JP5024628B2 - Manufacturing method of waste package - Google Patents

Description

  The present invention relates to a method of manufacturing a waste package, and in particular, surrounds a waste body including radioactive waste generated from nuclear power generation with a buffer made of a soil material such as bentonite, and covers the outside with a protective body. The present invention relates to a method of manufacturing a configured waste package.

  Conventionally, radioactive waste generated from nuclear power generation is mixed with molten glass to form solid waste to prevent environmental impact, and is buried in tunnels and other buried facilities via a buffer. (For example, refer to Patent Document 1).

  The buffer body is constructed by compacting a soil material formed by mixing, for example, bentonite and sand so as to have a predetermined elasticity and water impermeability. The shock absorber prevents the groundwater from coming into contact with the waste body, while the shock absorber is deformed according to the deformation of the tunnel due to the external force such as an earthquake, so that the external force applied to the waste body to be included is reduced. Function.

  When the waste body is buried in the buried facility through the buffer body, for example, in the factory, the soil material is compressed to form a disk-shaped buffer block and a hole corresponding to the outer diameter of the waste body in the center. A disk-shaped buffer block having a hole is formed, and then a disk-shaped buffer block is disposed inside the tunnel, and then a plurality of disk-shaped buffer blocks having a hole in the center are disposed inside the tunnel. Then, after the storage area for storing the waste body is formed by the hole, the disc-shaped buffer block is arranged inside the tunnel in such a manner as to close the storage area after the waste body is put in the storage area. (For example, refer to Patent Document 1).

  On the other hand, in a factory, a waste body, a disk-type buffer block constructed around the waste body, comprising a buffer block made of a bentonite-based soil material that has been compression-molded in advance, and a protective body that covers the buffer block A method for manufacturing a waste package is known (see, for example, Patent Documents 1 and 2).

  On the other hand, as another method for manufacturing such a waste package, for example, a method shown in FIG. 10A is known. In this method, as shown in FIG. 10-1, one of the semi-cylindrical containers obtained by dividing a cylindrical container as a protective body is divided horizontally, and a plurality of substantially semicircular disk-shaped buffers are placed in the container. Load the block. Next, a cylindrical waste body is fitted into a recess formed in the center by the loaded buffer block, and a plurality of substantially semicircular disk-shaped buffer blocks are placed thereon, and then the other semi-cylindrical container is mounted. By covering, a cylindrical waste package is manufactured. Further, as shown in FIG. 11A, a cylindrical waste package can be manufactured by a method in which a cylindrical container as a protective body is placed vertically and a waste body and a buffer block are loaded therein. .

  In addition, regarding the method or configuration for underground disposal of the radioactive waste described above, a cylindrical water-impervious layer (see, for example, Patent Documents 3 and 4) used for the disposal of radioactive waste, and the placement of a buffer material block A construction method (for example, see Patent Document 5) is known. Furthermore, a buffer compaction method constructed in a buried facility (for example, see Patent Document 6), a compaction method for making the density of the buffer uniform (see, for example, Patent Document 7), a clay-based poorly permeable material A compression molding method (for example, see Patent Document 8), a method for densifying a bentonite solid body (for example, see Patent Document 9), and a compaction method for bentonite solid body (for example, see Patent Document 10) are known. ing. Moreover, the method of using a bentonite slurry as a filler of an embedded waste is known (for example, refer patent document 11 and 12). Furthermore, a method of filling bentonite slurry containing ethanol in the ground is known (see, for example, Patent Documents 13, 14, and 15).

JP 2007-69112 A Japanese Patent Laid-Open No. 2007-232482 JP 2007-105634 A JP 2007-69111 A JP 2007-71656 A JP 2007-240153 A JP 2008-3033 A JP 2006-327092 A JP 2003-279589 A JP 2003-255087 A JP 2007-319732 A JP 2003-211113 A JP 2003-96763 A JP 2003-96450 A JP 2001-323453 A

  By the way, as shown in FIG. 10A or FIG. 11A, the conventional waste package manufacturing method described above creates a gap between the buffer block as the buffer and the inner surface of the protective container. In this case, there is a possibility that the shock absorber in the waste package may be damaged or the waste body may be displaced due to vibration or impact when the waste package is transported.

  This invention is made | formed in view of the said situation, and it aims at providing the manufacturing method of the waste body package which can make the clearance gap between a protection body and a buffer body small.

  In order to achieve the above object, a waste package manufacturing method according to claim 1 of the present invention includes a waste body, a buffer body provided around the waste body and made of a soil material, and the buffer body. A waste body package manufacturing method comprising a protective body covering the soil body, wherein the waste body is further compressed in advance around the waste body at the center of the protective body formed in a container shape. After a state in which the material is surrounded and installed in the protective body, at least one of a gap between the inner surface of the protective body and the soil material, or a gap between the soil material and the waste body It is characterized by filling with water.

