JP4329057B2 - Underground facility of high-level radioactive waste storage facility and its setting method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an underground facility of a high-level radioactive waste storage facility and a method for setting the underground facility, and in particular, to increase the safety when disposing high-level radioactive waste by preventing an increase in groundwater flow in the construction of a shaft. The present invention relates to an underground facility of high-level radioactive waste storage facility and its setting method.
[0002]
[Prior art]
In the nuclear fuel cycle centered on nuclear power plants, in order to recycle spent fuel, spent fuel is transferred directly or via a recycle fuel storage center to a reprocessing plant, where uranium and plutonium are recovered. It is configured to be processed and reused.
[0003]
Any radioactive waste that falls outside this fuel cycle is planned to be safely isolated. Among them, low-level radioactive waste discharged from nuclear power plants is safely processed at low-level radioactive waste burial centers.
[0004]
On the other hand, it is decided to dispose of high-level radioactive waste generated in the reprocessing plant at the geological disposal facility in the high-level radioactive waste storage facility, and the geological disposal facility will dispose of the radioactive waste. In addition, it is constructed as an underground facility with a depth of 300m or more.
[0005]
This geological disposal facility is classified into two facilities, hard rock and sedimentary rock, according to the rock type, and technical studies and plans for each facility are being carried out.
[0006]
As shown in FIG. 3, the geological disposal facility 10 represented by these is composed of an underground facility 11 and a vertical shaft 13 and an exhaust shaft 14 communicating with the ground receiving facility 12. The underground facility 11 is composed of a plurality of disposal tunnels 15 and a main tunnel 16 connecting them, and the shaft 13 includes a canister carry-in shaft 17, a personnel / material shaft 18, and an emergency shaft 19.
[0007]
The role of high-level radioactive waste storage facilities is to destroy the environment by disposal of radioactive nuclides from the waste after disposal into the surrounding groundwater due to overpack corrosion, etc. This period is considered to be 10,000 years or more, and is a very long period.
[0008]
And it is thought that the migration of nuclides is largely due to the flow of groundwater. Therefore, in high-level radioactive waste storage facilities, select rocks with low permeability and low groundwater flow as the installation location. Therefore, we are considering a construction that can cope with the above situation by increasing the time it takes for the groundwater in the deep underground to reach the ground surface by flowing.
[0009]
Even if the installation location of the high-level radioactive waste storage facility is selected as a bedrock having a low permeability coefficient and a small flow of groundwater, the underground facility 11, the shaft 13 and the exhaust shaft 14 are as shown in FIG. If the flow direction 21 of the groundwater 20 is arranged as shown in the figure, the flow direction 21 of the groundwater 20 that has passed through the shaft 13 or the exhaust shaft 14 becomes a water flow 22 that is transformed upward. , The time until the migrating nuclides reach the surface will be shortened unexpectedly.
[0010]
On the other hand, in the construction of underground facilities, it is known that the excavation of a mine shaft disturbs the rock around the mine, such as the occurrence of a damaged region due to blasting or the occurrence of a loose region due to stress redistribution. In such a disturbed region, the water permeability is in a state having a high value that is one digit to one digit greater than the water permeability in the natural state.
[0011]
Such a phenomenon is not an exception even in vertical shafts and exhaust shafts directly connected to the ground surface, and it becomes a state of high water permeability by disturbing the periphery like the rock around the shaft.
[0012]
Accordingly, a loosened rock region 23 is formed around the underground facility 11 such as the main tunnel and the disposal tunnel, and the permeability coefficient is one digit to one digit larger than that of the natural rock described above. Similarly, a loosened region 24 is also formed in the peripheral region of the shaft 13 and the exhaust shaft 14, and a water flow 26 having a higher flow rate than the groundwater flow 25 having a lower flow velocity is shown in FIG. It is formed in the ground direction along a shaft or the like in a state continuous to the underground facility 11.
[0013]
Since the speed at which these accelerated groundwater flows reach the ground and the natural world is thought to increase in proportion to the permeability coefficient increasing by one to one digit or more, the arrival time of migrating nuclides to the surface is In order to evaluate the safety after disposal of high-level radioactive waste, it will be unexpectedly shortened compared to the case where nuclides migrate with the flow of groundwater in the low-permeability rock mass. This is considered an important issue.
