Patent Description:
Hazardous waste is often placed in long-term, permanent, or semi-permanent storage so as to prevent health issues among a population living near the stored waste. Such hazardous waste storage is often challenging, for example, in terms of storage location identification and surety of containment. For instance, the safe storage of nuclear waste (e.g., spent nuclear fuel, whether from commercial power reactors, test reactors, or even high-grade military waste) is considered to be one of the outstanding challenges of energy technology. Safe storage of the long-lived radioactive waste is a major impediment to the adoption of nuclear power in the United States and around the world. <CIT> relates to a radiation irradiation method that effectively utilizes spent nuclear fuel and a cask container used therein.

In a general arrangement that is not covered by the scope of the invention, a canister to store spent nuclear fuel in an underground repository includes a first end portion; a second end portion; and a middle portion attachable to the first and second end portions to define an interior volume of the housing that is sized to enclose at least one spent nuclear fuel assembly. The first and second end portions comprise shielding.

In an aspect combinable with the general arrangement, the middle portion comprises a material configured to allow transmission of gamma rays therethrough.

In another aspect combinable with any one of the previous aspects, the material comprises a barrier to radioactive liquid, solid, and gas transmission therethrough.

In another aspect combinable with any one of the previous aspects, the radioactive gas comprises tritium gas.

In another aspect combinable with any one of the previous aspects, the middle portion comprises a circular cross-section.

In another aspect combinable with any one of the previous aspects, the second portion comprises a bottom member of the canister.

In another aspect combinable with any one of the previous aspects, the bottom member is mechanically attached to the middle portion.

In another aspect combinable with any one of the previous aspects, the mechanical attachment comprises a weld.

In another aspect combinable with any one of the previous aspects, the shielding comprises a barrier to gamma ray transmission therethrough, and the shielding comprises a barrier to radioactive liquid and gas transmission therethrough.

In another aspect combinable with any one of the previous aspects, the interior volume comprises a height dimension of between about <NUM> meters (<NUM> feet) and about <NUM> meters (<NUM> feet) and a cross-sectional diameter of between <NUM> (<NUM> inches) and <NUM> (<NUM> inches).

In another aspect combinable with any one of the previous aspects, the interior volume is sized to enclose a single spent nuclear fuel assembly.

In another aspect combinable with any one of the previous aspects, the interior volume comprises a height dimension that between about <NUM> meters (<NUM> feet) and about <NUM> meters (<NUM> feet) and a cross-sectional diameter of diameter of between <NUM> (<NUM> inches) and <NUM> (<NUM> inches).

In another aspect combinable with any one of the previous aspects, the interior volume is sized to enclose two or more spent nuclear fuel assemblies that are linearly arranged in the interior volume.

In another aspect combinable with any one of the previous aspects, the material comprises stainless or carbon steel.

In another aspect combinable with any one of the previous aspects, the material comprises titanium or a nickel-chromium alloy.

Another aspect combinable with any one of the previous aspects further includes one or more rollers or bearings mounted to the middle portion.

Another aspect combinable with any one of the previous aspects further includes an electrically non-conductive material attached to the middle portion.

In another aspect combinable with any one of the previous aspects, the non-conductive material comprises a plurality of quartz members attached to an exterior surface of the middle portion.

In another aspect combinable with any one of the previous aspects, at least a portion of the plurality of quartz members comprises spherical or partially-spherical quartz members.

Another aspect combinable with any one of the previous aspects further includes a non-conductive covering that encloses at least a portion of the non-conductive material.

In another aspect combinable with any one of the previous aspects, the non-conductive covering comprises a fiberglass sheath.

In another general arrangement that is not covered by the scope of the invention, a method for containing spent nuclear fuel material includes removing at least one spent nuclear fuel assembly from a nuclear reactor module; placing the at least one spent nuclear fuel assembly into an interior volume of a spent nuclear fuel canister, the spent nuclear fuel canister comprising a base portion and a middle portion attached to the base portion, the base and middle portions defining at least a part of the interior volume; and attaching a top portion of the spent nuclear fuel canister to the middle portion to enclose the at least one spent nuclear fuel assembly in the interior volume, the top and base portions comprising a shielding. The spent nuclear fuel canister is configured to store the at least one nuclear fuel assembly in an underground storage repository.

In an aspect combinable with the general arrangement the middle portion comprises a material configured to allow transmission of gamma rays therethrough.

In another aspect combinable with any one of the previous aspects, the interior volume comprises a height dimension of between about <NUM> meters (<NUM> feet) and about <NUM> meters (<NUM> feet)and a cross-sectional diameter of between <NUM> (<NUM> inches) and <NUM> (<NUM> inches).

In another aspect combinable with any one of the previous aspects, the unshielded material comprises stainless or carbon steel.

Another aspect combinable with any one of the previous aspects further includes a non-conductive material attached to the middle portion.

Another aspect combinable with any one of the previous aspects further includes moving the spent nuclear fuel canister through an entry of a drillhole that extends into a terranean surface, the entry at least proximate the terranean surface; moving the spent nuclear fuel canister through the drillhole that comprises a substantially vertical portion, a transition portion, and a substantially horizontal portion, the spent nuclear fuel canister sized to fit from the drillhole entry through the substantially vertical, the transition, and the substantially horizontal portions of the drillhole; moving the spent nuclear fuel canister into the underground storage repository that is coupled to the substantially horizontal portion of the drillhole, the underground storage repository located within or below a shale formation and vertically isolated, by the shale formation, from a subterranean zone that comprises mobile water; and forming a seal in the drillhole that isolates the storage portion of the drillhole from the entry of the drillhole.

In another aspect combinable with any one of the previous aspects, the underground storage repository is formed below the shale formation and is vertically isolated from the subterranean zone that comprises mobile water by the shale formation.

In another aspect combinable with any one of the previous aspects, the underground storage repository is formed within the shale formation, and is vertically isolated from the subterranean zone that comprises mobile water by at least a portion of the shale formation.

In another aspect combinable with any one of the previous aspects, the shale formation comprises geological properties comprising two or more of a permeability of less than about <NUM> millidarcys; a brittleness of less than about <NUM> MPa, where brittleness comprises a ratio of compressive stress of the shale formation to tensile strength of the shale formation; a thickness proximate the storage area of at least about <NUM> meters (<NUM> feet); or about <NUM> to <NUM>% weight by volume of organic material or clay.

In another aspect combinable with any one of the previous aspects, the drillhole further comprises at least one casing that extends from at or proximate the terranean surface, through the drillhole, and into the underground storage repository.

Another aspect combinable with any one of the previous aspects further includes prior to moving the spent nuclear fuel canister through the entry of the drillhole that extends into the terranean surface, forming the drillhole from the terranean surface to the shale formation.

Another aspect combinable with any one of the previous aspects further includes installing a casing in the drillhole that extends from at or proximate the terranean surface, through the drillhole, and into the underground storage repository.

Another aspect combinable with any one of the previous aspects further includes cementing the casing to the drillhole.

Another aspect combinable with any one of the previous aspects further includes, subsequent to forming the drillhole, producing hydrocarbon fluid from the shale formation, through the drillhole, and to the terranean surface.

Another aspect combinable with any one of the previous aspects further includes removing the seal from the drillhole; and retrieving the spent nuclear fuel canister from the underground storage repository to the terranean surface.

Another aspect combinable with any one of the previous aspects further includes monitoring at least one variable associated with the spent nuclear fuel canister from a sensor positioned proximate the underground storage repository; and recording the monitored variable at the terranean surface.

In another aspect combinable with any one of the previous aspects, the monitored variable comprises at least one of radiation level, temperature, pressure, presence of oxygen, presence of water vapor, presence of liquid water, acidity, or seismic activity.

Another aspect combinable with any one of the previous aspects further includes, based on the monitored variable exceeding a threshold value removing the seal from the drillhole; and retrieving the spent nuclear fuel canister from the underground storage repository to the terranean surface.

Another aspect combinable with any one of the previous aspects further includes placing a cylindrical shield that comprises the shielded material around the entry to the drillhole; and lowering the spent nuclear fuel canister through the cylindrical shield and into the entry of the drillhole.

In another aspect combinable with any one of the previous aspects, moving the spent nuclear fuel canister into the underground storage repository that is coupled to the substantially horizontal portion of the drillhole comprises moving the spent nuclear fuel canister on at least one wheel or roller.

In another general arrangement that is not covered by the scope of the invention, a canister to store spent nuclear fuel in an underground repository includes a first end portion; a second end portion; and a middle portion including of a material configured to allow transmission of gamma rays therethrough that is attachable to the first and second end portions to define an interior volume of the housing that is sized to enclose at least one spent nuclear fuel assembly. The first and second end portions include shielding that includes a barrier to gamma ray transmission therethrough.

In an aspect combinable with the general arrangement, the material includes a barrier to radioactive liquid, solid, and gas transmission therethrough.

In an aspect combinable with any one of the previous aspects, the radioactive gas includes tritium gas.

In an aspect combinable with any one of the previous aspects, the middle portion includes a circular cross-section.

In an aspect combinable with any one of the previous aspects, the second portion includes a bottom member of the canister.

In an aspect combinable with any one of the previous aspects, the bottom member is mechanically attached to the middle portion.

In an aspect combinable with any one of the previous aspects, wherein the shielding includes a barrier to radioactive liquid and gas transmission therethrough.

In an aspect combinable with any one of the previous aspects, the interior volume includes a height dimension of between about <NUM> meters (<NUM> feet) and about <NUM> meters (<NUM> feet) and a cross-sectional diameter of between <NUM> (<NUM> inches) and <NUM> (<NUM> inches).

In an aspect combinable with any one of the previous aspects, the interior volume is sized to enclose a single spent nuclear fuel assembly.

