JP2014089082A - Radiation shield lid for underground pit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radiation shield lid (hereinafter, referred to as a shield lid) for an underground pit which is easy to handle and readily detachable and attachable.SOLUTION: A shield lid 2 is used for an underground pit 1 of a radioactive waste 5 which is constituted of a recessed groove 11 for storing the radioactive waste 5 and a wall surface 12 for blocking both ends of the recessed groove 11. The shield lid 2 includes: a plate-like blocking part 21 for blocking an opening of the recessed groove 11; and a side surface 22 arranged on both ends of the blocking part. The side surface 22 is a surface which becomes an abutting face for the shield lids adjacent to each other when a plurality of shield lids 4 are laid so as to block the opening of the recessed groove 11. The problem is solved by a radioactive shield lid for the underground pit which is constituted by bowing or bending the side surface so as to become an uneven surface.

Description

The present invention relates to a radiation shielding lid used for underground pits for radioactive waste.

Substances that have become radioactive materials due to absorption of neutrons in the radiation control area or in the vicinity of the reactor core, or those that are contaminated with radioactive substances, are classified as low-level radioactive waste. Release.

Of the low-level radioactive waste, those that emit radiation at a level that affects the human body are buried in a depth corresponding to the radiation level and isolated from the living environment. For example, for waste with extremely low dose, a method called shallow trench disposal in which a shallow trench is dug in the soil and the waste is buried in the soil is used. For low-level used resin, etc., a method of embedding an artificial structure such as a concrete pit in a shallow area is adopted (shallow underground pit disposal).

For example, Patent Document 1 discloses a radioactive waste container and its lid. The container of Patent Document 1 seems to close the opening of the container with a single lid. If the opening of the container is closed with a single lid as in Patent Document 1, if the container is enlarged to increase the capacity of the container, the lid will also be enlarged and the weight will be excessive, reducing the work efficiency of removing and attaching the lid. However, the time for which the worker is exposed to radiation sometimes becomes long.

Japanese Patent Laid-Open No. 5-8217

An object of the present invention is to provide a radiation shielding lid for underground pits (hereinafter referred to as a shielding lid) that is easy to handle and can be easily attached and detached.

In order to reduce the weight of the long shielding lid and facilitate handling, a configuration in which the shielding lid is divided into a plurality of pieces and spread over the openings of the underground pits can be considered. However, simply laying a plurality of shielding lids creates a slight gap at the joint of the plurality of shielding lids, and there is a risk of radiation leaking out from there. Therefore, in the present invention, the side surface of the shielding lid is curved or bent to form an uneven surface. That is, the present invention is a shielding lid used for underground pits of radioactive waste comprising a concave groove for storing radioactive waste, and wall surfaces closing both ends of the concave groove, It comprises a plate-like cover that covers the opening of the groove and side surfaces disposed at both ends of the cover, and the side surface is adjacent when a plurality of shielding lids are laid so as to close the opening of the groove. A radiation shielding lid for underground buried pits, which is a surface serving as an abutting surface between matching shielding lids, and the side surfaces are curved or bent to form a concave and convex surface.

When a part of the side surface of one of the shielding lids is convex when the side surfaces are laid so as to close the openings of the concave grooves of the plurality of shielding lids, the corresponding part of the side surface of the other shielding lid is It is preferable to have a complementary shape that is concave. Thereby, the thickness necessary for shielding radiation can be ensured without forming a gap at the joint of the shielding lid.

The lid of the thickness needed to shield radiation and T _1, one of the radiation shielding lid and radiation incident from a gap of the other radiation shielding lid is formed when brought into contact is on the axis of the lid to pass It is preferable that the relationship of T ₁ ≦ T ₂ is established when the thickness is T ₂ . Thereby, also in the junction part of a shielding lid, the thickness required for shielding of a radiation is securable.