[0014]
As a countermeasure against the loosening region associated with the excavation of these shafts, a widened portion 27 is formed in the middle portion of the shaft 13 as shown in FIG. 6A, and a plug 28 using concrete or bentonite with low water permeability is installed. Thus, it is considered that the water flow 26 having a high flow velocity is partially replaced with the water flow 25 having a low flow velocity by partially replacing the high water permeability portion.
[0015]
Therefore, as shown in FIG. 6B, this countermeasure is newly developed by excavating the widened portion 27 on the outer side as well as when the digging of the mine tunnel is accompanied by a loose permeable region 23. There is a question as to whether or not the high-permeability slack region 29 is generated and is effective in improving the high-permeability slack region 24, and the slack region formed outside the plug 28 in a related experiment. In 29, it is also reported that the water flow 26 having a high groundwater flow rate remains.
[0016]
In addition, by using bentonite having high swellability for the plug 28, the portion of the plug 28 is subjected to volume expansion after disposal, and a compressive stress is generated in the surrounding rock mass, thereby disturbing the excavation. There is also an attempt to bring the to the initial state.
[0017]
However, this measure also considers the behavior of the surrounding rock mass that occurs in relation to the volume expansion of the excavation and plug part as an elastoplastic material, and the occurrence of loosening in the rock mass is a plastic strain and the result of permanent strain. It means that. Therefore, even if it can be brought close to the initial stress state, it cannot be expected to return to the initial bedrock state with low water permeability, and its action and effect may not be expected much.
[0018]
[Problems to be solved by the invention]
In other words, a high-permeability loose area is inevitably formed by excavation around shafts and underground facilities of high-level radioactive waste storage facilities, but at present there is no method for artificially preventing it. Similarly, the upward groundwater flow from the underground facility through the shaft to the ground is not caused by the mere high-permeability slack area generated by excavation around the shaft, but the topographical conditions around the shaft The groundwater environment conditions are the main factors, and it is formed by the positional relationship between underground facilities and shafts.
[0019]
In view of the above situation, the present invention proposes a high-level radioactive waste storage facility with improved safety, considering the flow of groundwater to the entire underground facility, and analyzing groundwater behavior based on geological surveys. The underground facility of the high-level radioactive waste storage facility that establishes the position of the shaft based on the behavior state of the groundwater by establishing the generation of downward water flow in the direction of groundwater flow in the loose area with high permeability and its construction method Is provided.
[0020]
[Means for Solving the Problems]
The underground facility of the high-level radioactive waste storage facility according to the present invention is basically an underground facility of a high-level radioactive waste storage facility composed of an above-ground facility and an underground facility joined to the above-ground facility by a plurality of shafts. The construction position of the shaft is set according to the direction of the groundwater flow. Specifically, the construction position of the shaft is set to the downstream direction of the groundwater flow, or the groundwater flow is set upstream of the underground facility. It is a feature.
[0021]
In this way, by selecting the positional relationship between underground facilities and shafts based on topographical conditions around the shafts and groundwater environmental conditions, it is possible to establish the generation of downward water flow in the highly permeable slack area around the shafts. Established safety after disposal of radioactive waste.
[0022]
A method for setting an underground facility according to the present invention is a method for setting an underground facility according to any one of claims 1 to 1, and sets a position of an underground facility and a position of a shaft, and relates to the setting based on the setting. Analyzing the groundwater flow of the entire high-level radioactive waste storage facility from topographical information and geological data, selecting the construction position of the shaft in the downstream direction of the groundwater flow, and then confirming the water conveyance gradient and flow direction By doing so, the position of the shaft is specified, and it is characterized by reselection by confirming the water conveyance gradient and the flow direction.
[0023]
In this way, by confirming the location of the underground facilities and shafts based on the topographical conditions around the shafts and the groundwater environmental conditions, it is possible to establish the generation of downward water flow in the highly permeable slack area. The position of the shaft is easily determined.
[0024]
DETAILED DESCRIPTION OF THE INVENTION
The underground facility of the high-level radioactive waste storage facility according to the present invention is a construction site of the shaft in the underground facility of the high-level radioactive waste storage facility composed of the ground facility and the underground facility joined with the ground facility by a plurality of shafts. Is set according to the direction of the groundwater flow, and as another embodiment, the construction position of the shaft is set to the downstream direction of the groundwater flow, or the groundwater flow is displayed upstream of the underground facility .