In an aspect combinable with any one of the previous aspects, the interior volume includes a height dimension that between about <NUM> meters (<NUM> feet) and about <NUM> meters (<NUM> feet)and a cross-sectional diameter of diameter of between <NUM> (<NUM> inches) and <NUM> (<NUM> inches).

In an aspect combinable with any one of the previous aspects, the interior volume is sized to enclose two or more spent nuclear fuel assemblies that are linearly arranged in the interior volume.

In an aspect combinable with any one of the previous aspects, the material includes at least one of stainless steel, carbon steel, titanium, or a nickel-chromium alloy.

An aspect combinable with any one of the previous aspects further includes one or more rollers or bearings mounted to the middle portion.

An aspect combinable with any one of the previous aspects further includes an electrically non-conductive material attached to the middle portion.

In an aspect combinable with any one of the previous aspects, the non-conductive material includes a plurality of quartz members attached to an exterior surface of the middle portion.

An aspect combinable with any one of the previous aspects further includes a non-conductive covering that encloses at least a portion of the non-conductive material.

In another general arrangement that is not covered by the scope of the invention, a method for containing spent nuclear fuel material includes placing at least one spent nuclear fuel assembly removed from a nuclear reactor module into an interior volume of a spent nuclear fuel canister, the spent nuclear fuel canister including a base portion and a middle portion attached to the base portion, the base and middle portions defining at least a part of the interior volume, the middle portion including a material configured to allow transmission of gamma rays therethrough; and attaching a top portion of the spent nuclear fuel canister to the middle portion to enclose the at least one spent nuclear fuel assembly in the interior volume, the top and base portions including a shielding that includes a barrier to gamma ray transmission therethrough. The spent nuclear fuel canister is configured to store the at least one nuclear fuel assembly in an underground storage repository.

In an aspect combinable with any one of the previous aspects, the shielding includes a barrier to radioactive liquid and gas transmission therethrough.

In an aspect combinable with any one of the previous aspects, the interior volume includes a height dimension of between about <NUM> meters (<NUM> feet) and about <NUM> meters (<NUM> feet)and a cross-sectional diameter of between <NUM> (<NUM> inches) and <NUM> (<NUM> inches).

In an aspect combinable with any one of the previous aspects, the material includes at least one of stainless steel, carbon steel, titanium, or nickel-chromium alloy.

In an aspect combinable with any one of the previous aspects, the spent nuclear fuel canister further includes one or more rollers or bearings mounted to the middle portion.

In an aspect combinable with any one of the previous aspects, the spent nuclear fuel canister further includes a non-conductive material attached to the middle portion.

In an aspect combinable with any one of the previous aspects, the spent nuclear fuel canister further includes a non-conductive covering that encloses at least a portion of the non-conductive material.

Implementations of a hazardous material canister according to the present disclosure may include one or more of the following features. For example, a hazardous material canister according to the present disclosure may provide for a faster and more economically efficient canister for long term storage and permanent disposal of spent nuclear fuel in particular storage locations. As another example, the hazardous material canister according to the present disclosure may allow for one or more spent nuclear fuel assemblies to move from a nuclear reactor, to one or more temporary storage locations (e.g., spent nuclear fuel pools, dry casks), and then to the canister in the same or substantially the same configuration, thereby reducing manpower hours and potential radiation exposure due to unpacking and repacking (perhaps several times) the fuel rods from the assembly. A hazardous material canister according to the present disclosure can also be more compact and lighter in weight than conventional containers used to store hazardous material, such as spent nuclear fuel, thereby improving safety while lowering the cost of handling such canisters. Further, a hazardous material according to the present disclosure that is unshielded at the sides but shielded at the ends may provide for the described advantages while also providing for the safe handling of the canisters above ground (e.g., between a nuclear reactor or spent nuclear fuel pool and a depository site). For example, a hazardous material canister that stores spent nuclear fuel can be slipped into a concrete (or steel or lead) container without a need to close the top or bottom of the container. That means, for example, that a connector (e.g., a handle, latch, or otherwise) at an end of the canister remains exposed for easy connection or disconnection, e.g. when the canister is placed in the upper part of a drillhole.

As described, a hazardous material canister according to the present disclosure may be stored in a hazardous material storage repository, which may allow for multiple levels of containment of hazardous material within a storage repository located thousands of feet underground, decoupled from any nearby mobile water. A hazardous material storage repository according to the present disclosure may also use proven techniques (e.g., drilling) to create or form a storage area for the hazardous material, in a subterranean zone. As another example, a hazardous material storage repository according to the present disclosure may provide long-term (e.g., thousands of years) storage for hazardous material (e.g., radioactive waste) in a formation (such as shale, salt, and other rock formations) that has geologic properties suitable for such storage, including low permeability, thickness, and ductility, among others. In addition, a greater volume of hazardous material may be stored at low cost - relative to conventional storage techniques - due in part to directional drilling techniques that facilitate long horizontal boreholes, often exceeding a mile in length. In addition, rock formations that have geologic properties suitable for such storage may be found in close proximity to sites at which hazardous material may be found or generated, thereby reducing dangers associated with transporting such hazardous material.

Implementations of a hazardous material storage repository according to the present disclosure may also include one or more of the following features. Large storage volumes, in turn, allow for the storage of hazardous materials to be emplaced without a need for complex prior treatment, such as concentration or transfer to different forms or canisters. As a further example, in the case of nuclear waste material from a reactor for instance, the waste can be kept in its original pellets, unmodified, or in its original fuel rods, or in its original fuel assemblies, which contain typically between <NUM> and <NUM> fuel rods. In another aspect, the hazardous material may be kept in an original holder but a cement or other material is injected into the holder to fill the gaps between the hazardous materials and the structure. For example, if the hazardous material is stored in fuel rods which are, in turn, stored in fuel assemblies, then the spaces between the rods (typically filled with water when inside a nuclear reactor) could be filled with cement, bentonite, or other material to provide yet an additional layer of isolation from the outside world. The material could be low oxygen, replaced by nitrogen or an inert gas, to reduce corrosion. As yet a further example, secure and low cost storage of hazardous material is facilitated while still permitting retrieval of such material if circumstances deem it advantageous to recover the stored materials.

The details of one or more implementations of the subject matter described in this disclosure are set forth in the accompanying drawings and the description below.

<FIG> is a schematic illustration of an example implementation of a hazardous material canister <NUM> according to the present disclosure. <FIG> illustrates an isometric view of the hazardous material canister <NUM>. In some aspects, the hazardous material canister <NUM> may be usable in a hazardous material storage repository system <NUM>, as shown in <FIG>, or other hazardous material storage repository system according to the present disclosure. The hazardous material canister <NUM> may be used to store chemical hazardous material, biological hazardous material, nuclear hazardous material, or otherwise. For example, in the illustrated implementation, the hazardous material canister <NUM> stores spent nuclear fuel in the form of one or more spent nuclear fuel assemblies.

As illustrated, the hazardous material canister <NUM> includes a housing <NUM> (e.g., a crush resistant housing) with a top portion <NUM> and a bottom portion <NUM> that, collectively, enclose a volume <NUM> to store the hazardous material. The housing <NUM>, or middle portion <NUM> of the canister, in this example, is shown as having a circular cross-section, to accommodate a general shape of a spent nuclear fuel assembly (as shown in <FIG>). However, other implementations of the canister <NUM> may have other cross-sectional shapes, such as oval, square, or otherwise.

The top and bottom portions <NUM> and <NUM> may be made from, or include, a shielding that is of a material of composition and thickness that forms a barrier to the transmission (into the canister <NUM> or out of the canister <NUM>) of any hazardous material (liquid, gas, or solid) therethrough. The shielding also reduces an intensity of a radiation to a level that allows safe handling of the canister <NUM> (e.g., by human operators). In some aspects, the shielding may be lead, tungsten, steel, titanium, nickel, or concrete, or an alloy or combination of such materials with a thickness sufficient to form a sufficient barrier to the transmission of radiation, such as gamma rays and x-rays (collectively, "gamma rays"), therethrough. The shielding on the top and bottom portions <NUM> and <NUM> allows for easier handling of the canisters with enhanced safety to people in its vicinity. An example thickness is between <NUM> and <NUM> (<NUM> and <NUM> inches) for a lead shielding, and between <NUM> meters and <NUM> meters (<NUM> and <NUM> feet) for a concrete shielding.

In example implementations of the hazardous material canister <NUM>, the middle portion <NUM> may be made from a material of a composition and thickness that forms a barrier to the transmission (into the canister <NUM> or out of the canister <NUM>) of any hazardous material (liquid, gas, or solid) therethrough, but is not a barrier to gamma rays. Further, in some aspects, the unshielded material may be steel, such as carbon steel, with a thickness sufficient to form a barrier to the transmission of any hazardous material (fluid or solid) therethrough, but is not a barrier to gamma rays. In particular implementations, the barrier to leakage of liquid, gas, or solid might be made from alloy-<NUM> (a nickel alloy) which is also used for the middle portion <NUM>, and a layer of lead that is placed only at the ends of the canister <NUM> to prevent gamma radiation from escaping in the direction of the long axis of the canister <NUM>.

Hazardous waste, and particular nuclear material waste such as spent nuclear fuel, may take several forms, such as solid, liquid, and gas. For example, the solid form of the nuclear waste in spent nuclear fuel may be or includes nuclear fuel pellets formed from, e.g., sintered uranium. A gaseous form of the nuclear waste may be, for example, tritium gas (or gas containing other radioisotopes) that may off-gas from the solid nuclear waste or be entrained in liquid that comes into contact with the solid nuclear waste. A liquid form of the nuclear waste may be, for example, any liquid that comes into contact with the solid or gaseous nuclear waste and absorbs some of the solid or gaseous nuclear waste material.

