JPH073477B2 - 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 resins, used control rods, etc., contaminated machines, protective clothing, etc.
Usually, after storing for a certain period of time to reduce radioactivity,
Solidified by cement or asphalt, stored in a designated storage facility, and wastes at a level that does not exceed the upper limit concentration based on the Nuclear Reactor Regulation Law are finally buried in a concrete pit under the ground. . In addition, high-level radioactive waste generated from the reprocessing of spent fuel is made into ceramics, vitrified with borosilicate glass, stored in a sealed container such as a canister, and dumped in the deep sea provided with predetermined conditions, It is disposed in rock layers such as granite layers. In this way, when radioactive waste is stored and stored in the rock layer storage / disposal room, the storage site is to take into consideration the characteristics of the bedrock, the stability of the bedrock and surrounding strata, and the hydraulic suitability of groundwater. Will be selected. Storage / disposal chambers should be constructed at a depth of at least a few hundred meters above the surface of the earth and with a fairly large area (eg, a few hundred meters wide x 1000 m long).

Conventionally, the storage / disposal chamber is excavated in the stratum in this way, and concrete is sprayed on the walls of the storage / disposal chamber to form a lining or backfill with an appropriate material to sufficiently close the space. Or, by forming a water barrier layer such as bentonite, or by providing a water collecting part around or inside the storage / disposal room, the groundwater level is changed to prevent the infiltration of groundwater into the storage / disposal room. However, if the water is to be stored for hundreds of years or more like high-level radioactive waste, groundwater will gradually infiltrate into the storage / disposal room, but a sufficient water shielding effect cannot be obtained. It was

<Problems to be Solved by the Invention> In the present invention, when the solidified body of radioactive waste or its enclosure is stored in the storage / disposal chamber for long-term storage as described above, Storage and disposal of radioactive waste by preventing groundwater from contacting the solidified body or its enclosure and preventing radioactive contamination of the groundwater as well as preventing corrosion of the solidified body or its enclosure by groundwater. The purpose is to provide an underground structure for use.

It is an object of the present invention to provide an underground structure for storing and disposing of radioactive waste, which enables a large amount of radioactive waste to be stored and disposed of at one time.

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

<Means for Solving Problems> For these purposes, according to the present invention, a storage / disposal chamber formed below the water table of a stratum by excavation, and a storage / disposal chamber disposed in the storage / disposal chamber, A platform on which a solidified body of waste or a container containing the solidified body is placed, and an attempt is made to fill the storage / disposal chamber around the solidified body or container on the platform to enter the storage / disposal chamber. There is provided an underground structure for storage and disposal of radioactive waste, which is composed of a non-hydrophilic liquid that is balanced with the water pressure of the ground water.

Similarly, according to the present invention, a storage / disposal chamber formed below the water table of the stratum by excavation, and a solid waste of radioactive waste or a container containing the solid waste and disposed therein. It has a mounted pedestal, a shielding body which surrounds the pedestal and the solidified body or the container, and shields the storage / disposal chamber from the filled inert gas inside the shielding body. There is also provided an underground structure for storing and disposing of radioactive waste, which is provided with a non-hydrophilic liquid soaked so as to balance with the water pressure of the ground water to be infiltrated between the plates.

<Operation> With the configuration of the present invention, groundwater from the surrounding strata 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 thus solidifies in the storage / disposal chamber. This prevents contact with the body and effectively prevents contact between radionuclides in radioactive waste and the biosphere via groundwater.

