EP1517337B1

EP1517337B1 - Method for disposing of power station facility directly below the original location

Info

Publication number: EP1517337B1
Application number: EP04255595A
Authority: EP
Inventors: Hiroshi Kawai; Masuo Kanda; Etsuko Nagai
Original assignee: Tobiyama Misa
Current assignee: TOBIYAMA, MISA
Priority date: 2003-09-16
Filing date: 2004-09-15
Publication date: 2010-04-28
Anticipated expiration: 2024-09-15
Also published as: ES2345333T3; ATE466366T1; EP1517337A1; DE602004026810D1; JP2005091059A

Abstract

A method for disposing of a power station facility after it is abolished, by drilling a disposal pit 3 directly below the power station facility 1, hanging down the power station facility 1 into the disposal pit 3 and backfilling the disposal pit 3. The method is cost effective, makes it easier to obtain consensus from residents, and eliminates the need for constructing a new disposal facility. <IMAGE>

Description

BACKGROUND OF THE INVENTION

FIELD OF THE INVENTION

This invention relates to a method of disposing of an abolished power station facility as defined in the pre-characterizing part of claim 1. As used herein, the phrase power station facility is intended to mean a nuclear power station facility or the like.

DESCRIPTION OF THE RELATED ART

Nuclear power generation in Japan has been playing a major role in power supply as an alternative energy source to oil until now since the start of operations in Tokai power plant in 1966. Power supply of about 46 million kilowatts is generated in a total of 52 nuclear reactors in 16 nuclear power stations nationwide as of 2003.
Meanwhile, because 30-40 years have passed since the start of operations of the power stations, it creates a new kind of problems such as dismantling and disposal of power station facilities due to aging or other reasons.
Although the construction of low-level disposal facility is now under way in Rokkasho village, Aomori prefecture, the disposal amount of dismantled power station facilities is expected to surpass the amount of disposal capacity by the low-level disposal facility, and there is an urgent need to take different measures to dispose of dismantled power station facilities.
Facilities' wastes, including reactor pressure vessels, are generally transported by land or sea to the low-level disposal facility and are disposed of in the ground at the disposal facility.
It has been disclosed in Japanese Patent 2001-116876 that for the construction of a reactor building, earth is dug deeply downward from directly below the reactor building beforehand, and a waste storage building is constructed adjacent to and beneath the reactor building body.
In other words, earth is dug deeply downward from the bottom floor (b) of the reactor building body (a), and the waste storage building (c) is constructed. The waste storage building (c) comprises a vessel waste storage shed (e) directly below the reactor pressure vessel (d), and waste storage shed for structures (g) to store various structures (f) within the reactor building (see FIG. 4).
The above conventional disposal technology for dismantled power station facility has the following problems. <1> When wastes are transported to a disposal facility outside a power station facility, even if they are low-level radioactive wastes or non-radioactive wastes, we cannot fully remove such risks as radioactive leakage during transportation. Therefore, delivery vehicle or carrying vessel needs to have structures to shut off radioactivity, which requires considerable expense. <2> The amount of wastes to be produced from dismantled power station facilities will exceed the permissible level of planned disposal facilities. For the construction of disposal facilities, it requires not only construction expenses but also a long time to gain residents' consensus on the construction of facilities. <3> For the future construction of power station facilities, it is important to build waste storage facilities directly below the buildings beforehand, but this cannot become a solution to dispose of wastes from the current power station facilities (which are considered not to have waste storage facilities directly below the buildings).
A method of disposing of an abolished power station facility as defined in the pre-characterizing part of claim 1 is known from prior published document DE 37 19 078 A . The method disclosed by the afore-mentioned document includes disposing the abolished power station facility directly below the original location, the power station facility being supported by mining equipment which is disposed below the power station facility and operated to drill a disposal pit into which the power station facility is lowered as the drilling of the pit progresses. Once the power station facility has reached its final position in the disposal pit, the pit is backfilled with concrete.
An object of the invention is to modify the method defined in the pre-characterizing part of claim 1 so that the power station facility can be disposed directly below the original location even though it may be difficult to drill the disposal pit from inside the building of the power station facility.
The object of the invention is achieved by creating a disposal pilot tunnel which extends into the ground below the power station facility, drilling said disposal pit after said pilot tunnel has been created, said disposal pilot tunnel and said disposal pit being created to communicate with one another, and drilling said disposal pit to a final prescribed depth before the power station facility is lowered into said disposal pit for storage in it.
As used herein, the phrase power station facilities are intended to mean, in nuclear power stations, all structures related to nuclear generation such as nuclear reactor buildings, fuel processing buildings, fuel enrichment buildings, reprocessing buildings, control buildings and pipe systems of every kind. Also, power station facilities are not limited to nuclear generation facilities but include a wide range of power station facilities including thermal power generation facilities and hydroelectric power generation facilities.
The method of disposing of a power station facility directly below the original location may comprise the steps of, drilling the disposal pit in the bedrock directly below the building of the power station facility from outside of the building so that the building and the disposal pit can be communicated after the disposal pilot tunnel has been drilled directly below the building, bringing the building and the disposal pit in communication by penetrating the bottom floor of the building, storing the generating device in the building within the disposal pit, or storing the generating device and the dismantled building in the disposal pit and backfilling the disposal pit.
As used herein, the phrase generating device is intended to mean a reactor pressure vessel or the like which changes cooling water into steam by undergoing fission internally. Also, as for storing a dismantled building within a disposal pit, the building can be hung down directly within the disposal pilot tunnel or can be stored within the disposal pit through the disposal pilot tunnel.
The dismantled parts are insulated with the use of material with buffer function and stored in an overpack, and buffer materials to control the movement of groundwater and radionuclide migration is filled up between the overpack and backfilling materials for insulation.
Furthermore, the disposal pit is backfilled by casting concrete to form artificial bedrock.
A method of this invention for disposing of a power station facility directly below the original location can achieve at least one result as follows by means to solve the above issues. <1> Because wastes are not transported outside power station facility yards, considerable expense required for transportation can be reduced. Moreover, there are no potential risks to the environment during transportation. <2> Because wastes are backfilled within power station facility yards, there is no need to build more disposal facilities like the ones being under construction. <3> Because wastes are backfilled within power station facility yards, it is easier to obtain consensus from residents and citizens. <4> For dismantling power station facilities, it does not require advanced technology to dismantle, and power station facilities can be dismantled and disposed of for a short period of time after the abolition of power station facilities.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an overall oblique perspective figure of the general description of a power station facility and disposal pits.
FIG. 2 is a sectional view, describing the situation of backfilling a reactor pressure vessel in a nuclear reactor building.
FIG. 3 is a sectional view, showing the embodiment that disposal pilot tunnels created from outside of buildings and disposal pits are communicated with buildings.
FIG. 4 is a sectional view of a conventional structure of a nuclear reactor building.