As shown in the example hazardous material canister <NUM> shown in <FIG>, the interior volume <NUM> may be sized (and shaped) to receive one or more spent nuclear fuel assemblies (e.g., arranged end-to-end), such as spent nuclear fuel assembly <NUM> shown in <FIG>. Turning briefly to <FIG>, a single nuclear fuel assembly <NUM> is shown. The nuclear fuel assembly <NUM>, also referred to as a "spent nuclear fuel assembly" <NUM> to signify when it has been removed from a nuclear reactor, such as a pressurized water reactor or other type of reactor, due to end-of-life operational occurrence, includes a top portion <NUM> and a bottom portion <NUM> between which are held multiple (e.g., <NUM>-<NUM>) nuclear fuel rods <NUM>.

As shown, the nuclear fuel assembly <NUM> also includes multiple control rods <NUM> positioned amongst the nuclear fuel rods <NUM>; the control rods <NUM> may be adjustably positioned (vertically, within the assembly), during operation (e.g., fission) of the nuclear fuel assembly <NUM> in a reactor vessel of a nuclear reactor, to control the nuclear reaction taking place in the reactor. Such control rods <NUM> may be removed from the nuclear fuel assembly <NUM> upon removal of the assembly <NUM> from the reactor. Thus, a spent nuclear fuel assembly <NUM> may not include the control rods <NUM>. Notably, as well, the nuclear fuel assembly <NUM> does not include any gamma or x-ray shielding that surrounds the nuclear fuel rods <NUM> positioned in the assembly <NUM>.

Turning briefly to <FIG>, an example nuclear fuel rod <NUM> is illustrated. The nuclear fuel rod <NUM> includes multiple (e.g., <NUM> or more) nuclear fuel pellets <NUM> encased in a cladding <NUM> (e.g., a zirconium alloy cladding). Each of the nuclear fuel pellets <NUM> may be formed of, for example, sintered uranium dioxide. One or more springs <NUM> may be positioned at a top portion of the rod <NUM> to hold the fuel pellets <NUM> sturdily within the cladding <NUM>. A base <NUM> is provided at the bottom of the fuel rod <NUM> to fit within the nuclear fuel assembly <NUM>.

The example nuclear fuel assembly <NUM> may be, for example, between <NUM> meters (<NUM> feet) and <NUM> meters (<NUM> feet) (e.g., from bottom of bottom portion <NUM> to top of top portion <NUM>). Further, the width and length dimensions may be, for example, about <NUM> and <NUM> (<NUM> to <NUM> inches) each (e.g., each side of the substantially square cross-section is between about <NUM> and <NUM> (<NUM> and <NUM> inches)). Thus, in some aspects, the canister <NUM> may have a height of between <NUM> meters (<NUM> feet) and <NUM> meters (<NUM> feet) (to store a single spent nuclear fuel assembly <NUM>) and a diameter of between (<NUM> inches) and <NUM> (<NUM> inches).

Returning to <FIG>, the top portion <NUM> (and, in some aspects, the bottom portion <NUM>) of the illustrated hazardous material canister <NUM> may include a connector portion. In some aspects, the connector portion may facilitate coupling of the hazardous material canister <NUM> to a downhole tool (e.g., downhole tool <NUM> shown in <FIG>) to permit deposit and retrieval of the hazardous material canister <NUM> to and from storage in a drillhole. Further, the connector portion may facilitate coupling of one hazardous material canister <NUM> to another hazardous material canister <NUM>. The connector portion, in some aspects, may be a threaded connection. For example, a connector portion on one end of the canister <NUM> may be a male threaded connection while a connector portion on the opposite end of the canister <NUM> may be a female threaded connection. In alternative aspects, the connector portion may be an interlocking latch, such that rotation (e.g., <NUM> degrees or less) may latch (or unlatch) the canister <NUM> to a downhole tool or other hazardous material canister <NUM>. In alternative aspects, the connector portion may include one or more magnets (e.g., rare Earth magnets, electromagnets, a combination thereof, or otherwise) which attractingly couple to, e.g., a downhole tool or another hazardous material canister <NUM>.

In this example, one or more spent nuclear fuel assemblies <NUM> is positioned in the interior volume <NUM> prior to sealing of the hazardous material canister <NUM>. As described, each spent nuclear fuel rod <NUM> comprises multiple spent nuclear fuel pellets <NUM> bounded on the ends. For example, the spent nuclear fuel pellets <NUM> contain most of the radioisotopes (including the tritium) of the spent nuclear fuel removed from a nuclear reactor. The cladding of the nuclear fuel rods <NUM> offers an additional level of containment.

In some aspects, the dimensions of the hazardous material canister <NUM> may be specified so as to enclose a single spent nuclear fuel assembly <NUM> that may be taken directly from a nuclear reactor and placed in the interior volume <NUM> (e.g., without any change or without substantive change to the spent nuclear fuel assembly <NUM>). In some aspects, the dimensions of the hazardous material canister <NUM> may be specified so as to enclose two or more spent nuclear fuel assemblies <NUM> that may be taken directly from a nuclear reactor and placed vertically (e.g., end to end) in the interior volume <NUM>.

Further, the dimensions of the hazardous material canister <NUM>, generally, may be designed to fit in a drillhole, such as the drillhole <NUM>. Example dimensions of the canister <NUM> may include a length, L, of between <NUM> meters (<NUM> feet) and <NUM> meters (<NUM> feet), and, in the case of a circular canister <NUM>, diameter between (<NUM> inches) and <NUM> (<NUM> inches). The canister <NUM>, in alternative aspects, may have a square cross-section sized to hold a spent nuclear fuel assembly <NUM>. In some examples, the hazardous material canister <NUM> may be sized (e.g., length and width/diameter) for efficient deposit and retrieval into and from the drillhole <NUM>. For example, the length may be determined based on, e.g., the radius dimension of the radiussed portion <NUM>, to ensure that the hazardous material canister <NUM> may be moved through the radiussed portion <NUM> and into the substantially horizontal portion <NUM>. As another example, the diameter may be determined based on a diameter of one or more of the casings in the drillhole <NUM>, such as the surface casing <NUM> and the production casing <NUM>.

<FIG> is a schematic illustration of another example implementation of a hazardous material canister <NUM> according to the present disclosure. <FIG> illustrates an isometric view of the hazardous material canister <NUM>. In some aspects, the hazardous material canister <NUM> may be usable in a hazardous material storage repository system <NUM>, along with or in place of canister <NUM>, or other hazardous material storage repository system according to the present disclosure. The hazardous material canister <NUM> may be used to store chemical hazardous material, biological hazardous material, nuclear hazardous material, or otherwise. For example, in the illustrated implementation, the hazardous material canister <NUM> stores spent nuclear fuel in the form of one or more spent nuclear fuel assemblies.

The top and bottom portions <NUM> and <NUM> may be made from, or include, a shielding that is of a material of composition and thickness that forms a barrier to the transmission (into the canister <NUM> or out of the canister <NUM>) of any hazardous material (liquid, gas, or solid) therethrough. The shielding also reduces an intensity of a radiation to a level that allows safe handling of the canister <NUM> (e.g., by human operators). In some aspects, the shielding may be lead, tungsten, steel, titanium, nickel, or concrete, or an alloy or combination of such materials with a thickness sufficient to form a sufficient barrier to the transmission of radiation, such as gamma rays therethrough. The shielding on the top and bottom portions <NUM> and <NUM> allows for easier handling of the canisters with enhanced safety to people in its vicinity. An example thickness is between <NUM> and <NUM> (<NUM> and <NUM> inches)for a lead shielding, and between <NUM> meters and <NUM> meters (<NUM> and <NUM> feet) for a concrete shielding.

In example implementations of the hazardous material canister <NUM>, the middle portion <NUM> may be made from a material of a composition and thickness that forms a barrier to the transmission (into the canister <NUM> or out of the canister <NUM>) of any hazardous material (liquid, gas, or solid) therethrough, but is not a barrier to gamma rays. Further, in some aspects, the unshielded material may be steel, such as carbon steel, with a thickness sufficient to form a barrier to the transmission of any hazardous material (fluid or solid) therethrough, but is not a barrier to gamma rays and x-rays.

As shown in the example hazardous material canister <NUM> shown in <FIG>, the interior volume <NUM> may be sized (and shaped) to receive one or more spent nuclear fuel assemblies (e.g., arranged end-to-end), such as spent nuclear fuel assembly <NUM> shown in <FIG>. The space in the fuel assembly could be filled with gas (such as nitrogen), with powder (such as bentonite), with liquid (such as a liquid hydrocarbon), or with a solid (such as cement or epoxy) or with a combination (such as oil and bentonite, or fiberglass, which consists of glass fibers and epoxy).

The top portion <NUM> (and, in some aspects, the bottom portion <NUM>) of the illustrated hazardous material canister <NUM> may include a connector portion. In some aspects, the connector portion may facilitate coupling of the hazardous material canister <NUM> to a downhole tool (e.g., downhole tool <NUM> shown in <FIG>) to permit deposit and retrieval of the hazardous material canister <NUM> to and from storage in a drillhole. Further, the connector portion may facilitate coupling of one hazardous material canister <NUM> to another hazardous material canister <NUM>. The connector portion, in some aspects, may be a threaded connection. For example, a connector portion on one end of the canister <NUM> may be a male threaded connection while a connector portion on the opposite end of the canister <NUM> may be a female threaded connection. In alternative aspects, the connector portion may be an interlocking latch, such that rotation (e.g., <NUM> degrees or less) may latch (or unlatch) the canister <NUM> to a downhole tool or other hazardous material canister <NUM>. In alternative aspects, the connector portion may include one or more magnets (e.g., rare Earth magnets, electromagnets, a combination thereof, or otherwise) which attractingly couple to, e.g., a downhole tool or another hazardous material canister <NUM>.

