Description
The production of helium gas from alpha decay of radionuclides in the waste package.
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.
Helium production from alpha-decay of radionuclides in the waste package may influence the release rate of radionuclides from certain kinds of waste. The produced helium will accumulate at defects in the structures of the waste materials and contribute to structural modification of the waste form. For example, within spent fuel, helium produced by alpha-decay may form bubbles and contribute to the physical expansion of the fuel. Helium generation will also result in an increase in gas pressurisation. Release of radionuclides will be influenced by the changes in the physical characteristics of the waste form and the pressure evolution.
2000 List
A reference to the related FEP(s) within the 2000 NEA IFEP List.
Related References
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F. A. Garner, B. M. Oliver, L. R. Greenwood, D. J. Edwards, and S. M. Bruemmer, M. L. Grossbeck (), Generation and Retention of Helium and Hydrogen in Austenitic Steels Irradiated in a Variety of LWR and Test Reactor Spectral Environments, DOE/ER-0313/30 - Volume 30, Semiannual Progress Report, June 30, 2001, p127-147, http://web.ornl.gov/sci/physical_sciences_directorate/mst/fusionreactor/pdf/june2001/06.2%20-%20127-147%20Garner.pdf
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Wheeler M, Sear Jr B (), Helium, The Disappearing Element, Springer, ISBN 978-3-319-15123-6, http://www.springer.com/gb/book/9783319151229