JPH073478B2 - Underground structure for storage and disposal of radioactive waste - Google Patents

Description

TECHNICAL FIELD The present invention relates to an underground structure for storing and disposing of radioactive waste, particularly relatively high level radioactive waste.

<Prior art> For radioactive waste generated by the operation of nuclear reactors,
There are gaseous ones, liquid ones and solid ones.
Of these, the radioactive waste in the gaseous form is volatile,
Some include floating particles, and these floating particles are mainly removed by a high-performance filter having high removal efficiency. For volatile substances, a method of removing them with an activated carbon filter or holding them in an activated carbon holdup device is used. Liquid wastes are mainly treated with ion exchange resins and evaporative concentrators, except for those with high viscosity such as sludge. Solid waste includes used resin, used control rods, etc., contaminated machinery, radioactive protection clothing, etc. These are usually stored for a certain period of time in the same manner as sludge to reduce the radioactivity. After that, it is solidified with cement or asphalt and stored in a predetermined storage facility, and the level of waste that does not exceed the concentration upper limit value based on the Nuclear Reactor Regulation Law is finally stored in the concrete pit that is installed underground. It is buried. In addition, the high-level radioactive waste generated from the reprocessing of spent fuel is made into ceramics, vitrified with borosilicate glass, stored in an enclosure such as a canister, and dumped in the deep sea provided with predetermined conditions, An underground storage / disposal room is formed in a stratum mainly composed of rock layers such as granite layers, and is stored inside. When storing radioactive waste in the underground storage / disposal room in this way, the storage site should be constructed in consideration of the nature of the surrounding rock mass, the stability of the surrounding strata, and the hydraulic suitability of groundwater. It will be selected. This underground storage / disposal room has a depth of at least a few hundred meters from the ground surface and a large area (for example, a width of 100 m x length of 1000 m), mainly for safety and economic reasons. Should be formed as.

By the way, a so-called engineering barrier such as a solidified body obtained by ceramicizing or vitrifying as described above or a canister containing the solidified body can sufficiently prevent migration of radionuclides to the surrounding strata. However, it is conceivable that radionuclides will leak out over the years. In this case, the released nuclide begins to move by the groundwater flow,
After being delayed by adsorption and desorption reactions with surrounding rocks,
Reach living areas such as rivers and lakes. In addition to these factors, mineralization and precipitation are factors that cause the transfer of nuclides. However, considering that groundwater is a useful water resource and is likely to be used for various purposes, it is desirable not to transfer nuclides in radioactive waste to groundwater as much as possible.

Conventionally, a storage / disposal room is excavated in the ground in this way, and a lining is formed by spraying concrete or the like on the surrounding wall of the storage / disposal room, or it is backfilled with an appropriate material to sufficiently close the space. However, the infiltration of groundwater into the storage / disposal room was prevented by providing a water collection unit around or inside the storage / disposal room to change the groundwater level. When storing for several hundred years or more, groundwater is gradually stored, but
Since it penetrates into the disposal room, a sufficient water-blocking effect could not be expected for a long time.

In the patent application (1) filed on the same day, instead of backfilling with a backfilling material, the present applicant filled the non-hydrophilic liquid with a lower specific gravity than groundwater such as crude oil and filled the groundwater that entered the storage / disposal room with a specific gravity difference. We proposed to collect and remove water by this method, but in addition to the water-blocking effect of this non-hydrophilic liquid, the adsorption effect of radionuclides on rocks isolated from the surrounding rock formations is also utilized, It is desirable to more completely prevent contact between groundwater and solidified bodies.

<Problems to be Solved by the Invention> As described above, the present invention is directed to the surrounding geological formation (mainly when the solidified body of radioactive waste or its enclosure is stored in the storage / disposal room for a long period of time. The groundwater from the rock layer) does not contact the solidified body or its enclosure to prevent radioactive contamination of the groundwater and the corrosion of the solidified body or its enclosure to groundwater. It aims to provide an underground structure for the storage and disposal of goods.

It is also an object of the present invention to provide an underground structure for storing and disposing of radioactive waste, capable of storing and disposing of a large amount of radioactive waste at one time.

