Abstract: A hazardous waste canister includes a housing that includes at least one open end and defines an interior volume; and an end cap sized and configured to attach to the at least one open end of the housing to enclose the interior volume. The housing is configured to enclose a plurality of nuclear waste forms within the interior volume, with at least one of the plurality of nuclear waste forms different than at least another of the plurality of nuclear waste forms.

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: A nuclear reactor system includes a first drillhole extending from a terranean surface through one or more subterranean formations; a reactor core positioned in the first drillhole, and including at least one nuclear fuel element; a second drillhole extending from the terranean surface through the one or more subterranean formations and separated from the first drillhole by a portion of a rock formation; a heat exchanger positioned in the second drillhole in thermal communication with the reactor core through the portion of the rock formation; and a coolant system thermally coupled to the heat exchanger and configured to transport a fluid coolant between the heat exchanger and the terranean surface.

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: Techniques for monitoring hazardous waste include identifying a hazardous waste drillhole formed from a terranean surface into one or more subterranean formations, the hazardous waste drillhole including an entry sized to receive a plurality of hazardous waste canisters that enclose hazardous waste into and through the entry, and a hazardous waste storage area formed in a storage subterranean formation and sized to receive the plurality of hazardous waste canisters; identifying a probe borehole formed from the terranean surface into the one or more subterranean formations adjacent the hazardous waste drillhole, the probe borehole having a diameter sized insufficiently to receive the plurality of hazardous waste canisters; and measuring, with at least one measurement instrument positioned in the probe borehole near the hazardous waste storage area, at least one parameter associated with the hazardous waste.

Abstract: A hazardous waste repository system includes at least one vertical access drillhole formed from a terranean surface into a subterranean formation. The system further includes a first horizontal drillhole portion coupled to the vertical access drillhole and sized to receive a first hazardous waste canister. The first horizontal drillhole portion includes a first hazardous waste repository area formed at a first depth within the subterranean formation. The system further includes a second horizontal drillhole portion coupled to the at least one vertical access drillhole and sized to receive a second hazardous waste canister. The second horizontal drillhole portion includes a second hazardous waste repository area formed at a second depth within the subterranean formation such that a difference between the first and second depths is at least as much as a vertical drilling uncertainty.

Abstract: An apparatus, including: a plurality of lens tiles; and a base housing and positioning the plurality of lens tiles in an array configuration; the base comprising a plurality of light-occluding barriers, wherein each of the plurality of light-occluding barriers is located between two adjacent of the plurality of lens tiles. Other embodiments are described herein.

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: A hazardous waste repository includes a substantially vertical drillhole portion that extends toward a subterranean rock formation from a terranean surface, the drillhole including an entry at least proximate the terranean surface; and a hazardous material storage drillhole portion formed in or under the subterranean rock formation and coupled to the substantially vertical drillhole portion, the hazardous material storage drillhole portion configured to store one or more hazardous material canisters that encloses nuclear waste. The substantially vertical drillhole portion includes an aspect ratio of surface area of the substantially vertical drillhole portion to a cross-sectional area of the substantially vertical drillhole portion that impedes movement of a hazardous component of a nuclear waste material from a first end of the substantially vertical drillhole portion to a second end of the substantially vertical drillhole portion through at least one of advective isolation or diffusive isolation.

Abstract: A hazardous waste repository includes a drillhole formed from a terranean surface into a subterranean formation, the drillhole including an entry at the terranean surface and an access portion that extends from the entry toward a storage portion within the subterranean formation; 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 configured to support at least a portion of a weight of each of the plurality of canisters.

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: 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: 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 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: 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: One embodiment provides an imaging device, including: a sparsely-filled optical aperture having a shape forming an outer portion of the optical aperture, wherein at least a portion of an inner portion formed by the outer portion of the optical aperture is not a part of the optical aperture; and imaging optics, wherein the imaging optics include at least one reflection device optically located after the optical aperture and at least one imaging sensor optically located after the at least one reflection device, wherein light entering the optical aperture reflects from the at least one reflection device onto the at least one imaging sensor. Other embodiments are described herein.

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: 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 nuclear waste storage system includes a human-unoccupiable directional drillhole formed from a terranean surface into a subterranean formation, the drillhole including a substantially vertical portion and a substantially horizontal portion that includes a hazardous waste repository for nuclear waste storage; a casing including one or more tubular sections sized to fit within the drillhole; and a coating attached to an exterior surface of the casing, the exterior surface facing a rock formation through which the drillhole is formed.