JP2002196098A - Underground plant for high-level-radioactive waste storage plant, and setting method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make the generation of a downward flow in a flow direction of ground-water established in a loosened zone high in water permeability, by ground-water behavior analysis based on geological survey while taking the flow of the ground-water to the whole underground plant into account, to set a position of a shaft based on a behavior condition of the ground-water. SOLUTION: This underground plant 11 of a high level radioactive waste storage plant 1 in the present invention is joined to a ground plant with the plural shafts 13, the construction position of the each shaft 13 is made to be located in a position where the ground-water flow 20 is directed downwards according to water flow direction 21 of the ground-water flow 20, and selected in an upstream of the underground plant 11 in view point of a stream in the ground-water flow. The selection is investigated by a setting method of analyzing ground-water behavior based on the geological survey, taking the flow of the ground-water to the whole underground plant into account.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an underground facility for a high-level radioactive waste storage facility and a method of setting the underground facility.
The present invention relates to an underground facility for a high-level radioactive waste storage facility and a method for setting the same, which prevents the rise of groundwater flow in the construction of a shaft and enhances the safety when disposing of high-level radioactive waste.

[0002]

2. Description of the Related Art In a nuclear fuel cycle centered on a nuclear power plant, in order to reuse spent fuel, uranium or plutonium is transferred to a reprocessing plant directly or via a recycled fuel storage center. Is collected, processed into fuel and reused.

[0003] It is planned that the radioactive waste out of the fuel cycle be safely separated and disposed of. Among them, low-level radioactive waste discharged from nuclear power plants is safely disposed of at the low-level radioactive waste burial center.

On the other hand, it is determined that high-level radioactive waste generated in a reprocessing plant should be disposed of in a geological disposal facility in a high-level radioactive waste storage facility. It has been constructed as an underground facility at a depth of 300 m or less for disposal.

[0005] The geological disposal facilities are classified into facilities for hard rock and sedimentary rock according to the type of rock, and technical studies and plans for each facility are being implemented.

[0006] The geological disposal facilities 10 represented by these are:
As shown in FIG. 3, the underground facility 11 is connected to a vertical shaft 13 and an exhaust vertical shaft 14 which communicate with the ground receiving facility 12. The underground facility 11 has a plurality of disposal tunnels 1
5 and a main tunnel 16 connecting them, and the shaft 13 has a canister carry-in shaft 17, a staff and material shaft 18, and an emergency shaft 19.

[0007] The high-level radioactive waste storage facility plays a role in that radioactive nuclides are eluted from the waste body into the surrounding groundwater due to corrosion of the overpack after disposal and flow out to the natural world together with the flow of the groundwater. It is required to prevent environmental destruction due to
It is considered to be more than ten thousand years, and it has been a very long period.

[0008] Since the migration of nuclides is considered to be largely caused by the flow of groundwater, high-level radioactive waste storage facilities use rock masses with low permeability and small groundwater flow as installation locations. We are considering a construction that can cope with the above situation by increasing the distance until the groundwater in the deep underground reaches the surface of the ground by flow, thereby increasing the arrival time.

Thus, even if the installation location of the high-level radioactive waste storage facility is selected to be a bedrock having a low permeability and a small flow of groundwater, the underground facility 11, the shaft 13, and the exhaust shaft 14 are connected as shown in FIG. Are arranged in a positional relationship like
In the case where the flow direction 21 of the groundwater 20 is formed as shown in the figure, the flow direction 21 of the groundwater 20 that has traveled through the shaft 13 or the exhaust shaft 14 is the water flow 22 that has been turned upward.
And the time it takes for the migrating nuclides to reach the surface is unexpectedly reduced.

On the other hand, in the construction of underground facilities, it has been known that excavation of a tunnel causes rocks around the tunnel to be disturbed, such as generation of a damaged area due to blasting and generation of a loose area due to stress redistribution. In addition, such a disturbed region is in a state of having a water permeability that shows a value higher by one to one order of magnitude in water permeability than the natural state water permeability.

[0011] Such a phenomenon is no exception in a vertical shaft or an exhaust shaft directly connected to the surface of the ground, and a state of high permeability is obtained by disturbing the surrounding rock like the rock around the tunnel.

