JP5774285B2 - Film formation method for jet pump - Google Patents

Description

  The present invention relates to a film formation method for a jet pump that forms a film in order to prevent the clad from adhering to the jet pump in a boiling water reactor.

  In general, a jet pump as an in-core structure in a boiling water reactor is installed between a core shroud and a reactor pressure vessel, and in order to extract heat generated in the core, coolant in the core is used. Internal circulation is used to effectively remove the heat from the core and generate steam.

  As shown in FIG. 11, the jet pump 1 is a set of two, and includes one riser pipe 2, two inlet mixers 3, and a diffuser 4 for each set. . The diffuser 4 is assembled by welding to a baffle plate of a reactor pressure vessel (not shown). The inlet mixer 3 includes a nozzle portion 3a and a throat portion 3b, and can be removed and carried out of the furnace.

  The recirculated water that has returned to the recirculation inlet nozzle 5 of the reactor pressure vessel entrains the reactor water in the annular portion between the core shroud and the reactor pressure vessel wall at the nozzle portion 3a of the jet pump 1 via the riser pipe 2. It is discharged to the lower part of the core as high-speed water. When this recirculated flowing water passes through the jet pump 1, clad (CRUD: iron oxide in the reactor water) is deposited on the inner surface of the jet pump 1. The clad adheres to and deposits on the nozzle portion 3a of the inlet mixer 3 to increase the inner surface roughness. As a result, a predetermined drive flow rate cannot be obtained from the riser pipe 2, and the flow rate is reduced to lower the circulation efficiency.

  Further, when the clad is deposited on the throat portion 3b of the inlet mixer 3 and the inner surface roughness is increased, the flow rate of the entire jet pump 1 to which the suction flow rate is added is reduced even if the drive flow rate is the same. This has the effect of increasing pressure loss, creating significant energy losses.

  Furthermore, in order to ensure the same core flow rate as in the case where the clad adheres to either the nozzle part 3a inner surface or the throat part 3b inner surface of the inlet mixer 3, the recirculation pump (hereinafter, It is necessary to increase the rotational speed compared to the rotational speed of the PLR pump. Increasing the rotational speed of the PLR pump in this way is problematic from the viewpoint of safety and economic loss, and therefore it is recommended to decrease the rotational speed of the PLR pump.

  In order to solve this problem, it is conceivable to replace the inlet mixer 3 on which the cladding is deposited with a new inlet mixer 3. However, replacement with a new inlet mixer 3 causes an increase in nuclear waste.

In addition, it has been proposed to form a film on the surface of the jet pump 1 in order to suppress clad adhesion itself to the jet pump 1. For example, Patent Document 1 and Patent Document 2 propose a method of forming an oxide film such as TiO ₂ , ZrO ₂ , Ta ₂ O ₅ , and SiO _{2 on the} surface of the jet pump by a CVD method (chemical vapor deposition method). Yes.

  Patent Document 3 and Patent Document 4 disclose plasma spraying of platinum, rhodium, iridium, palladium, silver, gold, or a metal alloy thereof on the surface of a structural component such as a jet pump, HVOF (high-speed flame spraying). ), CVD, PVD (Physical Vapor Deposition), electroplating and electroless plating have been proposed (see Patent Documents 1 to 4).

JP 2002-207094 A US Pat. No. 6,633,623 JP 2007-10668 A US Patent Application Publication No. 2007/0003001

  However, none of the above-described techniques has a sufficient effect of suppressing clad adhesion due to film formation, and an expensive apparatus is required for film formation, and there are limitations on the size and shape of members for forming the film. There were some problems.

  The present invention has been made in consideration of the above circumstances, and it is possible to suppress the deposition and deposition of clad on the jet pump, and to form a jet pump film capable of maintaining the initial performance of the jet pump for a long period of time. It aims to provide a method.