Both side surfaces of the cover portion are bilaterally inclined surfaces that are inclined with respect to the direction orthogonal to the lid, and it is preferable that the inclined surfaces be curved or bent to be uneven surfaces. In other words, since the shielding lid is trapezoidal by tilting the side of the shielding lid, a plurality of shielding lids are laid down so that the vertical direction of the shielding lid having such a shape is alternately reversed, thereby shielding at any place. The lid can be freely detached. At this time, the uneven surface obtained by curving or bending the left and right symmetrical inclined surface is configured to have a plurality of corners or arcs, and a side connecting one corner and the other corner or one arc It is preferable to configure the side connecting the other arc portion to be a depression angle. Since it is possible to correct the shift of the position of the shielding lid by making the side a depression angle, it is possible to improve workability when the shielding lid is spread in the concave groove of the pit.

Since the shielding lid of the present invention has a curved or bent side surface, the joint surface of the shielding lid becomes a complex surface when a plurality of sheets are laid so as to close the concave grooves of the pits. Since radiation always collides with complex surfaces, there is no risk of radiation leaking out of the pit through the gap of the shielding lid.

It is a perspective view which shows the operation | work which spreads the several radiation shielding cover of this invention on the ditch | groove of an underground pit. 1 is a perspective view of a radiation shielding lid of the present invention (Embodiment 1). FIG. It is a front view of the radiation shielding lid of the present invention (embodiment 1). FIG. 3 is a plan view of the radiation shielding lid of FIG. 2 (Embodiment 1). It is sectional drawing equivalent to the AA part of FIG. 1 which showed the procedure which installs the radiation shielding cover of Embodiment 1 on an underground pit. It is a front view of the radiation shielding lid | cover of this invention (Embodiment 2). FIG. 7 is a plan view of the radiation shielding lid of FIG. 6 (Embodiment 2). It is sectional drawing equivalent to the AA part of FIG. 1 which showed the state which installed the radiation shielding cover of Embodiment 2 on the underground pit. It is a front view of the radiation shielding lid | cover of this invention (Embodiment 3). FIG. 10 is a plan view of the radiation shielding lid of FIG. 9 (Embodiment 3). It is sectional drawing equivalent to the AA part of FIG. 1 which showed the state which installed the radiation shielding cover of Embodiment 3 on the underground pit. It is a front view of the radiation shielding lid | cover of this invention (Embodiment 4). FIG. 13 is a plan view of the radiation shielding lid of FIG. 12 (Embodiment 4). It is sectional drawing equivalent to the AA part of FIG. 1 which showed the state which installed the radiation shielding cover of Embodiment 4 on the underground pit. It is a front view of the radiation shielding lid | cover of this invention (Embodiment 5). FIG. 16 is a plan view of the radiation shielding lid of FIG. 15 (Embodiment 5). It is sectional drawing equivalent to the AA part of FIG. 1 which showed the procedure which installs the radiation shielding cover of Embodiment 5 on an underground pit. It is a front view of the radiation shielding lid | cover of this invention (Embodiment 6). FIG. 19 is a plan view of the radiation shielding lid of FIG. 18 (Embodiment 6). It is sectional drawing equivalent to the AA part of FIG. 1 which showed the state which installed the radiation shielding cover of Embodiment 6 on the underground pit. It is a front view of the radiation shielding lid | cover of this invention (Embodiment 7). FIG. 22 is a plan view of the radiation shielding lid of FIG. 21 (Embodiment 7). FIG. 22 is a bottom view of the radiation shielding lid of FIG. 21 (Embodiment 7). It is sectional drawing equivalent to the AA part of FIG. 1 which showed the state which installed the radiation shielding cover of Embodiment 7 on the underground pit. It is a front view of the radiation shielding lid | cover of this invention (Embodiment 8). FIG. 26 is a plan view of the radiation shielding lid of FIG. 25 (Embodiment 8). It is sectional drawing equivalent to the AA part of FIG. 1 which showed the state which installed the radiation shielding cover of Embodiment 8 on the underground pit. It is a front view of the radiation shielding lid | cover of this invention (Embodiment 9). FIG. 29 is a plan view of the radiation shielding lid of FIG. 28 (Embodiment 9). It is sectional drawing equivalent to the AA part of FIG. 1 which showed the state which installed the radiation shielding cover of Embodiment 9 on the underground pit. It is a front view of the radiation shielding lid | cover of this invention (Embodiment 10). FIG. 32 is a plan view of the radiation shielding lid of FIG. 31 (Embodiment 10). It is sectional drawing equivalent to the AA part of FIG. 1 which showed the state which installed the radiation shielding cover of Embodiment 10 on the underground pit. It is a front view of the radiation shielding lid | cover of this invention (Embodiment 11). FIG. 35 is a plan view of the radiation shielding lid of FIG. 34 (Embodiment 11). It is sectional drawing equivalent to the AA part of FIG. 1 which showed the state which installed the radiation shielding cover of Embodiment 11 on the underground pit. It is sectional drawing which showed the state which installed the radiation shielding cover comprised as a smooth surface which inclined the side surface on the underground pit. It is sectional drawing which showed the state which installed the radiation shielding cover of Embodiment 1 on the underground pit. It is an enlarged view of the area | region enclosed with the dashed-dotted line in FIG.