DETAILED DESCRIPTION OF THE INVENTION

<1> Power station facility

This invention relates to a method for landfilling an abolished power station facility 1 to be disposed into the ground directly below the power station facility 1. As used herein, the phrase power station facility 1 is intended to mean power station facilities for thermal power generation, hydroelectric power generation or the like besides nuclear generation facilities. In the following, we describe the case of a nuclear power station as the power station facility 1.
Nuclear power generation is a method of power generation, making fission through control of uranium fuel charged in a nuclear reactor with a control rod, boiling cooling water with heat created by the nuclear fission, taking the steam and rotating turbine thereby creating power by generator. The fission is made within a reactor pressure vessel 13 placed in a nuclear reactor building 12. The steam created by boiling cooling water in the reactor pressure vessel 13 is sent to a high-pressure turbine through pipes 14. Also, water (such as seawater) provided to the reactor pressure vessel 13 is sent through the pipes 14.
In addition to the above nuclear reactor building 12, nuclear power station facilities include fuel enrichment buildings for enriching uranium fuel, reprocessing buildings for uranium fuel and control buildings of every kind. The nuclear reactor building 12 and reprocessing buildings have separate facility yards.
In this invention, it means all structures related to the above nuclear generation when a nuclear power station is regarded as the power station facility 1.

<2> Disposal method

The disposal method of the abolished power station facility 1 (nuclear power station facility) is to dispose of the power station facility 1 by landfilling into the ground 2 directly below the original location of the power station facility 1 (see FIG. 1).
First of all, disposal pits 3 are drilled into the ground 2 directly below the power generation facility 1. As used herein, the phrase directly below the power station facility 1 means directly below each building 11 comprising the power station facility 1. It also means optional points within facility yards of the power station facility 1 and can include the case that is not directly below buildings 11.
Nuclear power station facilities are typically constructed on the firm ground 2 (on bedrock).
Therefore, the disposal pits 3 are created by drilling bedrock to a prescribed depth with heretofore known blasting method or auger drilling. Moreover, a tunnel bowling machine or the like can be used.
When the disposal pits 3 are created directly below buildings, it is preferred to create the disposal pits 3 with a drilling machine after each structure (including the reactor pressure vessel 13 and pipes 14) of the buildings 11 is dismantled.
Structures with a relatively high pollution level, including the reactor pressure vessel 13, are preferably backfilled within the disposal pits 3 having the pipes 14 connected to outside cut (see FIG. 2).
In addition, the size of the disposal pits 3 (such as diameter and length) can be decided considering the amount of wastes and influence of wastes to the surrounding environment. Especially, as measures to curb the influence of low-level radioactive or non-radioactive wastes to the surrounding environment (surrounding ground), it is also possible to drill the disposal pits 3 and construct strong pits with concrete and steel pipes.
The power station facility 1 is stored within the disposal pits 3 after the disposal pits 3 are drilled in bedrock, penetrating the bottom floor of the building thereby making the buildings 11 and disposal pits 3 being communicated,
As used herein, the phrase power station facility 1 could be only each structure (reactor pressure vessel 13 and pipes 14) within the above buildings 11 or could become a part of or all structures within facility yards including the dismantled buildings 11.
Storing is thought to use heavy machines such as a crane, but it can ensure high security during the hang-down operation with installment of airbag in the pits.
Also, it also can be stored using lifting and lowering device or the like installed within the disposal pits 3.
After the dismantled power station facility is stored in the disposal pits 3, the disposal pit s3 are backfilled.
Backfilling the disposal pits 3 is preferably conducted by recycling the surplus soil created when the disposal pits are drilled.
Moreover, when the dismantled buildings 11 are also backfilled within the disposal pits 3, it can be backfilled by cutting concrete mass being created to small pieces, casting concrete 5 which reuses the concrete mass as aggregate into the disposal pits 3.
This invention can not only increase the effect of blocking radionuclide of dismantled parts from the power station facility 1 stored within the disposal pits 3 but also prevent contact between dismantled parts of the power station facility 1 and groundwater, slow and weaken the radionuclide migration and ensure safety for a long time by making the surrounding bedrock, which forms the disposal pits 3, natural barrier and by the shielding effect of concrete 5 used for backfilling.
Also, when it is backfilled with concrete 5 after each dismantled structure (reactor pressure vessel 13 and pipes 14) is stored within the disposal pits 3, an overpack, which is not shown, and buffer materials can be used to contain radioactive materials and prevent contact with groundwater.
In other words, each dismantled structure is stored in the overpack, and the overpack and each structure are insulated with buffer materials and backfilled. Buffer materials can prevent the movement of groundwater and radionuclide migration with sorption, colloid filter or the like and have buffer effects physically and scientifically. For example, bentonite and clay can be used as buffer materials.
It is also possible to construct artificial bedrock and use as artificial barrier by using high-strength concrete with appropriate durability and strength or equivalent to surrounding bedrock for concrete 5.
As for facility yards after backfill, a power station facility 1 can be newly constructed there or local residents can use them for various purposes.