As shown in <FIG>, hazardous material canister <NUM> includes an electrically non-conductive ("non-conductive") material mounted to an exterior surface of the canister <NUM> in the form of multiple non-conductive members <NUM>. The non-conductive material (non-conductive member <NUM>) may not conduct electricity. Thus, in some aspects, the non-conductive material may prevent a direct electrically conductive ("conductive") path for electricity between the canister <NUM> and, for example, a casing in a drillhole in which the canister <NUM> is stored. Thus, to the extent a material of the casing (e.g., carbon steel) and a material of the middle portion <NUM> (e.g., titanium, a nickel-chromium alloy such as alloy <NUM>) form a "battery" (with a conductive liquid, such as brine, in the drillhole in between), the non-conductive material reduces the potential for an electrical current connecting the casing and the canister <NUM>.

In some aspects, the non-conductive members <NUM> may be quartz members that are spherical or partially spherical in shape and are attached to the exterior surface of the middle portion <NUM>. Other shapes (e.g., rod shaped, cube or partial-cube) are also contemplated for the non-conductive members <NUM> according to the present disclosure. Further, other non-conductive materials, such as glass, ceramic, plastic, rubber, may be used in place of quartz. Generally, quartz provided a non-conductive material that also does not degrade or disintegrate within the drillhole for hundreds if not thousands of years.

As further shown in <FIG>, a non-conductive sheath <NUM> covers at least a portion of the hazardous material canister <NUM> to enclose the non-conductive member <NUM>. In some aspects, the non-conductive sheath <NUM> may be formed from a flexible, non-conductive material such as fiberglass. The non-conductive sheath <NUM> may provide for a reduced-friction surface that facilitates easier movement of the canister <NUM> through one or more drillholes. The non-conductive sheath <NUM> may also provide some protection to the non-conductive members <NUM> during movement of the canister <NUM> through one or more drillholes. In some aspects, the non-conductive sheath <NUM> may eventually erode or disintegrate during long-term storage of the hazardous material canister <NUM> in an underground storage repository.

<FIG> are schematic illustrations of example implementations of a hazardous material storage repository system, e.g., a subterranean location for the long-term (e.g., tens, hundreds, or thousands of years or more) but retrievable safe and secure storage of hazardous material, during a deposit or retrieval operation according to the present disclosure. For example, turning to <FIG>, this figure illustrates an example hazardous material storage repository system <NUM> during a deposit (or retrieval, as described below) process, e.g., during deployment of one or more canisters of hazardous material in a subterranean formation. As illustrated, the hazardous material storage repository system <NUM> includes a drillhole <NUM> formed (e.g., drilled or otherwise) from a terranean surface <NUM> and through multiple subterranean layers <NUM>, <NUM>, <NUM>, and <NUM>. Although the terranean surface <NUM> is illustrated as a land surface, terranean surface <NUM> may be a sub-sea or other underwater surface, such as a lake or an ocean floor or other surface under a body of water. Thus, the present disclosure contemplates that the drillhole <NUM> may be formed under a body of water from a drilling location on or proximate the body of water.

The illustrated drillhole <NUM> is a directional drillhole in this example of hazardous material storage repository system <NUM>. For instance, the drillhole <NUM> includes a substantially vertical portion <NUM> coupled to a radiussed or curved portion <NUM>, which in turn is coupled to a substantially horizontal portion <NUM>. As used in the present disclosure, "substantially" in the context of a drillhole orientation, refers to drillholes that may not be exactly vertical (e.g., exactly perpendicular to the terranean surface <NUM>) or exactly horizontal (e.g., exactly parallel to the terranean surface <NUM>). Further, the substantially horizontal portion <NUM>, in some aspects, may be a slant drillhole or other directional drillhole that is oriented between exactly vertical and exactly horizontal. Further, the substantially horizontal portion <NUM>, in some aspects, may be a slant drillhole or other directional drillhole that is oriented to follow the slant of the formation. As illustrated in this example, the three portions of the drillhole <NUM> - the vertical portion <NUM>, the radiussed portion <NUM>, and the horizontal portion <NUM> - form a continuous drillhole <NUM> that extends into the Earth.

The illustrated drillhole <NUM> has a surface casing <NUM> positioned and set around the drillhole <NUM> from the terranean surface <NUM> into a particular depth in the Earth. For example, the surface casing <NUM> may be a relatively large-diameter tubular member (or string of members) set (e.g., cemented) around the drillhole <NUM> in a shallow formation. As used herein, "tubular" may refer to a member that has a circular cross-section, elliptical cross-section, or other shaped cross-section. For example, in this implementation of the hazardous material storage repository system <NUM>, the surface casing <NUM> extends from the terranean surface through a surface layer <NUM>. The surface layer <NUM>, in this example, is a geologic layer comprised of one or more layered rock formations. In some aspects, the surface layer <NUM> in this example may or may not include freshwater aquifers, salt water or brine sources, or other sources of mobile water (e.g., water that moves through a geologic formation). In some aspects, the surface casing <NUM> may isolate the drillhole <NUM> from such mobile water, and may also provide a hanging location for other casing strings to be installed in the drillhole <NUM>. Further, although not shown, a conductor casing may be set above the surface casing <NUM> (e.g., between the surface casing <NUM> and the surface <NUM> and within the surface layer <NUM>) to prevent drilling fluids from escaping into the surface layer <NUM>.

As illustrated, a production casing <NUM> is positioned and set within the drillhole <NUM> downhole of the surface casing <NUM>. Although termed a "production" casing, in this example, the casing <NUM> may or may not have been subject to hydrocarbon production operations. Thus, the casing <NUM> refers to and includes any form of tubular member that is set (e.g., cemented) in the drillhole <NUM> downhole of the surface casing <NUM>. In some examples of the hazardous material storage repository system <NUM>, the production casing <NUM> may begin at an end of the radiussed portion <NUM> and extend throughout the substantially horizontal portion <NUM>. The casing <NUM> could also extend into the radiussed portion <NUM> and into the vertical portion <NUM>.

As shown, cement <NUM> is positioned (e.g., pumped) around the casings <NUM> and <NUM> in an annulus between the casings <NUM> and <NUM> and the drillhole <NUM>. The cement <NUM>, for example, may secure the casings <NUM> and <NUM> (and any other casings or liners of the drillhole <NUM>) through the subterranean layers under the terranean surface <NUM>. In some aspects, the cement <NUM> may be installed along the entire length of the casings (e.g., casings <NUM> and <NUM> and any other casings), or the cement <NUM> could be used along certain portions of the casings if adequate for a particular drillhole <NUM>. The cement <NUM> can also provide an additional layer of confinement for the hazardous material in canisters <NUM>.

The drillhole <NUM> and associated casings <NUM> and <NUM> may be formed with various example dimensions and at various example depths (e.g., true vertical depth, or TVD). For instance, a conductor casing (not shown) may extend down to about <NUM> meters (<NUM> feet) TVD, with a diameter of between about <NUM> and <NUM> (<NUM> in. and <NUM> in). The surface casing <NUM> may extend down to about <NUM> meters (<NUM> feet) TVD, with a diameter of between about <NUM> and <NUM> (<NUM> in. and <NUM> in). An intermediate casing (not shown) between the surface casing <NUM> and production casing <NUM> may extend down to about <NUM> meters (<NUM> feet) TVD, with a diameter of between about <NUM> and <NUM> (<NUM> in. and <NUM> in). The production casing <NUM> may extend substantially horizontally (e.g., to case the substantially horizontal portion <NUM>) with a diameter of between about <NUM> and <NUM> (<NUM> in. and <NUM> in). The foregoing dimensions are merely provided as examples and other dimensions (e.g., diameters, TVDs, lengths) are contemplated by the present disclosure. For example, diameters and TVDs may depend on the particular geological composition of one or more of the multiple subterranean layers (<NUM>-<NUM>), particular drilling techniques, as well as a size, shape, or design of a hazardous material canister <NUM> that contains hazardous material to be deposited in the hazardous material storage repository system <NUM>. In some alternative examples, the production casing <NUM> (or other casing in the drillhole <NUM>) could be circular in cross-section, elliptical in cross-section, or some other shape.

As illustrated, the vertical portion <NUM> of the drillhole <NUM> extends through subterranean layers <NUM>, <NUM>, and <NUM>, and, in this example, lands in a subterranean layer <NUM>. As discussed above, the surface layer <NUM> may or may not include mobile water. Subterranean layer <NUM>, which is below the surface layer <NUM>, in this example, is a mobile water layer <NUM>. For instance, mobile water layer <NUM> may include one or more sources of mobile water, such as freshwater aquifers, salt water or brine, or other source of mobile water. In this example of hazardous material storage repository system <NUM>, mobile water may be water that moves through a subterranean layer based on a pressure differential across all or a part of the subterranean layer. For example, the mobile water layer <NUM> may be a permeable geologic formation in which water freely moves (e.g., due to pressure differences or otherwise) within the layer <NUM>. In some aspects, the mobile water layer <NUM> may be a primary source of human-consumable water in a particular geographic area. Examples of rock formations of which the mobile water layer <NUM> may be composed include porous sandstones and limestones, among other formations.

Other illustrated layers, such as the impermeable layer <NUM> and the storage layer <NUM>, may include immobile water. Immobile water, in some aspects, is water (e.g., fresh, salt, brine), that is not fit for human or animal consumption, or both. Immobile water, in some aspects, may be water that, by its motion through the layers <NUM> or <NUM> (or both), cannot reach the mobile water layer <NUM>, terranean surface <NUM>, or both, within <NUM>,<NUM> years or more (such as to <NUM>,<NUM>,<NUM> years).

Below the mobile water layer <NUM>, in this example implementation of hazardous material storage repository system <NUM>, is an impermeable layer <NUM>. The impermeable layer <NUM>, in this example, may not allow mobile water to pass through. Thus, relative to the mobile water layer <NUM>, the impermeable layer <NUM> may have low permeability, e.g., on the order of nanodarcy permeability. Additionally, in this example, the impermeable layer <NUM> may be a relatively non-ductile (i.e., brittle) geologic formation. One measure of non-ductility is brittleness, which is the ratio of compressive stress to tensile strength. In some examples, the brittleness of the impermeable layer <NUM> may be between about <NUM> MPa and <NUM> MPa.