As shown in FIG. 1, the present invention is a radioactive waste underground pit 1 (hereinafter referred to as a pit) comprising a concave groove 11 for containing radioactive waste, and a wall surface 12 that closes both ends of the concave groove 11. A radiation shielding lid 2 (hereinafter referred to as a shielding lid). The depth at which the pit 1 is buried is not particularly limited, but the present invention can be suitably used as a pit for pit disposal in a shallow area that is buried at a relatively shallow depth and temporarily stores low-level radioactive waste. Since the shielding lid 2 of the present invention can be easily opened and closed, it can be easily taken in and out when transporting radioactive waste to the final disposal site. In the example of FIG. 1, the burying depth of the pit 1 is very shallow, and is such a depth that the shielding lid 2 is always exposed to the ground surface. In FIG. 1, in order to show the shape of the pit 1, the soil in front is removed.

The pit 1 in FIG. 1 includes a total of four grooves 11, but the number of grooves 11 is not particularly limited. Moreover, although the ditch | groove 11 is comprised by elongate, you may make the length of the ditch | groove 11 shorter, for example, may be square shape. However, the shielding lid 2 of the present invention is easy to remove, and as shown by the arrows in FIG. 1, it is easy to remove the shielding lid 2 freely at an arbitrary location. Therefore, it can be suitably used for the pit 1 having a plurality of elongated grooves 11.

The material of the pit 1 and the shielding lid 2 may be made of a material having sufficient strength and capable of shielding radiation emitted from the radioactive waste accommodated in the pit. An example of such a material is reinforced concrete. The forming method is not particularly limited, but the pit 1 may be formed by placing a formwork on the installation site and forming it on-site, and the shielding lid 2 of the present invention may be formed by precast at the factory.

When a part of the side surface 22 of one shielding lid 2 is convex, the shielding lid 2 of the present invention has a complementary shape in which a part of the side surface of the other shielding lid 2 is concave. That is, by making the shapes complementary, it is possible to prevent radiation from being formed in the joint portion of the shielding lid 2 and to shield radiation reliably. However, in actuality, a slight gap is inevitable at the contact portion of the shielding lid 4, and as shown schematically in FIG. 37, when the side surface 41 is a smooth surface, Incident radiation may leak out. For convenience of explanation, radiation is shown by arrows in FIG.

Therefore, in the present invention, the side surface 22 of the shielding lid 2 is configured to be curved or bent so as to be an uneven surface. If the side surface 22 is configured as a complicated surface in this way, the radiation incident from the gap inside the pit 1 always collides with the convex surface of the shielding lid 2 as shown in FIGS. 38 and 39. Here, one of the shielding cover 2 and the other of the thickness of the axis of the lid through which the radiation incident from the gap formed in the shield cover 2 is abutted and T _2, required to shield radiation It is preferable to design the thickness of the shielding lid 2 so that the relationship of T ₁ ≦ T ₂ is established when the thickness of the lid is T ₁ . T ₁ depends on the dose of radioactive waste 5 accommodated in the pit, but in the case of low-level radioactive waste, it is 300 mm to 800 mm. At this time, in order to increase the T ₂ value, a protrusion 24 may be provided on the edge of the shielding lid 2 as in Embodiment 7 described later.