It is also an object of the present invention to provide an underground structure for the storage and disposal of radioactive waste, in which the isolation between the radioactive waste nuclide and the biosphere is performed as completely as possible.

<Means for Solving the Problems> For these purposes, according to the present invention, a storage / disposal chamber for a solidified body of radioactive waste formed under the water table of a formation by excavation or a sealed container thereof, Ground that is isolated from the surrounding strata surrounding the storage / disposal chamber, a loading / unloading passage that connects the storage / disposal chamber to the ground surface through the soil, and the loading / unloading passage and the ground are concentric. For storing and disposing of radioactive waste, which has a storage space that encloses a non-hydrophilic liquid that is surrounded in a circle and stores the non-hydrophilic liquid, and a support means that supports the lower surface of the ground from the bottom surface of the storage space. An underground structure is provided.

Similarly, according to the present invention, two or more storage / disposal chambers for solidified wastes of radioactive wastes or their enclosures formed under the water table of the formation by excavation and surrounding each of the storage / disposal chambers. The ground that is isolated from the surrounding strata,
A common loading / unloading passage for communicating the storage / disposal chamber with the ground surface, a storage space for storing the non-hydrophilic aqueous solution formed around the ground in each storage / disposal chamber, and each of the storage A common supply passage for the non-hydrophilic liquid that communicates the space with the ground surface, a groundwater pit formed so as to communicate with the storage space, and the lower surface of each ground to float from the bottom surface of the storage space. An underground structure for storage and disposal of radioactive waste having a supporting means for supporting is also provided.

<Operation> According to the configuration of the present invention, groundwater from the surrounding strata first comes into contact with the non-hydrophilic liquid and is collected in the lowest pit of the underground structure due to the difference in specific gravity, and permeates the non-hydrophilic liquid. Groundwater is delayed by the ground that is isolated from the surrounding strata, so it eventually loses contact with the solidified bodies in the storage / disposal chamber, and the contact between the nuclide in the radioactive waste and the biosphere through groundwater. Is effectively prevented.

<Example> Next, the example shown in the drawings will be described in more detail.

In FIG. 1, 10 is a storage / disposal chamber formed below the water table 9 by excavation from the ground surface 11, and 3 is the surrounding geological formation left around the storage / disposal chamber 10 during excavation. It is a rock bed isolated from No. 4. Around the bedrock 3, there is a space 14 filled with a non-hydrophilic liquid 7 such as crude oil, and on the outside thereof is a relatively strong formation 4 mainly composed of rock layers. Reference numeral 5 is a support made of a rigid continuous porous body interposed between the bottom surface of the bedrock 3 and the support surface 12 of the formation 4, for example, a porous ceramic or porous plastic bead sintered body. The support 5 may be arranged so as to cover the entire lower surface of the bedrock 3, but the support 5 may be arranged in a horizontally elongated shape or only at important points including the four corners, leaving an empty space between them and leaving this empty space. The non-hydrophilic liquid may enter between the supports 5, and the point is that the entire bedrock 3 surrounding the storage / disposal chamber 10 may be wrapped with the non-hydrophilic liquid.

To form the underground structure described above, from the ground surface,
In the stratum (mainly rock layer), a tunnel with a circular cross section is formed in the diameter of the space 14 of the non-hydrophilic liquid 7, and when it reaches the planned storage / disposal room 10, the rock mass is left in the center. As seen in the vertical cross section, dig into the sake bottle so that it extends laterally. After excavating to almost the bottom of the underground structure, the excavation proceeds from the outer periphery of the bottom toward the center. At that time, after excavating for a certain predetermined distance, the rigid continuous porous support 5 is arranged at the important points including at least the four corners, and the space between the supports 5 is filled with the non-hydrophilic liquid. Try to turn. By excavating to the center of the bottom of the underground structure in this way, the space 14 of the non-hydrophilic liquid becomes a continuation of the ground surface 11 and becomes a space.
The rock mass surrounded by 14 and supported by the support 5 on the support surface 12 of the formation 4 is left in the center. Next, the groundwater pit 8 is formed by excavation from the bottom surface of the underground structure. This groundwater pit, like the storage and disposal room 10,
As shown in the figure, it is advantageous to have a bottle shape in vertical cross section, but any other shape may be used. Next, a through hole is formed at the top end of the rock body left in the center, and the inside is hollowed out, and the shape of storage that expands laterally in a vertical cross section.
A disposal room 10 is formed. As shown in the figure, the storage / disposal chamber is surrounded by bedrock 3 from the upper end corresponding to the through hole to the lower end.

