JP2007192694A - Method for mitigating adhesion of rust and nuclear power plant - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize an ideal method for mitigating the adhesion of rust onto the surface of plant members. <P>SOLUTION: In the method for mitigating the adhesion of rust, a ferrite coating film is formed in a section in contact with water which contains suspended matter in it causing rust in a steam dryer/separator pool (DSP) 16, for example, constituting a plant or a cutting device 18 or a recovery device 20, for example, used for the plant. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a technique for reducing the adhesion of rust to the surface of a member used in a nuclear power plant or the like.

  As a plant represented by a boiling water nuclear power plant, a nuclear reactor that contains a fuel assembly, a pool for cutting members that communicated with the top of the nuclear reactor via a reactor well, and a reactor internal structure And a cutting device that cuts water in a pool.

  In such a plant, when the in-furnace structure is discarded and stored, the primary cutting for carrying the structure in the furnace to the pool and the secondary cutting for cutting the structure carried to the pool by a cutting device are performed. Is done. As a method of cutting the waste object here, for example, an abrasive water jet method in which a high-pressure water stream containing an abrasive is ejected from a cutting device to cut the waste object in a pool is used.

  By the way, when a waste object is cut in a pool, cutting powder, abrasives, etc. float in the water. Most of the suspended matter in the water is recovered by the recovery device, but a part of the suspended matter in the water is not recovered, and the corrosion reaction may proceed to become rust. The rust firmly adheres to the surface of a member (hereinafter referred to as a plant member) such as a wall or a floor or a cutting device constituting the pool. When rust adheres to the surface of plant members in this way, the amount of cleaning work to remove rust increases, and when rust is radioactive, decontamination work must be carried out, increasing work time. There is a risk.

  Therefore, in order to reduce the adhesion of rust to the surface of the plant member, a method of forming a rust prevention layer on the surface of the target member using liquid sodium (for example, Patent Document 1), or a resin-based rust prevention tape A method for covering the surface of the target member (for example, Patent Document 2) has been proposed.

JP 2003-129255 A JP-A-10-44320

  However, in a method such as Patent Document 1, since liquid sodium is highly active, such as having high reactivity with water, it is difficult to handle the liquid sodium, and thus the work of forming a rust prevention layer with liquid sodium is complicated and difficult. It is. In the method as described in Patent Document 2, since the resin-based rust preventive tape is immersed in water and irradiated with radiation from the internal structure of the furnace, the rust preventive tape itself deteriorates and is damaged or peeled off. May occur. Thus, there exists a point which should be improved in the method of reducing that rust adheres to the surface of a plant member.

  An object of the present invention is to realize a rust adhesion reduction method and a nuclear power plant that are more suitable for reducing the adhesion of rust to the surface of a plant member.

  In order to solve the above-mentioned problems, the method for reducing rust adhesion according to the present invention is based on the contact of water containing suspended matter in water that causes rust among the surfaces of members constituting the plant or the surfaces of members used in the plant. A ferrite film is formed on the water portion.

  In this way, the ferrite film (for example, a magnetite film or a nickel ferrite film) serves as a shielding film that prevents the suspended matter in water from coming into contact with the plant member, so that adhesion of rust to the plant member is avoided.

  And since the ferrite film formed from the ferrite raw material has a dense surface, even if rust adheres to the film surface, it is easy to remove the rust, so the time required for the work can be shortened. Further, since the ferrite raw material is relatively easy to handle due to its characteristics, the film forming operation of the ferrite film can be carried out easily and quickly. Furthermore, since the ferrite film is stable and excellent in durability even in water or under a radiation irradiation environment, it can exhibit a function as a shielding film for a relatively long time.

  In this case, the ferrite film is formed when the plant is shut down and before the plant waste is cut in water.

  Moreover, according to one desirable mode of the present invention, the member which constitutes the plant is the wall or floor which constitutes the pool from which the disposal subject is cut. The member used in the plant is at least one of a cutting device for cutting the waste object and a jig attached to the cutting device.

  Moreover, according to one desirable aspect of the present invention, the member used in the plant is formed with the ferrite film before being carried into the plant.

