JP4051885B2 - Radioactive waste disposal facility - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a radioactive waste disposal facility, and more particularly, to a gas barrier system using a gas generated from a radioactive waste disposal facility.
[0002]
[Prior art]
As a radioactive waste disposal facility, in order to prevent nuclides from migrating due to the gradient of groundwater flow, the waste is covered with a plurality of low water permeable materials. Specifically, radioactive waste is stored in a metal waste body, and this waste body is placed in an underground concrete structure, and a filling material such as cementitious material is filled in the gap between the waste bodies. Store. Moreover, the outer periphery material which consists of a low water-permeable material is filled around a structure, and it isolate | separates from the surrounding ground.
[0003]
FIG. 2 shows a longitudinal section of a conventional radioactive waste disposal facility, wherein 1 is a concrete structure composed of a bottom slab, side walls, and a top slab constructed below the groundwater level WL in the ground E, and 2 is a structure. This is a low water-permeable outer peripheral filler composed of a cement system, a bentonite system, or the like filled around the object 1. In this structure, for example, after the bottom plate and the side wall of the structure 1 are initially constructed, the metal waste bodies 3 containing radioactive waste are sequentially installed therein, and the filling material 4 is disposed between the waste bodies 3. Is repeated in order from the bottom to fill the inside of the structure 1 with waste, and thereafter, the top plate of the structure 1 is constructed, and the upper part is filled with the outer peripheral material 2 and then backfilled. As a result, the facility is closed.
[0004]
[Problems to be solved by the invention]
By the way, in the above storage method, it is avoided that groundwater etc. penetrate | infiltrate into the inside of the structure 1 with the passage of time, the metal of the waste body 3 is corroded and radioactively decomposed, and the organic substance is decomposed and gas is not generated. It has become difficult. When the gas permeation amount of the structure 1 is small compared to the amount of gas generated, the gas stays in the structure 1, the inner gas pressure of the structure 1 becomes larger than the outer groundwater pressure, and the concrete When the structure 1 reaches the tensile limit, the seam peels off or cracks occur, and as shown by the arrows in FIG. 2, gas may be released from the damaged portion at once, and the outer peripheral filler 2 may erupt. In order to avoid such a situation reliably, it is also considered to prevent the gas pressure from rising by forming a vent hole in the top plate of the concrete structure 1 in advance.
[0005]
However, in the case where a vent hole is formed in the top plate of the concrete structure 1, the vent hole becomes an air passage for the internally generated gas, and the gas is gradually discarded from the vent hole. The upper outer peripheral material 2 located in the air permeation path that is not subject to local restraint may be disturbed and damaged, and therefore sufficient verification and other reliable measures should be taken for the suppression of nuclide migration. It was necessary to take.
[0006]
The present invention solves the above-mentioned problems, and its object is to prevent cracks in a concrete structure and eruption and disturbance of a peripheral filler by using gas generated from waste. Provide a radioactive waste disposal facility.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a facility comprising a concrete structure constructed at a position lower than the groundwater level in the ground, and an outer peripheral material filled around the structure. In the radioactive waste disposal facility in which the wastes containing the radioactive waste are sequentially stored and the operation of filling the filling material between the wastes is repeated, and then the facility is closed. it is characterized in that it has a gas vent hole communicating with the prior Kigaishu material on the bottom plate of the object. Therefore, according to the present invention, when the internal pressure of the structure becomes larger than the groundwater pressure, gas escapes from the bottom side of the structure, so the internal pressure acting on the structure is limited to a differential pressure equal to or lower than the water pressure of the structure height. Is done. When the gas escapes, the outer peripheral material on the bottom side of the concrete structure is subjected to surface restraint by the bottom plate of the structure, so that even if the gas passes through the vent hole, this portion is not disturbed. In addition, the gas released into the outer peripheral material antagonizes the groundwater pressure, forms a low dynamic gradient zone to suppress the ingress of groundwater, or forms a gas unsaturated zone, and a gas barrier for preventing the ingress of groundwater. Function as.
[0008]
The invention according to claim 2 is characterized in that the outer peripheral material is made of a highly permeable filling material. Therefore, according to the present invention, since the gas supplied into the outer peripheral material is uniformly distributed to each part of the outer peripheral filler, the function as a gas barrier is increased.
[0009]
Furthermore, the invention described in claim 3 is characterized in that a sealing material is lined on the inner surface of the concrete structure. Therefore, in the present invention, the degassing part is surely specified only at the formation position of the degassing hole.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In addition, the same code | symbol is attached | subjected to the same location as the past, and it demonstrates using a different code | symbol only to a different location. FIG. 1 shows a radioactive waste disposal facility in which a gas barrier system using gas generated from a radioactive waste disposal facility according to the present invention is implemented.
[0011]
As in the prior art, an underground concrete structure 1 composed of a bottom plate, a side wall, and a top plate constructed at a position lower than the groundwater level WL, and an outer peripheral filler 2 composed of a low water-permeable material filled in the periphery thereof. It is made up of. After construction of the bottom plate and the side wall of the structure 1, the waste bodies 3 made of metal cylinders containing radioactive waste are sequentially installed in the interior from the bottom surface, and cement is placed in the gaps between the waste bodies 3. After filling the inside of the structure 1 with waste by repeating the work of filling the filling material 4 such as the system material in order from the bottom, the top plate of the structure 1 is constructed, and the outer peripheral material 2 is placed on the top. Filling and then backfilling will close the facility.