Therefore, a loose area 23 in which rock is disturbed is formed around the underground facility 11 such as a main tunnel and a disposal tunnel.
As in the case of showing a value one order of magnitude larger, a slack area 24 is also formed in the area around the shaft 13 and the exhaust shaft 14, and the water flow 26 having a higher flowing velocity than the water flow 25 of the groundwater having a lower flow velocity. However, as shown in FIG.
It is formed in the ground direction along the shaft and the like in a state continuous with 1.

The speed at which these increased groundwater flows reach the ground and in the natural world is thought to increase in proportion to the increase in permeability by one to one order of magnitude or more. The arrival time is unexpectedly reduced compared to the case where nuclides migrate along with the flow of groundwater in low-permeability rock, and evaluate the safety after disposal of high-level radioactive waste This is considered an important issue.

As a countermeasure against the loosened area caused by the excavation of the shaft, as shown in FIG. 6A, a widened portion 27 is formed at an intermediate portion of the shaft 13, and a plug 28 made of concrete or bentonite having low water permeability is used. It has been studied to replace the water flow 26 having a high flow velocity with the water flow 25 having a low flow velocity by replacing the water flow 26 with a part having high water permeability by installing the water flow part.

However, as shown in FIG. 6 (b), this countermeasure can be applied to the excavation of the tunnel in the loose area 23 having high permeability.
The widened portion 27 is also provided on the outside of the
Excavation creates a new highly permeable loose area 29, which remains questionable as to whether it is effective in improving the highly permeable loose area 24. It is also reported that a flowing water 26 having a high flowing velocity of groundwater remains in the formed loose area 29.

Further, by using bentonite having a high swelling property for the plug 28, the volume of the plug 28 is expanded after disposal, and a compressive stress is generated in the surrounding rock, so that turbulence accompanying excavation is caused. Attempts have been made to bring the region to the initial state.

However, considering this measure as well as the behavior of the surrounding rock which occurs in association with excavation and volume expansion of the plug portion as an elasto-plastic material, the occurrence of loosening in the rock
It is a plastic strain, which means that the result is a permanent strain. Therefore, even if the initial stress state can be approached, it is impossible to imagine returning to the initial rock state with low water permeability, and the operation and effect may not be expected much.

[0018]

That is, in the vicinity of the shaft or underground facility of the high-level radioactive waste storage facility, a loose area having high permeability is inevitably formed by excavation.
At present, no method has been found to prevent it artificially. Similarly, the upward flow of groundwater from the underground facility to the ground via the shaft is merely a matter of permeability, which is generated by excavation around the shaft. It is not caused by a high slack area, but mainly due to the topographical conditions around the shaft and the groundwater environment, and is formed by the positional relationship between the underground facilities and the shaft.

The present invention has been made in view of the above circumstances, and proposes a high-level radioactive waste storage facility with improved safety, taking into account the flow of groundwater to the entire underground facility and taking a geological survey into consideration. The groundwater behavior analysis establishes the generation of downward water flow in the direction of groundwater flow in the highly permeable loose area, and sets the position of the shaft based on the behavior state of the groundwater. We provide the construction method.

[0020]

The underground facility of the high-level radioactive waste storage facility according to the present invention is basically a high-level radioactive facility composed of a ground facility and an underground facility connected to the ground facility by a plurality of shafts. In underground facilities of waste storage facilities, 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 position of the groundwater flow, It is characterized by being located upstream of the underground facility.

In this way, by selecting the positional relationship between the underground facility and the shaft based on the topographical conditions around the shaft and the groundwater environment conditions, it is possible to establish the generation of a downward water flow in the highly permeable loose area around the shaft. Has established safety after disposal of high-level radioactive waste.

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, wherein the position of the underground facility and the position of the shaft are set, and based on the setting. Analyze the groundwater flow of the entire high-level radioactive waste storage facility from the relevant topographical information and geological data, select the vertical shaft construction position downstream of the groundwater flow, and then select the headrace gradient and flow direction The position of the shaft is specified by confirming the above conditions, and it is characterized in that the shaft is selected again by confirming the water conveyance gradient and the flow direction.