As shown in this example, the impermeable layer <NUM> is shallower (e.g., closer to the terranean surface <NUM>) than the storage layer <NUM>. In this example rock formations of which the impermeable layer <NUM> may be composed include, for example, certain kinds of sandstone, mudstone, limestone, clay, and slate that exhibit permeability and brittleness properties as described above. In alternative examples, the impermeable layer <NUM> may be deeper (e.g., further from the terranean surface <NUM>) than the storage layer <NUM>. In such alternative examples, the impermeable layer <NUM> may be composed of an igneous rock, such as granite or basalt.

Below the impermeable layer <NUM> is a storage layer <NUM>. The storage layer <NUM>, in this example, may be chosen as the landing for the substantially horizontal portion <NUM>, which stores the hazardous material, for several reasons. Relative to the impermeable layer <NUM> or other layers, the storage layer <NUM> may be thick, e.g., between about <NUM> and <NUM> meters (<NUM> and <NUM> feet) of total vertical thickness. Thickness of the storage layer <NUM> may allow for easier landing and directional drilling, thereby allowing the substantially horizontal portion <NUM> to be readily emplaced within the storage layer <NUM> during constructions (e.g., drilling). The landing layer could consist of more than one geologic formation; for example, it could consist of a layer of shale above a layer of sandstone. If formed through an approximate horizontal center of the storage layer <NUM>, the substantially horizontal portion <NUM> may be surrounded by about <NUM> to <NUM> meters (<NUM> to <NUM> feet) of the geologic formation that comprises the storage layer <NUM>. Further, the storage layer <NUM> may also have little or no mobile water, e.g., due to a very low permeability of the layer <NUM> (e.g., on the order of micro- or nanodarcys). In addition, the storage layer <NUM> may have sufficient ductility, such that a brittleness of the rock formation that comprises the layer <NUM> is between about <NUM> MPa and <NUM> MPa. Examples of rock formations of which the storage layer <NUM> may be composed include: shale and anhydrite. Further, in some aspects, hazardous material may be stored below the storage layer, even in a permeable formation such as sandstone or limestone, if the storage layer is of sufficient geologic properties to isolate the permeable layer from the mobile water layer <NUM>.

In some examples implementations of the hazardous material storage repository system <NUM>, the storage layer <NUM> is composed of shale. Shale, in some examples, may have properties that fit within those described above for the storage layer <NUM>. For example, shale formations may be suitable for a long-term confinement of hazardous material (e.g., in the hazardous material canisters <NUM>), and for their isolation from mobile water layer <NUM> (e.g., aquifers) and the terranean surface <NUM>. Shale formations may be found relatively deep in the Earth, typically <NUM> meters (<NUM> feet) or greater, and placed in isolation below any fresh water aquifers.

Shale formations, for instance, may include geologic properties that enhance the long-term (e.g., thousands of years) isolation of material. Such properties, for instance, have been illustrated through the long term storage (e.g., tens of millions of years) of hydrocarbon fluids (e.g., gas, liquid, mixed phase fluid) without escape of such fluids into surrounding layers (e.g., mobile water layer <NUM>). Indeed, shale has been shown to hold natural gas for millions of years or more, giving it a proven capability for long-term storage of hazardous material. Example shale formations (e.g., Marcellus, Eagle Ford, Barnett, and otherwise) has stratification that contains many redundant sealing layers that have been effective in preventing movement of water, oil, and gas for millions of years, lacks mobile water, and can be expected (e.g., based on geological considerations) to seal hazardous material (e.g., fluids or solids) for thousands of years after deposit.

Shale formations may also be at a suitable depth, e.g., between <NUM> and <NUM> (<NUM> and <NUM>,<NUM> feet) TVD. Such depths are typically below ground water aquifer (e.g., surface layer <NUM> and/or mobile water layer <NUM>). Further, the presence of soluble elements in shale, including salt, and the absence of these same elements in aquifer layers, demonstrates a fluid isolation between shale and the aquifer layers.

Another particular quality of shale that may advantageously lend itself to hazardous material storage is its clay content, which, in some aspects, provides a measure of ductility greater than that found in other impermeable rock formations (e.g., impermeable layer <NUM>). For example, shale may be stratified, made up of thinly alternating layers of clays (e.g., between about <NUM>-<NUM>% clay by volume) and other minerals. Such a composition may make shale less brittle and, thus less susceptible to fracturing (e.g., naturally or otherwise) as compared to rock formations in the impermeable layer (e.g., granite or otherwise). For example, rock formations in the impermeable layer <NUM> may have suitable permeability for the long term storage of hazardous material, but are too brittle and commonly are fractured. Thus, such formations may not have sufficient sealing qualities (as evidenced through their geologic properties) for the long term storage of hazardous material.

The present disclosure contemplates that there may be many other layers between or among the illustrated subterranean layers <NUM>, <NUM>, <NUM>, and <NUM>. For example, there may be repeating patterns (e.g., vertically), of one or more of the mobile water layer <NUM>, impermeable layer <NUM>, and storage layer <NUM>. Further, in some instances, the storage layer <NUM> may be directly adjacent (e.g., vertically) the mobile water layer <NUM>, i.e., without an intervening impermeable layer <NUM>.

<FIG> illustrates an example of a deposit operation of hazardous material in the substantially horizontal portion <NUM> of the drillhole <NUM>. For example, as shown, a work string <NUM> (e.g., tubing, coiled tubing, wireline, or otherwise) may be extended into the cased drillhole <NUM> to place one or more (three shown but there may be more or less) hazardous material canisters <NUM> into long term, but in some aspects, retrievable, storage in the portion <NUM>. For example, in the implementation shown in <FIG>, the work string <NUM> may include a downhole tool <NUM> that couples to the canister <NUM>, and with each trip into the drillhole <NUM>, the downhole tool <NUM> may deposit a particular hazardous material canister <NUM> in the substantially horizontal portion <NUM>.

The downhole tool <NUM> may couple to the canister <NUM> by, in some aspects, a threaded connection. In alternative aspects, the downhole tool <NUM> may couple to the canister <NUM> with an interlocking latch, such that rotation of the downhole tool <NUM> may latch to (or unlatch from) the canister <NUM>. In alternative aspects, the downhole tool <NUM> may include one or more magnets (e.g., rare Earth magnets, electromagnets, a combination thereof, or otherwise) which attractingly couple to the canister <NUM>. In some examples, the canister <NUM> may also include one or more magnets (e.g., rare Earth magnets, electromagnets, a combination thereof, or otherwise) of an opposite polarity as the magnets on the downhole tool <NUM>. In some examples, the canister <NUM> may be made from or include a ferrous or other material attractable to the magnets of the downhole tool <NUM>.

As another example, each canister <NUM> may be positioned within the drillhole <NUM> by a drillhole tractor (e.g., on a wireline or otherwise), which may push or pull the canister into the substantially horizontal portion <NUM> through motorized (e.g., electric) motion. As yet another example, each canister <NUM> may include or be mounted to rollers (e.g., wheels or bearings), so that the downhole tool <NUM> may push the canister <NUM> into the cased drillhole <NUM>.

In some example implementations, the canister <NUM>, one or more of the drillhole casings <NUM> and <NUM>, or both, may be coated with a friction-reducing coating prior to the deposit operation. For example, by applying a coating (e.g., petroleum-based product, resin, ceramic, or otherwise) to the canister <NUM> and/or drillhole casings, the canister <NUM> may be more easily moved through the cased drillhole <NUM> into the substantially horizontal portion <NUM>. In some aspects, only a portion of the drillhole casings may be coated. For example, in some aspects, the substantially vertical portion <NUM> may not be coated, but the radiussed portion <NUM> or the substantially horizontal portion <NUM>, or both, may be coated to facilitate easier deposit and retrieval of the canister <NUM>.

<FIG> also illustrates an example of a retrieval operation of hazardous material in the substantially horizontal portion <NUM> of the drillhole <NUM>. A retrieval operation may be the opposite of a deposit operation, such that the downhole tool <NUM> (e.g., a fishing tool) may be run into the drillhole <NUM>, coupled to the last-deposited canister <NUM> (e.g., threadingly, latched, by magnet, or otherwise), and pull the canister <NUM> to the terranean surface <NUM>. Multiple retrieval trips may be made by the downhole tool <NUM> in order to retrieve multiple canisters from the substantially horizontal portion <NUM> of the drillhole <NUM>.

Each canister <NUM> may enclose hazardous material. Such hazardous material, in some examples, may be biological or chemical waste or other biological or chemical hazardous material. In some examples, the hazardous material may include nuclear material, such as spent nuclear fuel recovered from a nuclear reactor (e.g., commercial power or test reactor) or military nuclear material. For example, a typical gigawatt nuclear plant may produce <NUM> tons of spent nuclear fuel per year. The density of that fuel is typically close to <NUM> (<NUM> gm/cm<NUM> = <NUM>/liter), so that the volume for a year of nuclear waste is about <NUM><NUM>. Spent nuclear fuel, in the form of nuclear fuel pellets, may be taken from the reactor and not modified. Nuclear fuel pellets are solid, and emit very little gas other than short-lived tritium (<NUM> year half-life).

In some aspects, the storage layer <NUM> should be able to contain any radioactive output (e.g., gases) within the layer <NUM>, even if such output escapes the canisters <NUM>. For example, the storage layer <NUM> may be selected based on diffusion times of radioactive output through the layer <NUM>. For example, a minimum diffusion time of radioactive output escaping the storage layer <NUM> may be set at, for example, fifty times a half-life for any particular component of the nuclear fuel pellets. Fifty half-lives as a minimum diffusion time would reduce an amount of radioactive output by a factor of <NUM> × <NUM>-<NUM>. As another example, setting a minimum diffusion time to thirty half-lives would reduce an amount of radioactive output by a factor of one billion.

