The present invention relates generally to a system and method of disposing of nuclear waste. More particularly, the invention relates to disposing of nuclear waste temporarily or permanently in underground rock formations using multilateral boreholes.
Numerous methods for disposing of nuclear waste are provided in the art. For example, an existing disposal method for nuclear waste is to bury the waste in shallow vaults also known as deep vertical wells. This method places the waste in vertical silos drilled into a mountain by a tunnel boring machine. The storage chambers are to be drilled approximately 1,000 feet into the mountain and can cost billions of dollars.
Another method proposed for disposing of nuclear waste is burial of the waste in suitable canisters in mud in the bottom of the ocean. This method is dangerous as the canisters may rupture and pollute the ocean, killing life found in the surrounding area.
A further proposal for disposing of nuclear waste is to place the waste into specially designed modules and launch the modules into space using the space shuttle. The modules will then be propelled into the sun for final incineration. This system would cost many billions of dollars and thus is not very practical.
Another method proposed is to bury the nuclear waste in suitable canisters and placing such canisters within salt caverns below the surface of earth. This method is not suitable as the salt caverns are located at quite shallow depths and in case there is a leakage, the water table may get contaminated.
It has also been proposed to bury the waste in near surface trenches or wells as used in landfills. This approach is not viable due to the great danger associated with disposing of the waste so close to the surface where leakage of the waste may do great harm to all life in the surrounding area.
It has further been proposed to bury the waste in deep vertical wells which will be sealed with cement or mud.
Burying the waste in the polar ice caps whereby the great masses of ice could enclose and isolate the radioactive material has also been proposed.
The above described methods are all illustrative of prior art methods of nuclear waste disposal. While these methods may be suitable for the particular purpose to which they address, they would not be as suitable for the purposes of the present invention as heretofore described.
The present invention is concerned with disposing of nuclear waste and, more specifically, to a method of disposing of nuclear waste in underground rock formations using multilateral horizontal boreholes.
A primary object of the present invention is to provide a method of disposing of nuclear waste in underground rock formations.
Another object of the present invention is to provide a method of disposing of nuclear waste in underground rock formations which will provide prolonged safety from the nuclear waste and added protection to human health and the environment.
An additional object of the present invention is to provide a method of disposing of nuclear waste in underground rock formations which will provide protection in case of rupturing or leaking of the canister in which the waste is stored.
Another object of the present invention is to provide a method of disposing of nuclear waste in underground rock formations which will provide safe storage of the waste for at least 10,000 years.
A further object of the present invention is to provide a method of disposing of nuclear waste in underground rock formations which is impervious to surface effects such as flooding, glaciation or seismic interference.
A still further object of the present invention is to provide a method of disposing of nuclear waste in underground rock formations which will bury the waste in horizontally extending boreholes positioned well below the earth's surface.
An even further object of the present invention is to provide a method of disposing of nuclear waste in underground rock formations which will drill a primary vertical wellbore and secondary horizontal laterals extending therefrom.
A yet further object of the present invention is to provide a method of disposing of nuclear waste in underground rock formations wherein the secondary laterals will include an inner lining made from layers of steel and optionally a lead lining.
A still further object of the present invention is to provide a method of disposing of nuclear waste in underground rock formations wherein front and end plugs will be placed within the secondary laterals for retaining canisters filled with waste.
An additional object of the present invention is to provide a method of retrieving back the disposed nuclear waste stored in the horizontal laterals in underground rock formations.
A method of disposing nuclear waste in underground rock formations is disclosed by the present invention. The method includes the steps of selecting an area of land having a rock formation positioned therebelow. The rock formation must be of a depth able to prevent radioactive material placed therein from reaching the surface and must be at least a predetermined distance from active water sources and drilling a vertical wellbore from the surface of the selected area which extends into the underground rock formation. A primary horizontal lateral is drilled from the vertical wellbore whereby the surface of the horizontal lateral is defined by the underground rock formation. A steel casing is placed within the horizontal lateral and cemented in place by circulating cement in the annular space between the steel casing and the wall of the wellbore. Nuclear waste to be stored within the lateral is placed in a canister and the encapsulated nuclear waste is positioned within the primary horizontal lateral. The primary horizontal lateral is then filled with cementitious material to seal the encapsulated nuclear waste therein. Additional primary horizontal laterals can be drilled from the vertical wellbore and secondary and tertiary horizontal laterals can be drilled from the primary horizontal lateral. Additional layers of lead, cement and steel may be used to cover the laterals and shield the rock formation from any radiation leakage. Furthermore, front and end plugs may be positioned at either end of the laterals, retaining the canisters therein and providing added protection from leakage of any solid, liquid or gaseous material.
