Waste handling and storage challenge overview
Radioactive waste handling and storage poses challenges due to the inherent chemical and physical hazards of the waste. The wastes from decommissioning range from wet, mobile slurries and sludges to large heavy pieces of plant and building structures.
Individually these wastes may be problematic due to radiological and chemotoxic hazards that may preclude direct man access to facilities in order to deploy equipment. The facilities containing waste do not have man-access. Further waste arising from decommissioning may be mixed and potentially need further segregation, for example pieces of plant such as tanks and vessels may still contain residual liquors, slurries or deposits.
Innovative tools and techniques for the remote handling of waste are required to work alongside or replace baseline technologies so that waste handling is more efficient.
Options that allow us to optimise our waste management hierarchy performance are important to Sellafield, to prioritise waste prevention, as the preferred option, followed by reuse, recycling, recovery including energy recovery (not an easy option with radioactive materials) and as a last option, safe disposal.
Once retrieved wastes need to be stored in a safe and secure manner, often for several decades before a national disposal facility becomes available. Innovative ways to efficiently package waste whilst still maintaining safety requirements that minimise the storage capacity required will be essential to reducing the cost of decommissioning the Sellafield Site.
A number of factors challenge the effective handling of wastes across the Sellafield site:
- Access may be restricted, so that often waste items and packages are limited to those handleable by a person
- The process of filling waste packages in restricted environments often leads to packages becoming contaminated and needing cleaning
- The weight of shielding often leads to the waste being loaded in a liner first which adds to the cost and waste volume
- Space limitations mean that there is often little opportunity for decontamination, sorting and segregation of waste where it is generated
- A range of different pH environments (pH<0 to greater than 11) in different plants
- Heterogeneity of materials
- Lack of ‘direct line of sight’, deployment inside shielded cells means that operators cannot see directly how equipment is engaging with the waste items nor can operators enter to make connections to waste items.
- Assessment of contents of redundant items and waste packages are assumed; assumptions have to be made about the contents, geometry, and mass etc. of the waste. Better measurement and assessment techniques could lead to a significant reduction in ‘phantom’ waste; this is waste that is consequently disposed via a different route which is less expensive.
- Waste sentencing – waste needs to be measured to confirm that it can be disposed of via a certain waste route. Techniques for waste measurement and decision making software’s are required.
Waste handling and storage vision
Imagine if we could with dismantle plant no human intervention into hazardous environments and pack those waste items into secure containers with optimum efficiency with the result that the minimum number and volume of waste packages is required for long-term on site storage and disposal.
Imagine that we had the ability to take all decommissioning materials and render them inert, or at least decontaminate, sort and segregate the waste to maximise our waste management hierarchy performance.
Imagine that we could package or render all types of waste passively safe until the radioactivity decays to a background level.