Abstract: A hazardous waste canister includes a housing that defines an inner volume sized to enclose a portion of hazardous waste and including an excess space between the enclosed portion of hazardous waste and an inner wall surface of the housing; a cap configured to seal an open end of the housing through which the portion of hazardous waste is inserted into the inner volume; and a pressure balancing material inserted into the inner volume to fill the excess space.

Abstract: A hazardous waste repository includes a directional drillhole formed from a terranean surface into at least one subterranean formation suitable for storing hazardous waste. The directional drillhole includes a storage region configured to store one or more hazardous waste canisters that is configured to enclose hazardous waste. The repository further includes a casing that extends to at or near the terranean surface, through the directional drillhole, and into the storage region of the substantially horizontal drillhole portion. The repository further includes a monitor borehole formed from the terranean surface into the at least one subterranean formation adjacent the storage region. The monitor borehole is sized to receive a measurement instrument run from the terranean surface to a portion of the monitor borehole adjacent the storage region. The measurement instrument is configured to detect a distortion of the casing.

Abstract: A hazardous material storage repository includes a borehole that extends into the Earth from a terranean surface. The borehole includes an entry and a hazardous material storage borehole portion formed in a subterranean salt formation. The repository includes a storage canister positioned in the hazardous material storage borehole portion. The storage canister is sized to fit from the entry through a substantially vertical borehole portion of the borehole, and into the hazardous material storage borehole portion. The storage canister includes an inner cavity sized to enclose nuclear waste material that includes TRansUranic waste.

Abstract: Techniques for determining the suitability of a subterranean formation as a hazardous waste repository include determining a neutron flux of a first isotope in a subterranean formation; calculating, based at least in part on the determined neutron flux of the first isotope, a predicted production rate of a second isotope in the subterranean formation; calculating a first ratio of the predicted production rate of the second isotope relative to a theoretical production rate of a stable form of the second isotope; measuring respective concentrations of the second isotope and the stable form of the second isotope in a subterranean water sample; calculating a second ratio of the measured concentration of the second isotope relative to the measured concentration of the stable form of the second isotope; and based on a comparison of the first and second ratios, determining that the subterranean formation is suitable as a hazardous waste repository.

Abstract: A casing joint includes a tubular including a particular length, a particular diameter, and a first wall thickness; a male connection formed on a first end of the tubular, the male connection including an axial length and a plurality of threads formed on a portion of an external surface of the male connection less than the axial length of the male connection; and a female connection formed on a second end of the tubular opposite the first end, the female connection including an axial length and a plurality of threads formed on a portion of an internal surface of the female connection less than the axial length of the female connection.

Abstract: A hazardous waste repository includes a drillhole formed from a terranean surface into a subterranean formation. The drillhole includes an entry at the terranean surface and an access portion that extends from the entry toward a storage portion within the subterranean formation. The hazardous waste repository further includes a plurality of hazardous waste canisters emplaced within the storage portion of the drillhole, each of the hazardous waste canisters enclosing hazardous waste; and a granular material installed in a volume of the drillhole between a casing and the plurality of canisters and between adjacent canisters of the plurality of canisters. The granular material is configured to support at least a portion of a weight of each of the plurality of canisters.

Abstract: Techniques for inspecting a weld of a nuclear waste canister include positioning a gamma ray image detector near a nuclear waste canister that encloses nuclear waste. The nuclear waste canister includes a housing that includes a volume in which the waste is enclosed and a top connected to the housing with at least one weld to seal the nuclear waste in the nuclear waste canister. The techniques further include receiving, at the gamma ray image detector, gamma rays from the nuclear waste that travel through one or more voids in the weld; generating an image of the received gamma rays with the gamma ray image detector; and based on the generated image, determining an integrity of the at least one weld.

Abstract: A power generator system includes one or more heat transfer members configured to contact: a heat source in a hazardous waste repository of a directional drillhole that stores nuclear waste in one or more nuclear waste canisters, and a heat sink in the hazardous waste repository; and one or more thermoelectric generators thermally coupled to the one or more heat transfer members and configured to generate electric power based on a temperature difference between the heat source and the heat sink.

Abstract: Techniques for determining the suitability of a subterranean formation as a hazardous waste repository include determining a neutron flux of a first isotope in a subterranean formation; calculating, based at least in part on the determined neutron flux of the first isotope, a predicted production rate of a second isotope in the subterranean formation; calculating a first ratio of the predicted production rate of the second isotope relative to a theoretical production rate of a stable form of the second isotope; measuring respective concentrations of the second isotope and the stable form of the second isotope in a subterranean water sample; calculating a second ratio of the measured concentration of the second isotope relative to the measured concentration of the stable form of the second isotope; and based on a comparison of the first and second ratios, determining that the subterranean formation is suitable as a hazardous waste repository.

Abstract: Methods for storing or disposing of nuclear waste include forming a drillhole that extends into the Earth from a terranean surface. The drillhole includes an entry at least proximate the terranean surface, a substantially vertical drillhole portion, and a hazardous material storage drillhole portion that is coupled to the substantially vertical drillhole portion and is formed in a subterranean salt formation. The methods further include moving a storage canister into the hazardous material storage drillhole portion. The storage canister is sized to fit from the drillhole entry through the substantially vertical drillhole portion, and into the hazardous material storage drillhole portion of the drillhole. The storage canister has an inner cavity that encloses nuclear waste material. The methods further include positioning a seal in the drillhole to isolate the hazardous material storage drillhole portion of the drillhole from the entry of the drillhole.