The foregoing and other objects, advantages and characterizing features will become apparent from the following description of certain illustrative embodiments of the invention.
The novel features which are considered characteristic for the invention are set forth in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of the specific embodiments when read and understood in connection with the accompanying drawings. Attention is called to the fact, however, that the drawings are illustrative only, and that changes may be made in the specific construction illustrated and described within the scope of the appended claims.
The present invention can be more fully understood by reading the following detailed description of some of the embodiments, with reference made to the accompanying drawings.
Branching off and extending horizontally from the vertical wellbore 14 at a depth below the earth's surface occupied by the layer of cap rock 18 are primary laterals 20. The primary laterals 20 may be at different depths or at the same depth and extending at an angle 22 from one another. Any number of primary laterals 20 may be drilled from the vertical wellbore, two primary laterals are shown in
Nuclear waste is placed and secured within a radioactive capsule or canister 38. The radioactive canister 38 is well known in the art and presently used for securing nuclear waste. Any known method for securing nuclear waste in a container or capsule for placement in a lateral as produced by the present method may be used. The nuclear waste includes the potentially hazardous to the environment waste including nuclear, chemical, warfare waste, biomedical waste.
In the present embodiment, the nuclear waste canisters 38 are mechanically modified with a connector 73 as shown in
The canister 38 is positioned in the laterals 20, 24, 26 and may be held in a fixed position within the laterals 20, 24, 26 by a plurality of centralizers 40. The sequence of layers coating the laterals 20, 24, 26 act to protect the rock formation 18 in which the laterals 20, 24, 26 extend from leakage of any nuclear waste.
In order to provide additional protection from leaking nuclear waste, a front plug 49 and an end plug 50 may be positioned within the lateral as is illustrated in
Other embodiments for the protective zone of the laterals are also possible. One such embodiment is illustrated in
A detachable or disengageable connector 73 is connected to the canisters 38. For placing the canister 38 in the lateral 20, 24, 26, the canister 38 is attached to the drill pipe 76 and inserted in to the lateral 20, 24, 26 from the surface of earth. Once deployed within the lateral, the drill pipe 76 is detached from the connector 73 of the canister 38 and is pulled back to the surface, thus depositing the canister 38 with the connector 73 within the lateral 20, 24, 26. The drill pipe 76 may then be used to place additional canisters 38 within the laterals until either the laterals are filled or all the canisters are stored. Further the plugging device 77 and the sealing material 75 is placed within the lateral 20, 24, 26 to avoid movement of nuclear waste from the lateral in case of an inadvertent leakage of the nuclear waste from the canister 38.
In operation, an isolated area is selected for placement of the wellbore 14 and laterals 20, 24 and 26. The area must include a rock formation 18 therebelow and at a depth great enough to prevent any nuclear waste which may leak from reaching the surface. The rock formation 18 must also be a predetermined safe distance from any underground active water sources.
Upon selection of an appropriate area, a drilling rig 10 such as is used to drill oil wells is used to create a vertical wellbore 14 which extends into the selected rock formation 18. A window 46 is then cut into the vertical wellbore 14 at a depth occupied by the rock formation 18 and at each position from which a primary lateral 20 is desired to extend. A primary lateral 20 is then drilled into the rock formation 18 extending from each window 46 to form each primary lateral 20. The primary laterals 20 may be at differing depths below the surface from one another as long as they extend more or less horizontally, i.e. perpendicular to the vertical wellbore 14, and have dimensions, i.e. sides, defined by the rock formations 18.
Windows 46 are then cut into each primary lateral 20 at each position from which a secondary lateral 24 is desired to extend. The secondary laterals 24 are each then drilled to extend from their respective window 46 and each extend horizontally through the rock formation 18 in the same plane as the primary lateral 20 from which they depend.
Windows 46 are then cut into each secondary lateral 20 at each position from which a tertiary lateral 24 is desired to extend. The tertiary laterals 24 are each then drilled to extend from their respective window 46 and each extend horizontally through the rock formation 18 in the same plane as the primary and secondary laterals 20, 24 from which they depend.
A first steel casing 32 is installed in each lateral 20, 24, 26 and is cemented in place by circulating the cement to form the cement layer 30 which forms the first outer layer. A second outer layer is of a steel casing 54 and is sealed within the first outer casing of cement 30. The first layer of cement is thus formed by circulating cement between the first steel casing 32 and the walls of tertiary lateral 20, 24, 26. Further, a second layer of cement 34 and a layer of lead 36 is provided within the steel casing of the tertiary lateral 20, 24, 26. In order to provide added protection from radiation, which may leak within the laterals 20, 24, 26, the second inner layer 36 of lead may be replaced by alternate constructions.
