Nuclear Waste Background
The nuclear industry produces a number of varied solid and liquid waste streams of low, intermediate and high level radiochemical character. Traditionally in the UK intermediate level wastes have been packaged using cementation processes in preparation for ultimate disposal at a national repository after intermediate storage. Low level waste is generally sent to the national low level waste repository where it is also stored after cement encapsulation.
The small quantities of high level waste produced from reprocessing nuclear fuel is vitrified after calcination and adding glass frit.
Plasma vitrification can be used on all waste types and offers an alternative to cementation with significant benefits.
Plasma Benefits for Nuclear Waste
- Waste conditioning using plasma vitrification reduces the waste volume by producing a dense passively stable monolithic product, whereas cementation increases the volume by a factor of 3-5 times of the original volume.
- Plasma technology is extremely versatile and can be used to treat a wide range of heterogeneous wasteforms producing a dense homogeneous waste product. .
- Characterisation of nuclear waste is often difficult; plasma vitrification can cope with the high variability of radioactive waste (eg ).
- High throughput can be achieved from a small plant that uses minimal moving parts and simple engineering for reliability in the nuclear industry.
- The waste product is highly stable on geological time scales and easily meets RWMD/NIREX conditions for acceptance.
- Tetronics nuclear plasma system is not lined with refractory material therefore avoiding erosion and contamination problems and the need for replacement of the lining.
- Power input is controlled independently of process chemistry resulting in high product and environmental control.
- Low carbon footprint: it has been demonstrated to be less than half that of cementation when considering full life cycle mass and energy requirements.
- Secondary waste can be fed back into system.
- It offers greater radionuclide retention than borosilicate glass.
- The plasma process is intensive with a small footprint enabling retrofit to existing installations
Demonstrated Application of Technology
Plasma vitrification has been demonstrated using a number of simulant wastes. These have included Magnox sludge, inorganic ion exchange media, organic filter material, plutonium contaminated materials (PCM) and asbestos.
Tailored Solution
Plasma vitrification is a ‘platform technology’ that can be tailored to suit particular waste streams. Examples of areas that can be tailored to meet particular requirements are:
- Controlled environment, a reducing or oxidising environment can be employed.
- A number of off gas systems are available if necessary for the requirements particular waste stream.
- The size of furnace and its power requirements can be tailored to suit throughput of a specific application.
- Separation of materials from mixed waste streams.
Tetronics has a number of test facilities at its head office site where it can carry out trials to optimise the system for a specific application.
