JP2018205110A - Pressure change suppressor and storage container - Google Patents

Abstract

To provide a pressure change suppressor capable of securely detecting abnormal pressure change in a space due to leakage of a gas, and a storage container using the same.SOLUTION: A pressure change suppressor 11 according to the present invention has: a container body 2 which contains a radioactive substance m; a primary lid 31 which closes an opening part of this container body 2; a secondary lid 32 which covers this primary lid 31; a space 6 formed between the primary lid 31 and secondary lid 32 and filled with a predetermined gas g; and a manometer 7 which measures the pressure in the space 6, the suppressor being arranged in the space 6 in a storage container 1 in which the space 6 is held under positive pressure with respect to the pressure in the container body 2, and also formed of a material having a smaller volume expansion rate than any of members 31, 32 and 2 surrounding the space 6.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a pressure change suppressing body and a storage container.

  Some of the spent nuclear fuel generated at nuclear power plants is stored for decades at intermediate storage facilities before being reprocessed. This storage method includes a wet type and a dry type. Particularly, a storage method using a metal storage container is implemented in Japan in that the amount of radioactive waste generated is small and maintenance is easy.

  A container that stores such a radioactive substance is required to prevent leakage of the stored radioactive substance to the outside for a long time for safety. In order to satisfy this requirement, for example, a double-structure lid is provided in the storage container, and a positive pressure gas is sealed in a space formed between the double-structure lids to monitor the temperature and pressure of the gas. Thus, a technique for detecting abnormalities in storage of radioactive substances has been proposed (see, for example, Patent Document 1).

  According to this technique, the temperature and pressure of the gas sealed in the space can be measured to eliminate the influence of the gas pressure change caused by the temperature change. Therefore, by monitoring the temperature and pressure, Abnormal gas leakage can be detected.

JP 2004-264162 A

  However, in the conventional technology as described above, it is necessary to provide a temperature sensor for measuring the temperature together with a pressure sensor for measuring the pressure of the gas. Risk may also increase.

  The present invention has been made based on the circumstances as described above, and an object of the present invention is to reliably detect an abnormal pressure change in a space due to gas leakage by being arranged in a storage container. An object of the present invention is to provide a pressure change suppressing body and a storage container using the same.

The present invention
(1) A container body that stores radioactive substances, a primary lid that closes the opening of the container body, a secondary lid that covers the primary lid, and a predetermined lid formed between the primary lid and the secondary lid. And a space in the storage container in which the pressure in the space is maintained at a positive pressure relative to the pressure in the container body. A suppressor disposed within the body,
A pressure change suppressor characterized by being formed of a material having a volume expansion coefficient smaller than the volume expansion coefficient of any member surrounding the space;
(2) The pressure change suppressor according to (1), which is formed of an iron nickel alloy and / or an iron nickel cobalt alloy,
(3) The pressure change suppressor according to (1) or (2), wherein a concave portion having a predetermined volume is provided on a surface exposed to the space,
(4) a container body for storing a radioactive substance;
A primary lid for closing the opening of the container body;
A secondary lid covering the primary lid;
A space formed between the primary lid and the secondary lid and filled with a predetermined gas;
A pressure gauge for measuring the pressure in the space;
A storage container comprising the pressure change suppressing body according to any one of (1) to (3) disposed in the space;
(5) The storage container according to (4), wherein the pressure change suppressing body can be inserted into and removed from the space, and (6) the pressure change suppressing body can be fixed within the space (4) or (5). It relates to the storage container described in 1.

  The present invention can provide a pressure change suppressing body capable of reliably detecting an abnormal pressure change in a space caused by gas leakage by being arranged in a storage container, and a storage container using the same. .

It is a schematic perspective view which shows the pressure change suppression body of the 1st Embodiment of this invention. It is a schematic perspective view which shows the other form of FIG. It is the schematic for demonstrating the effect | action of the pressure change suppressing body of this invention, (a) has shown the effect | action in the conventional storage container, (b) has each shown the effect | action in the storage container of this invention. It is a schematic longitudinal cross-sectional view of the storage container which shows the 2nd Embodiment of this invention. It is a schematic longitudinal cross-sectional view which expands and shows a part of FIG. It is a schematic perspective view which shows the further another form of FIG.

  Hereinafter, the first and second embodiments of the present invention will be described with reference to the drawings. However, the present invention is not limited to the embodiments described in the drawings.

