JP4679116B2 - Radioactive waste disposal container, system and method for diagnosing degradation and improving life - Google Patents

Description

  The present invention relates to a radioactive waste disposal container used for the disposal of radioactive waste generated from a nuclear facility, a system and method for diagnosing the soundness of the container, and a system and method for improving the life of the container. is there.

  The radioactive waste disposal containers currently being used or studied are planned to be buried underground from the viewpoint of preventing the diffusion of radioactive materials. In this case, the radioactive waste disposal container is required to have long-term durability and reliability so that the radioactive waste does not leak outside.

  Conventionally, when a radioactive waste having a low dose is disposed of, a drum can is used as a radioactive waste disposal container. In order to dispose of radioactive waste with a high dose, from the viewpoint of reducing exposure to workers and the like, a drum can provided with a radiation shielding function or a disposal container made of steel larger than a drum can is used or studied.

  For example, as a configuration for obtaining a radiation shielding function of a drum can used for disposal of radioactive waste having a high dose, it is common to provide a concrete lining on the inside of the drum can. When disposing of low-level radioactive waste (commonly known as L1 waste or high βγ waste) having a relatively high radioactivity concentration than waste, a disposal container made of steel larger than a drum can is being considered. In foreign countries, there is a track record of using large steel disposal containers other than drums. These containers generally take into account several centimeters to tens of centimeters of concrete shielding or iron shielding, depending on the dose of radioactive waste stored.

  As described above, the radioactive waste disposal containers conventionally used or studied are generally made of steel (see, for example, Patent Documents 1 and 2).

On the other hand, in recent years, attempts have been made to improve the durability of disposal containers from the viewpoint of long-term storage. Many of them have improved the corrosion resistance of the disposal container. As an example, there is a proposal to use a Ti alloy having excellent corrosion resistance as a material for the disposal container (see, for example, Patent Document 3). In addition, it has also been proposed that the corrosion resistance material Ti, Zr, or the like is formed on the surface of the steel so that the functions are shared to achieve both strength and corrosion resistance (see, for example, Patent Document 4).
Japanese Patent Laid-Open No. 10-31094 JP-A-9-304594 JP 2002-168995 A JP 2003-41615 A

  Among the above-described conventional techniques, in the case of a steel radioactive waste disposal container, there is a problem that the corrosion resistance is poor. Therefore, Ti radioactive waste disposal containers have also been proposed as means for improving corrosion resistance, but in this case, the thickness may have to be increased in order to provide sufficient radiation shielding performance. There are also problems in workability, such as difficulty in welding to form as.

  Furthermore, a radioactive waste disposal container has been proposed in which functions are shared by covering the surface of steel with a corrosion-resistant material such as Ti or Zr, thereby achieving both corrosion resistance and radiation shielding performance and strength. When the corrosion resistance barrier function of Ti or Zr, which is the corrosion resistant material formed on the outermost surface, is lost, the interface between the steel and the corrosion resistant material is exposed to the corrosive environment, and therefore, the metal that has a large tendency to ionize by electrolytic corrosion (base) There is a problem that the corrosion of the steel material on the side is accelerated.

  The above technique is an attempt to improve the corrosion resistance of the disposal container and improve the durability. However, unexpected events may occur during long storage periods * such as defects during production and deterioration of the corrosive environment due to changes in groundwater quality. In addition, after the radioactive waste disposal container is disposed of, it is difficult for humans to approach and examine the soundness from the viewpoint of reducing exposure.

  In such a situation, it is necessary to consider the possibility of groundwater entering the container, assuming that the external environment blocking function of the radioactive waste disposal container is lost. Therefore, it was necessary to design the disposal site on the safe side so that there would be no exposure problems even if nuclide migration occurred due to damage or corrosion of the container.

  This invention is made | formed in view of such a situation, and it aims at providing the radioactive waste disposal container which can hold | maintain a nuclide safely in a disposal container for a long period of time.

  In addition, the present invention provides a radioactive waste disposal container system and a deterioration diagnosis method that are excellent in shielding the external environment of a radioactive waste disposal container and have a function of diagnosing the progress of corrosion of the radioactive waste disposal container without approaching a person. For the purpose.

  Furthermore, an object of the present invention is to provide a radioactive waste disposal container system and a lifetime improvement method that can improve the lifetime of the radioactive waste disposal container.

In order to achieve the above object, according to the invention of claim 1, a cylindrical body having a bottom is used for embedding disposal of radioactive waste generated from a nuclear facility and accommodates the radioactive waste. container a radioactive waste disposal container which have a lid portion for closing the top opening, the walls constituting the said body portion and the lid portion of the radioactive waste disposal container for accommodating the radioactive waste a body material wall constituting the skeleton, and corrosion-resistant barrier material wall to be protected from external corrosive environment to cover the external surface surface of the body material wall, said body material wall constituting said body portion and the lid portion There is provided a radioactive waste disposal container which is assembled between the corrosion-resistant barrier material walls and includes an insulating material wall which electrically insulates the body material walls and the corrosion-resistant barrier material walls.

  According to a second aspect of the present invention, the main body material wall is made of Fe or Fe-based alloy, Co or Co-based alloy, Ni or Ni-based alloy having structural strength and radiation shielding performance. Provide waste disposal containers.

