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Federal Register / Vol. 49, No. 236 / Thursday, December 6, 1984 | Rules and Regulations

as follows: "The site shall be disqualified if the rock characteristics are such that the activities associated with repository construction, operation, or closure are predicted to cause significant risk to the health and safety of personnel, taking into account mitigating measures that use reasonably available technology."

Five commenters objected to the phrase "engineering measures beyond the state of the art" in the second potentially adverse condition in the alternative guideline. As explained in the discussion of the postclosure guideline on rock characteristics, this phrase was changed to "engineering measures beyond reasonably available technology."

Four comments asked the DOE to reclassify the potentially adverse conditions as disqualifying ones. This was not done because, by itself, none of the potentially adverse conditions are necessarily unacceptable and hence should not disqualify a site. Their designation as potentially adverse ensures that these conditions will be given due consideration. Another comment suggested that the converse of favorable condition 960.5.2.9(a)(1) be used as a disqualifying condition. The conyerse of this condition would not be disqualifying, because, while the flexibility of designing and locating a repository would be reduced, the ability of the host rock to contain a respository would not be eliminated.

Three commenters expressed concern that retrievability was not adequately addressed in the alternative guidelines and felt that preclosure rock characteristics were important to ensuring retrievability. The DOE agrees that rock characteristics are important to retrievability, but feels that many other guidelines are also important in this regard. However, the retrievability issue is more pertinent to repository design than to site selection, and, if the requirements of the final guidelines taken as a whole are met, retrievability will be ensured. Furthermore, the DOE is required by 10 CFR Part 60 to maintain retrieval as an option for 50 years if unforeseen circumstances would require the removal of emplaced wastes.

Among the issues raised in the comments was that of thermal effects on in-situ stresses. In response to this concern, the DOE added a potentially adverse condition, 960.4-2-3(c)(3), to specifically address thermal effects.

One commenter was concerned that the available data might not allow a complete analysis of the disqualifier contained in the proposed guidelines. This issue is covered by one of the implementation guidelines, "Basis for

Site Evaluations" (960.3–1-5), and Appendix III to the siting guidelines, which specifies what type of finding the DOE is to make at major decision points in the site-selection process.

Section 960.5-2-10 Hydrology. The preclosure technical guideline on hydrology is concerned with (1) the potential effects of ground water on the construction and sealing of shafts and other underground openings, including the repository itself; (2) the potential for flooding of underground workings by surface water, and (3) the availability of water for repository construction and operation. Ils objectives are to ensure that the geohydrologic setting will (1) be compatible with repository construction, operation, and closure and (2) not. compromise the functions of shaft liners and seals.

Eleven commenters objected to the term "state of the art" in the potentially adverse condition of the alternative guideline. Some argued that the potentially adverse condition, as written with the "state-of-the-art" phrase included, should be disqualifying. Others suggested that the phrase should be replaced by "reasonably available technology" or similar words. The DOE agrees that "state of the art" is inappropriate because it suggests technology that may not have been fully demonstrated and tested and substituted the term "reasonably available technology," which is defined in $ 960.2 of the guidelines.

The presence or absence of aquifers within or above the host rock was an issue raised by eight commenters. The absence of aquifers between the host rock and the land surface is recognized as a favorable condition in the preclosure guideline. Some commenters suggested that the presence of aquifers between the host rock and the land surface should be explicitly stated as a potentially adverse condition; others recommended that the absence of aquifers be a qualifying condition or, conversely, that the presence of aquifers be a disqualifying condition. The presence of aquifers between the host rock and the land surface must be carefully considered in repository design and construction. However, many mines and other underground facilities have been successfully constructed below aquifers, and accepted and proved engineering measures are available to allow underground construction and operation under many types of groundwater conditions. That is not to say that some ground-water conditions may not require very costly engineering measures, or that some ground-water conditions may not be so severe as to preclude construction. For these

reasons, the DOE did not stipulate the absence or presence of aquifers between the host rock in the qualifying condition of the preclosure hydrology guideline, but a potentially adverse condition deals with aquifers whose presence could raise serious questions about the feasibility of construction.

