{"data":{"id":"us/10-cfr-63.302","jurisdiction":"us","citation":"10 CFR 63.302","heading":"Definitions for subpart L.","body":"All definitions in subpart K of this part, and the following:\nAccessible environment means any point outside of the controlled area, including:\n(1) The atmosphere (including the atmosphere above the surface area of the controlled area);\n(2) Land surfaces;\n(3) Surface waters;\n(4) Oceans; and\n(5) The lithosphere.\nAquifer means a water-bearing underground geological formation, group of formations, or part of a formation (excluding perched water bodies) that can yield a significant amount of groundwater to a well or spring.\nControlled area means:\n(1) The surface area, identified by passive institutional controls, that encompasses no more than 300 square kilometers. It must not extend farther:\n(i) South than 36°40′13.6661″ North latitude, in the predominant direction of groundwater flow; and\n(ii) Than five kilometers from the repository footprint in any other direction; and\n(2) The subsurface underlying the surface area.\nDisposal means the emplacement of radioactive material into the Yucca Mountain disposal system with the intent of isolating it for as long as reasonably possible and with no intent of recovery, whether or not the design of the disposal system permits the ready recovery of the material. Disposal of radioactive material in the Yucca Mountain disposal system begins when all of the ramps and other openings into the Yucca Mountain repository are sealed.\nGroundwater means water that is below the land surface and in a saturated zone.\nHuman intrusion means breaching of any portion of the Yucca Mountain disposal system, within the repository footprint, by any human activity.\nPassive institutional controls means:\n(1) Markers, as permanent as practicable, placed on the Earth's surface;\n(2) Public records and archives;\n(3) Government ownership and regulations regarding land or resource use; and\n(4) Other reasonable methods of preserving knowledge about the location, design, and contents of the Yucca Mountain disposal system.\nPeak dose means the highest annual dose projected to be received by the reasonably maximally exposed individual.\nPeriod of geologic stability means the time during which the variability of geologic characteristics and their future behavior in and around the Yucca Mountain site can be bounded, that is, they can be projected within a reasonable range of possibilities. This period is defined to end at 1 million years after disposal.\nPlume of contamination means that volume of groundwater in the predominant direction of groundwater flow that contains radioactive contamination from releases from the Yucca Mountain repository. It does not include releases from any other potential sources on or near the Nevada Test Site.\nRepository footprint means the outline of the outermost locations of where the waste is emplaced in the Yucca Mountain repository.\nSlice of the plume means a cross-section of the plume of contamination with sufficient thickness parallel to the prevalent direction of flow of the plume that it contains the representative volume.\nTotal dissolved solids means the total dissolved (filterable) solids in water as determined by use of the method specified in 40 CFR part 136.\nUndisturbed performance means that human intrusion or the occurrence of unlikely natural features, events, and processes do not disturb the disposal system.\nUndisturbed Yucca Mountain disposal system means that the Yucca Mountain disposal system is not affected by human intrusion.\nWaste means any radioactive material emplaced for disposal into the Yucca Mountain repository.\nWell-capture zone means the volume from which a well pumping at a defined rate is withdrawing water from an aquifer. The dimensions of the well-capture zone are determined by the pumping rate in combination with aquifer characteristics assumed for calculations, such as hydraulic conductivity, gradient, and the screened interval.\nYucca Mountain disposal system means the combination of underground engineered and natural barriers within the controlled area that prevents or substantially reduces releases from the waste.","path":["Title 10—Energy","CHAPTER I—NUCLEAR REGULATORY COMMISSION","PART 63—DISPOSAL OF HIGH-LEVEL RADIOACTIVE WASTES IN A GEOLOGIC REPOSITORY AT YUCCA MOUNTAIN, NEVADA","Subpart L—Postclosure Public Health and Environmental Standards"],"source_url":"https://www.ecfr.gov/api/versioner/v1/full/2026-08-25/title-10.xml","current_through":"2026-08-25","vintage":"","retrieved_at":"2026-08-27T02:24:09Z","sha256":"b9306deddd234cb138c09eef2cb36d52db596b7cb50606b3d40b9aed7daee84b","source_id":"us-cfr","stale":true,"prev":"us/10-cfr-63.301","next":"us/10-cfr-63.303"},"notice":"GroundRules: Original legal text. Not legal advice."}