JP4343092B2 - Reactor material surface modification method and apparatus - Google Patents

Description

  The present invention relates to a method and apparatus for reforming a surface of a reactor material that removes and modifies an oxide film on the surface of the reactor material.

  Generally, the conventional method for modifying the surface of a reactor material in a nuclear power plant is applied in a situation where a thick oxide film is generated on the material surface. As one of such surface reforming methods for the reactor material, there is a method in which Pd, which is a surface modifying substance, is injected into the reactor water and adhered to the surface of the reactor material. The adhering Pd functions as a catalyst for hydrogen injected into the reactor water and suppresses corrosion (for example, see Patent Document 1).

  As a similar surface modification method, there is a method of injecting zinc. ZnO is injected into the reactor water and adhered to the surface of the reactor material. This method suppresses the uptake of radioactive materials such as Co-60 into structures such as piping, and reduces the exposure of operators and employees during regular inspections (for example, see Patent Document 2). ).

In addition, there is one in which heat transfer is improved by attaching TiO ₂ to the surface of the reactor material. If the heat transfer on the heat exchanger or fuel rod surface is improved, the heat removal performance is improved, so that safety and power generation efficiency are expected to be improved (for example, see Patent Document 3).

These technologies are mainly applied to existing plants. In this existing plant, it is already covered with a thick oxide film, and the properties of the film vary. For this reason, there is a disadvantage in that the control and effect of the amount of adhesion of Pd or TiO _{2 on the} surface of the reactor material is not constant.

  In addition, due to secular changes in nuclear power plants, there are many construction works such as maintenance and cleaning that repair cracks in metal materials, and accompanying decontamination. These constructions are directly related to a portion having a high possibility of cracking, and include a step of peeling the oxide film on the surface of the reactor material. For example, laser peening is to apply a compressive stress to the surface of a material at a site susceptible to cracking by applying a strong laser, and at the same time to peel the oxide film by irradiation (see, for example, Patent Document 4). .

  In many cases, decontamination work is carried out as a preparation for these works in order to reduce employee exposure. At this time, the oxide film adhering to the metal surface is peeled off, and the metal base material is exposed in a wide range (see, for example, Patent Document 5).

As described above, as a technique for mitigating the corrosive environment in the nuclear reactor, it has been studied to inject hydrogen by attaching a noble metal such as Rh or Pd in addition to the above-described Pt to the surface of the nuclear reactor structural material. It is also effective to take measures such as attaching TiO ₂ as described above. In order to attach these substances, a method of injecting a solution containing these substances into the reactor water is currently used.
Japanese Patent No. 3066265 Japanese Patent No. 2566972 International Publication No. WO01 / 033574 Japanese Patent No. 3373638 Japanese Patent No. 2587023

However, in the above-described conventional method for reforming the surface of the reactor material, the surface reforming substance such as Pd or TiO ₂ is attached without controlling the oxide film attached to the surface of the reactor material. The problem is how to maintain this effect because the amount of adhesion of these substances and the effect are not constant.

As a technology for mitigating the corrosive environment in the nuclear reactor, it is effective to take measures such as hydrogen injection by attaching noble metals such as Pt, Rh, Pd, etc. to the surface of the nuclear reactor structural material or TiO ₂ In addition, a method of injecting a solution containing these substances into the reactor water is used. In this method, since it is difficult to attach a sufficient amount of these elements and compounds to a predetermined location, it is necessary to inject a surface modifying substance in an amount greater than a necessary amount.

  However, if these substances adhere to the surface of the fuel cladding tube, corrosion may be accelerated. In addition, since the adhesion form of these substances to the surface of the nuclear reactor structure material is weak physical adhesion, it is easily peeled off by a thermal cycle or flow, and the effect of surface modification is lost. Moreover, when the oxide film loosely attached to the surface of the nuclear reactor structural material is thick, there is a problem that the effect of attaching the surface modifying substance cannot reach the base material and the effect is weakened.

  On the other hand, peening such as laser peening and water jet peening, repair welding, or surface modification is applied to parts that are sensitive to corrosion, but then the corrosion progresses again if the reactor is operated for a while without taking measures to prevent corrosion. There is a problem of doing.

  In addition, when the work related to the peening and repair described above is performed in the nuclear reactor, the radiation exposure amount of the employee increases. For this reason, decontamination work is carried out prior to the modification work on the surface of the reactor structural material. When the operation of the reactor is resumed after the decontamination work is completed, the growth of the oxide film is fast on the new surface of the reactor structural base material, and the uptake rate of radioactive material increases accordingly. There is a problem that the effect of is lost.