[0025]
Embodiments of the present invention will be described below with reference to the drawings. In order to facilitate understanding, the same parts as those in the prior art are denoted by the same reference numerals.
[0026]
FIG. 1 is a schematic cross-sectional view showing an embodiment of an underground facility of a high-level radioactive waste storage facility according to the present invention.
[0027]
The underground facility 1 of the high-level radioactive waste storage facility is installed according to the flow direction 21 of the groundwater 20 based on the topographic conditions of the ground 1 to be constructed and the groundwater stagnant conditions.
[0028]
That is, the positional relationship between the underground facility 12 and the vertical shaft 12 communicating with the ground receiving facility is in the position of the ground 1 selected in consideration of the topographical conditions and groundwater environmental conditions around the vertical shaft. The installation position of the shaft 13 with respect to the facility 11 is positioned on the upstream side in the direction 21 in which the groundwater 20 flows.
[0029]
Therefore, the loosened rock region 23 formed in the vicinity of the underground facility 11 and the loosened region 24 formed in the peripheral area of the vertical shaft 13 are one digit in terms of permeability compared to the natural rock as described above. Although it will show a value that is larger by one digit or more, even if the groundwater flow flowing there is a water flow 26 having a large flow velocity compared to the groundwater flow 25 having a small flow velocity flowing through the natural rock, It is not an upward flow toward the ground via a vertical shaft.
[0030]
Therefore, the high-level radioactive waste storage facility 1 reaches the ground surface even if radionuclides elute from the waste after disposal to the surrounding groundwater due to overpack corrosion, etc., and flow into the ground along with the groundwater flow. By ensuring a large distance to do so, it is configured to increase the arrival time, thereby suppressing the outflow to the natural world.
[0031]
As described above, the underground facility of the high-level radioactive waste storage facility according to the present invention has the permeability of the periphery of the shaft by selecting the positional relationship between the underground facility and the shaft based on the topographical conditions around the shaft and the groundwater environmental conditions. Establishing the generation of downward water flow in the high slack area, and establishing safety after disposal of high-level radioactive waste.
[0032]
Next, an embodiment related to a method for setting an underground facility according to the present invention will be described. This method is an investigation / design method for reliably setting the above underground facility.
[0033]
In the underground facility setting method according to the present invention, first, the position of the underground facility and the position of the shaft are set, and the groundwater flow of the entire high-level radioactive waste storage facility is determined from the related topographic information and geological data based on the setting. The shaft construction position is selected as the downstream position of the groundwater flow, and then the shaft position is identified by actually confirming the water gradient and flow direction by boring, etc. It is characterized by re-selection by checking the gradient and flow direction.
[0034]
Hereinafter, an embodiment of a method for setting an underground facility according to the present invention will be described in detail based on a flowchart shown in the drawings.
[0035]
In this flowchart, as shown in Fig. 1, the installation position of the vertical shaft is set on the upstream side of the underground facility in consideration of the groundwater flow of the entire underground facility. In order to prevent upward components from occurring in the direction, the investigation and design process to solve the problem is shown. Based on the groundwater behavior obtained from the geological survey and groundwater behavior analysis based on the survey It is configured so that the judgment can be carried out smoothly.
[0036]
FIG. 2 shows a flowchart based on the method for setting an underground facility according to the present invention, where the installation position of the shaft is selected through the following process and finally identified.
(1) Set the location of underground facilities and the layout of access shafts in high-level radioactive waste storage facilities.
(2) A three-dimensional groundwater flow analysis will be performed on the large area including underground facilities with the same layout from topographic information and geological data.
(3) Reexamine the layout based on whether the groundwater flow has a vertically downward component at the shaft position.
Judging from the analysis result, if it is not downward, it is determined whether it is necessary to change only the shaft position or to move the entire underground facility.
(4) Select the position where the groundwater flow has a vertically downward component as the vertical position.
▲ 5 ▼ Boring is conducted at the underground facilities and shafts to actually check the hydrodynamic gradient and flow direction.
(6) Reexamine the layout based on whether the groundwater flow has a vertically downward component at the shaft position.
If the actual hydrodynamic gradient and flow direction are different from the 3D groundwater flow analysis results, perform 3D analysis considering geological data and groundwater conditions by boring, and change only the shaft position or move the entire underground facility Determine if you need it.