  According to a third aspect of the present invention, there is provided the radioactive waste disposal container according to the first aspect, wherein the corrosion-resistant barrier material wall is made of a material having a smaller ionization tendency than the main body material wall.

  According to a fourth aspect of the present invention, the corrosion-resistant barrier material wall is a material having a small standard generation energy of oxide in at least one metal selected from Ti, Al, Zr, Mg, Be, Si, Ta, B, Nb and Cr. Alternatively, the radioactive waste disposal container according to claim 1, which is made of an alloy containing them as a main component, is provided.

According to a fifth aspect of the invention, there is provided the radioactive waste disposal container according to the first aspect, wherein the insulating material wall is made of a metal, an organic material, or an inorganic material having a specific resistance of 10 ³ Ωm or more.

In the invention of claim 6, the inorganic material is one or more oxide ceramics selected from Al ₂ O ₃ , BeO, CaO, MgO, SiO ₂ , TiO ₂ , ZrO ₂ and UO ₂ , or a main component thereof. The radioactive waste disposal container according to claim 5, which is a composite oxide ceramic.

  According to a seventh aspect of the present invention, there is provided the radioactive waste disposal container according to the fifth aspect, wherein the insulating material wall has a thickness of 0.1 mm or more.

  According to an eighth aspect of the present invention, there is provided the radioactive waste disposal container according to the first aspect, comprising one or more sets of wirings connected to the main body material wall and the corrosion-resistant barrier material wall to form an electric circuit.

  In a ninth aspect of the present invention, there is provided a radioactive waste disposal container system using the radioactive waste disposal container according to the eighth aspect, wherein the main material wall and the corrosion-resistant barrier material of the radioactive waste disposal container are connected to the wiring. An electrical resistance measurement device that measures electrical resistance between walls, a data recording device that records electrical resistance measurement data measured by the electrical resistance measurement device, and the corrosion resistance based on measurement data from the electrical resistance measurement device There is provided a radioactive waste disposal container system comprising a corrosion-resistant barrier function loss determining means for determining whether or not a corrosion-resistant barrier function of a barrier material wall is lost.

  The invention according to claim 10 is a radioactive waste disposal container system using the radioactive waste disposal container according to claim 8 provided with two or more sets of the wirings, wherein the radioactive waste is connected to each wiring. The corrosion resistance barrier function of the corrosion resistant barrier material wall is lost based on the electrical resistance measuring device for measuring the electrical resistance between the main body wall and the corrosion resistant barrier material wall of the disposal container and the measurement data by the electrical resistance measuring device. Corrosion-resistant barrier function loss determining means for determining whether or not the corrosion-resistant barrier function loss position of the corrosion-resistant barrier material wall in the radioactive waste disposal container when it is determined that the corrosion-resistant barrier function of the corrosion-resistant barrier material wall has been lost. Loss position calculation means to be obtained, electrical resistance measurement data measured by the electric resistance measurement device, and loss position obtained by the loss position calculation means Providing radioactive waste disposal container system characterized by comprising a data recording apparatus for recording data.

  In invention of Claim 11, it is a radioactive waste disposal container system using the radioactive waste disposal container of Claim 8 provided with two or more sets of said wiring, Comprising: It connects to the said wiring, and said radioactive waste disposal An electrical resistance measuring device for measuring the electrical resistance between the main body material wall and the corrosion-resistant barrier material wall of the container, and whether or not the corrosion-resistant barrier function of the corrosion-resistant barrier material wall is lost based on measurement data by the electrical resistance measuring device. Corrosion-resistant barrier function loss determining means for determining whether or not the corrosion-resistant barrier function of the corrosion-resistant barrier material wall is determined to have lost the corrosion-resistant barrier function-loss position of the corrosion-resistant barrier material wall in the radioactive waste disposal container Loss position calculation means, electrical resistance measurement data measured by the electrical resistance measurement device, and loss position obtained by the loss position calculation means A data recording device for recording data, a corrosion determining means for determining whether or not there is a possibility of corrosion on the main body material wall based on the data, and this corrosion determining means has determined that there is a possibility of corrosion A DC current supply command output means for outputting a DC current supply command to the body material wall, and a DC power source for supplying a DC current to the body material wall based on a command of the DC current supply command output means. A radioactive waste disposal container system is provided.

  In the invention of claim 12, the radioactive waste disposal container system according to claim 9 is used to detect a change in electrical resistance between the body material wall and the corrosion-resistant barrier material wall, and based on the detection result, the corrosion resistance Provided is a method for diagnosing degradation of a radioactive waste disposal container, characterized by estimating a loss of a corrosion-resistant barrier function of a barrier material wall.

  In a thirteenth aspect of the invention, using the radioactive waste disposal container system according to the tenth aspect, a change in electrical resistance between the body material wall and the corrosion-resistant barrier material wall at different positions of the radioactive waste disposal container is detected. And providing a method for diagnosing degradation of a radioactive waste disposal container, wherein the corrosion resistant barrier function loss position of the corrosion resistant barrier material wall is identified based on the difference between the detected values.