  As a method for reducing the uptake rate of this radioactive substance, Zn injection into reactor water has been studied. However, when injected into reactor water as in the prior art, there is a problem that Zn is deposited and deposited in unnecessary places, causing a problem of vibration due to a change in differential pressure or a change in flow.

Furthermore, by utilizing the property of the super-hydrophilic with a TiO _2, there is a technique for improving the heat transfer by deposition of a TiO ₂ on the surface of the fuel rod surface and the heat exchanger for heat exchange, deteriorating heat transfer There is a problem that the efficiency cannot be sufficiently improved in the state where the oxide film is attached.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a method for reforming the surface of a reactor material and an apparatus therefor provided with means for controlling the properties of the surface of the reactor material.

  In order to achieve the above object, in the method for reforming the surface of a reactor material according to the present invention, an oxide film removing step of removing the oxide film on the surface of the reactor material with a processing apparatus, and the reactor material from which the oxide film has been removed An element injection step of injecting at least one element selected from Pt, Rh, Ir, Pd, Ru, Os, Cr, Si, Zr, Ti, Zn, Ni or a compound containing the same into the surface by the processing apparatus; It is characterized by having.

  In order to achieve the above object, in the reactor material surface reforming apparatus of the present invention, a processing device for removing the oxide film on the surface of the reactor material, and Pt on the reactor material surface from which the oxide film has been removed. Element injection means for injecting at least one element selected from Rh, Ir, Pd, Ru, Os, Cr, Si, Zr, Ti, Zn, and Ni or a compound containing the element. It is.

  According to the present invention, the adhering element or the compound containing this penetrates to the inside of the structural material that is the nuclear reactor material, so that it is possible to exert a sustained effect without peeling after the restart of the nuclear reactor, Furthermore, it is possible to reduce the initial amount of elements to be deposited during construction.

  Embodiments of a method for reforming a surface of a nuclear reactor material and an apparatus therefor according to the present invention will be described below with reference to FIGS. Here, the same or similar parts are denoted by common reference numerals, and redundant description is omitted.

  FIG. 1 is a configuration diagram showing a configuration of a reactor material surface reforming apparatus according to an embodiment of the present invention. As shown in FIG. 1, the laser 20 generated by the laser generator 1 is irradiated to the surface of the structural material 6 that is a nuclear reactor material via the laser transmission device 2.

  On the other hand, the injection tank 3 stores a solution 21 mixed with at least one element selected from Pt, Rh, Ir, Pd, Ru, Os, Cr, Si, Zr, Ti, Zn, and Ni or a compound containing the element. Has been. The solution 21 mixed with the selected element or a compound containing the selected element is injected into the surface of the structural material 6 as the reactor material by the injection pump 4 via the injection line 5.

  In the present embodiment configured as described above, a structural material which is a nuclear reactor material by irradiating a strong laser 20 from the laser generator 1 at the time of in-reactor repair work such as peening, repair welding or cleaning. The oxide film can be removed from the surface of 6.

  After removing the oxide film, the laser generator 1 irradiates the weak laser 20 while injecting the solution 21 mixed with the selected element stored in the injection tank 3 or a compound containing the selected element. The above-mentioned selected element stored in the injection tank 3 or a compound containing the selected element can be attached to the surface of the structural material 6.

In the laser cleaning described above, the oxide film can be removed from the surface of the structural material 6 which is a nuclear reactor material by irradiating the laser 20 with energy of about 1 J / cm ² . In peening and repair welding, the oxide film is almost completely removed by irradiating the laser 20 with a higher energy of several tens of J / cm ² or several hundred J / cm ² .

After removing this oxide film, at least one element selected from Pt, Rh, Ir, Pd, Ru, Os, Cr, Si, Zr, Ti, Zn, Ni stored in the injection tank 3 or a compound containing the same While the solution 21 mixed with is injected into the water in the vicinity of the surface of the structural material 6 as the reactor material from the injection line 5, the structural material 6 as the nuclear reactor material is irradiated by irradiating the laser 20 at 1000 J / cm ² or less. The above-described at least one selected element or a compound containing the selected element can be attached to the surface.

  At the time of laser peening, oxygen in the water enters by several tens of μm by the irradiation of the laser 20, so that the above-mentioned at least one selected element or a compound containing this is about several tens of μm to the base material. It is thought to invade.

  According to the present embodiment, the selected element or the compound containing the element deposited by the irradiation of the laser 20 penetrates into the structural material 6 that is the nuclear reactor material, and therefore, it is peeled off after restarting the nuclear reactor. Long-term effects. Further, by controlling the concentration of the solution in the injection tank 3 and the injection speed, the concentration of elements contained in the reactor water in the vicinity of the structural material 6 as the reactor material is controlled, and the amount of laser irradiation is also controlled. Thus, it is possible to obtain an arbitrary amount of adhesion of the selected element or the compound containing the selected element.

