Patent Number: 
Section: claims

1. A hazardous material repository, comprising:a drillhole formed from a terranean surface into a subterranean zone that comprises a geologic formation, the drillhole comprising a vertical portion and a non-vertical portion coupled to the vertical portion by a transition portion, the non-vertical portion comprising a storage volume for hazardous waste;a casing installed between the geologic formation and the drillhole, the casing comprising one or more metallic tubular sections formed of API-5CT L80 steel;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 comprising an outer housing formed from a nickel-chromium-molybdenum alloy;an engineered filling inserted into the drillhole to fill at least a portion of the storage volume between the at least one canister and the casing, the engineered filling comprising a deaerated bentonite-based slurry; anda backfill material inserted into the at least one canister to fill a void between the portion of hazardous material and the canister, the backfill material comprising a quartz material. 2. The hazardous material repository of claim 1, wherein the hazardous material comprises radioactive material waste. 3. The hazardous material repository of claim 2, wherein the radioactive material waste comprises one or more portions of a spent nuclear fuel assembly. 4. The hazardous material repository of claim 2, wherein the geologic formation is at a depth in which a hydrostatic pressure at the depth is great enough to prevent boiling of water at a boiling point of about 310° C., or the geologic formation comprises pore water that is highly reducing, or the geologic formation comprises a rock in which pore waters are anoxic, or the geologic formation comprises a fully saturated rock formation. 5. The hazardous material repository of claim 1, wherein the nickel-chromium-molybdenum alloy comprises Alloy 625. 6. The hazardous material repository of claim 1, wherein a wall thickness of the at least one canister is between 9.25 mm and 10 mm. 7. The hazardous material repository of claim 6, wherein a wall thickness of the casing is 12.5 mm. 8. The hazardous material repository of claim 1, wherein a wall thickness of the casing is 12.5 mm. 9. The hazardous material repository of claim 1, wherein the bentonite-based slurry is pumped from the terranean surface into the non-vertical portion of the drillhole to fill the portion of the storage volume between the at least one canister and the casing. 10. The hazardous material repository of claim 1, wherein the geologic formation is at a depth in which a hydrostatic pressure at the depth is great enough to prevent boiling of water at a boiling point of about 310° C., or the geologic formation comprises pore water that is highly reducing, or the geologic formation comprises a rock in which pore waters are anoxic, or the geologic formation comprises a fully saturated rock formation. 11. The hazardous material repository of claim 1, wherein a thermal load of the hazardous material repository is controlled by spacing of the at least one canister within the storage volume. 12. The hazardous material repository of claim 1, wherein the nickel-chromium-molybdenum alloy is configured to self-form a passive protective film on an exterior surface of the outer housing of the at least one canister. 13. The hazardous material repository of claim 1, further comprising one or more expansion absorbers placed at predetermined locations in the casing. 14. The hazardous material repository of claim 1, wherein the deaerated bentonite-based slurry is pumped from the terranean surface into the non-vertical portion of the drillhole to fill the portion of the storage volume between the at least one canister and the casing to a level that extends uphole to at or near a drillhole seal that is positioned to isolate an entry of the drillhole at a terranean surface from the storage volume. 15. The hazardous material repository of claim 1, wherein the deaerated bentonite-based slurry comprises an insulator and a radioactive energy absorber between the at least one canister and the casing. 16. A method for forming an engineered barrier system for a hazardous material repository, comprising:forming a drillhole from a terranean surface into a subterranean zone that comprises a geologic formation, the drillhole comprising a vertical portion and a non-vertical portion coupled to the vertical portion by a transition portion, the non-vertical portion comprises a storage volume for hazardous waste;installing a casing between the geologic formation and the drillhole, the casing comprising one or more metallic tubular sections formed of API-5CT L80 steel;positioning at least one canister in the storage volume of the non-vertical portion of the drillhole, the at least one canister enclosing a portion of hazardous material and comprising an outer housing formed from a nickel-chromium-molybdenum alloy, the outer housing defining a volume that encloses the portion of the hazardous material and a backfill material that comprises a quartz material; andinserting an engineered filling into the drillhole to fill at least a portion of the storage volume between the at least one canister and the casing, the engineered filling comprising a deaerated bentonite-based slurry. 17. The method of claim 16, wherein the hazardous material comprises radioactive material waste. 18. The method of claim 17, wherein the radioactive material waste comprises one or more portions of a spent nuclear fuel assembly. 19. The method of claim 16, wherein the nickel-chromium-molybdenum alloy comprises Alloy 625. 20. The method of claim 16, wherein a wall thickness of the at least one canister is between 9.25 mm and 10 mm. 21. The method of claim 20, wherein a wall thickness of the casing is 12.5 mm. 22. The method of claim 16, wherein a wall thickness of the casing is 12.5 mm. 23. The method of claim 16, wherein inserting the engineered filling into the drillhole comprises pumping the bentonite-based slurry from the terranean surface into the non-vertical portion of the drillhole to fill the portion of the storage volume between the at least one canister and the casing. 24. The method of claim 16, wherein the geologic formation is at a depth in which a hydrostatic pressure at the depth is great enough to prevent boiling of water at a boiling point of about 310° C., or the geologic formation comprises pore water that is highly reducing, or the geologic formation comprises a rock in which pore waters are anoxic, or the geologic formation comprises a fully saturated rock formation. 25. The method of claim 16, wherein positioning the at least one canister in the storage volume of the non-vertical portion of the drillhole comprises:positioning a first canister in the storage volume of the non-vertical portion of the drillhole; andpositioning a second canister in the storage volume of the non-vertical portion of the drillhole apart from the first canister a specified distance based on a thermal load of the hazardous material repository. 26. The method of claim 16, further comprising, subsequent to the inserting the engineered filling into the drillhole, sealing the vertical portion of the drillhole from the terranean surface. 27. The method of claim 16, further comprising inserting one or more expansion absorbers at predetermined locations in the casing. 28. The method of claim 16, further comprising forming a passive protective film on an exterior surface of the outer housing by the nickel-chromium-molybdenum alloy.