Abstract: A hazardous material storage system includes a drillhole extending into the Earth and including an entry at least proximate a terranean surface. The drillhole includes a substantially vertical portion, a curved portion, and a horizontal portion that includes a hazardous waste repository formed within a first portion of the horizontal portion of the drillhole, the hazardous waste repository vertically isolated, by a rock formation, from a subterranean zone that includes mobile water, and a safety runway formed within a second portion of the horizontal portion exclusive of the hazardous waste repository and adjacent the curved portion, the safety runway defined by a particular length.

Abstract: A drillhole plug includes a frame or housing of a corrosion-resistant material and sized to fit within a milled portion of a directional drillhole that includes a hazardous waste repository; and a material that fills at least a portion of the frame or housing. The material exhibits creep such that the material fills one or more voids between the frame or housing and a subterranean formation adjacent the milled portion of the directional drillhole.

Abstract: Techniques for storing hazardous material include moving a storage canister sized to enclose radioactive hazardous material through an entry of a drillhole that extends into a terranean surface and is at least proximate the terranean surface; moving the storage canister from the entry through an angled drillhole portion that is coupled to the entry and deviates from true vertical at an angle; moving the storage canister from the angled drillhole portion to a hazardous material storage drillhole portion coupled to the angled drillhole portion; moving the storage canister into the hazardous material storage drillhole portion; and forming a seal in the drillhole that isolates the hazardous material storage portion of the drillhole from the entry of the drillhole.

Abstract: Techniques for inspecting a weld of a nuclear waste canister include positioning a gamma ray image detector near a nuclear waste canister that encloses nuclear waste. The nuclear waste canister includes a housing that includes a volume in which the waste is enclosed and a top connected to the housing with at least one weld to seal the nuclear waste in the nuclear waste canister. The techniques further include receiving, at the gamma ray image detector, gamma rays from the nuclear waste that travel through one or more voids in the weld; generating an image of the received gamma rays with the gamma ray image detector; and based on the generated image, determining an integrity of the at least one weld.

Abstract: A hazardous material repository includes a drillhole formed from a terranean surface into a subterranean zone that includes a geologic formation, where the drillhole includes a vertical portion and a non-vertical portion coupled to the vertical portion by a transition portion, the non-vertical portion includes a storage volume for hazardous waste; a casing installed between the geologic formation and the drillhole, the casing including one or more metallic tubular sections; at least one canister positioned in the storage volume of the non-vertical portion of the drillhole, the at least one canister sized to enclose a portion of hazardous material and including an outer housing formed from a non-corrosive metallic material; and a backfill material inserted into the non-vertical portion of the drillhole to fill at least a portion of the storage volume between the at least one canister and the casing.

Abstract: A hazardous material storage repository includes a drillhole extending into the Earth and including an entry. The drillhole includes a vertical drillhole portion, a transition drillhole portion coupled to the vertical drillhole portion, and a hazardous material storage drillhole portion coupled to the transition drillhole portion. The hazardous material storage drillhole portion is located below a self-healing geological formation and is vertically isolated, by the self-healing geological formation, from a zone that comprises mobile water. The repository includes a storage canister positioned in the hazardous material storage drillhole portion and sized to fit from the drillhole entry through the vertical drillhole portion, the transition drillhole portion, and into the hazardous material storage drillhole portion. The storage canister includes an inner cavity sized to enclose hazardous material.

Abstract: Techniques for determining the suitability of a subterranean formation as a hazardous waste repository include determining a neutron flux of a first isotope in a subterranean formation; calculating, based at least in part on the determined neutron flux of the first isotope, a predicted production rate of a second isotope in the subterranean formation; calculating a first ratio of the predicted production rate of the second isotope relative to a theoretical production rate of a stable form of the second isotope; measuring respective concentrations of the second isotope and the stable form of the second isotope in a subterranean water sample; calculating a second ratio of the measured concentration of the second isotope relative to the measured concentration of the stable form of the second isotope; and based on a comparison of the first and second ratios, determining that the subterranean formation is suitable as a hazardous waste repository.

Abstract: Techniques for inspecting a weld of a nuclear waste canister include positioning a gamma ray image detector near a nuclear waste canister that encloses nuclear waste. The nuclear waste canister includes a housing that includes a volume in which the waste is enclosed and a top connected to the housing with at least one weld to seal the nuclear waste in the nuclear waste canister. The techniques further include receiving, at the gamma ray image detector, gamma rays from the nuclear waste that travel through one or more voids in the weld; generating an image of the received gamma rays with the gamma ray image detector; and based on the generated image, determining an integrity of the at least one weld.

Abstract: A hazardous material storage repository includes a drillhole extending into the Earth and including an entry. The drillhole includes a vertical drillhole portion, a transition drillhole portion coupled to the vertical drillhole portion, and a hazardous material storage drillhole portion coupled to the transition drillhole portion. The hazardous material storage drillhole portion is located below a self-healing geological formation and is vertically isolated, by the self-healing geological formation, from a zone that comprises mobile water. The repository includes a storage canister positioned in the hazardous material storage drillhole portion and sized to fit from the drillhole entry through the vertical drillhole portion, the transition drillhole portion, and into the hazardous material storage drillhole portion. The storage canister includes an inner cavity sized to enclose hazardous material.

Abstract: Techniques for determining the suitability of a subterranean formation as a hazardous waste repository include determining a concentration of at least one noble gas isotope of a plurality of noble gas isotopes in fluid sample from a subterranean formation below a terranean surface; determining a produced amount of the at least one noble gas isotope in the subterranean formation based on a production rate of the at least one noble gas isotope and a minimum residence time; calculating a ratio of the determined concentration of the at least one noble gas isotope in the fluid sample to the determined produced amount of the at least one noble gas isotope; and based on the calculated ratio being at or near a threshold value, determining that the subterranean formation is suitable as a hazardous waste repository.