermore, since the flow path 30 is branched into two flow paths 31 and 32 and the flow rates of the flow paths 31 and 32 are adjustable, depending on the water state in the suppression chamber and the capacity of the activated carbon filter. The amount of the extracted water filtered through the activated carbon filter can be adjusted.

  In addition, the purification apparatus and the purification method of the water in the suppression chamber which concern on this invention are not limited to the said embodiment, A various change is possible in the range which does not deviate from the summary of this invention.

  For example, in the purification device and the purification method for water in the suppression chamber, a filter for removing contaminants is used separately from the activated carbon filter. However, the present invention is not limited to this. And acetic acid may be removed.

  Further, the activated carbon filter is not limited to one, and a plurality of filters may be provided. Similarly, the contaminant removing filter is not limited to a plurality, and only one may be provided.

  Furthermore, although the said valve | bulb was each provided in each branched flow path, only one may be provided in the branch location. Further, the purification device may not include a valve.

(A) shows a schematic view of a boiling water nuclear power plant, and (B) shows a top view of the reactor containment vessel. The schematic of the purification apparatus of the water stored in the suppression chamber which concerns on embodiment embodiment of this invention is shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Purification apparatus, 10 ... Contaminant removal filter, 11 ... First filter, 12 ... Second filter, 20 ... Activated carbon filter, 30 ... Channel, 31 ... Second channel, 32 ... First channel , 41, 42 ... Valve, 50 ... Boiling water nuclear power plant, 51 ... Reactor building, 52 ... Reactor containment vessel, 53 ... Reactor, 54 ... Drywell, 55 ... Suppression chamber, 56 ... Vent pipe, 57 ... turbine building, P ... pump, W ... water

Claims (4)

After the water is extracted from the suppression chamber in order to remove acetic acid which is eluted from the paint applied to the inner wall of the suppression chamber provided in the reactor containment vessel and is present in the water stored in the suppression chamber, The flow path returning to the suppression chamber includes an activated carbon filter that filters the water ,
On the upstream side of the activated carbon filter of the flow path, a contaminant removal filter for removing contaminants present in the water is provided,
The flow path includes a first flow path for returning water filtered through the contaminant removal filter to the suppression chamber, and a second flow path for further filtering through the activated carbon filter and returning the water to the suppression chamber. Branched to the flow path,
In addition, the flow rate of each branched flow path is adjusted to gradually reduce the flow rate of the second flow path when the pH of the water has recovered within a range of a reference value. Water purification device in the suppression chamber. After the water is extracted from the suppression chamber in order to remove acetic acid which is eluted from the paint applied to the inner wall of the suppression chamber provided in the reactor containment vessel and is present in the water stored in the suppression chamber, The flow path returning to the suppression chamber includes an activated carbon filter that filters the water,
On the upstream side of the activated carbon filter of the flow path, a contaminant removal filter for removing contaminants present in the water is provided,
The flow path includes a first flow path for returning water filtered through the contaminant removal filter to the suppression chamber, and a second flow path for further filtering through the activated carbon filter and returning the water to the suppression chamber. Branched to the flow path,
In addition, when the flow rate of each branched flow channel is desired to quickly restore the pH of the water within the range of the reference value, the flow to the first flow channel is stopped, and the total amount of the water is A device for purifying water in a suppression chamber, wherein the device is adjusted to flow in a second flow path. The purification device in a suppression chamber according to claim 1 or 2, wherein the means for measuring the pH is disposed in the second flow path. The first and second flow paths are each provided with a valve, and the flow rate of each flow path is adjusted by adjusting the valve opening based on the measured pH value obtained by the pH measuring means. The purification device in the suppression chamber according to claim 3.

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