Description

The dissociation of molecules by ionizing radiation in the waste package. The radiolysis of water within a waste package can produce molecular species such as hydrogen, oxygen, and hydrogen peroxide. The actual composition and amount of the radiolysis products that will be formed is controlled by the radiation dose rate and by the composition and amount of the air and water mixture contained 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.

Radiolysis is the dissociation of molecules by ionizing radiation in the waste package. Therefore, radiolysis may affect the rates at which radionuclides and other contaminants are released from solid matrices in the waste package, and the chemical and physical forms in which the releases occur. Radiolysis may impact the quantities and compositions of different fluids (water, gas, organic liquids) present within a waste package. For example, radiolysis of water will generate O₂ and H₂, while decreasing the quantity of water present. These effects may influence the evolution of pressure within a waste package. Radiolysis may directly affect the physical properties of solid materials present in the waste package. For example, if present, a bitumen encapsulant might degrade owing to radiolysis. The impact of radiolysis on chemical conditions may also indirectly affect the physical properties of the solid materials present. An example is the generation of O₂ by radiolysis of water causing enhanced corrosion of a steel container.

2000 List

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

2.1.13

Related References