  Further, the nuclear power plant of the present invention includes a reactor pressure vessel in which a fuel assembly is stored, a pool for cutting a member communicated with the top of the reactor pressure vessel via a reactor well, and the reactor pressure A cutting device for cutting the waste object in the container in the water of the pool is provided, and at least one surface of the wall or floor constituting the pool, the cutting device or a jig attached to the cutting device is rusted. It is characterized in that a ferrite film is formed on a water contact portion where water including suspended water in contact with water comes into contact.

  ADVANTAGE OF THE INVENTION According to this invention, it can implement | achieve the rust adhesion reduction method and nuclear power plant more suitable for reducing that rust adheres to the surface of a plant member.

  An embodiment of a rust adhesion reduction method and a nuclear power plant to which the present invention is applied will be described with reference to the drawings. FIG. 1 is a diagram illustrating a configuration of a boiling water nuclear power plant according to the present embodiment. In addition, although a boiling water nuclear power plant is demonstrated to an example, this invention is applicable also to the other plant in which rust generate | occur | produces in the water which contacts a plant member. Moreover, although shroud replacement | exchange work is demonstrated to an example, it is applicable also when exchanging other in-furnace structures.

  As shown in FIG. 1, the boiling water nuclear power plant communicates with a reactor pressure vessel 12 containing a shroud 10 surrounding a fuel assembly and a top of the reactor pressure vessel 12 via a reactor well 14. A separator separator pool 16 (hereinafter referred to as a DSP 16) as a pool for cutting the member, and a cutting device 18 for cutting a waste object (for example, the shroud 10) in the reactor pressure vessel 12 in the water of the DSP 16. Yes.

  And the boiling water type nuclear power plant of this embodiment is the water containing the underwater suspended matter which causes rust among the wall or floor which comprises DSP16, and the surface of the jig attached to the cutting device 18 or the cutting device 18. A ferrite film is formed on the water contact portion where the water contacts. In short, the method for reducing rust adhesion according to the present embodiment includes ferrite on the surface of the member constituting the plant or the surface of the member used in the plant, in contact with water that contains water suspended in water that causes rust. A film shall be formed. In addition, the member which comprises a plant is a wall surface or a floor surface including the draft surface of DSP16. The members used in the plant are the cutting device 18 and a jig attached thereto. Moreover, the member which comprises a plant and the member used for a plant are named generically with a plant member suitably.

  In this way, the ferrite film (for example, a magnetite film or a nickel ferrite film) serves as a shielding film that prevents the suspended matter in water from coming into contact with the plant member, so that adhesion of rust to the plant member is avoided. And since the ferrite film formed from the ferrite material here has a dense surface, it is easy to remove the rust even if it adheres to the film surface, so the time required for the removal work is shortened it can. In addition, since the ferrite raw material is relatively easy to handle due to its characteristics, the film forming operation of the ferrite film can be carried out easily and quickly. Furthermore, since the ferrite film is stable and excellent in durability even in water or in a radiation irradiation environment, the function as a shielding film can be exhibited for a relatively long time.

  In more detail, the rust adhesion reduction method and nuclear power plant of this embodiment are demonstrated. As shown in FIG. 1, the nuclear pressure vessel 12 is a cylindrical vessel provided upright in the vertical direction, and a dryer and a separator are detachably disposed on the top thereof. The shroud 10 is made of stainless steel disposed around the fuel assembly. The reactor well 14 is a space in which the nuclear pressure vessel 12 is stored at the bottom. The reactor well 14 is injected with water for shielding radiation irradiated from the waste object when the waste object (for example, the shroud 10) is disposed and stored.

  The DSP 16 is a space that communicates adjacent to the reactor well 14. For example, when the shroud 10 is discarded and stored, water is injected therein. When the shroud 10 is discarded and stored, a cutting device 18 and a recovery device 20 are disposed in the DSP 16. The cutting device 18 includes a gantry 22 and a cutting nozzle 24. On the gantry 22, for example, a shroud 10 ′ carried out by primary cutting from the reactor pressure vessel 12 is placed. The cutting nozzle 24 chops the shroud 10 'by ejecting a high-pressure water stream containing water, that is, a water jet. The collection device 20 collects cutting powder and abrasives generated by the cutting operation of the shroud 10 '.