Four comments recommended that the converse of the favorable condition pertaining to the availability of potable and construction water be explicitly stated as a disqualifying condition: they believe that the unavailability of water for construction and operation should disqualify a site. The issue lies in the meaning of the words "available" and "unavailable." Water might not be available locally at a site, but it might be available from a source some distance away. Water must be available for construction and operation, and locally available water would presumably be less expensive than water obtained from a more distant source. Thus in the preclosure hydrology guideline the DOE assumes that water can be made available and regards ready availability as a favorable condition.

One commenter suggested the addition of a potentially adverse condition pertaining to a geohydrologic system that would not allow predictive modeling before construction. The rationale for this suggestion is related to the potential for adverse effects on the hydrologic system caused by construction activities. The difficulty of modeling is addressed in the postclosure geohydrology guideline as a potentially adverse condition, and the DOE believes it would be redundant to include a similar statement in the preclosure guideline.

In consideration of the NRC's request. in preliminary concurrence condition 7, for additional disqualifying conditions that address the factors specified in Section 112(a) of the Act, the DOE agreed to develop a disqualifier for the final preclosure guideline on hydrology. This condition. 960.5–2-10(d). is concerned with the need to use engineering measures that are beyond reasonably available technology for exploratory-shaft construction or for repository construction, operation, or . closure.

Section 960.5-2-11 Tectonics. The objective of the preclosure guideline on tectonics is to ensure that the selected site is in a geologic setting in which any projected effects of expected tectonic phenomena or igneous activity will be such that the requirements of system . guideline $ 960.5-1(a)(3) can be met.

Five commenters complained that no disqualifying conditions were proposed

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Federal Register / Vol. 49, No. 236 / Thursday, December 6, 1984 / Rules and Regulations

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for the preclosure tectonics guideline. Some recommended that the opposite of the qualifying condition should be used. while others recommended that some of the potentially adverse conditions be changed to disqualifying ones. The DOE believed that the existence of a potentially adverse condition does not mean that the site is disqualified. The existence of any such condition would require an understanding of the condition to ensure that repository design and operation could adequately accommodate its effects. Using the converse of the qualifying conditions adds nothing to the guidelines since all acceptable sites must meet the requirements of the qualifying conditions. The guideline was therefore not changed to reflect these recommendations.

Two commenters felt that the historical record of earthquakes should be based solely on instrument recordings. This approach would severely limit the amount of historical data that could be considered because seismic recording equipment has been available for a relatively short period of time (20th century). In developing a historical record for seismicity, it is important to look as far back into the recorded past as can be done for a particular area of the country. While the DOE agrees that seismic-instrument recording should be included in the historical record, other historical records must also be used. For this reason the suggestion was not accepted.

One commenter recommended that "man-induced seismicity." a particular tectonic phenomenon, be added to the qualifying condition. The DOE believes that this particular aspect of tectonics is no more important than the other aspects and should not be called out separately. No change was made.

In response to the NRC's preliminary concurrence condition 7, the DOE reevaluated the preclosure guideline on tectonics and added a disqualifying condition. This condition is concerned with the need to use engineering measures beyond reasonably available technology to ensure that tectonic ground motion will not adversely affect exploratory-shaft construction or repository construction, operation, or closure. As shown in Appendix III to the siting guidelines, this disqualifying condition can be used early in the siting process (i.e., in the identification of potentially acceptable sites). V. References

1. U.S. Department of Energy. Final Environmental Impact StatementManagement of Commercially Generated

Radioactive Waste, DOE/EIS-0046F, October 1980.

2. U.S. Department of Energy. Mission Plan for the Civilian Radioactive Waste Management Program, draft, DOE/RW-0005, 1984.

3. U.S. Department of Energy. Program Objectives, Functional Requirements, and System Performance Criteria, NWTS-33(1), National Waste Terminal Storage Program, 1982

4. U.S. Department of Energy, Site Performance Criteria, NWTS-33(2). National Waste Terminal Storage Program, 1981.

5. National Research Council-National Academy of Sciences, Geologicel Criteria for Repositories for High-level Radioactive Waste, August 1978.

6. International Atomic Energy Agency, Site Selection Factor for Repositories of Solid High-Level and Alpha-Bearing Wastes in Ceologic Formations, Technical Report No. 177. October 1977.

7. G.D. Brunton and W.C. McClain, Geological Criteria for Radioactive Waste Repositories, Y/OWI/TM-47, Office of Waste Isolation, Union Carbide Corporation. November 28, 1977.