In order to achieve the above object, a film forming method for a jet pump according to the present invention includes a step of removing an inlet mixer as a component of a jet pump in a boiling water reactor from a riser pipe and a diffuser, Install the inlet mixer at a predetermined position in the water, close the gap of the nozzle part of the inlet mixer and the openings at both ends with a sealing member, and introduce the cleaning water into the inside to remove the clad adhering to the inlet mixer. A cleaning step for cleaning, and after the cleaning step, an oxide ceramic solution is held in the inlet mixer for a certain period of time, and then a flow rate adjusting valve attached to a pipe connected to a seal member at the lower end of the inlet mixer open withdrawn the oxide ceramic solution at a constant rate, the Inre' And solution coating step for applying the oxide ceramic solution on the inner surface of the mixer, the solution after the coating step, oxide ceramics an inner surface of the inlet mixer coated with the oxide ceramic solution heat treatment to A heat treatment step for forming a film comprising: a recovery step for attaching and recovering the inlet mixer having the film formed on the riser pipe and the diffuser.

  According to the present invention, the oxide ceramic solution is applied to at least a part of the inner surface of the constituent member constituting the jet pump, and the inner surface of the jet pump constituent member to which the oxide ceramic solution is applied is heat-treated. By forming a film made of oxide ceramics, it is possible to suppress the deposit and deposition of the clad on the jet pump, and to maintain the initial performance of the jet pump for a long period of time.

It is process drawing which shows one Embodiment of the film formation method of the jet pump which concerns on this invention. It is the schematic which shows the carrying-in state of an inlet mixer in 1st Example. It is a front view which shows the apparatus for the clad removal washing | cleaning of an inlet mixer in 1st Example. It is the schematic which shows the state which is cleaning the inlet mixer in 1st Example. It is the schematic which shows the state which has dried the inlet mixer in 1st Example. It is the schematic which shows the state which has coated the inlet mixer in 1st Example. It is the schematic which shows the state which heat-processes the inlet mixer in 1st Example. It is sectional drawing which shows the case where an inlet mixer is coated in 2nd Example. It is an enlarged view which shows the case where an inlet mixer is coated in 3rd Example. It is the schematic which shows the case where an inlet mixer is coated in 3rd Example. It is a front view which shows the principal part of a jet pump.

  Embodiments and examples of a jet pump film forming method according to the present invention will be described below with reference to the drawings. In the following embodiments and examples, the configuration of each part of the jet pump is the same as that shown in FIG. 11 and will be described using the same reference numerals.

(One embodiment)
FIG. 1 is a process diagram showing an embodiment of a jet pump film forming method according to the present invention.

  As shown in FIG. 1, first, in step S <b> 1, the inlet mixer 3 as a constituent member of the jet pump 1 is removed from the riser pipe 2 and the diffuser 4. Then, it is carried into the water such as a DS pool. The inlet mixer 3 has a structure that can be detached from and attached to the jet pump 1.

  In step S2, the clad adhering to the removed inlet mixer 3 is removed and cleaned.

  In step S3, the inlet mixer 3 is degreased with washing water, and then ion-exchanged water is injected into the inlet mixer 3 for washing.

  In step S4, in order to completely remove moisture on the inner surface of the inlet mixer 3, drying is performed using a dryer.

  In step S5, the oxide ceramic solution is applied and coated on the inner surface of the inlet mixer 3.

  In step S6, the inlet mixer 3 is dried again.

  In step S7, the inner surface of the inlet mixer 3 to which the oxide ceramic solution is applied is heated in an electric furnace to form a film made of oxide ceramic. The condition of the heat treatment is defined as a temperature at which no material sensitization occurs from the viewpoint of stress corrosion cracking.

  In step S8, the inlet mixer 3 processed as described above is attached to the riser pipe 2 and the diffuser 4 and restored.

  Next, specific embodiments of the jet pump film forming method will be described with reference to the drawings.

(First embodiment)
2-7 is a figure which shows 1st Example of the film formation method of the jet pump based on this invention. FIG. 2 is a schematic view showing a state where the inlet mixer is carried in the first embodiment.

  In addition, each Example demonstrated below is a process which apply | coats an oxide type ceramic solution to the inlet mixer which is a structural member which comprises the jet pump used in the furnace by underwater remote control, The oxide type ceramic solution Using a so-called chemical solution method comprising a step of forming a film by heat treatment.

  FIG. 2 corresponds to the inlet mixer removal step of step S1 in FIG. As shown in FIG. 2, the inlet mixer 3 of the jet pump 1 is detached from the riser pipe 2 and the diffuser 4, and is carried into the space where the cladding removal or coating can be performed from the inside of the furnace, for example, the DS pool 24.