  In the invention of claim 14, by using the radioactive waste disposal container system according to claim 11, the corrosion-resistant barrier function of the corrosion-resistant barrier material wall is lost, and the body material wall and the corrosion-resistant barrier material wall are electrically connected. If it is determined that the main body material wall is corroded by applying a reverse potential therebetween, a method for improving the life of the radioactive waste disposal container is provided.

  According to the first aspect of the present invention, even when the corrosion-resistant barrier function of the corrosion-resistant barrier material wall is lost, the interface between the main body material wall and the corrosion-resistant barrier material wall is not directly exposed to the external environment by the insulating material wall. The rapid progress of corrosion of the main body material wall due to electric corrosion can be prevented.

  According to the invention of claim 2, Fe or Fe-based alloy, Co or Co-based alloy, Ni or Ni-based alloy has structural strength and radiation shielding performance, and is excellent in workability. A skeleton can be made.

  According to the third and fourth aspects of the invention, Ti, Al, Zr, Mg, Be, Si, Ta, B, Nb, and Cr are easily oxidized due to their low standard generation energy in oxides, and the surface is chemically As a result, the subsequent progress of oxidative corrosion can be reduced.

According to the inventions of claims 5 to 7, a metal, an organic material, or an inorganic material having a specific resistance of 10 ³ Ωm or more is used as the insulating material wall, and the thickness of the insulating material wall is set to 0.1 mm or more. By using oxide ceramics such as Al ₂ O ₃ , BeO, CaO, MgO, SiO ₂ , TiO ₂ , ZrO ₂ , UO _2, or composite oxide ceramics containing them as the main component as the insulating material wall, It is stable and has little deterioration even under irradiation, and can maintain a large specific resistance (insulation performance) over a long period of time.

  Therefore, according to the above invention, the external environment shielding property of the container is excellent, and the nuclide can be safely held in the disposal container for a long period of time.

  According to the invention described in claim 8, the electrical resistance between the main body material wall and the anticorrosion barrier material wall can be measured by the wiring connected to each of the main body material wall and the anticorrosion barrier material wall. With the connected DC current supply wiring, the current flowing by applying a reverse potential to the main body material wall can be reduced.

  According to the ninth and twelfth aspects of the present invention, when the corrosion resistance barrier function of the corrosion resistant barrier material wall and the insulating function of the insulating material wall are lost, and when groundwater from the outside enters the surface of the main body material wall, By monitoring the decrease in electrical resistance between the corrosion-resistant barrier material walls, or conversely, by monitoring the electrical resistance between the body material wall and the corrosion-resistant barrier material wall, the corrosion-resistant barrier of the corrosion-resistant barrier material wall due to the progress of corrosion, etc. Functional changes can be diagnosed.

  According to the tenth and thirteenth inventions, when the corrosion resistance barrier function of the corrosion resistant barrier material wall and the insulation function of the insulating material wall are lost, and the groundwater from the outside enters the surface of the main material wall, the main material wall and the corrosion resistance Considering the fact that the electrical resistance between the barrier material walls is reduced and the electrical resistance varies depending on the distance between the conducting portion and the body material wall connection part, the electrical resistance between two or more sets of the body material walls and the corrosion resistant barrier material wall By measuring, it is possible to know in which part (corrosion-resistant barrier function loss site) the person conducts without approaching the person.

  According to the invention of claim 12, when the main body material wall and the corrosion-resistant barrier material wall are conducted, the base body material wall becomes the positive electrode and the noble corrosion-resistant barrier material wall becomes the negative electrode, and the corrosion due to electrolytic corrosion proceeds. Considering this, by reducing the current flowing by applying a reverse potential from the DC power supply, the corrosion rate due to electrolytic corrosion can be reduced, and the life of the container can be improved.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a cross-sectional view showing the overall configuration of the radioactive waste disposal container, and FIG. 2 is an enlarged view of part A of FIG.

  As shown in FIG. 1, the radioactive waste disposal container 1 of the present embodiment is formed in, for example, a rectangular parallelepiped shape (vertically long rectangular tube shape), and a bottomed cylindrical body portion 3 for storing the radioactive waste 2, The lid 4 that closes the upper end opening of the body 3 is brought into close contact by welding or the like, so that the radioactive waste 2 can be accommodated in a completely sealed state.

  As shown in the enlarged cross-sectional shape in FIG. 2, the walls constituting the trunk portion 3 and the lid portion 4 include a main body material wall 5 constituting a main wall constituting a container skeleton, and an outer surface of the main body material wall 5. It is assembled between a corrosion resistant barrier material wall 6 that covers and protects from the external corrosive environment, and the main body material wall 5 and the anticorrosion barrier material wall 6. The main body material wall 5 and the anticorrosion barrier material wall 6 are electrically connected to each other. And an insulating material wall 7 for insulation.

  For the main body material wall 5, for example, stainless steel excellent in structural strength and radiation shielding performance is applied, and the corrosion resistant barrier material wall 6 on the outer surface of the main body material wall 5 exposed to the external environment such as underground water in the ground, For example, a Ti alloy having excellent corrosion resistance is applied. As a result, the entire surface of the stainless steel is shielded from the external environment.

A ceramic material having high electrical insulation, for example, Al ₂ O ₃ 6 is applied to the insulating material wall 7 between the main body material wall 5 made of stainless steel and the corrosion-resistant barrier material wall 6 made of Ti alloy. ing. Thereby, stainless steel and Ti alloy are electrically completely insulated.