For example, plutonium-<NUM> is often considered a dangerous waste product in spent nuclear fuel because of its long half-life of <NUM>,<NUM> years. For this isotope, <NUM> half-lives would be <NUM> million years. Plutonium-<NUM> has low solubility in water, is not volatile, and as a solid is not capable of diffusion through a matrix of the rock formation that comprises the illustrated storage layer <NUM> (e.g., shale or other formation). The storage layer <NUM>, for example comprised of shale, may offer the capability to have such isolation times (e.g., millions of years) as shown by the geological history of containing gaseous hydrocarbons (e.g., methane and otherwise) for several million years. In contrast, in conventional nuclear material storage methods, there was a danger that some plutonium might dissolve in a layer that comprised mobile ground water upon confinement escape.

Turning to <FIG>, in alternative implementations, a fluid <NUM> (e.g., liquid or gas) may be circulated through the drillhole <NUM> prior to inserting the canisters <NUM> into the substantially horizontal drillhole portion <NUM>. In some aspects, the choice of fluid <NUM> may depend at least in part on a viscosity of the fluid <NUM>. For example, a fluid <NUM> may be chosen with enough viscosity to impede the drop of the canister <NUM> into the substantially vertical portion <NUM>. This resistance or impedance may provide a safety factor against a sudden drop of the canister <NUM>. The fluid <NUM> may also provide lubrication to reduce a sliding friction between the canister <NUM> and the casings <NUM> and <NUM>. The canister <NUM> can be conveyed within a casing filled with a liquid of controlled viscosity, density, and lubricant qualities. Also, a fluid-filled annulus between the inner diameter of the casings <NUM> and <NUM> and the outer diameter of the conveyed canister <NUM> represents an opening designed to dampen any high rate of canister motion, providing automatic passive protection in an unlikely decoupling of the conveyed canister <NUM>.

In some aspects, the canister <NUM> may include flexible or inflatable extensions (e.g., mounted to the housing <NUM>) that, in some aspects, can impede a flow of the fluid <NUM> (e.g., air or a drilling fluid) across the canister <NUM> during movement in the drillhole <NUM>. For example, the flexible or inflatable extensions could also slow a freefall of the canister <NUM>, such as if a latch or conveyance breaks.

In some aspects, other techniques may be employed to facilitate deposit of the canister <NUM> into the substantially horizontal portion <NUM>. For example, one or more of the installed casings (e.g., casings <NUM> and <NUM>) may have rails to guide the storage canister <NUM> into the drillhole <NUM> while reducing friction between the casings and the canister <NUM>. The storage canister <NUM> and the casings (or the rails) may be made of materials that slide easily against one another. The casings may have a surface that is easily lubricated, or one that is self-lubricating when subjected to the weight of the storage canister <NUM>.

Turning to <FIG>, another alternative deposit operation is illustrated. In this example deposit operation, the fluid <NUM> (e.g., liquid or gas) may be circulated through a tubular fluid control casing <NUM> to fluidly push the canisters <NUM> into the substantially horizontal drillhole portion <NUM>. The fluid <NUM> may circulate through an end of the substantially horizontal portion <NUM> in the fluid control casing <NUM> and recirculate back to the terranean surface <NUM> in an annulus between the fluid control casing <NUM> and the casings <NUM> and <NUM>. In some examples, each canister <NUM> may be fluidly pushed separately. The annulus between the fluid control casing <NUM> and the casings <NUM> and <NUM> may be filled with a fluid or compressed gas to reverse the flow of fluid <NUM>, e.g., in order to push the canisters <NUM> back towards the terranean surface <NUM>. In alternative aspects, two or more canisters <NUM> may be fluidly pushed, simultaneously, through the drillhole <NUM> for deposit into the substantially horizontal portion <NUM>. The fluid control casing <NUM> could be similar or identical to the production casing <NUM>. For that case, a separate tubular member could be enclosed in the drillhole <NUM> or within the production casing <NUM> to provide a return path for the fluid <NUM>.

In some aspects, the drillhole <NUM> may be formed for the primary purpose of long-term storage of hazardous materials. In alternative aspects, the drillhole <NUM> may have been previously formed for the primary purpose of hydrocarbon production (e.g., oil, gas). For example, storage layer <NUM> may be a hydrocarbon bearing formation from which hydrocarbons were produced into the drillhole <NUM> and to the terranean surface <NUM>. In some aspects, the storage layer <NUM> may have been hydraulically fractured prior to hydrocarbon production. Further in some aspects, the production casing <NUM> may have been perforated prior to hydraulic fracturing. In such aspects, the production casing <NUM> may be patched (e.g., cemented) to repair any holes made from the perforating process prior to a deposit operation of hazardous material. In addition, any cracks or openings in the cement between the casing and the drill hole can also be filled at that time.

For example, in the case of spent nuclear fuel as a hazardous material, the drillhole may be formed at a particular location, e.g., near a nuclear power plant, as a new drillhole provided that the location also includes an appropriate storage layer <NUM>, such as a shale formation. Alternatively, an existing well that has already produced shale gas, or one that was abandoned as "dry," (e.g., with sufficiently low organics that the gas in place is too low for commercial development), may be selected as the drillhole <NUM>. In some aspects, prior hydraulic fracturing of the storage layer <NUM> through the drillhole <NUM> may make little difference in the hazardous material storage capability of the drillhole <NUM>. But such a prior activity may also confirm the ability of the storage layer <NUM> to store gases and other fluids for millions of years. If, therefore, the hazardous material or output of the hazardous material (e.g., radioactive gasses or otherwise) were to escape from the canister <NUM> and enter the fractured formation of the storage layer <NUM>, such fractures may allow that material to spread relatively rapidly over a distance comparable in size to that of the fractures. In some aspects, the drillhole <NUM> may have been drilled for a production of hydrocarbons, but production of such hydrocarbons had failed, e.g., because the storage layer <NUM> comprised a rock formation (e.g., shale or otherwise) that was too ductile and difficult to fracture for production, but was advantageously ductile for the long-term storage of hazardous material.

The present disclosure, including <FIG>, describes a hazardous material storage repository system, which includes one or more drillholes formed into a subterranean zone to provide long-term (e.g., tens, hundreds, or even thousands of years) storage of hazardous material (e.g., biological, chemical, nuclear, or otherwise) in one or more underground storage volumes storage canisters. The subterranean zone includes multiple subterranean layers having different geological formations and properties. The storage canisters may be deposited in a particular subterranean layer based on one or more geologic properties of thatlayer, such as low permeability, sufficient thickness, low brittleness, and other properties. In some aspects, the particular subterranean layer comprises a shale formation, which forms an isolative seal between the storage canisters and another subterranean layer that comprises mobile water.

Referring generally to <FIG>, the example hazardous material storage repository system <NUM> (including hazardous material canisters <NUM>) may provide for multiple layers of containment to ensure that a hazardous material (e.g., biological, chemical, nuclear) is sealingly stored in an appropriate subterranean layer. In some example implementations, there may be at least twelve levels of containment. In alternative implementations, a fewer or a greater number of containment levels may be employed.

First, using spent nuclear fuel as an example hazardous material, the fuel pellets are taken from the reactor and not modified. They may be made from sintered uranium dioxide, a ceramic, and may remain solid and emit very little gas other than short-lived tritium. Unless the pellets are exposed to extremely corrosive conditions or other effects that damage the multiple layers of containment, most of the radioisotopes (including the tritium) will be contained in the pellets.

Second, the fuel pellets are surrounded by the zircaloy tubes of the fuel rods, just as in the reactor. As described, the tubes could be mounted in the original fuel assemblies, or removed from those assemblies for tighter packing. Further, the hazardous material canister allows ease of handling with low risk of damage to the (potentially) fragile zircaloy tubes.

Third, the tubes are placed in the sealed housings of the hazardous material canister. The housing may be a unified structure or multi-panel structure, with the multiple panels (e.g., sides, top, bottom) mechanically fastened (e.g., screws, rivets, welds, and otherwise).

Fourth, a material (e.g., solid or fluid or powder) may fill the hazardous material canister to provide a further buffer between the material and the exterior of the canister.

Fifth, the hazardous material canister(s) are positioned (as described above), in a drillhole that is lined with a steel or other sealing casing that extends, in some examples, throughout the entire drillhole (e.g., a substantially vertical portion, a radiussed portion, and a substantially horizontal portion). The casing is cemented in place, providing a relatively smooth surface (e.g., as compared to the drillhole wall) for the hazardous material canister to be moved through, thereby reducing the possibility of a leak or break during deposit or retrieval. In some aspects, material from which the middle portion <NUM> of the canister <NUM> is made (the unshielded material) may be selected in order to reduce a likelihood of corrosion when the hazardous waste is emplaced and during a subsequent period of storage. For example, this subsequent period could be <NUM> years or it could be <NUM>,<NUM> years (as well as greater and less time periods).

Sixth, the cement that holds or helps hold the casing in place, may also provide a sealing layer to contain the hazardous material should it escape the canister.

Seventh, the hazardous material canister is stored in a portion of the drillhole (e.g., the substantially horizontal portion) that is positioned within a thick (e.g., <NUM>-<NUM> meters (<NUM>-<NUM> feet)) seam of a rock formation that comprises a storage layer. The storage layer may be chosen due at least in part to the geologic properties of the rock formation (e.g., low mobile water, low permeability, thick, appropriate ductility or non-brittleness). For example, in the case of shale as the rock formation of the storage layer, this type of rock may offers a level of containment since it is known that shale has been a seal for hydrocarbon gas for millions of years. The shale may contain brine, but that brine is demonstrably immobile, and not in communication with surface fresh water.