  Here, when the shroud head 22 and the steam dryer 23 which are removed from the reactor pressure vessel 21 in the reactor and transferred in advance to the DS pool 24 are installed, a space that does not interfere with them is secured. However, when the space cannot be secured, the shroud head 22 and the steam dryer 23 may be transferred again to the reactor pressure vessel 21 in the reactor and attached.

  Next, referring to FIG. 3 and FIG. 4, the inlet mixer cladding removal and cleaning process in step S <b> 2 and the inlet mixer degreasing and cleaning process in step S <b> 3 in FIG. 1 will be described. FIG. 3 is a front view showing an apparatus for removing the clad from the inlet mixer in the first embodiment. FIG. 4 is a schematic view showing a state where the inlet mixer is cleaned in the first embodiment. 3 is omitted from FIG. 4 and subsequent figures.

  As shown in FIG. 3, the inlet mixer 3 carried out to a workable space such as the DS pool 24 is positioned and installed at a predetermined position in the DS pool 24 by a fixing member (not shown). The gap between the nozzle portion 3a and the openings (elbow portion 3c, throat portion 3b) at both ends are closed with a sealing member such as a shield cover 11, and the inner surface is completely removed so that water in the inlet mixer 3 can be drained. Keep sealed.

  Pump pipes 12a and 12b are connected to the elbow part 3c and the throat part 3b to which the shield cover 11 is attached, respectively. A pump 13 is attached to one pump pipe 12a, and an open / close valve 19 is attached to the other pump pipe 12b. By opening the on-off valve 19 and driving the pump 13, air can be sent from the elbow portion 3c to remove water in the inlet mixer 3.

  First, the process of removing the clad adhering to the inlet mixer 3 using the apparatus of FIG. 3 by underwater remote operation will be described with reference to FIG.

  As shown in FIG. 4, washing water is put into the water tank 14. Next, the pump pipe 12b connected to the inlet mixer 3 and the water tank 14 containing cleaning water are connected. Then, the opening / closing valve 19 is closed and the pump 13 is driven to inject cleaning water into the inlet mixer 3. When the inside of the inlet mixer 3 is filled with cleaning water, the inner surface is maintained for a certain period of time with the cleaning water penetrating the inner surface. If the temperature of the cleaning water is markedly reduced when the cleaning water is permeated into the inlet mixer 3, temperature adjustment such as preheating the cleaning water is performed. Then, the opening / closing valve 19 is opened, the washing water is extracted from the inside of the inlet mixer 3, and the clad adhering to the inlet mixer 3 is removed and washed.

  Next, in the degreasing / cleaning process of the inlet mixer in step S3, the water tank 14 containing the ion exchange water is connected to the pump pipe 12b, and the ion exchange water is sufficiently injected by driving the pump 13 in the same manner as described above. Wash.

  FIG. 5 is a schematic view showing a state where the inlet mixer in the first embodiment is dried. FIG. 5 corresponds to the inlet mixer drying step of step S4 in FIG. As shown in FIG. 5, the pump pipe 12 a is connected to the dryer 15 in order to completely remove the moisture on the inner surface of the inlet mixer 3. The inner surface of the inlet mixer 3 is heated using the dryer 15, and the drying is finished when the water is completely removed from the inner surface or when heating for a predetermined time is finished. For example, the drying temperature is 100 ° C. or more and the time is about 10 minutes.

  Next, the coating process (solution application process) on the inlet mixer in step S5 in FIG. 1 will be described with reference to FIG. FIG. 6 is a schematic view showing a state where the inlet mixer is coated in the first embodiment.

  As shown in FIG. 6, in order to coat the inner surface of the inlet mixer 3, a coating solution is put into the chemical solution tank 16. The material of this coating solution is selected from the viewpoints of clad adhesion effect and peeling resistance. For example, since the clad existing in the aqueous solution is charged at the interface, when the coating material has the zeta potential with the same sign, the clad adhesion to the inlet mixer 3 is suppressed by the electrostatic repulsion force. In addition, it is conceivable that the thermal decomposition reaction is completed at the temperature during the heat treatment and that the adhesion strength is sufficient. Furthermore, it is necessary to consider that the coating liquid does not affect the furnace even if it is released into the furnace water.