& U.S. Department of Energy. Final Environmental Impact Statement-Waste Isolation Pilot Plant, DOE/EIS-0028. October 1980

9. Comptroller General of the United States, The Nation's Nuclear Waste Proposals for Organization and Siting. EMD79-77, General Accounting Office, June 21, 10079.

10. Congressional Record-House, October 18, 1979. p. H 9367 to H 9371.

11. U.S. Nuclear Regulatory Commission. "Advance Notice of Rulemaking on Technical Criteria for Regulating Geologic Disposal of High-Level Radioactive Waste," 10 CFR Part 60. May 1980.

12. U.S. Environmental Protection Agency, "Environmental Radiation Protection Standards for Nuclear Power Operations," 40 CFR Part 190.

13. U.S. Nuclear Regulatory Commission, "Standards for Protection Against Radiation," 10 CFR Part 20

14. U.S. Nuclear Regulatory Commission, "Disposal of High-Level Radioactive Wastes in Geologic Repositories," 10 CFR Part 00 Subpart E (final draft). November 18, 1982.

15. U.S. Environmental Protection Agency, "Environmental Standards for the Management and Disposal of Spent Nuclear Fuel, High-Level and Transuranic Radioactive Wastes." 40 CFR Part 101. Federal Register, Vol. 47. pp. 58196-58206 December 29, 1982 (proposed rule)

16. U.S. Department of Energy. Record of Responses to Public Comments on Proposed General Guidelines for Recommendation of Sites for Nuclear Waste Repositories, DOE/ RW-0001, Washington, D.C., 1983.

17. U.S. Nuclear Regulatory Commission "Disposal of High-Level Radioactive Wastes in Geologic Repositories-Technical Criteria," 10 CFR Part 60. July 1983.

18. S.W. Lohman et al., Definitions of Selected Cround Water Terms-Revisions and Conceptual Refinements, U.S. Geological Survey Water Supply Paper 1948, U.S. Ceological Survey, 1972, p.21.

19.R.L. Bales and J.A. Jackson, eds.. Clossary of Geology, 2nd edition. American Ceological Institute. 1960. VI. Compliance with the National Environmental Policy Act (NEPA)

The issuance of these guidelines is a preliminary decision making activity pursuant to Section 112(e) of the Nuclear Waste Policy Act of 1982 and therefore does not require the preparation of an environmental impact statement pursuant to Section 102(2)(C) of NEPA or any other environmental review under Section 102(2)(E) or (F) of NEPA. VII. Regulatory Flexibility Analysis

The DOE certifies that these guidelines will not have a significant economic impact on a substantial number of small entities, since they merely articulate the proposed considerations for the Secretary of Energy's recommendations to the President of proposed sites for repositories. Accordingly, no regulatory flexibility analysis is required under the Regulatory Flexibility Act (5 U.S.C. 801 et seq.). VIII. Paperwork Reduction Analysis

This rule contains no new or amended recordkeeping. reporting, or application requirement, or any other type of information collection requirement subject to the Paperwork Reduction Act (Pub. L 96-511). IX. Executive Order No. 12291

These final guidelines were reviewed under Executive Order 12291 (48 FR 13193). The DOE has concluded that the guidelines are not a "major rule" under the Executive Order, because they will not result in (1) an annual effect on the economy of $100 million or more: (2) a major increase in costs or prices for consumers, individual industries, and Federal, State, or local government agencies, or geographic regions, or (3) significant adverse effects on competition, employment, investment, productivity, innovation, or the ability of United States-based enterprises to compete with foreign-based enterprises in domestic or export markets. Pursuant to Section 3(c)(3) of the Executive Order, the final guidelines were submitted to the Director of the Office of Management and Budget for a 10-day review. The Director has concluded his review and had no comments. List of Subjects fa 10 CFR Part 850

Environmental protection, Geologic repositories, Nuclear energy. Nuclear materials, Radiation protection, Waste disposal.