<Pressure change suppressor>
The pressure change suppressing body of the present invention includes a container main body that stores a radioactive substance, a primary lid that closes an opening of the container main body, a secondary lid that covers the primary lid, the primary lid, and the secondary lid, A space filled with a predetermined gas and a pressure gauge for measuring the pressure in the space, and the pressure in the space is maintained at a positive pressure relative to the pressure in the container body. It is a suppressing body disposed in the space in the storage container, and is formed of a material having a volume expansion coefficient smaller than that of any member surrounding the space.

[First Embodiment]
FIG. 1 is a schematic perspective view showing a pressure change suppressing body according to a first embodiment of the present invention. The said pressure change suppression body 11 is arrange | positioned at the storage container 1 etc. which are shown, for example in FIG.

  Here, first, the storage container 1 in which the pressure change suppressing body 11 is used will be described. For example, as shown in FIG. 4, the storage container 1 is roughly configured by a container body 2, a primary lid 31, a secondary lid 32, a space 6, and a pressure gauge 7.

  The container body 2 is used for a certain period of time at a nuclear power plant, for example, and stores a radioactive material m such as a nuclear fuel rod taken out from a reactor pressure vessel. The container main body 2 is a bottomed cylindrical main body as shown in FIG. 4, for example, and includes a main body barrel 21 and a bottom plate 22. In addition, although the pressure in the container main body 2 is about 0.08 MPa normally, as long as the pressure in the space 6 mentioned later is hold | maintained at the positive pressure with respect to the pressure in the container main body 2, it does not specifically limit. Examples of the material constituting the main body barrel 21 and the bottom plate 22 include carbon steel and stainless steel.

  The primary lid 31 closes the opening of the container body 2. Specifically, the primary lid 31 closes the container body 2 via the metal packing 4, and the primary lid 31 and the container body 2 are fastened by bolts 5 as shown in FIG. As a material constituting the primary lid 31, for example, a material similar to the material constituting the main body barrel 21 and the bottom plate 22 described above can be employed.

  Here, in order to suppress leakage of γ rays and neutron rays radiated from the radioactive substance m to the main body barrel 21, the bottom plate 22, and the primary lid 31, for example, polyethylene, polypropylene, etc. A shielding material 8 such as resin is enclosed.

  The secondary lid 32 covers the primary lid 31. Specifically, the secondary lid 32 closes a space 6 to be described later via the metal packing 4, and the secondary lid 32 and the body body 21 of the container body 2 are fastened by the bolt 5. As a material constituting the secondary lid 32, for example, a material similar to the material constituting the main body barrel 21 and the bottom plate 22 described above can be employed.

  The space 6 is formed between the primary lid 31 and the secondary lid 32, and is surrounded by the primary lid 31, the secondary lid 32, and the body trunk 21 of the container body 2. The space 6 is filled with a predetermined gas g, and the pressure in the space 6 is maintained at a positive pressure relative to the pressure in the container body 2a.

  Examples of the predetermined gas g include helium gas. The pressure in the space 6 is normally set to about 0.4 MPa, but is not particularly limited as long as the pressure in the space 6 is maintained at a positive pressure with respect to the pressure in the container body 2 described later.

  It should be noted that the rate of change in volume of the space filled with the gas with respect to the change in the ambient temperature (the region excluding the region occupied by the pressure change suppressing body 11 in the space 6) can be increased, and the gas g from the metal packing 4 From the viewpoint of improving the sensitivity of the pressure change accompanying the leakage of the above, it is preferable that the volume is smaller. On the other hand, if the volume is small, the frequency of replenishing the gas g increases. For this reason, it is preferable to determine the volume and the size of the pressure change suppressing body 11 associated therewith in consideration of the change rate and sensitivity of the volume and the replenishment frequency of the gas g. The replenishment of the gas g is performed in the space 6 due to movement (leakage) of a very small amount of gas g from the space 6 through the metal packing 4 generated during normal storage to the container body 2a and the atmosphere. This is an operation performed to compensate for the decrease in gas g. It is realistic if the frequency of this gas replenishment operation is about 3 to 4 months.

  The pressure gauge 7 measures the pressure in the space 6. The pressure gauge 7 is provided to monitor abnormal leakage of the gas g from the space 6 while the radioactive substance m is stored in the storage container 1. The pressure gauge 7 is not particularly limited as long as the pressure of the predetermined gas g can be accurately measured. For example, a mechanical pressure gauge such as a Bourdon tube gauge or a diaphragm barometer can be employed.