  In the present embodiment, as shown in FIG. 1, the radioactive waste disposal container 1 has a rectangular tube shape. However, as long as it is composed of a trunk portion and a lid portion, various other shapes are possible. It can be. For example, a cylindrical or spherical container can be used.

FIG. 3 is a graph showing the results of measuring the electrical resistance with respect to the thickness of Al ₂ O ₃ constituting the insulating material wall 7 of the radioactive waste disposal container 1 described above. Here, the later-described wiring is applied to the stainless steel main body material wall 5 and the Ti alloy corrosion-resistant barrier material wall 6 disposed on both surfaces of the insulating material wall 7, and the electric resistance between the two is given. It is measured.

As shown in FIG. 3, it can be seen that as the Al ₂ O ₃ thickness constituting the insulating material wall 7 increases, the electrical resistance between the stainless steel and the Ti alloy increases and tends to approach a constant value. That is, since Al ₂ O ₃ has a large electric resistance, it is possible to electrically insulate the stainless steel and the Ti alloy by forming Al ₂ O ₃ between the stainless steel and the Ti alloy.

Here, if the electrical resistance of Al ₂ O ₃ is less than 10 ³ Ωm, the electrical insulation function is not sufficient. Therefore, the electrical resistance of Al ₂ O ₃ is desirably 10 ³ Ωm or more.

FIG. 4 shows a case where a part of the Ti alloy of the radioactive waste disposal container 1 is broken and water enters the surface of Al ₂ O ₃ (accelerated with acid), and is stainless steel with respect to the thickness of Al ₂ O _3. It is a graph which shows the result of having measured the corrosion weight loss.

As shown in FIG. 4, the corrosion weight loss of stainless steel depends on the Al ₂ O ₃ thickness, and it can be seen that the stainless steel hardly corrodes when the thickness is 0.1 mm or more. This, together with Al ₂ O ₃ is corrosion-resistant barrier can be said to be due to electrolytic corrosion reduction of stainless steel due to insulation effect of the Al ₂ O _3. Therefore, it is desirable that the thickness of the insulating material wall 7 is 0.1 mm or more.

  According to the radioactive waste disposal container 1 of the present embodiment, even when the corrosion-resistant barrier function of the corrosion-resistant barrier material wall 6 is lost, the boundary surface between the main material wall 5 and the corrosion-resistant barrier material wall 6 is directly outside by the insulating material wall 7. Since it is not exposed to the environment, rapid progress of corrosion of the main body material wall 5 due to electric corrosion can be prevented. Therefore, the radioactive waste disposal container 1 is excellent in the external environment shielding property, and the nuclide can be safely held in the container for a long period of time.

  In the present embodiment, the main body wall is made of stainless steel, which is an Fe-based alloy. However, the structural strength and the metal other than Fe or Fe-based alloy, such as Co or Co-based alloy, Ni or Ni-based alloy, etc. Various materials can be applied as long as they have a radiation shielding performance, are excellent in workability, and can form a framework of a container.

  In this embodiment, the corrosion-resistant barrier material wall 6 is a Ti alloy. However, the present invention is not limited to this, and a material having a smaller ionization tendency than the main body material wall 5, for example, Al, Zr, Mg, Be, Si, Ta, B It is also possible to apply Nb, Cr. These metals easily oxidize because of the low standard energy generated in oxides, and form a chemically stable oxide film on the surface, resulting in a reduction in the subsequent progress of oxidative corrosion. . In short, the corrosion-resistant barrier material wall 6 is mainly made of a material having a small standard energy of formation of oxide in at least one metal selected from Ti, Al, Zr, Mg, Be, Si, Ta, B, Nb and Cr. Various alloys can be applied as long as they are alloys. Further, as the corrosion-resistant barrier material wall 6, it is also possible to use a Zr alloy that has been refined and recycled from Zircaloy such as a BWR used channel box. If Zircaloy such as a used channel box is used, the amount of radioactive waste itself to be disposed of can be further reduced.

Furthermore, although the insulating material wall 7 is made of Al ₂ O ₃ in this embodiment, various applications can be applied as long as the specific resistance is a metal, organic material, or inorganic material having a resistivity of 10 ³ Ωm or more. Specifically, oxide ceramics such as BeO, CaO, MgO, SiO ₂ , TiO ₂ , ZrO ₂ , UO _2, or composite oxide ceramics containing these as main components can be applied.

  Next, with reference to FIG. 5 to FIG. 9, the radioactive waste disposal container, the container system, the degradation diagnosis method, and the life improvement method for diagnosing the soundness and improving the life of the radioactive waste disposal container 1 will be described. .

  FIG. 5 is a diagram showing the configuration of the radioactive waste disposal container 1 and the configuration of the radioactive waste disposal container system.

  As shown in FIG. 5, for example, three sets of electrical resistance data acquisition wirings 8 a, 8 b, and 8 c are arranged at different positions on the main body material wall 5 and the corrosion-resistant barrier material wall 6 of the radioactive waste disposal container 1. The following system configuration is incorporated in these wirings 8a, 8b, and 8c.

