JP2009128224A - Device and method for purifying water in suppression chamber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device and method for purifying water in a suppression chamber for adjusting water quality to a suitable state by inexpensively, and easily and certainly removing acetic acid existing in the water stored in the suppression chamber disposed in a reactor containment vessel. <P>SOLUTION: In order to remove acetic acid that elutes from coating applied to the inner wall of the suppression chamber 55 disposed in the reactor containment vessel 52 and exists in the water W stored in the suppression chamber, the water W stored in the suppression chamber is filtered via an activated carbon filter 20. <P>COPYRIGHT: (C)2009,JPO&INPIT

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, an activated carbon filter for filtering water in the suppression chamber is provided.

  Further, the method 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 exists in the water stored in the suppression chamber. In order to remove acetic acid, water in the suppression chamber is filtered through an activated carbon filter.

  According to the water purification device or purification method in the suppression chamber having the above configuration, 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.

  Further, the water purification apparatus in the suppression chamber includes a flow path for extracting the water from the suppression chamber and then returning the water to the suppression chamber. The activated carbon filter is disposed in the flow path, and the flow path is provided in the flow path. Preferably, the filter for removing foreign substances that remove foreign substances present in the water is arranged upstream of the activated carbon filter.

  If it does in this way, after filtering the water through the contaminant removal filter in order to remove the contaminant which exists in the water, filtration by the activated carbon filter will be performed. 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.

  Further, the flow path includes a flow path for returning water filtered through the contaminant removal filter to the suppression chamber, and a flow path for further filtering through the activated carbon filter and then returning to the suppression chamber. It is preferable that the flow rate is branched and the flow rate of each branched flow path is adjustable.

  If it does in this way, according to the state of the water in a suppression chamber, and the capability of an activated carbon filter, the quantity which filters extracted water with an activated carbon filter can be adjusted. For example, the whole amount of extracted water is filtered through an activated carbon filter, only a part is filtered, or the whole amount is returned to the suppression chamber without being filtered.

  As described above, according to the apparatus and method for purifying water in a suppression chamber according to the present invention, acetic acid present in the water stored in the suppression chamber provided in the reactor containment vessel can be easily and inexpensively obtained. It can be reliably removed and 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 flow path 30 branches into two flow paths 31 and 32 on the downstream side of the contaminant removal filter 10 (specifically, the second filter 12). The activated carbon filter 20 for acetic acid is disposed in one flow path 31, the other flow path 32 reaches the suppression chamber 55, and water flowing into the one flow path 31 is filtered by the activated carbon filter 20. The water that has returned to the suppression chamber 55 and has flowed into the other flow path 32 is returned to the suppression chamber 55 as it is.

  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, a pH measurement unit that measures the pH of water flowing through the one flow path 31, and the valve 41, based on a measured value of pH input from the pH measurement unit. For example, a control means for controlling 42 is incorporated in the purifier 1 and the pH value and the opening degree of the valve are associated in advance, for example, and the opening degree of the valve is adjusted according to the measured pH value. It is done.

  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 the 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, 1 have a suppression chamber having an annular shape in top view so as to purify the water W as far away as possible. 55 are arranged at two locations that are as far apart as possible (for example, two locations on a circle that is point-symmetric about the center point of the 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 one flow path 31 is returned to the suppression chamber 55 as it is. On the other hand, the water introduced into the second flow path 32 is introduced into the activated carbon filter 20 and filtered, and 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 rate of each of the 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 one of the flow paths 31 is gradually increased. The usage method is taken to reduce (or completely eliminate). 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 other flow path 32 is set to a state where no water is allowed to flow, and the entire amount of water pumped up is transferred to the one flow path. It may be used in such a manner that it is passed through 31 and 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 ... One channel, 32 ... Other 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 (5)

  Activated carbon that elutes from the paint applied to the inner wall of the suppression chamber provided in the reactor containment vessel and filters the water in the suppression chamber to remove acetic acid present in the water stored in the suppression chamber. A device for purifying water in a suppression chamber, comprising a filter.   A flow path for extracting the water from the suppression chamber and then returning the water to the suppression chamber is provided, and the activated carbon filter is disposed in the flow path, and impurities present in the water are removed from the flow path. 2. The apparatus for purifying water in a suppression chamber according to claim 1, wherein a filter for removing contaminants is disposed upstream of the activated carbon filter.   The flow path is branched into a flow path for returning water filtered through the contaminant removal filter to the suppression chamber and a flow path for further filtering through the activated carbon filter and returning the water to the suppression chamber. Moreover, the apparatus for purifying water in a suppression chamber according to claim 2, wherein the flow rate of each branched flow path is adjustable.   In order to remove acetic acid eluted from the coating applied to the inner wall of the suppression chamber provided in the reactor containment vessel and present in the water stored in the suppression chamber, the activated carbon filter is used to remove the water in the suppression chamber. The method of purifying the water in the suppression chamber is characterized by filtering through the filter.   5. The suppression chamber according to claim 4, wherein the water is filtered through a filter for removing contaminants so as to remove contaminants present in the water, and then the activated carbon filter is used for filtration. Water purification method.

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