[0012]
In addition to the above, in the present embodiment, the sealing material 10 is lined on the inner surface of the concrete structure 1 to improve the airtightness of the structure 1, and the bottom plate 1a of the structure 1 is provided with a gas vent hole 12 penetrating inside and outside. The bottom-side outer peripheral material 2 is formed so as to be flush with the upper surface of the bottom plate 1a. In the figure, only one vent hole 12 is shown, but a plurality of locations can be formed according to the scale. Moreover, the diameter of each degassing hole 12 is set to a dimension that allows degassing in accordance with the predicted increase in internal pressure. Furthermore, a safety valve or a one-way valve can be installed in the gas vent hole 12 so that the valve is opened only when the internal pressure of the structure 1 exceeds a certain pressure, and the gas is allowed to escape to the outside. is there.
[0013]
Moreover, the said outer peripheral material 2 is comprised from the low water-permeable filler materials, such as a bentonite, the mixed material of a bentonite and sand, and a cement type filler. In addition, it can replace with a low water-permeable filling material, and can also comprise the outer periphery material 2 with air-permeable filling materials, such as a gravel and sand mixture material and porous concrete.
[0014]
In the above configuration, during the closing, the metal of the waste body 3 is corroded and radioactively decomposed, and the organic matter is decomposed, so that gas is generated in the concrete structure 1, and the gas stays in the structure 1. When the inner gas pressure of the structure 1 becomes larger than the outer groundwater pressure, and this pressure is equal to or higher than the pressure corresponding to the water pressure at the bottom of the structure 1, the gas gradually passes through the vent holes 12 as shown by the arrows. Therefore, the internal pressure acting on the structure 1 through the outer peripheral material 2 side is limited to a differential pressure equal to or lower than the water pressure corresponding to the height of the structure 1, so that damage to the structure is small. Eventually, in the present invention, the gas generated from the waste 3 can be stored in the concrete structure 1, and the gas pressure can be controlled to be not less than the outer groundwater pressure and not more than the cracking pressure of the structure 1 housing.
[0015]
When the gas escapes, the outer peripheral member 2 on the bottom side of the structure 1 is subjected to surface restraint by the bottom plate of the structure 1, so that even if the gas passes through the vent hole 12, this portion may be disturbed. In addition, the function as a low water permeability layer can be maintained. In addition, the gas released into the outer peripheral material 2 functions as a gas barrier to prevent infiltration of groundwater by forming a low hydrodynamic gradient zone or gas unsaturated zone that antagonizes groundwater pressure and suppresses ingress of groundwater. Thus, the infiltration of groundwater into the structure 1 is suppressed. Furthermore, since the corrosion of metal and the decomposition of organic substances are suppressed by the effect of suppressing the intrusion of groundwater, a synergistic effect that gas generation itself can be suppressed is also obtained.
[0016]
In the above embodiment, the sealing material 10 is provided on the entire inner surface of the structure 1. This is for enhancing the air leakage prevention effect of the structure 1 itself, but is not necessarily required when the air permeability of the structure 1 itself is sufficiently low.
[0017]
In the above embodiment, the outer peripheral filler 2 covering the outer periphery of the concrete structure 1 is made of a low water permeable material. However, when the outer peripheral filler 2 is made of a gas permeable or highly air permeable filler material, Is gradually released from the gas vent hole 12 and spreads uniformly in each part of the outer peripheral filler 2, or an unsaturated body is formed on the outer periphery of the concrete structure 1 to form a gas barrier isolated from the groundwater.
[0018]
【The invention's effect】
As is clear from the above description, in the radioactive waste disposal facility according to the present invention, the gas generated inside the structure is gradually released through the vent hole, so that the structure cracks due to the increase in internal pressure, The peripheral material eruption phenomenon can be prevented in advance. Moreover, the intrusion into the structure of the groundwater can be suppressed, whereby the gas generation itself can be suppressed, and the reinforcement corrosion and the hydrate dissolution that deteriorate the reinforced concrete are also suppressed.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view for explaining a radioactive waste disposal facility according to the present invention.
FIG. 2 is a sectional view for explaining a conventional radioactive waste disposal facility.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Underground concrete structure 2 Peripheral material 3 Waste body 4 Filling material 10 Sealing material 12 Gas vent hole E Ground WL Groundwater level

Claims (3)

A facility with a concrete structure constructed below the groundwater level in the ground and an outer peripheral material filled around the structure, and a waste body containing radioactive waste inside the structure In the radioactive waste disposal facility in which the facility is closed after sequentially storing and filling the filling material between the waste bodies , the outer peripheral material communicates with the bottom plate of the structure. A radioactive waste disposal facility characterized by the formation of vent holes. The radioactive waste disposal facility according to claim 1, wherein the outer peripheral material is made of a highly permeable filling material. The radioactive waste disposal facility according to claim 1, wherein a sealing material is lined on an inner surface of the concrete structure.

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