  The first system configuration includes three sets of electrical resistance measurement circuits 9a, 9b, and 9c for carrying out the deterioration diagnosis method. That is, each wiring 8a, 8b, 8c constitutes an individual closed circuit, and the electric resistance between the main body material wall 5 and the corrosion-resistant barrier material wall 6 of the radioactive waste disposal container 1 is measured in each closed circuit. The electrical resistance measuring devices 10a, 10b, and 10c and the switches 11a, 11b, and 11c for opening and closing the circuit are provided. Each of the electrical resistance measuring devices 10a, 10b, 10c and the switches 11a, 11b, 11c are driven by a command from the data acquisition / control computer 12. The switches 11a, 11b, and 11c are closed by the switch drive circuits 13a, 13b, and 13c based on a command from the data acquisition / control computer 12 when measuring the electrical resistance. By closing the switch, the electrical resistance measuring devices 10a, 10b, and 10c can be energized, and the electrical resistance between the main body material wall 5 and the corrosion-resistant barrier material wall 6 is measured. The measured electrical resistance value is input to the data acquisition / control computer 12 and recorded in the data recording device 14.

  The second system configuration includes three sets of DC power supply circuits 15a, 15b, and 15c for carrying out the lifetime improvement method. That is, DC power supplies 16a, 16b, 16c for supplying a DC current (weak current) to the body material wall 5 and the corrosion-resistant barrier material wall 6 in parallel with the electrical resistance measurement circuits 9a, 9b, 9c, and a circuit opening / closing switch 17a, 17b, and 17c are provided. Each DC power supply 16a, 16b, 16c and switches 17a, 17b, 17c are driven by commands from the data acquisition / control computer 12. The switches 17a, 17b, and 17c are closed by the switch drive circuits 13a, 13b, and 13c based on a command from the data acquisition / control computer 12 when a reverse current is supplied, which will be described later. At the same time, the power supply drive circuits 18a, 18b, 18c are started based on a command from the data acquisition / control computer 12, and a direct current is supplied from the DC power supplies 16a, 16b, 16c to the main body material wall 5 and the corrosion-resistant barrier material wall 6. The

  Thus, in this embodiment, three sets of wirings 8a, 8b, and 8c for acquiring electrical resistance data are provided, and the position where the resistance value is minimized is detected three-dimensionally from the difference in the obtained electrical resistance value. Can be done. Further, the configuration is simplified by adopting a configuration in which these wirings 8a, 8b, 8 also serve as a direct current supply wiring. It is also possible to separate the electrical resistance data acquisition wiring and the direct current supply wiring. These wirings can be implemented as one or more sets. In order to obtain the position specifying function, at least two sets of wirings may be provided.

  The data acquisition / control computer 12 according to this embodiment determines whether or not the corrosion resistance barrier function of the corrosion resistance barrier material wall 6 has been lost based on the measurement data obtained by the electrical resistance measurement devices 10a, 10b, and 10c. A loss determining means 19; and a loss position calculating means 20 for determining a corrosion-resistant barrier function loss position of the corrosion-resistant barrier material wall 6 in the radioactive waste disposal container 1 when it is determined that the corrosion-resistant barrier function of the corrosion-resistant barrier material wall 6 has been lost. Is provided. The electrical resistance measurement data measured by the electrical resistance measuring devices 10a, 10b, and 10c and the lost position data obtained by the lost position calculating means are recorded in the data recording device 14.

  In addition, the data acquisition / control computer 12 of the present embodiment uses the corrosion determination means 21 for determining whether or not the main body material wall 5 is corroded based on the recorded data, and the corrosion determination means 21. DC current supply command output means 22 for outputting a DC current supply command to the main body material wall 5 when it is determined that there is a possibility of corrosion. Based on the command of the DC current supply command output means 22, a DC current can be supplied to the main body material wall 5 from the DC power sources 16 a, 16 b and 16 c.

  And in the degradation diagnostic method of this embodiment, the change of the electrical resistance between each material which comprises the radioactive waste disposal container 1 is detected using said radioactive waste disposal container system, Based on the detection result Thus, the loss of the anticorrosion barrier function of the anticorrosion barrier material wall 6 is estimated.

  Moreover, in the lifetime improvement method of this embodiment, when the corrosion-resistant barrier function of the corrosion-resistant barrier material wall 6 is lost and the main body material wall 5 and the corrosion-resistant barrier material wall 6 are conducted, the above-mentioned radioactive waste disposal container system is used. Thus, by applying a reverse potential, corrosion of the main body material wall 5 is reduced.

  FIG. 6 is a flowchart showing a series of procedures for sequentially performing both the deterioration diagnosis method and the life improvement method of the present embodiment using the above system.

  As shown in FIG. 6, first, the switches 11a, 11b, and 11c of the electric resistance measuring circuits 9a, 9b, and 9c are closed, and the stainless steel of the radioactive waste disposal container 1 is made by the electric resistance measuring devices 10a, 10b, and 10c. The electrical resistance between the body material wall 5 and the outer Ti alloy corrosion-resistant barrier material wall 6 is measured, and the measurement signal is sent to the data acquisition / control computer 12 (S101).