  A crane 26 for taking out, for example, the shroud 10 of the nuclear pressure vessel 12 is disposed on the ceiling. A fuel pool 28 for storing the fuel assembly is provided on the opposite side of the DSP 16 with the reactor well 14 interposed therebetween.

  The shroud replacement work of the boiling water nuclear power plant configured as described above will be described with reference to FIG. FIG. 2 is a diagram showing an entire process of shroud replacement work. First, when the plant is in operation, the operation is stopped (S1). Next, the reactor pressure vessel 12 is opened (S2). Thereafter, in-furnace devices such as a dryer and a separator are removed (S3). Water is injected into the reactor well 14 and the DSP 16 after the equipment in the reactor is removed. Next, after the fuel in the reactor pressure vessel 12 is taken out (S4), a cutting device for primary cutting for carrying out the shroud 10 from the reactor pressure vessel 12 is installed (S5). The shroud 10 is primarily cut by the cutting device for primary cutting (S6).

  On the other hand, the cutting device 18 and the recovery device 20 are installed in the DSP 16 (S7). And the process which forms a ferrite membrane | film | coat on the surface of a plant member is performed (S8). The plant member here includes the cutting device 18, the recovery device 20, and the inner surface of the DSP 16. Next, the shroud 10 cut in step S6 is unloaded through the reactor well 14 while being suspended by the crane 26 (S9). The shroud 10 'after carrying out is placed on the gantry 22 (S10). The shroud 10 'on the gantry 22 is secondarily cut by the cutting device 18 (S11). The shroud shredded by the secondary cutting is carried out from the DSP 16 after being stored in the transport container (S12). The transport container here has a function of shielding the radiation irradiated from the shroud subsection. The shroud after carrying out is stored in the site banker pool (S13).

  After the shroud is carried out from the DSP 16, the cutting device 18 and the recovery device 20 in the DSP 16 are decontaminated and removed (S14, S15). Further, the cutting device for primary cutting in the reactor pressure vessel 12 is also removed from the reactor pressure vessel 12 after the radioactivity and rust adhering to the surface thereof are removed by the cleaning process (S16). After cleaning the inside of the reactor pressure vessel 12, a new shroud 10 is installed (S17). Thereafter, fuel is reloaded into the shroud 10 (S18). Next, after the water in the reactor well 14 and the DSP 16 is extracted, the in-reactor equipment such as a dryer and a separator is re-installed (S19). Then, after the reactor pressure vessel 12 is closed (S20), the plant is restarted (S21).

  In short, according to the step shown in FIG. 2, before the shroud 10 is secondarily cut in step S11, a ferrite film is formed on the surface of the plant member in step S8. Thereby, it can reduce that rust adheres to the surface of a plant member, and even if rust adheres to the surface of a ferrite membrane | film | coat, the time required for the decontamination operation | work of process S14 can be shortened.

  With reference to FIGS. 3-5, the film-forming process (S8) of a ferrite film, the secondary cutting process (S11) of shroud 10 ', and the decontamination process (S14) of a plant member are further demonstrated. FIG. 3 is a diagram showing details of each of these steps. FIG. 4 is a diagram showing a configuration of an apparatus for forming a ferrite film. FIG. 5 is a diagram showing a device configuration when the shroud 10 ′ is secondarily cut.

  First, as shown in FIG. 4, a film forming apparatus for forming a ferrite film on the surface of a plant member includes a ferrite raw material supply apparatus 30 for supplying a ferrite raw material, and a ferrite raw material supply apparatus 30 through a raw material supply pipe 32. The coating material application device 34 that injects the supplied material onto the target member, the recovery collector 36 that receives the scattered ferrite material that has not contributed to the formation of the ferrite film, and the ferrite material is recovered from the recovery collector 36 through the transfer pipe 38. A raw material recovery device 40 is provided. Note that the ferrite raw material supply device 30 and the raw material recovery device 40 are disposed outside the DSP 16. The film construction device 34 is held by the operator 42. The collection collector 36 is installed at a position corresponding to the spray hole of the coating apparatus 34 on the floor surface in the DSP 16. The ferrite raw material here is a mixed solution of a solution in which iron (II) ions, which are the main components of the film, are dissolved with an organic acid, and a solution containing an oxidizing agent and a pH adjusting agent.