  Further, the manufacturing method of the waste package according to claim 2 of the present invention is the gap between the inner surface of the protective body and the soil material or the soil material and the waste body according to claim 1 described above. Before or during filling of at least one of the gaps between the water, the protective body is in a vacuum or negative pressure state.

  According to the method for manufacturing a waste package according to claim 1 of the present invention, the volume of the injected water is reduced by being absorbed from the compression-molded unsaturated soil material that has been previously installed. On the other hand, the water absorbed by the pre-installed soil material is first spent to fill the gap of the soil material, and after being saturated with the pore water, the water-absorbing swelling clay contained in the soil material It expands by the volume equivalent to the water absorption expansion. As a result, the gap between the inner surface of the protective body and the previously installed soil material and between the soil material and the waste body is reduced. Therefore, it is possible to prevent rattling when the waste package is transported and placed in the buried facility, and to prevent the buffer body and waste body in the package from being damaged or misaligned.

  According to the method for manufacturing a waste package according to claim 2 of the present invention, the water to be injected is prevented from flowing by the air existing in the gap by putting the protective body in a vacuum or a negative pressure state. Without any problems, the entire gap in the protective body is quickly and reliably distributed. For this reason, the average density of the buffer in the protective body can be made faster and more uniform.

  Exemplary embodiments of a method for manufacturing a waste package according to the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1-1 is a schematic flowchart for the horizontal manufacturing method of the waste package manufacturing method according to the present invention, and FIG. 10-2 is a conceptual diagram of the waste package manufacturing method according to the horizontal manufacturing method. . FIG. 1-2 is a schematic flowchart in the case of the vertical manufacturing method, and FIG. 11-2 is a conceptual diagram of the manufacturing method by the vertical manufacturing method.

As shown in FIGS. 1-1 and 10-2, or FIGS. 1-2 and 11-2, the method of manufacturing a waste package according to the present invention is provided around the waste body 10 and the waste body 10. This is a method for manufacturing a waste package 100 including a buffer body 20 made of a soil material and a protective body 30 covering the buffer body 20. In the case of the horizontal type manufacturing method, the present invention, as shown in FIG. 1-1 and FIG. 10-2, is a shock absorber that has been compression-molded in advance in the lower half of the protective body 30 formed in a half-contained container shape. The soil material 22 as 20 is installed. Next, the waste body 10 is installed inside the soil material 22 installed in the protective body 30. Subsequently, the soil material 22 is installed in the upper half of the container-shaped protective body 30, and the upper half of the half-divided container-shaped protective body 30 is placed over the lower half of the half-shaped container-shaped protective body 30. Link. Thereafter, the gap between the inner surface of the protective body 30 and the soil material 22 is filled with water.
In the case of the latter vertical manufacturing method, as shown in FIGS. 1-2 and 11-2, first, a soil material as a buffer 20 is provided at the bottom of the vertically placed cylindrical container-shaped protective body 30. Next, the waste body 10 and the surrounding soil material 22 are installed. Subsequently, the gap between the inner surface of the protective body 30 and the soil material 22 and the gap between the waste body 10 and the soil material 22 are filled with water. Thereafter, the soil material 22 is installed in the upper part of the protective body 30, the gap is filled with water, and then the upper cover of the protective body 30 is installed and connected to manufacture the waste package 100.

  For example, after the molten glass and radioactive waste are mixed and injected into a cylindrical metal container (not shown) to form a columnar glass solidified body, the waste body 10 is formed into a cylindrical glass solidified body. It is configured in an overpack (not shown).

  The buffer body 20 is, for example, a bentonite-based soil material in which bentonite and sand are mixed, and has predetermined elasticity and water-imperviousness by compacting and compressing the soil material. As shown, it is composed of a plurality of semicircular annular blocks 22a and semicircular blocks 22b (buffer blocks). The discs configured by arranging the two semi-disc blocks 22b so as to face each other are arranged concentrically at both ends of the cylindrical waste body 10. An annulus constituted by two semicircular annular blocks 22 a arranged opposite to each other with the outer periphery of the waste body 10 interposed therebetween is disposed concentrically on the outer periphery of the waste body 10. By doing so, the cylindrical waste body 10 is accommodated in the substantially cylindrical buffer body 20 constituted by a plurality of blocks 22a and 22b.

  The protection body 30 is a cylindrical container that covers and protects the waste body 10 and the buffer body 20, as shown in FIG. 10-2, for example, iron that has rigidity and can block water from entering. It is composed of a metal material. The cylindrical container is composed of two half-cylindrical containers 30a and 30b divided in half by a plane passing through the central axis of the circle.