  The data acquisition / control computer 12 is provided with a database 23 indicating the relationship between the electrical resistance and the change in the Ti alloy serving as a corrosion barrier, and the measured electrical resistance is always checked against the information in the database 23. The measured electrical resistance is recorded in the data recording device 14 (S102).

  Next, the corrosion determination means 21 determines whether or not the corrosion resistance barrier function has been lost due to loss of the corrosion resistance barrier material of the corrosion resistance barrier material wall 6 (S103). Here, the loss of the corrosion-resistant barrier function will be described with reference to FIG.

  FIG. 7 shows electrical resistance measuring apparatuses 10a, 10b, and 10c when the Ti alloy corrosion-resistant barrier material wall 6 is present on the outermost surface of the radioactive waste disposal container 1 (sound) and when it is not present (partially destroyed). This is a comparison of the difference in the measured values. From FIG. 7, it can be seen that the electrical resistance between the stainless steel and the Ti alloy varies depending on whether the outermost Ti alloy corrosion-resistant barrier material wall 6 is present (sound) or not (partially broken). This is because when a part of the Ti alloy corrosion-resistant barrier material wall 6 is broken, water reaches the surface of the stainless steel body material wall 5 and both are conducted through the water. From this, it is possible to know the soundness of the Ti alloy of the corrosion-resistant barrier material wall 6 by monitoring the electrical resistance between the stainless steel body material wall 5 and the Ti alloy-made corrosion-resistant barrier material wall 6.

  In such soundness judgment, when the corrosion-resistant barrier function is not lost (S103; NO), the electrical resistance measurement (S101) is repeated.

  On the other hand, when the corrosion-resistant barrier function is lost (S103; YES), the process proceeds to the loss position calculation by the loss position calculation means 20 (S104). Here, a specific example of loss position calculation, that is, a deterioration diagnosis method will be described with reference to FIGS.

  FIG. 8 shows the distance from the terminal attached to the main body material wall 5 or the corrosion-resistant barrier material wall 6 to the position where the corrosion-resistant barrier material wall 6 is broken when a part of the outermost corrosion-resistant barrier material wall 6 is broken. And the relationship between the electrical resistance between the stainless steel and the Ti alloy.

  From FIG. 8, the larger the distance from the terminal position attached to the stainless steel body material wall 5 or the Ti alloy corrosion-resistant barrier material wall 6 to the position where the Ti alloy corrosion-resistant barrier material wall 6 was destroyed, the larger the distance. It can be seen that the electrical resistance tends to increase linearly. That is, by measuring the electrical resistance, the distance from the terminal position attached to the stainless steel body material wall 5 or the Ti alloy corrosion-resistant barrier material wall 6 to the fracture position of the Ti alloy corrosion-resistant barrier material wall 6 is obtained. It is done.

  This is conducted at the portion where the Ti alloy corrosion-resistant barrier material wall 6 is broken and becomes a circuit through stainless steel or Ti alloy. However, the stainless steel body material wall 5 and the Ti alloy corrosion-resistant barrier material wall 6 are connected to each other. It can be said that the longer the distance between the attached terminal and the position where the Ti alloy corrosion-resistant barrier material wall 6 is destroyed, the longer the path between the stainless steel and the Ti alloy.

  FIG. 9 shows a method of identifying the position where the Ti alloy corrosion-resistant barrier material wall 6 is broken. As shown in FIG. 9, the distance corresponding to each electric resistance (R1, R2, R3) from the terminal positions of the wirings 8a, 8b, 8c described above (refer to the measurement units A, B, C in FIG. 5) is shown in FIG. When the circle is drawn with the calculated distance as the radius, it can be seen that the position of the intersection B where all the three circles intersect is the breaking point.

  Therefore, by measuring the electrical resistance, applying the fact that the distance from the stainless steel of the main body material wall 5 or the terminal attached to the Ti alloy of the corrosion resistant barrier material wall 6 to the location where the Ti alloy was destroyed is applied, the stainless steel Further, by measuring three or more sets of electrical resistances between the Ti alloys, the position where the Ti alloy is broken can be specified.

  As described above, in step (S104), when the resistance against the corrosion resistance of the Ti alloy is lost, the database 24 indicating the relationship between the electrical resistance and the distance provided in the data acquisition / control computer 12 is used. The position where the corrosion resistance barrier function of the Ti alloy is lost is calculated, and the result of calculating the lost position is recorded in the recording device, and the deterioration diagnosis is finished (S105).

  Next, as a step of the life enhancement method, it is determined whether there is a possibility of corrosion based on the recorded data (S106). Here, when the main body material wall 5 and the corrosion-resistant barrier material wall 6 are conducted, it is determined that there is a possibility of corrosion, and by applying a reverse potential to the main body material wall 5, the corrosion of the main body material wall 5 is reduced. FIG. 10 is a diagram comparing the corrosion weight loss between the case where the stainless steel and the Ti alloy are electrically connected because a part of the Ti alloy is broken, and the case where the current is canceled from the DC power source. .