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

In Figs. 1 and 2, reference numeral 10 denotes a hollow storage / disposal chamber formed by excavation from the ground surface 11, which extends from the entrance tunnel on the ground surface 11 side to the lower part of the groundwater layer 9 with almost the same width. After that, to form a storage space for radioactive waste,
The width can be widened. In FIG. 1, the entire vertical sectional shape of the storage / disposal chamber 10 is a bottle shape, but the present invention is not limited to this particular shape. Groundwater that is about to enter the storage / disposal chamber 10 of the excavation from the surrounding stratum (mostly rock layer) is stopped by the grout injection or the water stop plate during the excavation. Next, the gantry 2 is placed on the bottom of the storage / disposal room 10. In the illustrated example, this mount includes a leg portion 5 and a bottom plate 4.
Although it is a two-layer multi-chamber structure including the partition wall 6 and the top plate 3, it may be a multi-layer multi-chamber structure having more than two layers as required.

As shown in FIGS. 1 and 2, the leg portions 5 are provided in appropriate numbers in the vertical and horizontal directions of the storage / disposal chamber 10 so that non-hydrophilic liquid such as petroleum can freely flow into and out of all the spaces therebetween. . In addition,
The size of the disposal chamber 10 is several tens of meters in the horizontal direction (horizontal direction in FIG. 2) and several hundred meters in the vertical direction (horizontal direction in FIG. 1) mainly for economic reasons, and the diameter of the tunnel is , Stand 2
The top plate 3, the bottom plate 4, the legs 5, the partition wall 6, the submersible pump 12 (described later) or the solidified body 1 (described later), which are the respective constituent parts of the, are sized so that they can be carried in by an elevator temporarily installed after excavation. .

As shown in FIG. 2, a pump room is located below the floor of the storage / disposal room 10 just below the tunnel leading to the storage / disposal room 10. Inside the pump room, there is a submersible pump 12 Is stored and is connected by a pumping pipe 13 to a drainage part (not shown) on the ground surface 11.

In Figures 1 and 2, 1 is a solidified body of radioactive waste,
It is preferably housed in a sealed container such as a canister and sealed, but it may be a solidified body as it is. Among radioactive wastes, those that can be stored according to the present invention include liquid ones such as sludge or waste liquid, and solid ones such as used resins or used control rods, which are usually
Cement or asphalt is mixed and solidified or vitrified to obtain a solidified body 1.

After installing the gantry 2 and the solidified body 1 on the floor of the storage / disposal chamber 10, before the groundwater begins to spout from the wall of the storage / disposal chamber 10, as soon as possible, a non-hydrophilic liquid from the tunnel side, for example, The crude oil is filled from the surrounding formation to the liquid level 7'which is in equilibrium with the water pressure. 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 strata cannot reach the solidified body due to this non-hydrophilic liquid, so groundwater that prevents contamination of the groundwater by radioactivity will try to infiltrate into the interior of the storage and disposal chamber 10 from the bottom. However, because of the legs 5 of the pedestal 2, the non-hydrophilic liquid is present between the lower solidified body 1 and the bottom of the storage / disposal chamber 10, so that the ground water and the solidified body 1 are directly connected to each other. Contact is prevented.

Groundwater that has entered the storage / disposal room 10 from the surrounding wall of the storage / disposal room 10 comes into contact with the non-hydrophilic liquid that fills it, and is collected in the lower pump room due to the difference in specific gravity. It is pumped up and removed on the ground surface 11 through the pipe 13.

In this embodiment, a multi-stage multi-chamber type pedestal provided with a plurality of mounting legs was used, but the lower surface of the solidified body 1 or its enclosure is supported at a position higher than the bottom surface of the storage / disposal chamber 10. Any structure may be used as long as the non-hydrophilic liquid surrounds the entire surface of the solidified body 1 or the enclosed container including the bottom surface. For example, the case where the gantry 2 is suspended from the ceiling of the storage / disposal room 10 is also included in the scope of the present invention.

In the embodiment shown in FIGS. 3 and 4, after covering the portion of the pedestal 2 excluding the legs 5 and the solidified body 1 with a shield 14 made of a metal material such as stainless steel, piping is provided inside the shield 14. 15
An inert gas such as nitrogen gas is filled in through. In this case, the solidified body 1 on the pedestal 2 is doubly shielded from the groundwater from the surrounding strata by the non-hydrophilic liquid and the inert gas, so that the risk of radioactive contamination of the groundwater is further reduced. . In other respects, the embodiment shown in FIGS. 3 and 4 is exactly the same as the embodiment shown in FIGS.