Federal Register / Vol. 49. No. 236 / Thursday, December 6, 1984 / Rules and Regulations

(The Atomic Energy Act of 1954, as amended
(42 U.S.C. 2011 et seq.): Energy
Reorganization Act of 1974 (42 U.S.C. 5801 et
seq.); Department of Energy Organization Act
of 1977 (42 U.S.C. 7101 et seq.): Nuclear
Waste Policy Act of 1962 (Pub. L. 97-425, 98
Stat. 2201))

For the reasons set out in the preamble, Chapter III of Title 10 of the Code of Federal Regulations is amended as follows:

Issued at Washington, D.C., November 30,
Donald Paul Hodel,
Secretary of Energy

Part 960 is added to 10 CFR Chapter
III to read as follows:
Subpart A-General Provisions
960.1 Applicability.
960.2 Definitions.
Subpart B-Implementation Guidelines
900.3 Implementation guidelines.
960.3-1 Siting provisions.
960.3-1-1 Diversity of geohydrologic

settings. 960.3-1-2 Diversity of rock types. 900 3-1-3 Regionality, 960.3-1-4 Evidence of siting decisions. 900.3-1-4-1 Site identification as potentially

acceptable 900.3-1-4-2 Site nomination for

characterization. 960.3-1-4-3 Site recommendation for

characterization. 900.3-1-44 Site recommendation for

repository development, 960.3-1-5 Basis for site evaluations. 900 3-2 Siting process 960.3-2-1 Stte screening for potentially

acceptable sites 900.3-2-2 Nomination of sites as suitable for

characterization 960.32-2-1 Evaluation of all potentially

acceptable sites 980.2-2-2-2 Selection of sites within

geohydrologic settings. 900.3–2-2-3 Comparative evaluation of all

sites proposed for nomination 900.3-2-2-4 The environmental assessment. 980. 3-2-2-5 Formal site nomination 900.3-2-3 Recommendation of sites for

characterization. 960.3-2-4 Recommendation of sites for the

development of repositories. 900.33 Consultation. 980.3 Environmental impacts. Subpart C-Postclosure guidelines 960.4 Postclosure guidelines. 9004-1 System guideline. 900.42 Technical guidelines. 960.2-1 Geohydrology 900 -2-2 Geochemistry 90.4-2-3 Rock characteristics 9504-3-4 Climatic changes. 9602-5 Erosion


otherwise update the guidelines as 960.4-2-6 Dissolution.

necessary. The DOE will submit the 960.4-2-7 Tectonics.

revisions to the NRC and obtain its
900.2-8 Human interference.
980.4-2-8-1 Natural resources.

concurrence before issuance.
960.4-2-8-2 Site ownership and control. $980.2 Definition
Subpart D Preclosure Guidelines

As used in this part:
960.5 Preclosure guidelines.

"Accessible environment" means the 960.5-1 System guidelines.

atmosphere, the land surface, surface 960.5-2 Technical guidelines.

water, oceans, and the portion of the 960.5-2-1 Population density and distribution.

lithosphere that is outside the controlled 960,5-2-2 Site ownership and control.

area. 960.5-2-3 Meteorology.

• "Act" means the Nuclear Waste 960.5-2-4 Offsite installations and

Policy Act of 1982. operations.

"Active fault" means a fault along Environment, Socioeconomics, and

which there is recurrent movement. Transportation

which is usually indicated by small. 960.5-2-5 Environmental quality.

periodic displacements or seismic 960.5-2-1 Socioeconomic impacts.

activity. 960.5-2-7 Transportation.

"Affected area" means either the area Ease and Cost of Siting. Construction,

of socioeconomic impact or the area of Operation and Closure

environmental impact, each of which 960.5-2-4 Surface characteristics.

will vary in size among potential 960.5-2-9 Rock characteristics.

repository sites. 960.5-2-10 Hydrology.

"Affected Indian tribe" means any 960.5-2-11 Tectonics.

Indian tribe (1) within whose
Appendix |-NRC and EPA Requirements for reservation boundaries a repository for

Postclosure Repository Performance radioactive waste is proposed to be
Appendix 11-NRC and EPA Requirements

located or (2) whose federally defined for Preclosure Repository Performance Appendix III- Application of the System and

possessory or usage rights to other lands Technical Guidelines During the Siting

outside the reservation's boundaries Process

arising out of congressionally ratified Appendix IV-Types of Information for the treaties may

be substantially and Nomination of Sites as Suitable for adversely affected by the locating ol Characterization

such a facility. Provided That the Authority: The Atomic Energy Act of 1954. Secretary of the Interior finds, upon the as amended (42 U.S.C. 2011 et seq.): Energy petition of the appropriate governmental Reorganization Act of 1974 (42 U.S.C. et seq.):

officials of the tribe, that such effects Department of Energy Organization Act of 1977 (42 U.S.C. 7101 et seq.. Nuclear Waste

are both substantial and adverse to the

Policy Act of 1982 (Pub. L. 97-425. Stat.