Eighth, in some aspects, the rock formation of the storage layer may have other unique geological properties that offer another level of containment. For example, shale rock often contains reactive components, such as iron sulfide, that reduce the likelihood that hazardous materials (e.g., spent nuclear fuel and its radioactive output) can migrate through the storage layer without reacting in ways that reduce the diffusion rate of such output even further. Further, the storage layer may include components, such as clay and organic matter, which typically have extremely low diffusivity. For example, shale may be stratified and composed of thinly alternating layers of clays and other minerals. Such a stratification of a rock formation in the storage layer, such as shale, may offer this additional layer of containment.

Ninth, the storage layer may be located deeper than, and under, an impermeable layer, which separates the storage layer (e.g., vertically) from a mobile water layer.

Tenth, the storage layer may be selected based on a depth (e.g., <NUM> to <NUM> meters (<NUM> to <NUM>,<NUM> ft. )) of such a layer within the subterranean layers. Such depths are typically far below any layers that contain mobile water, and thus, the sheer depth of the storage layer provides an additional layer of containment.

Eleventh, example implementations of the hazardous material storage repository system of the present disclosure facilitate monitoring of the stored hazardous material. For example, if monitored data indicates a leak or otherwise of the hazardous material (e.g., change in temperature, radioactivity, or otherwise), or even tampering or intrusion of the canister, the hazardous material canister may be retrieved for repair or inspection.

Twelfth, the one or more hazardous material canisters may be retrievable for periodic inspection, conditioning, or repair, as necessary (e.g., with or without monitoring). Thus, any problem with the canisters may be addressed without allowing hazardous material to leak or escape from the canisters unabated.

Thirteenth, even if hazardous material escaped from the canisters and no impermeable layer was located between the leaked hazardous material and the terranean surface, the leaked hazardous material may be contained within the drillhole at a location that has no upward path to the surface or to aquifers (e.g., mobile water layers) or to other zones that would be considered hazardous to humans. For example, the location, which may be a dead end of an inclined drillhole, a J-section drillhole, or peaks of a vertically undulating drillhole, may have no direct upward (e.g., toward the surface) path to a vertical portion of the drillhole.

<FIG> are schematic illustrations of example implementations of a hazardous material storage repository system during storage and monitoring operations according to the present disclosure. For example, <FIG> illustrates the hazardous material storage repository system <NUM> in a long term storage operation. One or more hazardous material canisters <NUM> are positioned in the substantially horizontal portion <NUM> of the drillhole <NUM>. A seal <NUM> is placed in the drillhole <NUM> between the location of the canisters <NUM> in the substantially horizontal portion <NUM> and an opening of the substantially vertical portion <NUM> at the terranean surface <NUM> (e.g., a well head). In this example, the seal <NUM> is placed at an uphole end of the substantially vertical portion <NUM>. Alternatively, the seal <NUM> may be positioned at another location within the substantially vertical portion <NUM>, in the radiussed portion <NUM>, or even within the substantially horizontal portion <NUM> uphole of the canisters <NUM>. In some aspects, the seal <NUM> may be placed at least deeper than any source of mobile water, such as the mobile water layer <NUM>, within the drillhole <NUM>. In some aspects, the seal <NUM> may be formed substantially along an entire length of the substantially vertical portion <NUM>.

As illustrated, the seal <NUM> fluidly isolates the volume of the substantially horizontal portion <NUM> that stores the canisters <NUM> from the opening of the substantially vertical portion <NUM> at the terranean surface <NUM>. Thus, any hazardous material (e.g., radioactive material) that does escape the canisters <NUM> may be sealed (e.g., such that liquid, gas, or solid hazardous material) does not escape the drillhole <NUM>. The seal <NUM>, in some aspects, may be a cement plug or other plug, that is positioned or formed in the drillhole <NUM>. As another example, the seal <NUM> may be formed from one or more inflatable or otherwise expandable packers positioned in the drillhole <NUM>.

Prior to a retrieval operation (e.g., as discussed with reference to <FIG>), the seal <NUM> may be removed. For example, in the case of a cement or other permanently set seal <NUM>, the seal <NUM> may be drilled through or otherwise milled away. In the case of semi-permanent or removable seals, such as packers, the seal <NUM> may be removed from the drillhole <NUM> through a conventional process as is known.

<FIG> illustrates an example monitoring operation during long term storage of the canisters <NUM>. For example, in some aspects, it may be advantageous or required to monitor one or more variables during long term storage of the hazardous material in the canisters <NUM>. In this example of <FIG>, the monitoring system includes one or more sensors <NUM> placed in the drillhole <NUM> (e.g., within the substantially horizontal portion <NUM>) and communicably coupled to a monitoring control system <NUM> through a cable <NUM> (e.g., electrical, optical, hydraulic, or otherwise). Although illustrated as within drillhole <NUM> (e.g., inside of the casings), the sensors <NUM> may be placed outside of the casings, or even built into the casings before the casings are installed in the drillhole <NUM>. Sensors <NUM> could also be placed outside the casing (e.g., casings <NUM> and/or <NUM>), or outside the fluid control casing <NUM>.

As shown, the sensors <NUM> may monitor one or more variables, such as, for example, radiation levels, temperature, pressure, presence of oxygen, a presence of water vapor, a presence of liquid water, acidity (pH), seismic activity, or a combination thereof. Data values related to such variables may be transmitted along the cable <NUM> to the monitoring control system <NUM>. The monitoring control system <NUM>, in turn, may record the data, determine trends in the data (e.g., rise of temperature, rise of radioactive levels), send data to other monitoring locations, such as national security or environmental center locations, and may further automatically recommend actions (e.g., retrieval of the canisters <NUM>) based on such data or trends. For example, a rise in temperature or radioactive level in the drillhole <NUM> above a particular threshold level may trigger a retrieval recommendation, e.g., to ensure that the canisters <NUM> are not leaking radioactive material. In some aspects, there may be a one-to-one ratio of sensors <NUM> to canisters <NUM>. In alternative aspects, there may be multiple sensors <NUM> per canister <NUM>, or there may be fewer.

<FIG> shows another example monitoring operation during long term storage of the canisters <NUM>. In this example, sensors <NUM> are positioned within a secondary horizontal drillhole <NUM> that is formed separately from the substantially vertical portion <NUM>. The secondary horizontal drillhole <NUM> may be an uncased drillhole, through which the cable <NUM> may extend between the monitoring control system <NUM> and the sensors <NUM>. In this example, the secondary horizontal drillhole <NUM> is formed above the substantially horizontal portion <NUM> but within the storage layer <NUM>. Thus, the sensors <NUM> may record data (e.g., radiation levels, temperature, acidity, seismic activity) of the storage layer <NUM>. In alternative aspects, the secondary horizontal drillhole <NUM> may be formed below the storage layer <NUM>, above the storage layer in the impermeable layer <NUM>, or in other layers. Further, although <FIG> shows the secondary horizontal drillhole <NUM> formed from the same substantially vertical portion <NUM> as the substantially horizontal portion <NUM>, the secondary horizontal drillhole <NUM> may be formed from a separate vertical drillhole and radiussed drillhole.

<FIG> shows another example monitoring operation during long term storage of the canisters <NUM>. In this example, sensors <NUM> are positioned within a secondary vertical drillhole <NUM> that is formed separately from the drillhole <NUM>. The secondary vertical drillhole <NUM> may be a cased or an uncased drillhole, through which the cable <NUM> may extend between the monitoring control system <NUM> and the sensors <NUM>. In this example, the secondary vertical drillhole <NUM> bottoms out above the substantially horizontal portion <NUM> but within the storage layer <NUM>. Thus, the sensors <NUM> may record data (e.g., radiation levels, temperature, acidity, seismic activity) of the storage layer <NUM>. In alternative aspects, the secondary vertical drillhole <NUM> may bottom out below the storage layer <NUM>, above the storage layer in the impermeable layer <NUM>, or in other layers. Further, although shown placed in the secondary vertical drillhole <NUM> at a level adjacent the storage layer <NUM>, sensors <NUM> may be placed anywhere within the secondary vertical drillhole <NUM>. Alternatively, the secondary vertical drillhole <NUM> may, in some aspects, be constructed prior to drillhole <NUM>, thereby permitting monitoring by installed sensors <NUM> during construction of the drillhole <NUM>. Also, the monitoring borehole <NUM> could be sealed to prevent the possibility that material that leaks into borehole <NUM> would have a path to the terranean surface <NUM>.

<FIG> shows another example monitoring operation during long term storage of the canisters <NUM>. In this example, sensors <NUM> are positioned within a secondary directional drillhole <NUM> that is formed separately from the drillhole <NUM>. The secondary directional drillhole <NUM> may be an uncased drillhole, through which the cable <NUM> may extend between the monitoring control system <NUM> and the sensors <NUM>. In this example, the secondary directional drillhole <NUM> lands adjacent the substantially horizontal portion <NUM> and within the storage layer <NUM>. Thus, the sensors <NUM> may record data (e.g., radiation levels, temperature, acidity, seismic activity) of the storage layer <NUM>. In alternative aspects, the secondary directional drillhole <NUM> may land below the storage layer <NUM>, above the storage layer in the impermeable layer <NUM>, or in other layers. Further, although shown placed in the secondary directional drillhole <NUM> at a level adjacent the storage layer <NUM>, sensors <NUM> may be placed anywhere within the secondary directional drillhole <NUM>. In some aspects, the secondary directional drillhole <NUM> may be used for retrieval of the canisters <NUM>, for example, in case the drillhole <NUM> is inaccessible.