Thus, by confirming while selecting the positional relationship between the underground facility and the shaft based on the topographical conditions around the shaft and the groundwater environment conditions, it is possible to establish the generation of the downward water flow in the loose area having high water permeability. The positional relationship between the underground facility and the shaft has been easily determined.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION An underground facility of a high-level radioactive waste storage facility according to the present invention is an underground facility of a high-level radioactive waste storage facility composed of a ground facility and an underground facility connected to the ground facility by a plurality of shafts. In the facility, the construction position of the shaft is set according to the direction of the groundwater flow, and as another embodiment, the construction position of the shaft is set to the position facing the downstream of the groundwater flow, or as the groundwater flow, upstream of the underground facility That you are doing.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. To facilitate understanding, parts similar to those in the related art are denoted by the same reference numerals.

FIG. 1 is a schematic sectional view showing an embodiment of an underground facility of a high-level radioactive waste storage facility according to the present invention.

The underground facility 1 of the high-level radioactive waste storage facility is installed in accordance with the flow direction 21 of the groundwater 20 based on the topographic condition of the ground 1 to be constructed and the condition of groundwater stagnant.

That is, the positional relationship between the underground facility 12 and the shaft 12 that communicates with the ground receiving facility is at the position of the ground 1 selected in consideration of the topographical conditions around the shaft and the groundwater environment conditions. Thus, the installation position of the shaft 13 with respect to the underground facility 11 is positioned on the upstream side in the direction 21 in which the groundwater 20 flows.

As described above, the loose area 23 formed in the rock around the underground facility 11 and the loose area 24 formed in the area around the shaft 13 have a higher permeability than the rock in the natural state as described above. In this case, the groundwater flow flowing therethrough is larger than that of the groundwater flow 25 having a small flow velocity flowing through the rock in the natural state. It is not an upward flow from the underground facility to the ground via the shaft.

Therefore, the high-level radioactive waste storage facility 1
By securing a large distance until radioactive nuclides from the disposed wastes reach the ground surface even if they elute into the surrounding groundwater due to corrosion of the overpack and flow out into the ground with the flow of groundwater. In addition, it is configured to extend the arrival time, thereby suppressing outflow to the natural world.

As described above, the underground facility of the high-level radioactive waste storage facility according to the present invention can be used for the topographical conditions around the shaft,
By selecting the positional relationship between the underground facilities and the shaft based on the groundwater environment conditions, the generation of downward water flow in the highly permeable loose area around the shaft is established, and the safety after disposal of high-level radioactive waste is established. Established.

Next, an embodiment of a method for setting an underground facility according to the present invention will be described. This method is a survey / design method for reliably setting the above-mentioned underground facility.

In the method of setting an underground facility according to the present invention, first, the position of the underground facility and the position of the shaft are set, and based on the settings, the relevant topographical information and geological data are used to determine the entire high-level radioactive waste storage facility. Analysis of groundwater flow
Select the construction position of the shaft to be located downstream of the groundwater flow,
Thereafter, the position of the shaft is identified by actually confirming the headrace gradient and the flow direction by boring, etc.
The re-selection is characterized by confirming the headrace gradient and the flow direction.

An embodiment of the method for setting an underground facility according to the present invention will be described below in detail with reference to the flowchart shown in the drawings.

In this flowchart, as shown in FIG. 1, the installation position of the shaft is set on the upstream side of the underground facility from the viewpoint of the groundwater flow by considering the groundwater flow of the entire underground facility. In order to prevent the generation of upward components in the flow direction of groundwater, the process of investigation and design to solve the problem is shown.The groundwater obtained by the geological survey and groundwater behavior analysis based on the survey is shown. It is configured so that the judgment based on the behavior can be smoothly performed.

FIG. 2 shows a flowchart based on the method of setting an underground facility according to the present invention. The installation position of a shaft is selected through the following steps, and the final specification is performed. Set the location of underground facilities and the layout of access shafts in the high-level radioactive waste storage facility. For a large area including underground facilities with the same layout, three-dimensional groundwater flow analysis is performed from topographical information and geological data. The layout will be reconsidered depending on whether the groundwater flow has a vertical downward component at the shaft position. Judging from the analysis result, if it is not downward, it is judged whether only the shaft position should be changed or the entire underground facility needs to be moved. As the shaft position, a position where the groundwater flow has a vertically downward component is selected. Boring is performed at underground facilities and shafts to check the hydraulic gradient and flow direction. The layout will be reconsidered depending on whether the groundwater flow has a vertical downward component at the shaft position. If the actual hydraulic gradient or flow direction is different from the 3D groundwater flow analysis result, perform 3D analysis taking into account geological data and groundwater conditions by drilling, and change only the shaft position or move the entire underground facility. Is required.