  As shown in FIG. 10, in the radioactive waste disposal system, when a part of the Ti alloy is broken and the stainless steel and the Ti alloy are electrically connected, when left as it is (stainless steel is the positive electrode; Ti alloy is the negative electrode) Comparing with the corrosion weight loss when a current that cancels it from the DC power supply is flowed, the corrosion weight loss is greatly reduced when the current is supplied from the stainless steel side to the Ti alloy side by the DC power sources 16a, 16b, 16c. I understand that. That is, by supplying a reverse current from a Ti alloy having a small ionization tendency to a large stainless steel, the electrolytic corrosion of the stainless steel can be reduced.

  Therefore, in this embodiment, when it is determined that there is a possibility of corrosion (S106; YES), a reverse current is supplied to the main body material wall 5 (S107). That is, at the same time that the Ti alloy has lost electrical resistance, the switches 11a, 11b, and 11c to which the electrical resistance measuring devices 10a, 10b, and 10c are connected are turned off, and the switches 11a, 11b, and 16c to which the DC power supplies 16a, 16b, and 16c are connected. 11b and 11c are turned on.

  Then, in accordance with an instruction from the data acquisition / control computer 12, control is performed in which a weak current is supplied until the current from the DC power sources 16a, 16b, and 16c becomes 0 A or the Ti alloy becomes a positive electrode. Thus, corrosion of the main body material wall 5 is reduced by applying a reverse potential to the main body material wall 5.

  When it is determined that there is no possibility of corrosion (S106; NO, electrical resistance measurement (S101) is repeated.

According to the above embodiment, the structural strength and the radioactive blocking performance, which are necessary functions as the radioactive waste disposal container 1, are made of stainless steel, the corrosion resistance is made of a Ti alloy, and the insulation between them is insulated with Al ₂ O ₃ . Even when a part of the Ti alloy is broken, it is possible to prevent abrupt corrosion of stainless steel due to electrolytic corrosion or the like. As a result, durability and reliability as a radioactive waste disposal container are improved.

  In addition, by monitoring the electrical resistance between the stainless steel body material wall 5 inside the container and the Ti alloy corrosion-resistant barrier material wall 6 outside the container, it is possible to know whether the Ti alloy is damaged in the corrosion-resistant barrier material wall 6. Can do. With the diagnostic function, the soundness of the radioactive waste disposal container 1 can be evaluated without approaching a person.

  In addition, by utilizing the relationship between the electrical resistance and the distance between the terminals attached to the stainless steel body material wall 5 and the Ti alloy corrosion-resistant barrier material wall 6 and the Ti alloy destruction position, Three or more sets of electrical resistance between Ti alloys can be measured, and the location where the Ti alloy is broken can be identified three-dimensionally.

  Further, when the Ti alloy constituting the corrosion-resistant barrier material wall 6 is damaged, the electrolytic corrosion of the stainless steel can be reduced by flowing a reverse current from the Ti alloy having a small ionization tendency to the large stainless steel. In this way, it is possible to prevent sudden corrosion of stainless steel due to electric corrosion or the like, and it is possible to improve the durability and soundness of the radioactive waste disposal container 1 itself.

Sectional drawing which shows the whole structure of the radioactive waste disposal container by one Embodiment of this invention. The A section expanded sectional view of FIG. The characteristic view which shows the electrical resistance measurement result of the radioactive waste disposal container by one Embodiment of this invention. The characteristic view which shows the corrosion weight loss measurement result of the radioactive waste disposal container by one Embodiment of this invention. 1 is a schematic electric circuit diagram showing a configuration of a radioactive waste disposal container system according to an embodiment of the present invention. The flowchart which shows the procedure of the degradation diagnostic method and lifetime improvement method by one Embodiment of this invention. The characteristic view which compared the difference of the measured value by the electrical resistance measuring apparatus in one Embodiment of this invention. The characteristic view which shows the relationship between the distance of a destruction location and electrical resistance in one Embodiment of this invention. Explanatory drawing which shows the method of specifying Ti alloy fracture position in one Embodiment of this invention. Explanatory drawing which shows the corrosion weight loss by reverse current in one Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Radioactive waste disposal container 2 Radioactive waste 3 Body part 4 Lid part 5 Main body material wall 6 Corrosion-resistant barrier material wall 7 Insulation material wall 8a, 8b, 8c Wiring 9a, 9b, 9c Electric resistance measurement circuit 10a, 10b, 10c Electricity Resistance measuring devices 11a, 11b, 11c Circuit switch 12 Data acquisition / control computers 13a, 13b, 13c Switch drive circuit 14 Data recording devices 15a, 15b, 15c DC power supply circuits 16a, 16b, 16c DC power supplies 17a, 17b , 17c Switch 18a, 18b, 18c Power supply drive circuit 19 Corrosion-resistant barrier function loss determination means 20 Loss position calculation means 21 Corrosion determination means 22 DC current supply command output means 23, 24 Database

Claims (14)