  From this, the attached element or the compound containing this penetrates into the structure material which is the reactor material, and can exert a sustained effect without peeling after the restart of the reactor. It is possible to reduce the initial amount of elements to be deposited during construction.

  FIG. 2 is a graph showing the relationship between hydrogen and corrosion potential when noble metal is deposited. As shown in FIG. 2, after depositing a noble metal such as Pt, Rh, Ir, Pd, Ru, and Os on the surface of the material and adding a small amount of hydrogen after starting the reactor, compared to the case of no noble metal injection, The potential drops significantly. In the case of stainless steel, which is a typical structural material, it is said that corrosion does not occur if the corrosion potential falls below 230 mV-SHE, and the corrosion potential should be sufficiently reduced by introducing hydrogen into the reactor water. I can see that

  From the viewpoint of sufficiently reducing the corrosion potential, in the present embodiment, Ti is adhered to the surface of the structural material 6 that is the surface of the nuclear reactor material at a surface area of 2% or more or a total surface area of 2% or more.

  FIG. 3 is a graph showing the precious metal remaining rate after one cycle operation of the nuclear reactor. As shown in FIG. 3, in the conventional deposition method using the noble metal injection method, only about 38% remains after 10000 hours, which is the operation period of one cycle of the reactor. This is because the noble metal is deposited on the oxide film, so that it decreases with the peeling of the oxide film. This indicates that it is necessary to perform the initial construction so that about 3 times as much as the minimum amount of adhesion that causes the effect of noble metal adhesion occurs.

  According to the present embodiment, since noble metal has entered the surface of the base material and the inside of the base material, 90% or more remains in one cycle, and a high sustaining effect is obtained. This phenomenon related to the precious metal adhesion is the same for all other elements. That is, it is possible to reduce the initial amount of the element to be deposited at the time of construction according to the present embodiment to 1/3 as compared with the conventional case.

  FIG. 4 is a configuration diagram showing a configuration of a water jet device according to another embodiment of the present invention. The embodiment shown in FIG. 4 uses a water jet instead of the laser in the embodiment shown in FIG. 1, and the same or similar parts are denoted by the same reference numerals, and redundant description is omitted. .

  The water jet device is used for peening and cleaning in the nuclear reactor as with the laser irradiation device. As shown in FIG. 4, the water jet apparatus injects the aqueous solution stored in the water jet tank 8 onto the surface of the structural material 6 as the reactor material by the water jet pump 7 through the water jet line 9. To do.

  In this water jet cleaning, water is struck by the water jet pump 7 having a discharge pressure of about 30 MPa against the surface of the structural material 6 as the reactor material, and the water jet peening is about one digit stronger than that. The pump 7 gives compressive stress.

  In the present embodiment configured as described above, the oxide film on the surface of the structural material 6 which is a nuclear reactor material can be removed as in the case of laser peening.

According to the present embodiment, the water jet is applied to the surface of the structural material 6 that is a nuclear reactor material from the vertical direction, and the solution 21 mixed with at least one selected element or a compound containing the selected element. Similarly, the flow is from the vertical direction. The flow of water in many parts of the reactor structural material often flows parallel to the material, and a high pressing pressure is generated by adhering with a water jet, so that it is considered that the sustaining effect is enhanced. Therefore, since the selected selected element or the compound containing the same penetrates into the structural material 6 which is a nuclear reactor material, it exerts a continuous effect without peeling after the restart of the nuclear reactor. In addition, it is possible to reduce the amount of adhesion.

  FIG. 5 is a configuration diagram showing the configuration of the shot device according to the third embodiment of the present invention. This embodiment uses a shot instead of the laser in the embodiment shown in FIG.

  As shown in FIG. 5, the shot apparatus applies a shot made of a metal ball or the like stored in the shot tank 14 to the surface of the structural material 6 that is a reactor material by using a shot pump 13 via a shot line 15. It is to be jetted. Further, at least one element selected from Pt, Rh, Ir, Pd, Ru, Os, Cr, Si, Zr, Ti, Zn, Ni as a material such as a metal sphere stored in the coating shot tank 10 Or the coating shot which coated the compound containing this is injected on the surface of the structural material 6 which is a nuclear reactor material with the mixing pump 11 via the mixing line 12. FIG.

  In the present embodiment configured as described above, the shot device is used for blasting that performs peening and cleaning in the same manner as the water jet device. It can be made to adhere mechanically by including an adhering element on the surface of the sphere used for the coating shot of this shot device.