  Next, the pressure change suppressing body 11 will be described. The pressure change suppressing body 11 is disposed in the space 6 in the storage container 1. The pressure change suppressing body 11 is formed of a material having a volume expansion coefficient smaller than that of any member surrounding the space 6.

  The material for forming the pressure change suppressing body 11 is not particularly limited as long as it has the above volume expansion coefficient. For example, a metal material, a ceramic material, or the like can be adopted.

  Among these, as a material for forming the pressure change suppressing body 11, an iron nickel alloy, an iron nickel cobalt alloy, and a ceramic are preferable, and an iron-nickel alloy and an iron-nickel-cobalt alloy are more preferable. Examples of the iron-nickel alloy include Invar (36Ni-Fe). Examples of the iron-nickel-cobalt alloy include super invar (32Ni-5Co-Fe), kovar (29Ni-17Co-Fe), and the like. In addition, you may use the said material in combination of 2 or more types.

  In this way, by forming the pressure change suppressing body 11 with the above material, it is possible to suppress a change in volume expansion with respect to the temperature of the pressure change suppressing body 11, and an abnormality in the space 6 due to leakage of the gas g. It is possible to detect a change in pressure more reliably. Moreover, by forming with these materials, it is possible to expect an improvement in the shielding ability of γ rays and neutron rays, an improvement in the strength of the pressure change suppressor 11 and an improvement in the cooling ability of the radioactive substance m.

  The shape of the pressure change suppressing body 11 is not particularly limited as long as the volume filled with the gas g in the space 6 can be defined within a predetermined range. For example, the pressure change suppressing body 11 has a disk shape as shown in FIG. However, it is preferable that the concave portion 120 having a predetermined volume is provided on the surface exposed to the space 6. As the recess 120, for example, a notch 121, a hole 122, or a combination thereof can be adopted as in the pressure change suppressing body 12 shown in FIG. 2.

  Thus, by making the said pressure change suppression body 11 into the said shape, the volume in the space 6 with which the gas g is filled can be adjusted appropriately, and the temperature of the gas g with which the said space 6 was filled The pressure change with respect to can be adjusted.

  Here, the operation and effect of the pressure change suppressing body 11 will be described. The pressure of the gas g enclosed in the space 6 is (1) pressure change due to temperature change of the gas g, and (2) container body 2, primary lid 31 and The pressure changes due to two factors, the pressure change due to the volume change of the space accompanying the temperature change of the secondary lid 32.

  For example, when the ambient temperature of the storage container 1 is increased, the pressure of the gas g is increased due to the above factor (1) and decreased due to the increase in volume due to the above factor (2). ) And (2) cause pressure changes to cancel each other. Since the action due to the factor (2) is smaller than the action due to the factor (1), the gas pressure increases as the temperature rises in a conventional storage container that does not include the pressure change suppressing body 11 (FIG. 3 (a)). However, in the storage container 1 provided with the pressure change suppressing body 11, since the volume expansion coefficient of the pressure change suppressing body 11 is small, the volume change in the region filled with the gas g in the space 6 due to the increase in the ambient temperature is further increased. Can be increased ((V4 / V3)> (V2 / V1): V1 to V4 are the volumes of the region 6 filled with the gas g in the space 6, and V1 is a conventional storage container before the temperature rises. The volume, V2 is the volume of the conventional storage container after the temperature rise, V3 is the volume of the storage container 1 before the temperature rise, and V4 is the volume of the storage container 1 after the temperature rise). The change in pressure can be further reduced by increasing the action (see FIG. 3B). As a result, in the storage container 1 including the pressure change suppressing body 11, the pressure change suppressing body 11 has an effect of reducing (or eliminating) the pressure change of the gas g accompanying the change in the ambient temperature.

  In this way, the pressure change suppressing body 11 has a volume expansion coefficient smaller than the volume expansion coefficient of any member (in this embodiment, the primary lid 31, the secondary lid 32, and the container body 2) that surrounds the space 6. Since it is formed with the material which has, the abnormal pressure change in the space 6 resulting from the leakage of the gas g can be detected reliably.

<Storage container>
The storage container of the present invention includes a container main body for storing a radioactive substance, a primary lid for closing the opening of the container main body, a secondary lid for covering the primary lid, and the primary lid and the secondary lid. A space filled with a predetermined gas, a pressure gauge for measuring the pressure in the space, and the pressure change suppressing body pressure change suppressing body disposed in the space.

