Patent Number: 
Section: claims

1. A method, comprising:identifying a drillhole that extends from a terranean surface and into one or more subterranean formations, the drillhole comprising a vertical portion, a curved portion, and a horizontal portion that comprises a hazardous waste repository formed within the horizontal portion of the drillhole;dropping a test canister into the drillhole in a free fall event;determining, based on a travel distance of the dropped test canister into the horizontal portion of the drillhole, a length of a safety runway of the horizontal portion of the drillhole that is approximately equal to the travel distance from into the horizontal portion of the drillhole from a transition between the vertical portion and the horizontal portion;moving at least one hazardous waste canister through an entry of the drillhole, the at least one hazardous waste canister comprising an inner cavity that encloses hazardous waste material;moving the at least one hazardous waste canister through the vertical portion of the drillhole and through the curved portion of the drillhole;moving the at least one hazardous waste canister from the curved portion through the safety runway of the horizontal portion of the drillhole;moving the at least one hazardous waste canister from the safety runway of the horizontal portion of the drillhole into the hazardous waste repository of the horizontal portion of the drillhole, the at least one hazardous waste canister sized to fit from the entry through the vertical portion, the curved portion, the safety runway of the horizontal portion of the drillhole, and into the hazardous waste repository of the horizontal portion of the drillhole; andpositioning the at least one hazardous waste canister exclusively in the hazardous waste repository and externally to the safety runway. 2. The method of claim 1, wherein the hazardous waste material comprises nuclear waste. 3. The method of claim 2, wherein the nuclear waste comprises at least one of spent nuclear fuel or high level radioactive waste. 4. The method of claim 1, wherein the length of the safety runway is determined based at least in part on a terminal velocity of the test canister during the free fall event and a coefficient of friction between the hazardous waste canister or the test canister and the drillhole. 5. The method of claim 1, wherein the drillhole further comprises an inclined portion coupled between the curved portion and the horizontal portion. 6. The method of claim 5, further comprising moving each hazardous waste canister of the at least one hazardous waste canister sequentially from the curved portion into the inclined portion of the drillhole and from the inclined portion into the horizontal portion. 7. The method of claim 5, wherein the length of the safety runway is determined based at least in part on a terminal velocity of the test canister during the free fall event, a coefficient of friction between the hazardous waste canister or the test canister and the drillhole, and an angle of inclination of the inclined portion. 8. The method of claim 5, wherein the inclined portion is angled toward the terranean surface from the curved portion. 9. The method of claim 1, further comprising positioning a seal in the drillhole that isolates the hazardous waste repository from the entry of the drillhole. 10. The method of claim 1, wherein moving the at least one hazardous waste canister through the entry of the drillhole comprises moving each of a plurality of hazardous waste canisters sequentially through the entry. 11. The method of claim 1, wherein moving the at least one hazardous waste canister through the vertical portion of the drillhole and through the curved portion of the drillhole comprises moving each of a plurality of hazardous waste canisters sequentially through the vertical portion of the drillhole and through the curved portion of the drillhole. 12. The method of claim 1, wherein moving the at least one hazardous waste canister from the curved portion through the safety runway of the horizontal portion of the drillhole comprises moving each of a plurality of hazardous waste canisters sequentially from the curved portion through the safety runway of the horizontal portion of the drillhole. 13. The method of claim 1, wherein moving the at least one hazardous waste canister from the safety runway of the horizontal portion of the drillhole into the hazardous waste repository of the horizontal portion of the drillhole comprises moving each of a plurality of hazardous waste canisters sequentially from the safety runway of the horizontal portion of the drillhole into the hazardous waste repository of the horizontal portion of the drillhole. 14. The method of claim 1, wherein the drillhole comprises a single vertical portion, a single curved portion contiguously coupled to the single vertical portion, and a single horizontal portion contiguously coupled to the single curved portion. 15. The method of claim 14, wherein the drillhole further comprises an inclined portion coupled between the single curved portion and the single horizontal portion. 16. The method of claim 15, wherein the length of the safety runway is determined based at least in part on a terminal velocity of the test canister during the free fall event, a coefficient of friction between the hazardous waste canister or the test canister and the drillhole, and an angle of inclination of the inclined portion. 17. The method of claim 15, wherein the inclined portion is angled toward the terranean surface from the single curved portion. 18. The method of claim 1, wherein the test canister is approximately the same size as the at least one hazardous waste canister. 19. The method of claim 1, wherein the test canister is approximately the same weight as the at least one hazardous waste canister. 20. The method of claim 1, further comprising filling the drillhole with a fluid. 21. The method of claim 1, further comprising positioning a casing around the drillhole. 22. The method of claim 1, further comprising roughening a surface of the casing or a surface of the at least one hazardous waste canister. 23. The method of claim 1, further comprising removing the test canister from the drillhole before moving the at least one hazardous waste canister through the entry of the drillhole. 24. The method of claim 1, wherein the test canister is sized to fit from the entry through the vertical portion, the curved portion, the safety runway of the horizontal portion of the drillhole, and into the hazardous waste repository of the horizontal portion of the drillhole. 25. The method of claim 1, wherein dropping the test canister into the drillhole comprises dropping a set of test canisters into the drillhole, the set of test canisters including the test canister. 26. A method, comprising:identifying a drillhole that extends from a terranean surface and into one or more subterranean formations, the drillhole comprising a vertical portion, a curved portion, and a horizontal portion that comprises a hazardous waste repository formed within the horizontal portion of the drillhole;dropping a test canister into the drillhole in a free fall event;determining, based on a travel distance of the dropped test canister into the horizontal portion of the drillhole, a length of a safety runway of the horizontal portion of the drillhole that is approximately equal to the travel distance into the horizontal portion of the drillhole from a transition between the vertical portion and the horizontal portion; andsubsequent to the determination, moving at least one hazardous waste canister through an entry of the drillhole, the at least one hazardous waste canister comprising an inner cavity that encloses hazardous waste material. 27. The method of claim 26, wherein the hazardous waste material comprises nuclear waste. 28. The method of claim 27, wherein the nuclear waste comprises at least one of spent nuclear fuel or high level radioactive waste. 29. The method of claim 26, wherein the length of the safety runway is determined based at least in part on a terminal velocity of the test canister during the free fall event and a coefficient of friction between the at least one hazardous waste canister or the test canister and the drillhole. 30. The method of claim 26, wherein the drillhole further comprises an inclined portion coupled between the curved portion and the horizontal portion. 31. The method of claim 30, further comprising moving the at least one hazardous waste canister from the curved portion into the inclined portion of the drillhole and from the inclined portion into the horizontal portion. 32. The method of claim 30, wherein the length of the safety runway is determined based at least in part on a terminal velocity of the test canister during the free fall event, a coefficient of friction between the at least one hazardous waste canister or the test canister and the drillhole, and an angle of inclination of the inclined portion. 33. The method of claim 30, wherein the inclined portion is angled toward the terranean surface from the curved portion. 34. The method of claim 26, further comprising positioning a seal in the drillhole that isolates the hazardous waste repository from the entry of the drillhole. 35. The method of claim 26, wherein the test canister is approximately the same size as the at least one hazardous waste canister. 36. The method of claim 26, wherein the test canister is approximately the same weight as the at least one hazardous waste canister.