  By using such a film forming apparatus, an operator forms a ferrite film over a predetermined range. The predetermined range here is, for example, the cutting nozzle 24 to which the abrasive material bounced off from the shroud during the secondary cutting of the shroud, the cutting device 18, the water supply hose 44 attached to the cutting nozzle 24, and the abrasive supply hose 46. , At least one of the following points: a scanning mechanism 48 that scans the cutting nozzle 24, a wall surface of the DSP 16 that includes the vicinity of the draft surface where rust tends to collect, and a floor surface that includes the lower surface of the shroud where the abrasive sinks accumulate. It is desirable to include. In addition, the film formation process of a ferrite film is performed before water is inject | poured into DSP16.

  Next, as shown in FIG. 5, when the shroud 10 ′ is cut by secondary cutting, a processing base 43 on which the shroud 10 ′ is placed, a cutting device 18, a water supply hose 44, and an abrasive supply A hose 46 and a scanning mechanism 48 are arranged in the DSP 16. An ultrahigh pressure pump 45 connected to the upstream end of the water supply hose 44 and an abrasive supply device 47 connected to the upstream end of the abrasive supply hose 46 are arranged outside the DSP 16.

  Further, the recovery device 20 that recovers the underwater suspended matter generated when the shroud 10 ′ is cut includes a collector 50 as a suction port for the underwater suspended matter, a suction pump 52 that sucks the underwater suspended matter through the collector 50, and a suction pump. An air / water separator 54 for performing an air / water separation process on the discharged fluid 52, a separator 58 for separating waste from the water discharged from the air / water separator 54 via the transfer pipe 56, and a separator 58 A waste storage container 60 for storing the waste discharged from the apparatus, a filter storage container 62 for performing a filtering process on the water discharged from the separation device 58, and the like. Note that a scanning mechanism 64 serving as a work place for the worker 42 spans the DSP 16. Further, the predetermined range for forming the ferrite film may include the surfaces of the collector 50, the suction pump 52, the steam separator 54, the separator 58, the waste storage container 60, the filter storage container 62, and the like.

  Reference is now made to FIG. First, a ferrite film is formed on the surface of the plant member by the film forming apparatus shown in FIG. 4 (S101). After the film forming process is performed, the shroud 10 ′ is carried into the DSP 16 from the reactor pressure vessel 12. Then, the shroud 10 'is secondarily cut by the apparatus shown in FIG. 5 (S102). When the shroud 10 'is secondarily cut, a floating substance made of the shroud 10' cut powder or abrasive pulverized powder is generated (S103). Most of the suspended matter is collected by the collection device 20 set in the DSP 16 (S104). On the other hand, part of the suspended matter is scattered in the water in the DSP 16 without being collected by the collection device 20 (S105). The suspended matter scattered in the DSP 16 is rusted by the progress of the corrosion reaction and adheres to the surface of plant members such as the DSP 16, the cutting device 18 and the recovery device 20 (S106). Here, in this embodiment, since the ferrite film is formed on the surface of the plant member, adhesion of rust to the surface of the plant member is reduced. In addition, although the example which applied the abrasive water jet method as a method of carrying out secondary cutting | disconnection of shroud 10 'was demonstrated, you may apply other cutting methods, such as discharge cutting, plasma cutting, and laser cutting. In short, the present invention may be applied when a suspended matter in water that causes rust is generated.

  FIG. 6 is a graph showing an example of the measurement result of the rust adhesion amount. In this example, a stainless steel test piece is immersed in sample water, and the weight change of the test piece after immersion is measured. The sample water here is pure water mixed with pulverized powder of cast steel abrasive as suspended matter in water. The underwater suspended matter becomes rust as the corrosion reaction proceeds and adheres to the surface of the test piece. The test piece a has a ferrite film not yet applied. The test piece b has a ferrite film formed on the surface thereof by being immersed in a treated water bath having a water temperature of 90 ° C. mixed with a ferrite raw material. The ferrite raw material is a mixed solution of a solution in which iron (II) ions as a main component of the film are dissolved with an organic acid, and a solution containing an oxidizing agent and a pH adjusting agent. In addition, regarding the measurement using the test piece a and the measurement using the test piece b, the concentration of the suspended matter in water per unit volume, the surface area of the test piece, and the immersion time of the test piece in the sample water are the same. Set.