[Second Embodiment]
FIG. 4 is a schematic longitudinal sectional view of a storage container showing a second embodiment of the present invention. FIG. 5 is a schematic longitudinal sectional view showing a part of FIG. 4 in an enlarged manner. As shown in FIGS. 4 and 5, the storage container 1 schematically includes a container body 2, a primary lid 31, a secondary lid 32, a space 6, a pressure gauge 7, and a pressure change suppressing body 11. It is comprised by.

  In the storage container 1, the container body 2 stores the radioactive substance m. The primary lid 31 closes the opening of the container body 2. The secondary lid 32 covers the primary lid 31. The space 6 is formed between the primary lid 31 and the secondary lid 32 and filled with a predetermined gas g. The pressure gauge 7 measures the pressure in the space 6. The pressure change suppressing body 11 is disposed in the space 6.

  The configurations of the container body 2, the primary lid 31, the secondary lid 32, the space 6, the pressure gauge 7, and the pressure change suppression body 11 in the present embodiment are the same as those described above in the section <Pressure change suppression body>. Therefore, the same parts are denoted by the same reference numerals, and detailed description thereof is omitted.

  Here, the storage container 1 is preferably such that the pressure change suppressing body 11 can be inserted into and removed from the space. The attachment / detachment mechanism for the pressure change suppressing body 11 in the space 6 is not particularly limited, and for example, an attachment / detachment mechanism using a hook or the like can be employed. Thereby, for example, when the radioactive substance m is stored (immediately before storage in the intermediate storage facility, etc.), the pressure change suppressing body 11 can be disposed in the space 6, and the storage container 1 can be handled until the storage. It can be done easily.

  Further, the storage container 1 is preferably such that the pressure change suppressing body 11 can be fixed in the space 6. The mechanism for fixing the pressure change suppressing body 11 in the space 6 is not particularly limited. For example, at least a part of the outer periphery of the pressure change suppressing body 11 is contacted with the inner wall of at least one member surrounding the space 6. The pressure change suppressing body 11 may be fixed by using a fixing member (not shown) such as a bolt or a hook. Thereby, the collision with the members (for example, the primary lid 31, the secondary lid 32, the container main body 2 etc.) surrounding the space 6 can be prevented, and the damage to the members and the pressure change suppressing body 11 can be prevented. be able to.

  Thus, the said storage container 1 can detect reliably the abnormal pressure change in the space 6 resulting from the leakage of gas g because it is the said structure.

  In addition, this invention is not limited to the structure of embodiment mentioned above, is shown by the claim, and intends that all the changes within the meaning and range equivalent to a claim are included. Is done.

  For example, in the above-described embodiment, the disk-shaped pressure change suppressing body 11 and the pressure change suppressing body 12 having the notch 121 and the hole 122 have been described, but the volume in the space 6 filled with the gas g is adjusted. As shown in FIG. 6, for example, as shown in FIG. 6, the pressure change suppressing body 13 having a protrusion 123 that fills the gap between the bolts 5 that fix the primary lid 31 and the container body 2, and a storage container ( (Not shown).

m Radioactive substance 11, 12, 13 Pressure change suppressor 1 Storage container 2 Container body 31 Primary lid 32 Secondary lid 6 Space 7 Pressure gauge

Claims (6)

A container body that stores radioactive substances, a primary lid that closes the opening of the container body, a secondary lid that covers the primary lid, and a predetermined gas formed between the primary lid and the secondary lid. It has a filled space and a pressure gauge for measuring the pressure in the space, and is disposed in the space in the storage container in which the pressure in the space is held at a positive pressure relative to the pressure in the container body. A suppressed body,
A pressure change suppressing body characterized in that it is formed of a material having a volume expansion coefficient smaller than that of any member surrounding the space.   The pressure change suppressing body according to claim 1, wherein the pressure change suppressing body is formed of an iron nickel alloy and / or an iron nickel cobalt alloy.   The pressure change suppression body according to claim 1 or 2, wherein a concave portion having a predetermined volume is provided on a surface exposed to the space. A container body for storing radioactive substances;
A primary lid for closing the opening of the container body;
A secondary lid covering the primary lid;
A space formed between the primary lid and the secondary lid and filled with a predetermined gas;
A pressure gauge for measuring the pressure in the space;
The storage container provided with the pressure change suppression body of any one of Claims 1-3 arrange | positioned in the said space.   The storage container according to claim 4, wherein the pressure change suppressing body can be inserted into and removed from the space.   The storage container according to claim 4 or 5, wherein the pressure change suppressing body can be fixed in the space.

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