An Introduction to Nuclear Waste Immobilisation

Pre-treatment is a key part of any decommissioning programme and involves a variety of processes applied to liquid and solid radioactive waste. It is defined as any or all of the operations preceding waste treatment. Pre-treatment comprises such operations as collection, segregation, adjustment and decontamination. The main objectives of pre-treatment are:
to segregate waste into active and non-active streams;
to facilitate transport, treatment, conditioning and packaging by separating active streams into components or converting the waste into a form suitable for such operations;
to recover products for recycling.
A number of factors need to be considered when selecting a pre-treatment method including:
radiological protection standards and objectives;
waste minimisation;
availability of pre-treatment technologies;
economic aspects;
requirements for the further treatment, conditioning, storage, off-site transport and final disposal of the waste.
Pre-treatment results in improved safety, lowered radiation exposure and significantly lower costs in subsequent waste management operations. These benefits need to be balanced with radiation exposure and pre-treatment costs.
Collection involves the receipt of waste from the waste-generating processes. Collection and segregation lead to additional exposure for personnel. Segregation is where waste or materials (radioactive or inactive) are separated or are kept separate according to radiological, chemical, biological and/or physical properties, which facilitate waste handling and/or processing. The main factors considered in segregation are:
physical and chemical characteristics of the waste;
type and half-lives of radionuclides;
concentration of radionuclides;
specifications or requirements to be fulfilled for further waste processing.
Segregation should be carried...