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Appendix G Glossary Adaptive Staging: a flexible decision-based process in which stages are predicated on the outcome of previous ones and are separated by Decision Points. Backfill: material used to refill excavated portions of a repository after waste has been emplaced. Buffer storage: a surface facility that acts as a “capacitor” giving flexibility in timing the transfer of any goods on to the next step in a process. This area receives waste, holds it, and blends it before underground emplacement. Decision Point: the re-evaluation period that separates stages within a phase of geologic repository development. Decision Points provide the opportunity to integrate newly acquired knowledge into the program, evaluate the program’s status, and decide how to proceed. Decision Points focus the implementer on identifying program improvements with respect to, for instance, environmental impact, safety, cost, and schedule. Demonstration activities: activities performed by the implementer to illustrate in particular to other stakeholders and the public, that the chosen repository design and operating mode does indeed perform as expected. Demonstration activities start only after defining the reference configuration (i.e., after the pilot activities conclude) and continue through repository closure. Direct demonstration of long-term safety is, of course, not feasible. Demonstration facility: dedicated area in the as-built repository but with added measures for monitoring. Demonstration facilities may be a part of the main disposal area or may be in separate but still representative areas to allow intensive monitoring without compromising the integrity of the repository. High-level waste (HLW): radioactive material emitting high doses of ionizing radiation representing a health hazard for very long times into the future unless measures are taken to isolate it from the human environment. In this report high-level waste refers to commercial spent nuclear fuel, naval spent nuclear fuel, defense-related high-level waste, highly enriched uranium, and Plutonium. Key characteristics of these materials are (1) the type of radiation emitted, (2) the rate at which the intensity decreases with time, and (3) the ease with which the material can be misused in nuclear weapons. Implementer: the agent, either an agency of the government or a private company, that locates, develops, and operates the geologic repository. Interim storage: any surface storage that is decoupled from emplacement (i.e., storage can be for an open-ended time) and does not require that there be an operating repository. Linear Staging: management process characterized by a single path in which stages are defined primarily by milestones driven by program schedule and cost.
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Long-term science and technology program: an ongoing program to improve the scientific understanding of the geologic repository system. The program includes scientific activities to (1) update the safety case, (2) investigate engineering alternatives to optimize repository design, and (3) and confirm (or invalidate) previous assumptions, data, and analyses. Monitoring program: sampling programs to measure and record conditions and temporal changes in parameters relevant to the repository program. These parameters may be the physical and chemical indicators of repository behavior and of its surroundings or social science indicators of public beliefs, concerns, and attitudes about the repository project. Oversight body: advisory groups not mandated by legislation that advise and guide implementers and regulators. Performance confirmation program: program to test, evaluate, and confirm that the repository system (at the site, elsewhere in the field, or in the laboratory) and its natural environment are behaving as expected and within acceptable safety margins. Phase: a primary element of repository development: selection of a geologic disposal option, site selection and characterization, licensing, construction, operation, closure, and post-closure. Multiple stages and the Decision Points that separate each stage constitute a phase. Pilot activities: preliminary tests of alternative repository designs and operating modes carried out in configurations increasingly close to those foreseen for the final repository. The objective is to learn about the system and processes under realistic conditions and then apply this learning to finalize the chosen design and operational procedures. Pilot activities at the repository site can begin with nonradioactive material and continue with radioactive waste when the license to operate the repository is obtained. Normally pilot activities cease with the transition to full-scale operation, but late introduction of a major new emplacement technology, for example, could be preceded by pilot activities. Pilot facility: a facility that hosts pilot activities. Pilot activities concerning the engineering barriers (e.g., canister sealing) may take place in any laboratory or workshop facility. Pilot facilities specific to the repository are located within the repository’s footprint in one or more dedicated disposal tunnels or drifts. Reference framework: the path for developing a successful geologic repository with Adaptive Staging. The reference framework is based on the best scientific and societal knowledge available at a given time. The reference framework includes, for instance, a reference repository design and a proposal for stages and a decision-making process. The framework is not a rigid roadmap attempting to define all future activities to successful project implementation. At the end of each stage the details of the reference framework may be adapted (i.e., the repository design and number of Decision Points may change) according to knowledge gathered along the way. Regulator: agencies, usually identified by national legislation, that set standards and criteria for developing and operating the repository and assure adherence to these standards. Repository program: the program that organizes the operation, closure, and post-closure phases of a geologic repository.
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Repository system: system including the geologic repository as well as transportation and interim (surface) storage programs. Retrievability: the possibility of reversing the action of waste emplacement. It is thus a special case of reversibility. Reversibility: a distinct option to abandon an earlier decided-upon path and reverse the course of action to a previous stage if new information warrants. Safety case: a collection of arguments, repeated and reaffirmed at stages of repository development, in support of the long-term safety of the repository. See Sidebars 2.1 and 5.1 in Chapters 2 and 5, respectively. Stage: a part of a phase in geologic repository development that concludes with a Decision Point. Stakeholder: see Sidebars 3.2 and 5.2 in Chapters 3 and 5, respectively. Test activities: scientific tests to learn about the performance of a geologic repository. Tests activities begin early (i.e., before concept or site are finalized) and continue until no further significant learning occurs. Test facility: a facility hosting test activities. To ensure that tests are relevant the facility is located in an environment similar to the repository environment (i.e., in the same host rock), but it may be physically separate from the actual disposal area to ensure that the tests, which can go beyond design expectations, do not compromise the repository integrity. Thermal blending: selecting for emplacement in the repository waste packages with differing heat output, and thus determining the temperature distribution in the repository throughout the repository lifetime. Thermal operating mode: mode of operation of the underground facilities with respect to the temperatures of drift walls and waste packages, as well as relative humidity. In a higher-temperature operating mode the temperature of the average waste package would rise significantly (over 160°C) after the repository is closed. In a lower-temperature mode the waste package surface temperature would be kept much lower (approximately 85°C).
Representative terms from entire chapter: