Radioactive waste management involves a series of stages, including planning and preparation, treatment, packaging, storage and disposal.
Most radioactive wastes are managed in the following way:
- Planning and preparation: Wherever possible, sites aim to reduce the amount of waste they produce. They also plan how to manage waste before it arises.
- Waste treatment: Waste treatment typically occurs in some form soon after it arises. Waste treatment techniques depend on the type of waste and the intended disposal route. Examples of treatment include decontaminating, shredding, compacting, drying and solidifying the waste.
- Packaging: Most radioactive waste requires packaging in specially engineered containers for safe storage and disposal. This also allows for easier handling and transport.
- Storage: Interim facilities will store certain waste types until a suitable disposal route becomes available. Storage may last from a few months to many decades.
- Disposal: This involves placing wastes into engineered facilities where they will remain permanently.
Wastes may be transported for treatment, packaging, storage and disposal. Transport is usually by road or rail and is subject to strict conditions. Some waste may not require packaging or disposal; it may be possible to treat the waste for reuse or recycling.
Management of High Level Waste
Treatment and Packaging
High Level Waste (HLW) typically arises in liquid form, generated as a by-product during the reprocessing of spent fuel from nuclear reactors. The liquid HLW is mixed with crushed glass in a furnace to produce a molten product. The molten product is then poured into stainless steel canisters, which hold approximately 150 litres of waste. This is a process called ‘vitrification’ and converts the waste into a stable, solid form for long-term storage and disposal. This process takes place at the Sellafield site in Cumbria.
Storage
The canisters are placed into an air-cooled store until a suitable disposal route becomes available. Current practice is for the facility to store the vitrified HLW for at least 50 years before disposal. This allows much of the radioactivity to decay away and the waste to cool. The waste is then easier to transport and dispose of. When a disposal facility becomes available, each individual canister will be placed inside two further containers before disposal.
Long-term Management
The UK government is working with technical specialists, local communities and regulators to find a safe disposal route for HLW. The preferred option for managing HLW is ‘geological disposal’. This involves placing packaged radioactive waste in an engineered, underground facility or ‘repository’. The geology (rock structure) provides a barrier against the escape of radioactivity. There is no intention to retrieve the waste once the facility is closed. Radioactive Waste Management Limited (a subsidiary of the NDA) is responsible for implementing the long-term solution for managing Higher Activity Wastes in England and Wales. The Department for Business Energy and Industrial Strategy (BEIS) and the Scottish Government are responsible for developing policies for managing these wastes safely.
Source: Sellafield Ltd.
Management of Intermediate Level Waste
Treatment and Packaging
Intermediate Level Waste (ILW) may need treatment before being packaged for storage and disposal. Treatment may involve super-compacting, cutting or drying. Nuclear Waste Services (a subsidiary of the NDA) is responsible for preparing standards and specifications for ILW packages, and for providing advice to waste producers on the packaging of ILW. For most ILW, packaging involves placing the waste into a suitable container and immobilising the waste in cement-based materials. Typical packages include 500 litre stainless steel drums or 3m3 stainless steel boxes. Larger items are packed into higher capacity stainless steel, concrete boxes or ductile cast iron containers. The packages ensure that the ILW can be safely stored, transported and disposed of.
Storage
ILW packages are held in interim stores until a suitable disposal route becomes available.
Long-term Management
The UK government has been working closely with technical specialists, local communities and regulators to find a way to dispose of these wastes. The preferred option in England and Wales for managing ILW is ‘geological disposal’. This involves placing packaged radioactive waste in an engineered, underground facility or ‘repository’. The geology (rock structure) provides a barrier against the escape of radioactivity. There is no intention to retrieve the waste after the closure of the facility. The preferred option in Scotland for managing ILW is ‘near-surface disposal’. The location of these facilities should be as close as possible to the waste generating site. Radioactive Waste Management Limited is responsible for implementing the long-term solution for managing Higher Activity Wastes in England and Wales. The Department for Business Energy and Industrial Strategy (BEIS) and the Scottish Government are responsible for developing policies for managing these wastes safely.
Source: Nuclear Decommissioning Authority
Management of Low Level Waste
Source: Nuclear Decommissioning Authority
Most Low Level Waste (LLW) from across the UK has been disposed at the Low Level Waste Repository (LLWR) in Cumbria since 1959. Waste was initially placed into landfill-style trenches but is now grouted in metal containers before being stacked in concrete lined, highly engineered vaults. A cap will cover the containers when the vaults are full.
In the North of Scotland, the Dounreay site also has a new LLW repository. This repository will only accept solid waste from Dounreay site operations and the nearby Ministry of Defence’s Vulcan Naval Reactor Test Establishment.
Existing LLW disposal facilities have very specific limits on the amounts of different radionuclides that they can accept. A very small fraction of solid LLW, most notably graphite from reactor cores, cannot be disposed of in existing facilities because it would take facilities close to their permitted radioactivity limits. This waste may also be difficult to separate from associated Intermediate Level Wastes (ILW). As a result, this small proportion of LLW must also be considered when developing the long-term disposal option for Higher Activity Wastes.
Authorised landfill sites can accept LLW with very low levels of radioactivity for disposal alongside municipal and commercial wastes. There are strict limitations on how much waste can be disposed of in this way.
Changing the approach to LLW management
Application of the waste hierarchy has encouraged new approaches for managing LLW in a more sustainable way. Sites divert waste away from the LLWR by using different waste treatment and disposal options. These options include incineration, metals recycling and alternative disposal. This approach will also help to extend the operational life of the Low Level Waste Repository (LLWR) in Cumbria.
LLW treatment and disposal options
Metals Recycling – Metals with low levels of surface radioactivity can be recycled. The waste is cut into pieces before being placed into large containers, similar to shipping containers. The metals are then taken to a recycling facility, where the surface of the metal is removed by shot blasting, leaving clean metal beneath. The clean metal is then rigorously checked for any leftover contamination before it can be approved for recycling alongside other metals. Metals with slightly higher levels of radioactivity can also be recycled. This metal is melted, the radioactive contaminants removed and the clean, molten metal separated out for recycling. A very small volume of radioactive waste remains for direct disposal in an authorised LLW facility.
Incineration – Some LLW, such as plastic, textiles and oils, can be incinerated. This burns the waste at high temperatures in a controlled chamber and reduces the volume of waste for disposal by around 90% or more. After incineration, only ash and filter dust remains.
Direct Disposal – LLW destined for disposal in a repository is typically placed in large metal containers, similar to shipping containers. The waste may also need cutting or super-compacting to reduce its volume. Super-compaction places wastes under pressures of up to 2,000 tonnes per square metre. Cement (grout) poured into the container prevents any waste from escaping; this is ‘immobilisation’. After this, the waste containers are carefully arranged in highly engineered vaults for disposal.
Alternative Disposal – Permitted landfill sites can accept some Very Low Level Waste (VLLW) alongside non-radioactive wastes. There are strict controls on the amount of radioactive waste that can be disposed of at regular landfill sites.
Management of Nuclear Materials
Nuclear materials are radioactive items which have potential value and are not currently considered as waste. This includes uranium and plutonium, which can be used to make nuclear fuel. This also includes spent nuclear fuels, which could be reprocessed and reused.
At present, these materials are safely stored in case there is a need for them in future. If the UK government decides that these materials have no future use, they will reclassify the material as waste. The UK government will make this decision based on economic, environmental and safety grounds.