Examples of the coating material include oxide ceramics such as zirconium dioxide (ZrO ₂ ), silicon dioxide (SiO ₂ ), alumina (AL ₂ O ₃ ), and titanium dioxide (TiO ₂ ). The material is selected. As a result of evaluating the adhesion of the coating film, the ZrO ₂ coating film had the best performance. Further, coating with ZrO ₂ has been confirmed to have an effect of suppressing oxidation in a steam environment, and it can be expected to suppress corrosion even in reactor water.

Furthermore, since the clad adhesion suppression effect is confirmed by the coating of TiO ₂ , zirconium titanate (TiZrO ₄ ) will be described in this example.

Using a test piece coated with TiZrO ₄ by the sol-gel method, a clad adhesion test in a high flow rate and high temperature water simulating the flow rate of the nozzle part of the inlet mixer was performed, and the amount of clad after the test was analyzed by fluorescent X-ray Measured with

For example, the test conditions are a temperature of 270 ° C., a flow rate of 63 m / sec, and a cladding concentration of about 50 bpm. As a result, it was confirmed that the TiZrO ₄ coating had a remarkable clad adhesion suppression effect as compared with the clad adhesion rate value of the test piece without coating.
As a method for adjusting the coating liquid, since hematite (FeO ₃ ) and magnetite (Fe ₃ O ₄ ) exist as an adhesion clad in an actual machine environment, the ratio of TiO ₂ and ZrO ₂ is examined. For example, the ratio of Ti and Zr is such that both are mixed at a molar ratio of 1: 1. When these coating liquids are used after being diluted, they are diluted and mixed so that the molar ratio is Ti: Zr = 1: 1. For example, the Ti concentration is 4.8% by weight and the Zr concentration is 4.8% by weight. After a predetermined amount of TiO ₂ and ZrO ₂ are mixed in a container made of polyethylene or stainless steel, mixing is performed for a certain period of time with a stirring device such as a magnetic stirrer. The mixing time is, for example, 1 hour.

  As for the storage method of the coating solution, it is stored in a cool and dark place in a sealed state in a polyethylene or stainless steel container. In addition, when using the coating solution for a long period of time, for example, about 3 months, a part of the coating solution is heated and held, and the solid content is calculated by measuring the weight change, so that the isopropial is adjusted to a predetermined concentration. Adjust with alcohol.

  As shown in FIG. 6, the pump pipe 12 b is connected to the chemical tank 16 through a flow rate adjustment valve 17 and the like. Then, the coating liquid is injected into the inlet mixer 3 by driving the pump 13. In this case, the temperature at the time of coating construction shall be 40 degrees C or less, for example. When the coating liquid is filled inside, it is kept in that state for a certain time. The holding time is, for example, 1 minute.

  After holding the coating liquid in the inlet mixer 3 for a certain period of time, the flow rate adjusting valve 17 attached to the pump pipe 12b is opened, and the coating liquid is extracted. At this time, the flow rate adjusting valve 17 is a valve capable of adjusting the flow rate in order to extract the extracted coating material at a constant speed. It is desirable to adopt a method in which the extraction speed is such that the interface of the coating material on the inner surface of the inlet mixer 3 is lowered at a constant speed. For example, the coating liquid interface is reduced at 5 mm / sec. Then, after supplying air from an air supply source such as an air compressor (not shown) to the pump pipe 12a to extract all the coating liquid, the coating on the inner surface of the inlet mixer 3 is completed.

  Next, in the drying process of step S6 in FIG. 1, the inlet mixer 3 is again dried in the same manner as the drying process described above, and after drying, heating for alcohol removal is performed.

  Next, the heat treatment process of the inlet mixer in step S7 in FIG. 1 will be described based on FIG. FIG. 7 is a schematic view showing a state where the inlet mixer is heat-treated in the first embodiment.

  As shown in FIG. 7, in the heat treatment step, heat treatment is performed on the inlet mixer 3 with an electric furnace 31. That is, the electric furnace 31 is suspended in the DS pool 24 by a crane or the like (not shown), and the inlet mixer 3 that has undergone the above steps is housed in the electric furnace 31 and heat-treated at a constant temperature.