“Affected State" means any State that

(1) has been notified by the DOE in Subpart A-General Provisions

accordance with Section 1164) of the 1960.1 Applicability.

Act as containing a potentially These guidelines were developed in acceptable site; (2) contains a candidate accordance with the requirements of

site for site characterization or Section 112(a) of the Nuclear Waste repository development; or (3) contains Policy Act of 1982 for use by the

a site selected for repository Secretary of Energy in evaluating the development suitability of sites for the development "Application" means the act of of repositories. The guidelines will be making a finding of compliance or used for suitability evaluations and noncompliance with the qualifying or determinations made pursuant to

disqualifying conditions specified in the Section 112(b) and any preliminary guidelines ol Subparts Cand D. in suilability determinations required by accordance with the types of findings Section 114/7. The guidelines set forth in specified in Appendix In this Part are intended to complement the "Aquifer“ means a formation group requirements set forth in the Act, 10 CFR of formations, or a part of • formation Part 60, and 40 CFR Part 191. The DOE that contains sufficient saturated recognizes NRC jurisdiction for the permeable material to yield significant resolution of differences between the quantities of water to wells and springs guidelines and 10 CFR Part 60. The

“Bartier" means any material ar guidelines have received the

structure that prevents or substantially concurrence of the NRC. The DOE delays the movement of water at contemplates revising the guidelines radionuclides from time to time, as permitted by the "Candidate site means en area Act, to take into account revisions made within a geohydrologic setting that is to the above regulations and to recommended by the Secretary of

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Energy under Section 112 of the Act for site characterization, approved by the President under Section 112 of the Act for characterization, or undergoing site characterization under Section 113 of the Act.

"Closure" means final backfilling of the remaining open operational areas of the underground facility and boreholes after the termination of waste emplacement, culminating in the sealing of shafts.

"Confining unit" means a body of impermeable or distinctly less permeable material stratigraphically adjacent to one or more aquifers.

"Containment" means the confinement of radioactive waste within a designated boundary.

"Controlled area" means a surface location, to be marked by suitable monuments, extending horizontally no more than 10 kilometers in any direction from the outer boundary of the underground facility, and the underlying subsurface, which area has been committed to use as a geologic repository and from which incompatible activities would be prohibited before and after permanent closure.

"Cumulative releases of radionuclides" means the total number of curies of radionuclides entering the accessible environment in any 10.000 year period, normalized on the basis of radiotoxicity in accordance with 40 CFR Part 191. The peak cumulative release of radionuclides refers to the 10,000-year period during which any such release attains its maximum predicted value.

"Decommissioning" means the permanent removal from service of surface facilities and components neceessary for preclosure operations only, after repository closure, in accordance with regulatory requirements and environmental policies.

"Determination" means a decision by the Secretary that a site is suitable for site characterization for the selection of a repository site or that a site is suitable for the development of a repository, consistent with applications of the guidelines of Subparts C and D in accordance with the provisions set forth in Subpart B.

"Disposal" means the emplacement in a repository of high-level radioactive waste, spent nuclear fuel, or other highly radioactive material with no foreseeable intent of recovery, whether or not such emplacement permits the recovery of such waste, and the isolation of such waste from the accessible environment.

"Disqualifying condition" means a " condition that, if present at a site, would eliminate that site from further consideration

"Disturbed zone" means that portion of the controlled area, excluding shafts, whose physical or chemical properties are predicted to change as a result of underground facility construction or heat generated by the emplaced radioactive waste such that the resultant change of properties could have a significant effect on the preformance of the geologic repository.

"DOE" means the U.S. Department of Energy or its duly authorized representatives.

"Effective porosity" means the amount of interconnected pore space and fracture openings available for the transmission of fluids, expressed as the ratio of the volume of interconnected pores and openings to the volume of rock.

