Description

The production of radon gas from the decay of uranium, thorium and radium in the waste package. The main radon isotope considered in assessments is Rn-222 (the longest-lived isotope at 3.82 days).

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.

Radon is a radioactive noble gas, which hence is relatively mobile. All except 5 of the 17 isotopes of radon are alpha-emitters. These alpha-emitters include the longest-lived isotope, Rn-222 (half-life 3.82 days). Radon is produced by the decay of uranium, thorium and radium in the waste package and would contribute directly to radiological risk if there is an exposure pathway between the waste and a receptor. However, the very short half-life means that in practice the exposure pathway would need to be very short and / or transport of radon along the pathway would need to be very rapid.

2000 List

A reference to the related FEP(s) within the 2000 NEA IFEP List.

3.1.06

Related References