  When performing peening or blasting, a sphere that is not a coating shot is used, and when the effect is exhibited and the oxide film is sufficiently removed, the coating shot is mixed from the mixing line 12 to the shot line 15. As a result, the coated element collides with the structural material 6 which is a nuclear reactor material, and the element sinks into and adheres to the inside.

  According to the present embodiment, since the adhering element exists up to the inside, it is possible to improve the durability of the adhering element and reduce the amount of adhesion.

  FIG. 6 is a configuration diagram illustrating a configuration of an electric discharge machining apparatus or an electrolytic machining apparatus according to another embodiment. In this embodiment, processing is performed by electric discharge or electrolysis instead of the laser in the embodiment shown in FIG. 1, and the same or similar parts are denoted by common reference numerals, and redundant description is omitted.

  The electric discharge machining apparatus or the electrolytic machining apparatus is used for peening and cleaning in the nuclear reactor, similarly to the laser irradiation apparatus. As shown in FIG. 6, in the electric discharge machining apparatus or the electrolytic machining apparatus, the constant current / voltage generator 16 is connected to the structural material 6 as a reactor material and the surface thereof via a probe wire 17 and a counter lead wire 19. A connection is made between the arranged probes 18.

  In the present embodiment configured as described above, the electric discharge machining apparatus and the electrolytic machining apparatus melt and process the structural material, which is a nuclear reactor material, by applying a voltage to the structural material and the probe 18 in the water in the vicinity thereof. Is.

  According to the present embodiment, the oxide film on the surface of the structural material is completely removed, and further the base material can be dissolved. After removing the oxide film, a solution 21 containing at least one element selected from Pt, Rh, Ir, Pd, Ru, Os, Cr, Si, Zr, Ti, Zn, and Ni or a compound containing the same is injected. However, by connecting the positive and negative voltages opposite to each other, it is possible to adhere to a metal base material that is a structural material like plating.

  In this way, in order to deposit electrochemically, the deposited element or the compound containing it penetrates into the structural material, which is a nuclear reactor material, so that it does not peel off after the reactor is restarted. The effect can be exhibited, and it is possible to further reduce the initial amount of elements to be deposited during construction.

The block diagram which shows the structure of the laser generator of embodiment of this invention. The graph which shows the relationship between hydrogen and the corrosion potential at the time of noble metal adhesion. The graph which shows the residual rate of the noble metal after 1 cycle operation | movement of a nuclear reactor. The block diagram which shows the structure of the water jet apparatus of other embodiment of this invention. The block diagram which shows the structure of the shot apparatus of other embodiment of this invention. The block diagram which shows the structure of the electric discharge machining apparatus or electrolytic machining apparatus of other embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Laser generator, 2 ... Laser transmission apparatus, 3 ... Injection tank, 4 ... Injection pump, 5 ... Injection line, 6 ... Structural material, 7 ... Water jet pump, 8 ... Water jet tank, 9 ... Water jet line, DESCRIPTION OF SYMBOLS 10 ... Coating shot tank, 11 ... Mixed pump, 12 ... Mixed line, 13 ... Shot pump, 14 ... Shot tank, 15 ... Shot line, 16 ... Constant current / voltage generator, 17 ... Probe wire, 18 ... Probe, 19 ... counter lead wire.

Claims (6)

An oxide film removal step for removing the oxide film on the surface of the nuclear reactor material using a processing device, and Pt, Rh, Ir, Pd, Ru, Os,
An element injecting step of injecting at least one element selected from Cr, Si, Zr, Ti, Zn, Ni or a compound containing the same by changing the operating conditions using the processing apparatus;
A method for reforming the surface of a nuclear reactor material, characterized by comprising:   The method for reforming a surface of a nuclear reactor material according to claim 1, wherein the processing device includes at least one of a laser device, a water jet device, a shot device, an electric discharge processing device, and an electrolytic processing device.   3. The method for reforming a surface of a reactor material according to claim 2, wherein in the element implantation step, Ti of 2% or more is adhered to the surface of the reactor material by the laser device. 4.   3. The method for reforming a reactor material surface according to claim 2, wherein the oxide film removing step includes peening or cleaning the surface of the reactor material with the water jet device.   3. The method for reforming a reactor material surface according to claim 2, wherein the oxide film removing step includes peening or cleaning the reactor material surface with the shot device. A processing device for removing the oxide film on the surface of the reactor material;
An injection tank for storing at least one element selected from Pt, Rh, Ir, Pd, Ru, Os, Cr, Si, Zr, Ti, Zn, Ni or a compound containing the same;
Injecting means for injecting an element supplied from the injection tank or a compound containing the element into the reactor material surface from which the oxide film has been removed while changing the operating conditions of the processing apparatus;
A reactor material surface reforming apparatus characterized by comprising:

Images