Hereinafter, the shielding lid 2 of the present invention will be described with reference to the drawings for each embodiment. The shielding lid 2 of any embodiment is common in that it includes a plate-like cover portion 21 that covers the opening of the concave groove 11 of the pit 1 and side surfaces 22 that are arranged at both ends of the cover portion. In the following embodiments, the shape of the side surface 22 is different. In the first to seventh embodiments, both side surfaces 22 of the cover portion 21 are symmetrically inclined surfaces that are inclined with respect to the plane orthogonal direction of the lid, and the inclined surfaces are curved or bent to be uneven surfaces. On the other hand, in the eighth to eleventh embodiments, a vertical surface along the plane orthogonal direction of the lid is used, and the vertical surface is curved or bent to form an uneven surface.

[Embodiment 1]
As illustrated in FIGS. 2 to 5, the shielding lid 2 of the present embodiment has a shape in which a symmetrically inclined surface is bent in multiple stages. Specifically, it is a shape in which four corners having an angle of 90 ° are formed on the side surface 21. A side 23 connecting one corner to another adjacent corner is a depression angle (about −26 ° with respect to the plane of the cover 21 or a horizontal plane parallel to the bottom surface). Although the rear view, the bottom view, and the left and right side views are omitted, the shape of the shielding lid 2 of the present embodiment is a shape obtained by directly projecting the shape of the front view in the back direction.

[Embodiment 2]
As shown in FIGS. 6 to 8, the shielding lid 2 of the present embodiment has a shape in which a symmetrically inclined surface is bent in multiple stages. Specifically, the shape is such that three corners having an angle of 130 ° are formed on the side surface 21. A side 23 connecting one corner to another adjacent corner is parallel to the bottom surface or plane of the cover 21. Although the rear view, the bottom view, and the left and right side views are omitted, the shape of the shielding lid 2 of the present embodiment is a shape obtained by directly projecting the shape of the front view in the back direction.

[Embodiment 3]
As shown in FIGS. 9 to 11, the shielding lid 2 of the present embodiment has a shape in which a symmetric inclined surface is curved in multiple stages. Specifically, it is a wavy shape combining five convex arcs and concave arcs. Although the rear view, the bottom view, and the left and right side views are omitted, the shape of the shielding lid 2 of the present embodiment is a shape obtained by directly projecting the shape of the front view in the back direction.

[Embodiment 4]
As shown in FIGS. 12 to 14, the shielding lid 2 of the present embodiment has a shape in which a symmetrically inclined surface is curved in multiple stages. Specifically, it is an S-shape combining one convex arc and a concave arc. A side 23 connecting one arc and the other arc is parallel to the plane or bottom surface of the cover 21. Although the rear view, the bottom view, and the left and right side views are omitted, the shape of the shielding lid 2 of the present embodiment is a shape obtained by directly projecting the shape of the front view in the back direction.

[Embodiment 5]
As shown in FIGS. 15 to 17, the shielding lid 2 of the present embodiment has a shape in which a symmetrically inclined surface is curved in multiple stages. Specifically, it is an S-shape formed by combining one convex arc and a concave arc, and has a shape that is more curved than the curved surface of the fourth embodiment. The side 23 connecting one arc and the other arc has a depression angle (about −18 ° with respect to a horizontal plane parallel to the flat surface or the bottom surface of the cover portion 21). Although the rear view, the bottom view, and the left and right side views are omitted, the shape of the shielding lid 2 of the present embodiment is a shape obtained by directly projecting the shape of the front view in the back direction.