  Here, the heat treatment condition is defined as a temperature at which no material sensitization occurs from the viewpoint of stress corrosion cracking. For example, the temperature is 400 ° C. for 10 minutes in the atmosphere. The temperature is controlled by fixing the thermocouple 32 or the like to the inlet mixer 3 and measuring the surface temperature of the inlet mixer 3. However, the heating rate and the cooling rate during the heat treatment may or may not be controlled.

  When the above procedure is completed, if the coating film thickness of the inlet mixer 3 satisfies a predetermined condition, it is transferred into the furnace as it is, and the process proceeds to the restoration process of the inlet mixer 3 in step S8 in FIG. The predetermined condition is, for example, a coating film thickness of 1.2 μm. In addition, when predetermined conditions are not satisfied, the procedure of coating, drying, and heat treatment is repeated again and transferred to the furnace when the predetermined film thickness is reached. The coating film thickness is calculated from a change in weight.

  Therefore, in this embodiment, the inlet mixer 3 of the jet pump 1 to which the cladding is attached can be coated while removing the cladding by underwater remote operation.

  As described above, according to the present embodiment, the clad adheres to the inner surface of the inlet mixer 3, and the operation efficiency of the jet pump 1 in which energy loss has occurred can be restored to a state equivalent to that during plant operation. Further, by applying a coating to the inner surface of the inlet mixer 3, it is possible to suppress clad adhesion and maintain the performance of the jet pump 1 at the beginning of operation for a long period of time.

  Further, according to this embodiment, it is possible to reduce the material required for coating by coating the inner surface without coating the outer surface of the inlet mixer 3.

  Furthermore, according to the present embodiment, by coating the inlet mixer 3 by underwater remote work, it is possible to ensure a sufficient water shielding state above the jet pump 1 exposed to radioactivity, so that coating is being performed. It becomes possible to keep the exposure dose of the substance low.

  Further, according to this embodiment, it is possible to restore the performance of the jet pump 1 without increasing the nuclear waste by returning the used jet pump to the furnace again instead of replacing the jet pump. Become.

  Furthermore, according to the present embodiment, when the coating material is pulled out from the flow rate adjusting valve 17 at a constant speed, the reduction speed of the interface of the coating material inside the inlet mixer 3 can be made substantially constant and formed on the inner surface. The effect of suppressing the unevenness of the coating is obtained.

(Second embodiment)
FIG. 8 is a sectional view showing a case where the inlet mixer is coated in the second embodiment. Note that the same or corresponding parts as those in the first embodiment are denoted by the same reference numerals, and different configurations and operations will be described. The same applies to other examples.

  In the said 1st Example, the inlet mixer 3 carried out from the inside of a furnace was sealed with the shield cover 11, and it was made airtight by draining water.

  In this embodiment, the core 35 is inserted into the inlet mixer 3 in the procedure before sealing with the shield cover 11. After that, the shield cover 11 is sealed, and cleaning, coating, and heat treatment are performed. The shape of the core 35 is made substantially the same as the shape of the inner surface of the inlet mixer 3, so that the gap interval between the core 35 and the inlet mixer 3 is made constant. It is desirable that the gap between the inner surface of the inlet mixer 3 and the core 35 be as narrow as possible from the viewpoint of reducing the coating material. However, in consideration of installation properties, the gap interval is set to 10 mm, for example.

  Thus, also in the second embodiment, the same operations and effects as in the first embodiment can be obtained. Further, according to the present embodiment, by inserting the core 35 into the inlet mixer 3, an effect of reducing the cleaning liquid and the coating material can be obtained.

  Furthermore, according to the present embodiment, when the coating material is pulled out from the flow rate adjusting valve 17 at a constant speed as in the first embodiment, the decreasing speed of the interface of the coating material inside the inlet mixer 3 is also made substantially constant. Thus, the same effect as in the first embodiment can be obtained.

(Third embodiment)
FIG. 9 is an enlarged view showing a case where the inlet mixer is coated in the third embodiment. FIG. 10 is a schematic view showing a case where the inlet mixer is coated in the third embodiment. In FIG. 9 and FIG. 10, the hump piping is indicated by reference numeral 12.