The size of the storage / disposal room 10 is, for economic reasons mainly, several tens of meters in the lateral direction (left and right direction in FIG. 1) and about 1000 m in the longitudinal direction (direction perpendicular to the paper surface of FIG. 1). The size and the diameter of the structure are set such that the solidified body 1 or the container containing the solidified body 1 and necessary mechanical devices and the like can be carried in and out by a temporary elevator.

Next, from the ground surface to the through hole, insert a pipe having rigidity such as a concrete pile 6 that becomes the loading / unloading passage 2.
The lower end portion is fixed to the bedrock 3 by, for example, a lock anchor to form the loading / unloading passage 2, and the upper half portion of the annular space 14 for the non-hydrophilic liquid 7 is defined around the loading / unloading passage 2.

The solidified body 1 of radioactive waste is radioactive waste ranging from liquid such as sludge or waste liquid to solid such as used resin or used control rod, particularly high-level radioactive waste, cement or The asphalt is mixed and solidified, or vitrified with borosilicate glass. If necessary, it is stored in a sealed container such as a canister and then sealed.

The solidified bodies 1 are installed side by side on the floor of the storage / disposal room 10,
Before groundwater begins to spring from the wall surface of 10, the non-hydrophilic liquid 7 fills the space 14 from the ground surface 11 to the liquid level 7'equilibrium with the groundwater from the surrounding formation as soon as possible. As the non-hydrophilic liquid, in addition to crude oil, various liquids having lower specific gravity and lower cost than groundwater, such as waste oil obtained from various manufacturing processes, can be used. Groundwater from the surrounding stratum 4 is doubly blocked by the non-hydrophilic liquid 7 and the bedrock 3 and cannot reach the solid body 1, so that the groundwater is prevented from being contaminated by radionuclides. Groundwater tries to infiltrate into the interior of the chamber 10 from the bottom surface of the chamber 10, but the non-hydrophilic liquid 7 and the bottom of the bedrock 3 that impregnate the continuous porous body 5 and fill the surrounding space and voids, The solidified body 1 and groundwater cannot be directly contacted.

Groundwater that has entered the non-hydrophilic liquid 7 from the surrounding stratum 4 is
Due to the difference in specific gravity, water is collected in the groundwater pit 8 below, and is pumped up and removed by the submersible pump 15 on the ground surface 11 at any time through a pipe (not shown).

In the embodiment shown in FIG. 2, the carry-in / carry-out passage 2 and the supply passage 16 for the non-hydrophilic liquid 7 are formed separately instead of being formed concentrically,
Two storage / disposal chambers 10 are formed side by side, and these chambers 10 are commonly connected to the loading / unloading passage 2, and a space 14 for the non-hydrophilic liquid 7 is formed.
Is similar to the embodiment of FIG. 1 except that it is commonly connected to its common passage 16. In order to form the underground structure shown in FIG. 2, the common passage 16 and the loading / unloading passage 2 are formed on the ground surface.
11 to form a groundwater pit 8 at the lower end of the supply passage 16 and then laterally excavated to reach the bottom of both chambers 10. The chamber 10 is dug from the bottom side so as to leave the ground 3 isolated from the surrounding stratum 4. The bottom of the bedrock 3 is supported in the same manner as in the embodiment shown in FIG.

For the portion where the carry-in / carry-out passage 2 passes through the supply passage 16, for example, an iron pipe can be used. The loading / unloading passage 2 and the common passage 16 are formed by passing a rigid pipe such as a concrete pile. More than two storage / disposal chambers 10 may be formed side by side.