Used in embedded disposal of radioactive waste from nuclear facilities, radioactive waste closed bottomed cylindrical body portion that houses the radiation waste and a lid portion for closing the upper end opening of the barrel portion A disposal container,
The wall constituting the trunk and lid of this radioactive waste disposal container is
A body material wall constituting a skeleton of a container containing the radioactive waste;
A corrosion-resistant barrier material wall to be protected from external corrosive environment to cover the external surface surface of the body material wall,
An insulating material wall is provided between the main body material wall and the anticorrosion barrier material wall constituting the trunk portion and the lid , and electrically insulates the main body material wall and the anticorrosion barrier material wall. A radioactive waste disposal container characterized by that. The radioactive waste disposal container according to claim 1, wherein the main body material wall is made of Fe or Fe-based alloy, Co or Co-based alloy, Ni or Ni-based alloy having structural strength and radiation shielding performance. The radioactive waste disposal container according to claim 1, wherein the corrosion-resistant barrier material wall is made of a material having a smaller ionization tendency than the main body material wall. The corrosion-resistant barrier material wall is composed mainly of a material having a small standard energy of formation of oxide in at least one metal selected from Ti, Al, Zr, Mg, Be, Si, Ta, B, Nb and Cr, or a main component thereof. The radioactive waste disposal container according to claim 1, which is made of an alloy. 2. The radioactive waste disposal container according to claim 1, wherein the insulating material wall is made of a metal, an organic material, or an inorganic material having a specific resistance of 103 Ωm or more. The radioactive material according to claim 5, wherein the inorganic material is one or more oxide ceramics selected from Al 2 O 3, BeO, CaO, MgO, SiO 2, TiO 2, ZrO 2, and UO 2, or a composite oxide ceramic containing them as a main component. Waste disposal container. The radioactive waste disposal container according to claim 5, wherein the insulating material wall has a thickness of 0.1 mm or more. The radioactive waste disposal container according to claim 1, further comprising one or more sets of wirings connected to the body material wall and the corrosion-resistant barrier material wall to form an electric circuit. A radioactive waste disposal container system using the radioactive waste disposal container according to claim 8, wherein the electrical resistance between the main material wall and the corrosion-resistant barrier material wall of the radioactive waste disposal container connected to the wiring is measured. An electrical resistance measuring device, a data recording device for recording electrical resistance measurement data measured by the electrical resistance measuring device, and a corrosion-resistant barrier function of the corrosion-resistant barrier material wall based on measurement data by the electrical resistance measuring device A radioactive waste disposal container system, comprising: a corrosion-resistant barrier function loss judging means for judging whether or not the water is lost. The radioactive waste disposal container system using the radioactive waste disposal container according to claim 8, comprising two or more sets of the wirings, the main material wall of the radioactive waste disposal container being connected to each wiring, and An electrical resistance measuring device for measuring electrical resistance between the corrosion resistant barrier material walls, and a corrosion resistant barrier for judging whether or not the corrosion resistant barrier function of the corrosion resistant barrier material wall is lost based on measurement data by the electrical resistance measuring device. A loss-of-function determining means; a loss position calculating means for determining a corrosion-resistant barrier function loss position of the corrosion-resistant barrier material wall in the radioactive waste disposal container when it is determined that the corrosion-resistant barrier function of the corrosion-resistant barrier material wall has been lost; Data for recording electrical resistance measurement data measured by the electrical resistance measurement device and lost position data obtained by the lost position calculation means. Radioactive waste disposal container system characterized by comprising a recording apparatus. 9. A radioactive waste disposal container system using the radioactive waste disposal container according to claim 8, comprising two or more sets of the wiring, wherein the main material wall and the corrosion resistance of the radioactive waste disposal container are connected to the wiring. An electrical resistance measuring device that measures electrical resistance between barrier material walls, and a corrosion resistant barrier function that determines whether or not the corrosion resistant barrier function of the corrosion resistant barrier material wall is lost based on measurement data obtained by the electrical resistance measuring device Loss determination means, loss position calculation means for obtaining a corrosion resistance barrier function loss position of the corrosion resistance barrier material wall in the radioactive waste disposal container when it is determined that the corrosion resistance barrier function of the corrosion resistance barrier material wall has been lost, and Data for recording electrical resistance measurement data measured by an electrical resistance measurement device and lost position data obtained by the lost position calculation means Recording apparatus, corrosion determination means for determining whether or not there is a possibility of corrosion on the main body material wall based on the data, and the main body material wall when the corrosion determination means determines that there is a possibility of corrosion DC current supply command output means for outputting a DC current supply command to the DC power supply, and a DC power supply for supplying DC current to the body material wall based on a command from the DC current supply command output means Radioactive waste disposal container system. The radioactive waste disposal container system according to claim 9 is used to detect a change in electrical resistance between the main body material wall and the corrosion-resistant barrier material wall, and based on the detection result, the corrosion-resistant barrier function of the corrosion-resistant barrier material wall. A method for diagnosing deterioration of a radioactive waste disposal container, characterized by estimating loss. The radioactive waste disposal container system according to claim 10 is used to detect a change in electrical resistance between the main body material wall and the corrosion-resistant barrier material wall at different positions of the radioactive waste disposal container, and for each of the detected values. A method for diagnosing deterioration of a radioactive waste disposal container, wherein a corrosion-resistant barrier function loss position of the corrosion-resistant barrier material wall is identified based on a difference. When the radioactive waste disposal container system according to claim 11 is used, when it is determined that the corrosion-resistant barrier function of the corrosion-resistant barrier material wall is lost and the main body material wall and the corrosion-resistant barrier material wall are conducted, A method for improving the lifetime of a radioactive waste disposal container, wherein corrosion of the main body material wall is reduced by applying a reverse potential between them.

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