Description
Any type of drilling activity in the vicinity of or within the repository.
Category
Categorisation as a Feature, Event and/or Process.
Features
are physical components of the disposal system and environment being assessed. Examples include waste packaging, backfill, surface soils. Features typically interact with one another via processes and in some cases events.Events
are dynamic interactions among features that occur over time periods that are short compared to the safety assessment timeframe such as a gas explosion or meteorite impact.- "Processes" are issues or dynamic interactions among features that generally occur over a significant proportion of the safety assessment timeframe and may occur over the whole of this timeframe. Events and processes may be coupled to one another (i.e. may influence one another).
The classification of a FEP as an event or process depends upon the assessment context, because the classification is undertaken with reference to an assessment timeframe. In this generic IFEP List, many IFEPs are classified as both Events and Processes; users will need to decide which of these classifications is relevant to their context and its timeframes.
- Event
- Process
Comments
The “Comments” field, when present, contains any additional explanation of the IFEP, beyond that implicit in the FEP's description and provided in the “Relevance to Performance and Safety” field. This additional explanation may include, where appropriate, the IFEPs characteristics, the circumstances under which it might be relevant and its relationship to other (especially similar) IFEPs.
Drilling activities may be undertaken with or without knowledge of the repository (FEP 1.4.4).
Relevance to Performance and Safety
The “Relevance to Performance and Safety” field contains an explanation of how the IFEP might influence the performance and safety of the disposal system under consideration through its impact on the evolution of the repository system and on the release, migration and/or uptake of repository-derived contaminants.
Drilling activities are relevant to the performance and safety of a repository because they will disturb the geosphere around the repository and/or engineered barriers to some degree. The boreholes themselves may provide pathways by which radionuclides and/or other contaminants may be transported to the biosphere, either directly from the repository (if the borehole connects the biosphere to the repository) or from a plume of radionuclides and / or other contaminants that has already been released from the repository, but not reached the biosphere (if the borehole connects the biosphere to such a plume). The borehole could behave as a pathway either during drilling or sometime thereafter (in the event that the borehole is improperly sealed). If a borehole produced by drilling was to penetrate waste containers (e.g. in the event of accidental intrusion) then radionuclides and other contaminants could be released from the wastes. A borehole could also form part of a pathway for radionuclides and/or other contaminants to migrate from the repository to the biosphere, such as when a short investigation borehole that is drilled underground connects the repository to a naturally transmissive fracture zone that extends to the biosphere. Drilling activities may perturb the chemistry of the rock-groundwater system, which may in turn impact upon the transport or radionuclides or other contaminants. For example, borehole drilling may involve the use of organic fluids which could form mobile complexes with certain radionuclides. Some materials used in borehole drilling could react adversely with certain barrier materials. For example, cement is often used in boreholes and could interact with any bentonite barrier with which it comes into contact. Borehole drilling may also involve pumping water, which could lead to a disturbance of the groundwater system surrounding the borehole. One effect of pumping water from a borehole could be to cause radionuclides or other contaminants to be drawn towards the borehole and thereafter transported to the biosphere. If, on the other hand, fluids are pumped into the borehole during drilling groundwater pressures and water chemistry could be perturbed.
2000 List
A reference to the related FEP(s) within the 2000 NEA IFEP List.
Related References
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NEA (), Future Human Actions at Disposal Sites, A Report of the NEA Working Group on Assessment of Future Human Actions at Radioactive Waste Disposal Sites, Nuclear Energy Agency/Organisation for Economic Cooperation and Development, ISBN 92-64-14372-6, https://www.oecd-nea.org/rwm/reports/1995/nea6431-human-actions.pdf
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Smith G M, Molinero J, Delos A, Valls A, Conesa A, Smith K, Hjerpe T (), Human intruder dose assessment for deep geological disposal, Posiva Working Report 2013-23, Posiva Oy, Finland, http://www.posiva.fi/files/3301/WR_2013-23.pdf