The operation and action of the above configuration will be described by taking the horizontal manufacturing method of FIG. 10-2 as an example.
As shown in FIG. 10-2, the semi-cylindrical container 30a is placed horizontally so that the central axis direction is horizontal. A plurality of semicircular annular blocks 22a and semicircular blocks 22b are installed in the semicylindrical container 30a. The cylindrical waste body 10 is fitted into a recess 26 formed substantially in the center by these blocks 22a and 22b. Next, a plurality of semi-annular blocks 22a and semi-disc blocks 22b are placed above them. By covering the semi-cylindrical container 30b on the upper side, a cylindrical waste package is manufactured.

  In this waste package, a gap 50 is formed between the buffer body 20 and the inner wall of the container 30. Therefore, as shown in FIG. 2, water is injected into the container 30 from the injection port 40 provided in the upper semi-cylindrical container 30b. As a result, the gap 50 between the inner wall of the container 30 and the buffer body 20 is filled with water. In this case, the volume of the unsaturated compressed soil material 22 as the buffer body 20 is increased by absorbing a part of water and expanding. On the other hand, since water is partially absorbed by the compressed soil material 22, the volume is reduced. As a result, the gap 50 between the buffer body 20 and the inner wall of the container 30 can be reduced. Therefore, it is possible to prevent rattling when the waste package 100 of the present invention manufactured in this way is transported and placed in an embedding facility, etc., and to prevent the buffer body 20 and the waste body 10 in the package 100 from being damaged or misaligned. can do. Further, the gap between the plurality of semi-annular blocks 22a and semi-disc blocks 22b juxtaposed in the lateral direction is filled with water, and the buffer body absorbs and expands, whereby this gap can also be reduced. Thereby, it is possible to prevent damage due to rattling between the blocks 22 at the time of conveyance or the like. The same applies to the vertical manufacturing method shown in FIG.

  In the above embodiment, before or during the step 3 of injecting water, as shown in FIG. 3, evacuation or negative pressure from the suction port 42 also serving as the exhaust port provided in the semi-cylindrical container 30b. Water may be injected into the container 30 while suctioning. By carrying out like this, water can be spread to every corner of the gap 50.

Next, a water injection model experiment conducted for verifying the effect of the present invention will be described with reference to the drawings and photographs.
FIG. 4 is a schematic perspective view of an experimental apparatus in which the simulated shock absorber 20 is disposed in the transparent simulated cylindrical container 30, and FIG. 5 is a photograph showing an experimental state of the experimental apparatus. As shown in FIG. 4 and FIG. 5, the experiment is to inject and fill water into the container 30 in a vacuumed state, and promote the expansion of the simulated buffer 20 by absorbing a part of the water. . Here, the simulated buffer used in the experiment was obtained by juxtaposing three disk-like blocks in the horizontal direction with a bentonite content of 100%, a dry density ρd = 1.85 Mg / m ³ , and a water saturation Sr = 100%. Used. The dimensions of the disk-shaped block are a diameter of 160 mm and a thickness of 80 mm, and the thickness of the three juxtaposed blocks is 240 mm.

  The dimensions of the simulated cylindrical container 30 are a diameter of 180 mm and a body length of 260 mm, and the cylinder is axially placed horizontally. A gap 50 having a maximum length of 20 mm is formed between the simulated cylindrical container 30 and the buffer body 20 above and on both sides of the container 30, respectively. A water inlet 40a is provided below the left end surface of the simulated cylindrical container 30, a water inlet 40b is provided at the upper end of the left end surface, and a vacuum suction port 42 that also serves as an exhaust port is provided at the upper end of the right end surface.

  FIG. 6A is a photograph showing a situation immediately after the start of water injection. As shown in FIGS. 6A and 4, the inside of the simulated cylindrical container 30 was evacuated through the suction port 42, and then water was sucked into the container 30 from the injection port 40 a and injected. It was observed that water was filled with vigor.

  FIG. 6B is a photograph showing the situation during water injection. As shown in FIG. 6B, the water immediately after filling temporarily generated bubbles due to the negative pressure, but it was observed that the gap was uniformly filled when the pressure was returned to atmospheric pressure.

  FIG.6 (c) is a photograph which shows the condition immediately after completion of water injection. As shown in FIG. 6C, the injected water almost fills the gap 50 although a slight gap is formed above the container.

  FIGS. 7A to 7C are photographs showing the appearance of the experimental apparatus after two weeks have passed since the end of water injection. FIG. 7A is a photograph of the horizontally placed simulated cylindrical container 30 taken from the upper side, (b) from the end face side, and (c) from the lower side.