[0037]
Based on the above flow chart, the positional relationship between underground facilities and shafts is selected based on topographical conditions and groundwater environmental conditions around the shafts while conducting a three-dimensional groundwater flow analysis, in addition to the actual hydrodynamic gradient and flow direction. By confirming the above, the generation of downward water flow in the loose area with high water permeability is easily determined.
[0038]
As mentioned above, although the present invention has been described in detail based on the embodiment, the underground facility of the high-level radioactive waste storage facility and the setting method thereof according to the present invention are not limited to the above embodiment at all. Naturally, various modifications can be made without departing from the spirit of the present invention.
[0039]
【The invention's effect】
The underground facility of the high-level radioactive waste storage facility according to the present invention is basically an underground facility of a high-level radioactive waste storage facility composed of an above-ground facility and an underground facility joined to the above-ground facility by a plurality of shafts. The construction position of the shaft is set according to the direction of the groundwater flow. Specifically, the construction position of the shaft is set to the downstream direction of the groundwater flow, or the groundwater flow is set upstream of the underground facility. Because it is a feature, it has the following effects.
(1) Establish safety after disposing of high-level radioactive waste by generating downward water flow in the highly permeable loose area around the shaft.
(2) With regard to safety, it is possible to avoid the influence of the loose area of high permeability due to construction.
(3) Reduce restrictions and restrictions on construction to avoid loose areas with high water permeability.
(4) Eliminates the need for plugs for preventing water permeable zones in vertical shafts, improving economic efficiency.
[0040]
The underground facility setting method according to the present invention is a method for setting the above-mentioned underground facility, and sets the position of the underground facility and the position of the shaft, and based on the setting, the high-level from the related topographic information and geological data. Analyzing the groundwater flow of the entire radioactive waste storage facility, selecting the construction position of the shaft as the downstream direction of the groundwater flow, and then identifying the position of the shaft by checking the water conveyance gradient and flow direction. It is characterized by reselection by confirming the water conveyance gradient and flow direction, so it is possible to confirm while selecting the positional relationship between underground facilities and shafts based on topographical conditions around the shafts and groundwater environmental conditions. It has the effect of easily establishing the positional relationship between underground facilities and shafts by establishing the generation of downward water flow in a loose area with high water permeability.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view showing an embodiment of an underground facility of a high-level radioactive waste storage facility according to the present invention. FIG. 2 is a flowchart based on a method for setting an underground facility according to the present invention. Perspective view of underground facility in waste storage facility [Figure 4] Outline sectional view showing the positional relationship between the underground facility and shafts in the past [Figure 5] Outline sectional view showing the flow of groundwater flow in the conventional underground facility and shafts [ [Fig.6] Cross-sectional view of a conventional water-insulating plug in an underground facility
1 high-level radioactive waste storage facility, 2 ground,
10 geological disposal facilities, 11 underground facilities, 12 ground receiving facilities,
13 shafts, 14 exhaust shafts, 15 disposal tunnels,
16 main tunnels, 17 canister loading shafts, 18 material shafts,
19 Emergency shafts,
20 groundwater, 21 flow direction, 22 water flow,
23, 24 Loose area, 25 Small water flow,
26 Water flow with large flow velocity, 27 Widening section, 28 Plug,
29 Loose area,

Claims (4)

  An underground facility of a high-level radioactive waste storage facility composed of a ground facility and an underground facility joined to the ground facility by a plurality of shafts, and the construction position of the shaft is set according to the direction of the groundwater flow An underground facility for high-level radioactive waste storage facilities.   The underground facility of the high-level radioactive waste storage facility according to claim 1, wherein the construction position of the shaft is a position facing the downstream of the groundwater flow.   The underground facility of the high-level radioactive waste storage facility according to claim 1 or 2, wherein the construction position of the shaft is upstream of the underground facility in terms of groundwater flow. The position of the underground facility and the position of the shaft are set, and the groundwater flow of the entire high-level radioactive waste storage facility is analyzed from the relevant topographic information and geological data based on the setting, and the position of the shaft is determined The underground facility setting according to any one of claims 1 to 3, wherein a downstream direction position is selected, and then the water conveyance gradient and the flow direction are actually confirmed at the position to determine whether or not the shaft is located. Method.

Images