EXAMPLE

With reference to FIG. 3, disposal pilot tunnels 4 are drilled in the ground 2 from outside of the buildings 11. The disposal pilot tunnels 4 are a pilot tunnel to construct the disposal pits 3 later that is created directly below the buildings 11. The disposal pilot tunnels 4 are preferably created directly below the buildings 11, for example, by drilling horizontally, after the disposal pilot tunnels 4 are drilled vertically in the ground and reach the prescribed depth. Also, they can be created directly below the buildings 11 by drilling the disposal pilot tunnels 4 diagonally downward from outside of the buildings 11.
As for creation of the above disposal pilot tunnels 4, blasting method, auger construction method, tunnel bowling machine or the like can be used.
After the disposal pilot tunnels 4 are created directly below the buildings 11, the disposal pits 3 are created vertically upward from inside of the disposal pilot tunnels 4, for example, penetrating the bottom floor of the buildings 11 thereby making the buildings 11 and disposal pits 3 being communicated. The disposal pits 3 can be dug deeply downward from the communicating part with the disposal pilot tunnels 4.
After creation of the disposal pits 3 as mentioned above, the power station facility 1 is hung down and is backfilled. As for backfilling, the disposal pilot tunnels are preferably backfilled as well. In addition, the dismantled buildings 11 can be transported/stored within the disposal pits 3 through the disposal pilot tunnels 4.

Claims

A method of disposing of an abolished power station facility (1) into the ground (2) directly below the original location of the power station facility (1), said method comprising the steps of drilling a disposal pit (3) into the ground (2) directly below the power station (1), storing the power station facility (1) in the disposal pit (3), and backfilling the disposal pit (3), characterized in that said method further comprises the steps of creating a disposal pilot tunnel (4) which extends into the ground (2) below the power station facility (1), drilling said disposal pit after said pilot tunnel (4) has been created, said disposal pilot tunnel (4) and said disposal pit (3) being created to communicate with one another, and drilling said disposal pit (3) to a final prescribed depth before the power station facility (1) is lowered into said disposal pit (3) for storage in it.
A method as claimed in claim 1, said power station facility (1) being within or forming a part of a building (11, 12) having a floor above said disposal pit (3), wherein said method further comprises the step of penetrating said floor after drilling said disposal pit (3), thereby bringing the power station facility (1) in communication with said disposal pit (3).
A method as claimed in claim 1, said power station facility being within or forming part of a building (11, 12) having a bottom floor, and comprising a generating device (13) within said building (11, 12), said method further comprising the steps of drilling said disposal pit (3) in the bedrock (2) directly below said building (11, 12), penetrating said floor of the building (11, 12) so as to bring the inside of the building (11, 12) in communication with the disposal pit (3), and storing said generating device (13) in the disposal pit (3).
A method as claimed in claim 3, wherein said building (11, 12) is dismantled and stored in said disposal pit (3).
A method as claimed in claim 3 or 4 wherein said building (11, 12) is dismantled, thereby creating dismantled parts which are stored in an overpack, and wherein buffer materials to control the movement of groundwater and radionuclide migration are filled up between the overpack and backfilling materials for insulation.
A method as claimed in anyone of claims 1 to 4, wherein the disposal pit (3) is backfilled by casting concrete to form artificial bedrock.