<FIG> is a flowchart that illustrates an example method <NUM> associated with storing hazardous material, such as, for example, spent nuclear fuel contained in spent nuclear fuel assemblies. Method <NUM> may begin at step <NUM>, which includes removing at least one spent nuclear fuel assembly from a nuclear reactor module. For example, nuclear fuel assemblies <NUM> may be part of a nuclear reactor during operation of the reactor to use the nuclear fissionable material in the assemblies <NUM> to generate, ultimately, electrical power. Once the nuclear fuel assemblies <NUM> reach their end-of-life, i.e., the nuclear fuel is spent, the spent nuclear fuel assemblies <NUM> may be removed from the nuclear reactor.

Method <NUM> may continue at step <NUM>, which includes placing the spent nuclear fuel assembly into an interior volume of an at least partially unshielded spent nuclear fuel canister (for example, a canister that has shielding to gamma ray transmission on top and bottom ends but not a middle portion, such as canister <NUM>). For example, spent nuclear fuel assembly <NUM> may be taken directly from reactor <NUM> and placed, without modification or without substantial modification, into the hazardous material canister <NUM>. At least a portion of the hazardous material canister <NUM>, such as the middle portion or housing <NUM>, is made from a material that has no shielding to gamma ray transmission but may provide a barrier to the transmission of nuclear waste solids, liquid, and gases.

In some aspects, a single spent nuclear fuel assembly <NUM> is placed in the hazardous material canister <NUM> due to, e.g., the specified size and shape of the interior volume of the canister <NUM>. In alternative aspects, two or more nuclear fuel assemblies <NUM> may be positioned, e.g., vertically and end-to-end, within the canister <NUM>. Thus, the hazardous material canister <NUM> may have a height dimension sized to enclose only a single spent nuclear fuel assembly <NUM>, or multiple spent nuclear fuel assemblies <NUM> (e.g., a height that is a multiple of a height dimension of the assembly <NUM>). The canister <NUM> may have, however, a cross-sectional dimensional area sized to enclose only a single spent nuclear fuel assembly <NUM>.

In some aspects, the spent nuclear fuel assembly <NUM> may be stored in one or more other storage locations between steps <NUM> and <NUM>. For example, the spent nuclear fuel assembly <NUM> may be moved from the nuclear reactor to a cooling pool (e.g., a spent fuel pool). The spent nuclear fuel assembly <NUM> may then be moved from the spent fuel pool to a dry cask canister for further storage. However, neither the spent fuel pool nor dry cask canister are designed for long term storage of the spent nuclear fuel assembly <NUM> (e.g., greater than <NUM>-<NUM> years).

The spent nuclear fuel assembly <NUM> may then be moved from the dry cask canister to the hazardous material canister <NUM> for long term storage, e.g., in a hazardous material storage repository <NUM>. Preferably (e.g., due to safety and cost concerns), the spent nuclear fuel assembly <NUM> is not modified between steps <NUM> and <NUM>. In other words, the spent nuclear fuel assembly <NUM> is removed from the nuclear reactor in a particular configuration (as shown in <FIG>) and is moved to the spent fuel pool, and then dry cask, and then canister <NUM> in the same (or substantially the same) configuration.

In some aspects, one or more intermediate storage steps (e.g., between the nuclear reactor and long term storage in a hazardous material storage repository as described in this application) may be skipped due to, for instance, the design of the hazardous material canister <NUM>. For example, in some aspects, a spent nuclear fuel assembly <NUM> may be placed into a hazardous material canister <NUM> once a time period for storage of the assembly <NUM> in a spent nuclear fuel pool is complete. In some instances, the spent nuclear fuel assembly <NUM> may be placed into the hazardous material canister <NUM> within the pool. Next, the canister <NUM> (enclosing the spent nuclear fuel assembly <NUM>) may be transported (e.g., within a transportation cask) to a well site (the hazardous material storage repository system <NUM>). During transportation, the shielded material of the top and bottom portions of the canister <NUM> may protect or help protect those handling the canister from hazardous material, as well as radioactive gamma and x-rays. The transportation cask, which surrounds the unshielded middle portion of the canister <NUM>, may provide gamma and x-ray shielding. Further, due to the shielded material of the top portion of the canister <NUM>, the transportation cask may have an open top for ease of insertion and removal of the canister <NUM> therein.

Method <NUM> may continue at step <NUM>, which includes enclosing the spent nuclear fuel assembly in the interior volume of the spent nuclear fuel canister. For example, the top portion <NUM> of the hazardous material canister <NUM> may be attached (e.g., welded or otherwise) to the middle portion <NUM> to physically seal the spent nuclear fuel assembly <NUM> into the volume <NUM> of the canister <NUM>.

Method <NUM> may continue at step <NUM>, which includes moving the spent nuclear fuel canister into an underground hazardous material storage repository. Step <NUM> may be performed, for example, as described with reference to <FIG>. Step <NUM> may also include, for example, transportation of the canister <NUM> (or canisters <NUM>) from a nuclear reactor location to, e.g., a well site as part of hazardous material storage repository system <NUM>.

<FIG> is a schematic illustration of an example controller <NUM> (or control system) for a hazardous waste monitoring system. For example, the controller <NUM> can be used for the operations described previously, for example as or as part of the monitoring control system <NUM>. For example, the controller <NUM> may be communicably coupled with, or as a part of, a hazardous material storage repository system as described herein.

The controller <NUM> is intended to include various forms of digital computers, such as printed circuit boards (PCB), processors, digital circuitry, or otherwise that is part of a vehicle. Additionally the system can include portable storage media, such as, Universal Serial Bus (USB) flash drives. For example, the USB flash drives may store operating systems and other applications. The USB flash drives can include input/output components, such as a wireless transmitter or USB connector that may be inserted into a USB port of another computing device.

The controller <NUM> includes a processor <NUM>, a memory <NUM>, a storage device <NUM>, and an input/output device <NUM>. Each of the components <NUM>, <NUM>, <NUM>, and <NUM> are interconnected using a system bus <NUM>. The processor <NUM> is capable of processing instructions for execution within the controller <NUM>. The processor may be designed using any of a number of architectures. For example, the processor <NUM> may be a CISC (Complex Instruction Set Computers) processor, a RISC (Reduced Instruction Set Computer) processor, or a MISC (Minimal Instruction Set Computer) processor.

In one implementation, the processor <NUM> is a single-threaded processor. In another implementation, the processor <NUM> is a multi-threaded processor. The processor <NUM> is capable of processing instructions stored in the memory <NUM> or on the storage device <NUM> to display graphical information for a user interface on the input/output device <NUM>.

The memory <NUM> stores information within the controller <NUM>.

The storage device <NUM> is capable of providing mass storage for the controller <NUM>. In various different implementations, the storage device <NUM> may be a floppy disk device, a hard disk device, an optical disk device, a tape device, flash memory, a solid state device (SSD), or a combination thereof.

The input/output device <NUM> provides input/output operations for the controller <NUM>.

The features described can be implemented in digital electronic circuitry, or in computer hardware, firmware, software, or in combinations of them. The apparatus can be implemented in a computer program product tangibly embodied in an information carrier, for example, in a machine-readable storage device for execution by a programmable processor; and method steps can be performed by a programmable processor executing a program of instructions to perform functions of the described implementations by operating on input data and generating output. The described features can be implemented advantageously in one or more computer programs that are executable on a programmable system including at least one programmable processor coupled to receive data and instructions from, and to transmit data and instructions to, a data storage system, at least one input device, and at least one output device. A computer program is a set of instructions that can be used, directly or indirectly, in a computer to perform a certain activity or bring about a certain result.

Storage devices suitable for tangibly embodying computer program instructions and data include all forms of non-volatile memory, including by way of example semiconductor memory devices, such as EPROM, EEPROM, solid state drives (SSDs), and flash memory devices; magnetic disks such as internal hard disks and removable disks; magneto-optical disks; and CD-ROM and DVD-ROM disks.

To provide for interaction with a user, the features can be implemented on a computer having a display device such as a CRT (cathode ray tube) or LCD (liquid crystal display) or LED (light-emitting diode) monitor for displaying information to the user and a keyboard and a pointing device such as a mouse or a trackball by which the user can provide input to the computer. Additionally, such activities can be implemented via touchscreen flat-panel displays and other appropriate mechanisms.

The features can be implemented in a control system that includes a back-end component, such as a data server, or that includes a middleware component, such as an application server or an Internet server, or that includes a front-end component, such as a client computer having a graphical user interface or an Internet browser, or any combination of them. Examples of communication networks include a local area network ("LAN"), a wide area network ("WAN"), peer-to-peer networks (having ad-hoc or static members), grid computing infrastructures, and the Internet.

While this specification contains many specific implementation details, these should not be construed as limitations on the scope of what may be claimed, but rather as descriptions of features specific to particular implementations.

Claim 1:
A canister (<NUM>) arranged for storing spent nuclear fuel, comprising:
a first end portion (<NUM>);
a second end portion (<NUM>), wherein the second end portion comprises a connector portion arranged for facilitaing coupling of the canister to a downhole tool (<NUM>) to permit deposit and retrieval of the canister to and from storage in a drillhole; and
a middle portion (<NUM>) comprised of a first material of a composition and thickness that allow transmission of gamma rays therethrough and out of the canister, wherein
i) the middle portion (<NUM>) is attached to the first and second end portions such that the middle portion (<NUM>), first end portion (<NUM>), and second end portion (<NUM>) collectively enclose an interior volume (<NUM>, <NUM>) of the canister that is sized to store at least one spent nuclear fuel assembly, wherein the interior volume has a height dimension and a cross-sectional diameter sized to enclose the at least one spent nuclear fuel assembly, and
ii) the first and second end portions comprise shielding of a second material of a composition and thickness that reduce an intensity of gamma ray radiation to a level that allows safe handling of the canister, wherein the second material comprises lead with a thickness between <NUM> (<NUM> inches) and <NUM> (<NUM> inches) or concrete with a thickness between <NUM> (<NUM> feet) and <NUM> (<NUM> feet).