Description
The formation in the waste package of a molecular entity by loose association involving two or more component molecular entities (ionic or uncharged), or the corresponding chemical species. Complexation is promoted through the presence of complexing agents (organics, inorganic ligands and microbes). Sources of these agents include organics in the waste package and inflowing water.
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.
- Process
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.
The formation of complexes between radionuclides or other contaminants and ligands such as Cl- or HCO₃₋ will influence the partitioning of the radionuclides or other contaminants between immobile solid phases and any coexisting potentially mobile fluid phase. Generally, the aqueous solubilities of radionuclides or other contaminants will be increased if the aqueous phase contains ligands with which these components form aqueous complexes, compared to the solubilities in the absence of ligands. More generally, the formation of chemical complexes has the potential to influence the chemical conditions (e.g. pH, Eh) in the waste package.
2000 List
A reference to the related FEP(s) within the 2000 NEA IFEP List.
Related References
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NEA (), Cementitious materials in safety cases for radioactive waste: role, evolution and interactions. A workshop organised by the OECD/NEA Integration Group in the Safety Case and hosted by ONDRAF/NIRAS, NEW/RWM/R(2012)3/REV, Nuclear Energy Agency/Organisation for Economic Cooperation and Development, http://www.oecd.org/officialdocuments/publicdisplaydocumentpdf/?cote=NEA/RWM/R(2012)3/REV&docLanguage=En
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Langmuir D (), Aqueous Environmental Geochemistry, Prentice Hall, ISBN 0-02-367412-1, https://www.pearson.com/us/higher-education/program/Langmuir-Aqueous-Environmental-Geochemistry/PGM139571.html