"Engineered-barrier system" means the manmade components of a disposal system designed to prevent the release of radionuclides from the underground facility or into the geohydrologic setting. Such term includes the radioactivewaste form, radioactive-waste canisters, materials placed over and around such canistera, any other components of the waste package, and barriers used to seal penetrations in and into the underground facility.

"Environmental assessment" means the document required by Section 112(b)(1)(E) of the Nuclear Waste Policy Act of 1982.

"Environmental impact statement" means the document required by Section 102(2)(C) of the National Environmental Policy Act of 1969. Sections 114(a) and 114(1) of the Nuclear Waste Policy Act of 1982 include certain limitations on the National Environmental Policy Act requirements as they apply to the preparation of an environmental impact statement for the development of a repository at a characterized site.

"EPA" means the U.S. Environmental Protection Agency or its duly authorized representatives.

"Evaluation" means the act of carefully examining the characteristics of a site in relation to the requirements of the qualifying or disqualifying conditions specified in the guidelines of Subparts Cand D. Evaluation includes the consideration of favorable and potentially adverse conditions.

"Excepted" means assumed to be probable or certain on the basis of existing evidence and in the absence of significant evidence to the contrary.

"Expected repository performance" means the manner in which the repository is predicted to function, consideration those conditions, processes, and events that are likely to prevail or may occur during the time period of interest.

"Facility" means any structure, system, or system component, including engineered barriers, created by the DOE to meet repository-performance or functional objectives.

"Fault" means a fracture or a zone of fractures along which there has been displacement of the side relative to one another parallel to the fracture or zone of fractures.

"Faulting" means the process of fracturing and displacement that produces a fault.

"Favorable condition" means a condition that, though not necessary to qualify a site, is presumed, if present, to enhance confidence that the qualifying condition of a particular guideline can be met.

"Finding" means a conclusion that is reached after evaluation.

"Geohydrologic setting" means the system of geohydrologic units that is located within a given geologic setting.

"Geohydrologic system" means the geohydrologic units within a geologic setting, including any recharge, discharge, interconnections between units, and any natural or man-induced processes or events that could affect ground-water flow within or among those units.

"Geohydrologic unit" means an aquifer, a confining unit, or a combination of aquifers and confining units comprising a framework for a reasonably distinct geohydrologic system.

"Geologic repository" means a system, requiring licensing by the NRC, that is intended to be used, or may be used, for the disposal of radioactive waste in excavated geologic media. A geologic repository includes (1) the geologic-repository operations area and (2) the portion of the geologic setting that provides isolation of the radioactiv waste and is located within the controlled area.

"Geologic-repository operations area' means a radioactive-waste facility that is part of the geologic repository. including both surface and subsurface areas and facilities where wastehandling activities are conducted.

"Geologic setting" means the geology hydrologic, and geochemical systems o the region in which a geologic-repositor operations area is or may be located.

"Geomorphic processes" means geologic processes that are responsible for the general configuration of the Earth's surface, including the development of present landforms and their relationships to underlying structures, and are responsible for the geologic changes recorded by these surface features.


Federal Register / Vol. 49, No. 236 / Thursday, December 6, 1984 / Rules and Regulations

"Ground water" means all subsurface water as distinct from surface water.

"Ground-water flux" means the rate of ground-water Now per unit area of porous or fractured media measured perpendicular to the direction of flow.

"Ground-water sources" means aquifers that have been or could be economically and technologically developed as sources of water in the foreseeable future.

"Ground-water travel time" means the time required for a unit volume of ground water to travel between two locations. The travel time is the length of the flow path divided by the velocity. where velocity is the average groundwater flux passing through the crosssectional area of the geologic medium through which flow occurs, perpendicular to the flow direction, divided by the effective porosity along the flow path. If discrete segments of the flow path have different hydrologic properties, the total travel time will be the sum of the travel times for each discrete segment.

"Guideline" means a statement of policy or procedure that may include, when appropriate, qualifying. disqualifying. favorable, or potentially adverse conditions as specified in the "guidelines."

"Guidelines" means Part 960 of Title 10 of the Code of Federal Regulations General Guidelines for the Recommendation of Sites for Nuclear Waste Repositories.

"High-level radioactive waste“ means (1) the highly radioactive material resulting from the reprocessing of spent nuclear fuel, including liquid waste produced directly in reprocessing and any solid material derived from such liquid waste that contains fission products in sufficient concentrations and (2) other highly radioactive material that the NRC, consistent with existing law, determines by rule requires permanent isolation.