  In the first embodiment and the second embodiment, the interior of the inlet mixer 3 was made airtight and coated, and then transferred to the electric furnace 31 to perform heat treatment.

  In the present embodiment, the inlet mixer 3 is carried into a sealed container having the electric furnace 31 in a state where the nozzle portion 3 a of the inlet mixer 3 is shielded by the shield cover 11. The electric furnace 31 is provided with a shield cover 11 at a position where the nozzle 3a and the throat 3b of the inlet mixer 3 are closed. After the inlet mixer 3 is installed, the electric furnace 31 (not shown) The lid is closed. After the lid of the electric furnace 31 is closed, the inside of the electric furnace 31 is airtight with air. After the water inside the electric furnace 31 is completely removed, coating is performed on the inside of the inlet mixer 3 in the same procedure as in the first embodiment, and heat treatment is performed.

  In the present embodiment, the core 35 of the second embodiment is installed on the shield cover 11 that closes the opening of the throat portion 3b.

  Thus, also in this embodiment, the same operation and effect as the first example and the second example can be obtained.

  In addition, according to the present embodiment, since the core 35 of the second embodiment is installed in the shield cover 11 that closes the opening of the throat portion 3b, when attaching the throat portion 3b to the shield cover 11, The child 35 becomes a guide member, and the attachment work of the throat portion 3b to the shield cover 11 is surely and easily performed.

  The present invention is not limited to the above embodiment and each example, and various modifications can be made. For example, in each of the above embodiments, an example in which the inlet mixer used in the furnace is coated in water has been described. However, the present invention is not limited to this, and in the case of coating an unused inlet mixer in the furnace, It can also be implemented at factories and sites. Therefore, in the present invention, since the coating operation can be performed not only at the factory but also at the site, the coating process can be shortened.

  In each of the above embodiments, the example in which the inlet mixer 3 of the jet pump 1 is coated has been described. However, the present invention is not limited to this, and the riser pipe 2 and the diffuser 4 may be coated.

  Further, in each of the above embodiments, the entire inner surface of the inlet mixer 3 is coated. However, the present invention is not limited to this, and a portion where the clad easily adheres may be locally coated.

DESCRIPTION OF SYMBOLS 1 ... Jet pump 2 ... Riser pipe 3 ... Inlet mixer (component)
4 ... Diffuser 11 ... Shield cover 12, 12a, 12b ... Pump pipe 13 ... Pump 14 ... Water tank 15 ... Dryer 16 ... Chemical tank 17 ... Flow rate adjusting valve 22 ... Shroud head 23 ... Steam dryer 24 ... DS pool 31 ... Electricity Furnace 32 ... Thermocouple 35 ... Core

Claims (5)

Removing the inlet mixer as a component of the jet pump in the boiling water reactor from the riser pipe and the diffuser;
The removed inlet mixer is installed at a predetermined position in the water, the gap portion of the nozzle portion of the inlet mixer and the openings at both ends are closed with seal members, and the clad adhering to the inlet mixer by introducing cleaning water into the inside is installed. A cleaning step to remove and wash;
After the cleaning step, the oxide ceramic solution is held in the inlet mixer for a certain period of time, and then a flow control valve attached to a pipe connected to a seal member at the lower end of the inlet mixer is opened, and the oxide withdrawn system ceramics solution at a constant rate, and solution coating step of applying the oxide ceramic solution on the inner surface of the inlet mixer,
After the solution coating step, a heat treatment step of heat-treating the inner surface of the inlet mixer coated with the oxide ceramic solution to form a film made of oxide ceramic;
A recovery step of attaching and recovering the inlet mixer with the film formed on the riser pipe and the diffuser;
A method for forming a film of a jet pump, comprising: The method for forming a film of a jet pump according to claim 1, wherein the solution applying step is applied to the inlet mixer by remote operation in water. The method for forming a film of a jet pump according to claim 1, wherein the solution applying step is performed in a state where a core is put in the inlet mixer . 4. The coating film forming method for a jet pump according to claim 1, wherein in the heat treatment step, the inlet mixer is housed in an electric furnace suspended in water and subjected to heat treatment. 5. The method for forming a film of a jet pump according to any one of claims 1 to 4, further comprising a drying step for drying an inner surface of the inlet mixer before the solution applying step.

Images