[Embodiment 6]
As shown in FIGS. 18 to 20, the shielding lid 2 of the present embodiment has a shape in which a symmetrically inclined surface is bent in multiple stages. Specifically, the shape is a combination of one convex trapezoid and a concave trapezoid. Although the rear view, the bottom view, and the left and right side views are omitted, the shape of the shielding lid 2 of the present embodiment is a shape obtained by directly projecting the shape of the front view in the back direction.

[Embodiment 7]
As shown in FIGS. 21 to 23, the shielding lid 2 of the present embodiment has a shape in which a symmetrically inclined surface is bent in multiple stages. The basic shape is the same as that of the sixth embodiment, but the protrusion 24 is provided on the edge of the shielding lid 2 to increase the thickness of the shielding lid 2. Although the rear view and the left and right side views are omitted, the shape of the shielding lid 2 of the present embodiment is a shape obtained by directly projecting the shape of the front view in the back direction. As shown in FIG. 23, the shielding lid 2 of this embodiment is used together with the shielding lid 2 according to the sixth embodiment. In other words, two shielding lids 2 according to the sixth embodiment are arranged in the middle with an interval in which one shielding lid 2 can be accommodated, and the shielding lid 2 according to the seventh embodiment which is vertically inverted is fitted into the space. To do.

[Embodiment 8]
As shown in FIGS. 25 to 27, the shielding lid 2 of the present embodiment has a shape in which a symmetrical vertical plane is curved in multiple stages. Specifically, it is an S-shape combining one convex arc and a concave arc. Although the rear view, the bottom view, and the left and right side views are omitted, the shape of the shielding lid 2 of the present embodiment is a shape obtained by directly projecting the shape of the front view in the back direction.

[Embodiment 9]
As shown in FIGS. 28 to 30, the shielding lid 2 of the present embodiment has a shape obtained by bending a bilaterally symmetric vertical surface in multiple stages. Specifically, it is a fractured shape in which four bent portions are formed. Although the rear view, the bottom view, and the left and right side views are omitted, the shape of the shielding lid 2 of the present embodiment is a shape obtained by directly projecting the shape of the front view in the back direction.

[Embodiment 10]
As shown in FIGS. 31 to 33, the shielding lid 2 of the present embodiment has a shape in which a symmetrical vertical plane is bent in multiple stages. Specifically, it is a fractured shape in which eight bent portions are formed. Although the rear view, the bottom view, and the left and right side views are omitted, the shape of the shielding lid 2 of the present embodiment is a shape obtained by directly projecting the shape of the front view in the back direction.

[Embodiment 11]
As shown in FIGS. 34 to 36, the shielding lid 2 of the present embodiment has a shape in which a symmetrical vertical plane is bent in multiple stages. Specifically, it has a zigzag shape in which nine bent portions are formed. Although the rear view, the bottom view, and the left and right side views are omitted, the shape of the shielding lid 2 of the present embodiment is a shape obtained by directly projecting the shape of the front view in the back direction.

In the shielding lid 2 of the first to seventh embodiments, the side surface 22 is a left-right symmetrical inclined surface, and the inclined surface is an uneven surface. In order to close the openings by installing a plurality of shielding lids 2 in the openings of the concave grooves 11 of the pit 1, it is shown in FIGS. 1, 5, 8, 11, 14, 17, 20, and 24. As described above, the shielding lid 2 is turned upside down so that the side surfaces are alternately in contact with each other. Since the side surface 22 of the shielding lid 2 of the first to seventh embodiments is a symmetrical slope, it is possible to remove the shielding lid 2 at an arbitrary position and put radioactive waste into and out of the pit 1 as shown in FIG. Is possible.

As described above, in Embodiment 1, the side 23 connecting one corner and the other corner is formed as a depression angle. Similarly, in the fifth embodiment, a side 23 connecting one arc and the other arc is formed as a depression angle. Therefore, as shown in FIG. 5 and FIG. 17, when installing a plurality of shielding lids 2, a set of three shielding lids 2 is set to a concave groove so that the shielding lids 2 are first crested left and right. 11 is installed. At this time, an interval is set so that one shielding cover 2 can be fitted in the middle. When the shielding lid 2 is fitted in the middle, the side 23 forms a depression, and the weight of the right and left shielding lids 2 acts toward the middle due to the weight of the middle shielding lid 2. It is possible to correct the positional deviation that occurs when installing 2. For this reason, the shielding lid | cover 2 of Embodiment 1 and 5 has favorable workability | operativity in the case of installation.