Based on the above flow chart, the positional relationship between the underground facility and the shaft is selected while performing three-dimensional groundwater flow analysis based on the topographical conditions around the shaft and the groundwater environment conditions, and in addition to the actual hydraulic By confirming the gradient and flow direction, it is easy to determine the generation of a downward water flow in a loose area with high water permeability.

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-described embodiment. Rather, various changes can be made without departing from the spirit of the present invention.

[0039]

The underground facility of the high-level radioactive waste storage facility according to the present invention is basically a high-level radioactive waste storage facility composed of a ground facility and an underground facility connected to the ground facility by a plurality of shafts. In the underground facilities, 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 position of the groundwater flow, It has the following effects because it is characterized by being on the side. Establish safety after disposal of high-level radioactive waste by generating a downward water flow in a highly permeable loose area around a shaft. With regard to safety, the influence of the high-permeability loose area caused by construction can be avoided. Reduce restrictions and restrictions on construction to avoid high permeability loose areas. A plug for preventing a permeation zone is not required in a shaft or the like, and the economic efficiency is improved.

The method for setting an underground facility according to the present invention is a method for setting the above-mentioned underground facility, in which the position of the underground facility and the position of the shaft are set, and the related topographic information and geological data are set based on the setting. Analyze the groundwater flow of the entire high-level radioactive waste storage facility from, select the construction position of the shaft in the downstream direction of the groundwater flow, and then check the water transfer gradient and the flow direction to confirm the position of the shaft It is characterized by re-selection by confirming the headrace gradient and flow direction, so it is confirmed while selecting the positional relationship between the underground facility and the shaft based on the topographical conditions around the shaft and the groundwater environment conditions By doing so, it is possible to establish the generation of a downward water flow in a highly permeable loose area, and to easily determine the positional relationship between the underground facility and the shaft.

[Brief description of the drawings]

FIG. 1 is a schematic 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.

FIG. 3 is a perspective view of an underground facility in a conventional high-level radioactive waste storage facility.

FIG. 4 is a schematic sectional view showing a positional relationship between a conventional underground facility and a shaft.

FIG. 5 is a schematic sectional view showing the flow of groundwater flow in a conventional underground facility and shaft.

FIG. 6 is a schematic cross-sectional view of a waterproof plug in a conventional underground facility.

[Explanation of symbols]

1 High-level radioactive waste storage facility, 2 Ground, 10
Geological disposal facility, 11 underground facility, 12 ground receiving facility, 13 shaft, 14 exhaust shaft, 15 disposal tunnel, 16 main tunnel, 17 canister carry-in shaft, 18 material shaft, 19 emergency shaft, 20
Groundwater, 21 Flow direction, 22 Water flow, 23, 24
Loose area, 25 Water flow with low flow velocity, 26 Water flow with high flow velocity, 27 Widening section, 28 Plug, 29
Loose area,

Claims (5)

[Claims] 1. An underground facility of a high-level radioactive waste storage facility comprising an aboveground facility and an underground facility connected to the aboveground facility by a plurality of shafts, wherein the construction position of the shaft is set according to the direction of the groundwater flow. An underground facility for a high-level radioactive waste storage facility. 2. The underground facility of a high-level radioactive waste storage facility according to claim 1, wherein the position where the shaft is constructed is a position facing the downstream of the groundwater flow. 3. The underground facility of a high-level radioactive waste storage facility according to claim 1, wherein the shaft is constructed at a location upstream of the underground facility in terms of groundwater flow. 4. 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 related topographical information and geological data based on the setting, and the position of the shaft is determined. The method according to any one of claims 1 to 3, wherein the construction position is selected as a position facing the downstream of the groundwater flow, and thereafter, the position of the shaft is identified by confirming the water conveyance gradient and the flow direction. . 5. The method for setting up an underground facility according to claim 2, wherein the position of the shaft is determined again by confirming the water conveyance gradient and the flow direction.