<Effects of the Invention> According to the present invention, a hollow storage / disposal chamber is formed in the stratum, and the surrounding wall of the storage / disposal chamber is lined with concrete or the like, and an internal void portion is backfilled. Non-hydrophilic liquid such as crude oil was filled and immersed in the empty space without backfilling it with water, etc. Since it collects at the bottom of the hydrophilic liquid and can be sucked out by a pump at any time, infiltration of groundwater is prevented for a long period of time, resulting in radioactive contamination of groundwater and corrosion of solidified bodies or their enclosures by groundwater. And are prevented. 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. Moreover, the technical problem of storing non-hydrophilic liquid in the ground can be easily solved by directly applying the technology demonstrated by underground oil storage. Further, in the embodiment of FIGS. 3 and 4, when the pedestal in the storage / disposal room and the solidified body placed on it are covered with a shield such as stainless steel, and the inside is filled with an inert gas such as nitrogen gas, With this inert gas and the non-hydrophilic liquid, a double water shield effect can be achieved.

[Brief description of drawings]

1 is a longitudinal sectional view showing an underground structure according to a first embodiment of the present invention, FIG. 2 is a transverse sectional view cut along the line AA in FIG. 1, and FIG. FIG. 4 is a vertical sectional view showing an underground structure according to a second embodiment of the present invention, and FIG.
It is the cross-sectional view cut and shown along the B line. 1 ... Solidified body, 7 ... Non-hydrophilic liquid, 10 ... Storage / disposal room, 11 ... Ground surface.

Claims (8)

[Claims] 1. A storage / disposal chamber formed below the water table of the stratum by excavation, and a solidified body of radioactive waste or a container containing the solidified body placed in the storage / disposal room. And a non-hydrophilic liquid that fills the storage / disposal chamber around the solidified body or container on the platform and balances with the water pressure of the ground water to enter the storage / disposal chamber. Underground structure for storage and disposal of radioactive waste. 2. The underground structure for storing and disposing of radioactive waste according to claim 1, wherein a liquid having a lower specific gravity than groundwater is used as the non-hydrophilic liquid. 3. A storage / disposal chamber at the bottom of the bottom,
The radioactive waste according to claim 1 or 2, further comprising: a pit configured to collect groundwater entering from a stratum around the disposal room by a difference in specific gravity and pump the collected water to the ground surface. An underground structure for the storage and disposal of goods. 4. The underground for storage / disposal of radioactive waste according to claim 1, wherein the gantry is supported above a bottom surface of the storage / disposal chamber by a plurality of support legs. Structure. 5. A storage / disposal chamber formed below the water table of the stratum by excavation, and a solidified body of radioactive waste or a container containing the solidified body placed in the storage / disposal room. And a shield that surrounds the solid and the solidified body or container, and the inside of the shield is filled with an inert gas, and between the storage / disposal chamber and the shield plate. Is an underground structure for storage and disposal of radioactive waste, which is provided with a non-hydrophilic liquid soaked to balance with the water pressure of the ground water to be infiltrated. 6. The underground structure for storing and disposing of radioactive waste according to claim 5, wherein a liquid having a lower specific gravity than groundwater is used as the non-hydrophilic liquid. 7. A storage / disposal chamber is provided at the bottom of the storage / disposal chamber.
The radioactive substance according to claim 6 or 7, further comprising: a pit configured to collect groundwater entering from a stratum around the disposal room by a difference in specific gravity and pump the collected water to the ground surface. An underground structure for waste storage and disposal. 8. An underground structure for storage / disposal of radioactive waste according to claim 5, wherein the gantry is supported above the bottom surfaces of a plurality of storage / disposal chambers. .