As described above, the projection lid 24 is arranged on the edge of the shielding lid 2 of the seventh embodiment. By providing the projection 24, the thickness (T ₂ ) of the lid on the axis line through which the radiation passes can be increased. Since the seventh embodiment increases only the thickness (T ₂ ) of the axial lid through which radiation passes, the weight of the shielding lid 2 can be reduced.

The shielding lid 2 according to the eighth to eleventh embodiments has a side surface 22 as a vertical surface, and the vertical surface is curved or bent to be an uneven surface. In order to install a plurality of shielding lids 2 in the openings of the concave grooves 11 of the pits 1 and close the openings, as shown in FIGS. 27, 30, 33 and 36, the side surfaces of the shielding lids 2 are not reversed. Will be arranged so that they abut. Since the side surface 22 of the shielding lid 2 of the eighth to eleventh embodiments has a vertical surface that is concave and convex, the convex surface and concave surface of the adjacent shielding lid 2 mesh with each other in a complementary manner. As in the first to seventh embodiments, the shielding lid 2 according to the eighth to eleventh embodiments cannot be removed at any location. Therefore, it can be suitably used when radioactive waste is not taken in and out from the pit 1.

What is necessary is just to change suitably the magnitude | size and thickness of the shielding lid | cover of this invention by the magnitude | size of the pit 1, or the dose of the radioactive substance to expropriate. For example, the shielding lids of Embodiments 1 to 11 have a thickness of 500 mm, a width of 2000 to 3000 mm, and a length of 4000 to 5000 mm. The depth of the concave groove 11 of the pit 1 is 3800 mm.

DESCRIPTION OF SYMBOLS 1 Underground pit 11 Concave groove 12 Wall surface 2 Radiation shielding lid 21 Cover part 22 Side surface 23 Side 24 Projection part 4 Shielding lid (comparison)
41 Side 5 Radioactive waste

Claims (5)

A radiation shielding lid used for underground pits for radioactive waste, comprising: a concave groove for storing radioactive waste; and a wall surface that closes both ends of the concave groove;
The radiation shielding lid is composed of a plate-like cover portion covering the opening of the concave groove, and side surfaces disposed at both ends of the cover portion,
The side surface is a surface that becomes a contact surface between adjacent radiation shielding lids when a plurality of radiation shielding lids are laid down so as to close the opening of the concave groove, and the side surfaces are curved or bent to be uneven. A radiation shielding lid for underground pits, characterized in that it is configured as: When a part of the side surface of one radiation shielding lid is convex when a plurality of radiation shielding lids are laid so as to close the opening of the concave groove, the side surface corresponds to the side surface of the other radiation shielding lid. The radiation shielding lid for underground buried pits according to claim 1, which has a complementary shape with a concave portion. Let T ₁ be the thickness of the lid necessary to shield radiation,
The thickness of the axis of the lid radiation incident from the gap through which is formed when brought into contact with one of the radiation shielding lid and the other radiation shielding lid when the T _2,
T ₁ ≦ T ₂
The radiation shielding lid for underground pits according to claim 2, wherein the relationship is established. The both side surfaces of the cover part are left and right symmetrical inclined surfaces inclined with respect to the plane orthogonal direction of the lid, and the inclined surfaces are curved or bent to be uneven surfaces. Radiation shielding lid for underground buried pit as described. An uneven surface obtained by bending or bending a symmetrical inclined surface has a plurality of corners or arcs, and a side connecting one corner and the other corner or one arc and the other arc. The radiation shielding lid for underground buried pits according to claim 4, wherein the connecting side is formed as a depression.

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