<Effects of the Invention> According to the present invention, a hollow storage / disposal chamber 10 is formed in a relatively strong stratum such as a rock layer so as to leave the bedrock 3 around it, and the bedrock 3 is formed around the bedrock 3. Since the space 14 for the non-hydrophilic liquid 7 is formed, groundwater trying to enter the inside of the chamber 10 from the surrounding stratum 4 is double blocked by the bedrock 3 and the non-hydrophilic liquid 7, and as a result, As a result, it is possible to prevent radioactive contamination of groundwater and corrosion of the solidified body or a container containing the solidified body by groundwater. In addition, since the non-hydrophilic liquid layer is a liquid and is in equilibrium with the groundwater pressure, it is always stable and is not destroyed by fluctuations in the ground pressure. Further, the technical problem of storing the non-hydrophilic liquid in the ground can be easily solved by directly applying the technique demonstrated by the underground petroleum stockpiling. Further, as in the embodiment shown in FIG. 2, a storage / disposal room
When two or more 10s are formed side by side, the effect of significantly increasing the underground disposal capacity of radioactive waste can be obtained.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing an underground structure according to a first embodiment of the present invention, and FIG. 2 is a vertical sectional view showing an underground structure according to a second embodiment of the present invention. 1 ... Solidified body, 2 ... Carry-in / out passage, 3 ... Ground, 5 ...
Support (supporting means), 10 ... storage / disposal room, 11 ... ground surface, 12 ... storage space.

Claims (10)

[Claims] 1. Storage for a solidified body of radioactive waste formed under the water table of the formation by excavation or its enclosure.
A disposal chamber, a ground isolated from the surrounding strata surrounding the storage / disposal chamber, a loading / unloading passage connecting the storage / disposal chamber with the ground surface through the ground, the loading / unloading passage, and Storage of radioactive waste having a storage space that stores a non-hydrophilic liquid that concentrically surrounds the ground and communicates with the ground surface, and a support means that supports the lower surface of the ground from the bottom surface of the storage space -Underground structure for disposal. 2. The underground structure for storing and disposing of radioactive waste according to claim 1, wherein the supporting means is formed of a rigid continuous porous body that covers the entire lower surface of the ground. 3. The support means is formed by a rigid continuous porous body that covers a part of the lower surface of the ground, and a void in the middle is filled with a non-hydrophilic liquid. An underground structure for storage and disposal of radioactive waste according to item 2 or item 2. 4. An underground structure for storage and disposal of radioactive waste according to any one of claims 1 to 3, wherein the non-hydrophilic liquid is a liquid having a lower specific gravity than groundwater. . 5. Groundwater infiltrating from the surrounding stratum is collected at the lowermost bottom of the storage space by a difference in specific gravity,
The underground structure for storing and disposing of radioactive waste according to any one of claims 1 to 4, comprising a pit for collecting water collected to the ground surface. body. 6. A solidified body of radioactive waste formed under the water table of the formation by excavation or a container for the solidified body of the radioactive waste.
The above storage / disposal chambers, the ground surrounding each of the storage / disposal chambers, isolated from the surrounding stratum, and a common loading / unloading passage that connects the storage / disposal chambers to the ground surface, A storage space for storing the non-hydrophilic liquid formed around the ground in each of the storage / disposal chambers, and a common supply passage for the non-hydrophilic liquid that communicates each of the storage spaces with the ground surface,
An underground structure for storing and disposing of radioactive waste, which has a groundwater pit formed so as to communicate with the storage space and a support means for supporting the lower surface of each ground from the bottom surface of the storage space in a floating manner. . 7. The support according to claim 6, wherein the supporting means is formed by a continuous porous body that covers the entire lower surface of the ground.
Underground structure for storage / disposal of radioactive waste as described in paragraph. 8. The method according to claim 6, wherein the supporting means is formed of a rigid continuous porous body that covers a part of the lower surface of the ground, and a void in the middle thereof is filled with a non-hydrophilic liquid. An underground structure for storage / disposal of radioactive waste according to the item 7 or 7. 9. An underground structure for storage / disposal of radioactive waste according to claim 6, wherein the non-hydrophilic liquid is a liquid having a lower specific gravity than groundwater. 10. The lowermost bottom of the storage space,
The radioactive substance according to any one of claims 6 to 9, comprising a pit configured to collect groundwater entering from a surrounding strata by a difference in specific gravity and pump the collected water to the ground surface. An underground structure for waste storage and disposal.