In an alternate embodiment of the present invention, a first steel casing 32 is installed in the laterals 20, 24, 26. Then a first layer of cement 30 is circulated in the laterals 20, 24 or 26. Further a second steel casing 54 is placed within the first steel casing 32 and a second layer of cement 34 is formed by circulating cement between the second steel casing 54 and the first steel casing 32. Further, a layer of lead 52 is placed within the second steel casing 54, said layer of lead 52 is separated from the second steel casing 54 by a plurality of liner supports 56 placed between the second steel casing 54 and the layer of lead 52. This liner material acts as a radiation shield. The liner support 56 extends only to the entry point of the lateral 20, 24 or 26, i.e. the position at which the window 46 is cut.
A second alternate construction for the second inner layer 36 is also formed of a three-tiered structure. In this construction, a first layer of steel 60 is positioned within the first inner layer of cement 34. A layer of lead 58 is then positioned within the first inner layer of steel 60 and a second layer of steel 62 is positioned within the layer of lead 58 acting to sandwich the layer of lead 58 between the first and second layers of steel 60, 62. In an alternate construction, the layer of lead 58 only extends to the entry point of the lateral. The first and second layers of steel 60, 62 are positioned to cover the entire surface of the lateral in which they are placed and extend through each lateral from which it depends and the vertical wellbore 14. A third layer of steel 64 is positioned between the first and second layers of steel 60, 62 and extends between the sandwiching layers of steel 60, 62 from the entry point of the lateral to the top of the vertical wellbore 14. Portions of the third steel layer 64 may be replaced by a layer of lead 58 within the depending laterals which will house canisters 38 containing nuclear waste. These additional layers 58, 60, 62 and 64 provide added protection from radiation, which may leak from the canisters, preventing the radiation from leaving the lateral and entering the host rock formation 18.
An end plug may then be inserted into each of the lateral 20, 24 or 26 in which it is desired to store canisters 38 containing nuclear waste. The laterals are now prepared for storing the canisters containing nuclear waste. A plurality of centralizers 40 may be connected to the canisters 38 to hold the canisters 38 stationary within the lateral in which they are stored.
The canister 38 is modified with a detachable connector 73. The connector 73 is attached to the drill pipe 76 and is then directed through the vertical wellbore 14 and through the network of laterals until it reaches its final destination for storage. The connector 73 is then separated from the drill pipe 76 and is removed from the network through the laterals and the vertical wellbore 14 and up to the surface 12 of the selected area by hoisting up the tubular string 72. The tubular string 72 is then used to position another canister 38 within the network of laterals 20, 24 or 26. This process is repeated until the network is full or all the canisters 38 are positioned within the network.
The plugging device 77 may then be positioned at the entry point of the lateral 20, 24 or 26, i.e. at the point at which the windows 46 are cut, to seal each lateral and prevent any solid, liquid or gaseous material from escaping from the sealed lateral. The network is further filled with sealing material 75 to seal the canisters 38 in place within their respective lateral 20, 24 or 26 and also act to prevent any nuclear waste which may leak from reaching either the rock formation 18 housing the laterals or the surface of the selected area.
Alternatively, a front plug 49 may be placed within the lateral 20, 24 or 26 and an end plug 50 be placed at the terminating end of the lateral 20, 24 or 26 for sealing the canisters 38 within the lateral 20, 24 or 26 to prevent leakage of the nuclear waste.
From the above description, it is evident that the present invention provides a method of disposing of nuclear waste in underground rock formations and provides prolonged safety from the nuclear waste and added protection to human health and the environment. This method also provides protection in case of rupturing or leaking of the canister in which the waste is stored and safe storage of the waste for at least 10,000 years. It also provides storage of nuclear waste, which is impervious to surface effects such as flooding, glaciation or seismic interference. The laterals in which the waste is stored include an inner lining made from layers of cement, steel and lead and possibly also include front and end plugs to provide the above benefits.
It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of applications differing from the type described above.
While the invention has been illustrated and described as shown in the drawings, it is not intended to be limited to the details shown, since it will be understood that various omissions, modifications, substitutions and changes in the forms and details of the formulation illustrated and in its operation can be made by those skilled in the art without departing in any way from the spirit of the present invention.
Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of this invention.
Number | Date | Country | |
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61209801 | Mar 2009 | US |