  The vertical axis in FIG. 6 is the rust adhesion amount converted from the weight change before and after the immersion of the test piece, and is the relative weight ratio with the value of the test piece a being 100. As shown in FIG. 6, when the measurement result using the test piece a is compared with the measurement result using the test piece b, the amount of rust attached to the test piece b is, for example, 1/5 when the test piece a is used. Met. As can be seen from these test results, when a ferrite film is formed on the surface of the test piece, the ferrite film is a dense film, so that the amount of rust attached to the test piece is reduced.

  Now, when the secondary cutting operation of the shroud 10 'of FIG. 3 is completed (S107), the decontamination process is performed on the cutting device 18 and the recovery device 20 (S108). That is, a part of the rust adhering to the cutting device 18 or the recovery device 20 is originally a shroud cutting powder that is a radiation irradiated portion, and therefore has a relatively high radioactivity. Therefore, before removing the cutting device 18 and the recovery device 20 from the DSP 16, the rust attached to the cutting device 18 and the recovery device 20 is removed by the decontamination device shown in FIG. 7 and the process shown in FIG. When the decontamination process is completed, the cutting device 18 and the collection device 20 are removed (S109). And after the water in DSP16 is drained (S110), the decontamination process is performed also to the inner surface of DSP16 (S111).

  FIG. 7 is a diagram illustrating a configuration of the decontamination apparatus. FIG. 8 is a diagram illustrating a process of decontamination processing by the decontamination apparatus of FIG. The decontamination process includes a mechanical decontamination method and a chemical decontamination method. The mechanical decontamination method is a method for removing adhesion rust by high-pressure water or brushing. Chemical decontamination is a technique for removing attached rust using a detergent, an organic solvent, an acid, an alkali, or the like. Here, an example in which the mechanical decontamination method is applied will be described.

  As shown in FIG. 7, the decontamination apparatus of this embodiment is replaced with a mechanical decontamination supply apparatus 70 disposed in place of the ferrite raw material supply apparatus 30 of the film forming apparatus in FIG. A mechanical decontamination device 72 provided, a rust recovery device 74 disposed in place of the raw material recovery device 40, and the like are provided. The machine decontamination supply device 70 supplies cleaning water necessary for machine decontamination and an electric signal for driving to the machine decontamination device 72. The mechanical decontamination device 72 includes a water injection mechanism that injects the cleaning water supplied from the mechanical decontamination supply device 70, and a brushing device that is rotationally driven in accordance with an electric signal for driving. The rust recovery device 74 recovers rust by transferring from the recovery collector 36 via the transfer pipe 38.

  As shown in FIG. 8, first, a command to start mechanical decontamination is input to the mechanical decontamination supply device 70 (S201). When the start command is input, the mechanical decontamination supply device 70 supplies cleaning water to the mechanical decontamination device 72, whereby the surface of the member to which rust is attached, that is, the surface of the ferrite film, is applied to the mechanical decontamination device 72. Water is jetted from (S202). Thereafter, the radiation dose is measured at a radiation measurement position defined in advance (S203). When the measured value of the radiation dose exceeds the threshold value, for example, the mechanical decontamination supply device 70 supplies a drive signal to the mechanical decontamination device 72, so that the surface of the ferrite film is subjected to the mechanical decontamination device 72. Brushing is performed with a brushing device (S204). Here, the threshold value is an allowable value for removing a member (for example, the cutting device 18 or the recovery device 20). In addition, when brushing, you may use another instrument (for example, hand drill). After the brushing is completed, the radiation dose is measured again (S205). If the measurement value of the radiation dose still exceeds the threshold value, the brushing operation in step S204 is repeated until the radiation dose becomes equal to or less than the threshold value. In the radiation measurement work in step S203 or step S205, the mechanical decontamination work ends when the measured value of the radiation dose is equal to or less than the threshold value (S206).

  In such mechanical decontamination work, the brushing work in step S204 has a larger work amount than the water jetting work in step S202. Therefore, it is desirable to remove as much rust as possible by the water jet operation in step S202. FIG. 9 is a graph showing the rust removal characteristics by water washing of the present embodiment. In this example, ultrasonic cleaning was performed on the test pieces a and b shown in FIG. 6, and the rust removal rate was measured from the change in weight of the test pieces a and b before and after cleaning. The ultrasonic cleaning here simulates the water cleaning of this embodiment.