  As shown in the photographs of FIGS. 7 (a) and 7 (b), the simulated buffer 20 absorbs a part of the injected water and has a volume expansion equivalent to the volume of the absorbed water. It can be seen that the gap 50 between 20 and the simulated cylindrical container 30 is reduced. Moreover, as shown in the photograph seen from the container lower side of FIG.7 (c), injection water is absorbed by the simulation buffer 20, and it turns out that the swollen range is almost solidified. Moreover, even if the container 30 is turned upside down, the simulated buffer body 20 in the container 30 does not move down, so it can be seen that the simulated buffer body 20 absorbs and swells water to such an extent that the movement is restricted.

FIG. 8 is a diagram illustrating an example of a dry density distribution in the simulated cylindrical container 30 after water injection. As shown in FIG. 8, the dry density was measured in the vicinity of the right end surface of the disk-like block on the injection port 40 side when two weeks passed after the injection. As shown in FIG. 8, a gap 50 of 20 mm was formed above the vertical axis before water injection. Then, it can be seen that the simulated buffer body 20 absorbs and expands by the water injection of the present invention, so that the simulated buffer body having a dry density of about 500 to 700 kg / m ³ is interposed in the gap 50 portion.

FIG. 9 is a diagram showing an example of the relationship between effective bentonite dry density and uniaxial compressive strength (reference: basic properties of calcium-type and calcium-type bentonite: swelling pressure, hydraulic conductivity, uniaxial compressive strength and elastic modulus), Power Reactor / Nuclear Fuel Development Corporation Tokai Office, March 1998). As shown in FIG. 9, the effective bentonite dry density and the uniaxial compressive strength are in the relationship of the following equation.
(Equation 1)
log ₁₀ qu = 1.731ρd−2.775

Here, qu is uniaxial compressive strength (MPa), and ρd is effective bentonite dry density (g / cm ³ ). Thereby, the uniaxial compressive strength of the dry density 500 kg / m ³ (0.5 g / cm ³ ) to 700 kg / m ³ (0.7 g / cm ³ ) in the gap 50 in FIG. 8 is 0.025 to 0.055 MPa. Estimated.

  As described above, the embodiment of the method for manufacturing the waste package according to the present invention has been described with the confirmation experiment of the effect by the model. According to the present invention, since the buffer body absorbs and expands by injecting water into the container-shaped protective body, at least one gap between the protective body wall and the buffer body or between the soil material and the waste body is reduced. can do. For this reason, it is possible to prevent rattling when the waste package is transported and placed in the burying facility, and to prevent the buffer body and waste body in the package from being damaged or misaligned.

It is a flowchart figure which shows an example of this invention, and is a figure in the case of a horizontal type manufacturing system. It is a flowchart figure which shows an example of this invention, and is a figure in the case of a vertical type manufacturing system. It is a schematic perspective view which shows an example of the water injection | pouring condition by this invention. It is a schematic perspective view which shows an example of evacuation or negative pressure suction by this invention. It is a conceptual diagram of the experimental apparatus which confirms the effect of this invention. It is a photograph which shows the experimental condition which confirms the effect of this invention. It is a photograph which shows the water injection condition in experiment. It is a photograph which shows the condition after the completion of water injection in the experiment. It is a dry density distribution map in the simulation cylindrical container in experiment. It is a related figure of effective bentonite dry density and uniaxial compressive strength. It is a conceptual diagram explaining the manufacturing method of the conventional waste body package, and is a figure in the case of a horizontal type manufacturing system. It is a conceptual diagram explaining the manufacturing method of the waste package incorporating the process of this invention, and is a figure in the case of a horizontal type manufacturing system. It is a conceptual diagram explaining the manufacturing method of the conventional waste body package, and is a figure in the case of a vertical manufacturing system. It is a conceptual diagram explaining the manufacturing method of the waste package incorporating the process of this invention, and is a figure in the case of a vertical manufacturing system.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Waste body 20 Buffer body 22 Soil material 30 Protective body 50 Crevice 100 Waste body package

Claims (2)

A waste body package manufacturing method comprising a waste body, a buffer body provided around the waste body, and made of a soil material, and a protective body covering the buffer body,
After the state in which the waste body is installed in the protective body so as to surround the waste body in the central part of the protective body formed in a container shape, and the soil material previously compressed and molded around the waste body. A method of manufacturing a waste package, comprising filling at least one of a gap between a body inner surface and the soil material or a gap between the soil material and the waste body.   At least one of the gap between the inner surface of the protective body and the soil material or the gap between the soil material and the waste body is filled with the water before or during filling with the water. 2. The method of manufacturing a waste package according to claim 1, wherein the vacuum is in a vacuum or negative pressure state.