"Highly populated area" means any incoporated place (recognized by the decennial reports of the U.S. Bureau of the Census) of 2,500 or more persons or any census designated place (as defined and delineated by the Bureau) of 2,500 or more persons, unless it can be demonstrated that any such place has a lower population density than the mean value for the continental United States. Counties or county equivalents, whether incorporated or not, are specifically excluded form the definition of "place" as used herein.

"Host rock" means the geologic medium in which the waste is emplaced. specifically the geologic materials that directly encompass and are in close proximity to the underground facility.

"Hydraulic conductivity" means the volume of water that will move through a medium in a unit of time under a unit hydraulic gradient through a unit area measured perpendicular to the direction of flow.

"Hydraulic gradient" means a change in the static pressure of ground water, expressed in terms of the height of water above a datum, per unit of distance in a given direction.

“Hydrologic process" means any hydrologic phenomenon that exhibits a continuous change in time, whether slow or rapid.

"Hydrologic properties" means those properties of a rock that govern the entrance of water and the capacity to hold, transmit, and deliver water, such as porosity, effective porosity, specific retention, permeability, and the directions of maximum and minimum permeabilities.

"Igneous activity" means the emplacement (intrusion) of molten rock material (magma) into material in the Earth's crust or the expulsion (extrusion) of such material onto the Earth's surface or into its atmosphere or surface water.

"Isolation" means inhibiting the transport of radioactive material so that the amounts and concentrations of this material entering the accessible environment will be kept within prescribed limits.

"Likely" means processing or displaying the qualities, characteristics, or attributes that provide a reasonable basis for confidence that what is expected indeed exists or will occur.

“Lithosphere" means the solid part of the Earth, including any ground water contained within it.

"Member of the public" means any individual who is not engaged in operations involving the management, storage, and disposal of radioactive waste. A worker so engaged is a member of the public except when on duty at the geologic-repository operations area.

"Mitigation" means (1) avoiding the impact allogether by not taking a certain action or parts of an action: (2) minimizing impacts by limiting the degree or magnitude of the action and its implementation; (3) rectifying the impact by repairing, rehabilitating, or restoring the affected environment: (0) reducing or eliminating the impact over time by preservation and maintenance operations during the life of the action; or (5) compensating for the impact by replacing or providing substitute resources or environments.

"Model" means a conceptual description and the associated mathematical representation of a system, subsystem, component, or

condition that is used to predict changes from a baseline state as a function of internal and/or external stimuli and as a function of time and space.

"NRC" means the U.S. Nuclear Regulatory Commission or its duly authorized representatives.

"Perched ground water" means unconfined ground water separated from an underlying body of ground water by an unsaturated zone. Its water table is a perched water table. Perched ground water is held up by a perching bed whose permeability is so low that water percolating downward through it is not able to bring water in the underlying unsaturated zone above atmospheric pressure.

"Performance assessment" means any analysis that predicts the behavior of a system or system component under a given set of constant and/or transient conditions. Performance assessments will include estimates of the effects of uncertainties in data and modeling.

"Permanent closure" is synonymous with "closure."

"Postclosure" means the period of time after the closure of the geologic repository

**Potentially acceptable site" means any site at which, after geologic studies and field mapping but before detailed geologic data gathering. the DOE undertakes preliminary drilling and geophysical testing for the definition of site location.

"Potentially adverse condition" means a condition that is presumed to detract from expected system performance, but further evaluation, additional data. of the identification of compensating or mitigating factors may indicate that it effect on the expected system performance is acceptable.

"Preclosure" means the period of time before and during the closure of the geologic repository

"Pre-waste-emplacement means before the authorization of repository construction by the NRC

"Qualifying condition" means a condition that must be satisfied for site to be considered acceptable with respect to a specific guideline.

"Quaternary Period" means the second period of the Cenozoic Ern. following the Tertiary beginning 2 to 3 million yeans ago and extending to the present

"Radioactive waste" or "waste" means high-level radioactive waste and other radioactive matenals, including spent nuclear fuel, that are received for emplacement in a geologic repository

"Radioactive waste facility means a facility subject to the licensing and related regulatory authority of the NRC

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