  As shown in FIG. 9, in the case of the test piece a, the removal rate of the rust was, for example, 20% by weight of the rust adhered before cleaning. On the other hand, in the case of the test piece b, the removal rate of the rust was, for example, 95% by weight of the rust adhered before washing. That is, the test piece b having the ferrite film formed on the surface thereof was rust removed four times or more by ultrasonic cleaning as compared with the test piece a in which the ferrite film was not applied. As can be seen from these test results, when a ferrite film is formed on the surface of the plant member, the ferrite film is a dense film. Even if rust adheres, the rust can be effectively removed. That is, when the ferrite film is formed, the amount of brushing work is reduced as compared with the case where the ferrite film is not applied, so that the time required for the decontamination work can be shortened.

  As mentioned above, although the rust adhesion reduction method and nuclear power plant of this invention were demonstrated by the above-mentioned embodiment, it is not restricted to this. For example, the form shown in FIG. 4 is an example in which a ferrite film is formed on the surface of a plant member in the DSP 16. Of the plant members, for example, the cutting device 18 and the recovery device 20 are not always installed in the DSP 16. When the plant operation is stopped, it is carried into the DSP 16 from outside the plant and is removed from the DSP 16 after the work is completed. Therefore, as shown in FIG. 10, a ferrite film may be formed in the manufacturing or assembling process for plant members such as the cutting device 18 and the recovery device 20. The film forming apparatus and the film forming process of the ferrite film are the same as those in the above embodiment. The operation of cutting and collecting the object to be discarded is limited in time, but according to the embodiment shown in FIG. 10, the plant members such as the cutting device 18 and the collecting device 20 are not covered during the cutting and collecting operation. Therefore, it is possible to further reduce the time required for cutting and collecting the object to be discarded.

It is a figure which shows the structure of one Embodiment of the boiling water nuclear power plant to which this invention is applied. It is a figure which shows the whole process of the operation | work which replaces the shroud of FIG. It is a figure which shows the detail of the film-forming process of FIG. 2, a secondary cutting process, and a decontamination process. It is the figure which showed the structure of the apparatus which forms a ferrite membrane | film | coat. It is the figure which showed the apparatus structure at the time of carrying out secondary cutting | disconnection of a shroud. It is a graph which shows the example of a rust adhesion amount measurement result. It is a figure which shows the structure of a decontamination apparatus. It is a figure which shows the process of the decontamination process by the decontamination apparatus of FIG. It is a graph which shows the rust removal characteristic by water washing. It is the figure which showed the other structure of the apparatus which forms a ferrite membrane | film | coat.

Explanation of symbols

10 shroud 12 reactor pressure vessel 16 DSP
18 Cutting device 20 Collection device 30 Ferrite raw material supply device 34 Coating construction device 45 Super high pressure pump 47 Abrasive supply device 70 Mechanical decontamination supply device 72 Mechanical decontamination device

Claims (6)

  Rust adhesion characterized by depositing a ferrite film on the surface of the parts that make up the plant or the surface of the parts used in the plant that comes into contact with water that contains water suspended matter that causes rust Reduction method.   The method for reducing rust adhesion according to claim 1, wherein the ferrite film is formed when the plant is shut down and before the plant waste is cut in water.   The member constituting the plant is a wall or a floor constituting a pool from which the waste object is cut, The method for reducing rust adhesion according to claim 2.   The member used in the plant is at least one of a cutting device for cutting the waste object and a jig attached to the cutting device.   The method for reducing rust adhesion according to any one of claims 1 to 4, wherein the member used in the plant is formed with the ferrite film before being carried into the plant. A reactor pressure vessel in which a fuel assembly is housed; a pool for cutting members connected to the top of the reactor pressure vessel via a reactor well; and a waste to be discarded in the reactor pressure vessel. In a nuclear power plant equipped with a cutting device that cuts underwater
Of the wall or floor constituting the pool, the cutting device or at least one surface of the jig attached to the cutting device, the ferrite film is on the water contact portion where water containing the suspended matter in water that causes rust comes into contact. A nuclear power plant characterized by being formed into a film.

Images