Dounreay Site Restoration Ltd

Liquid

Radioactive waste is generated wherever nuclear materials exist. It can contaminate other materials, effluents and airflows.

Nuclear materials in their different forms are normally contained in areas of facilities where access is controlled. These can be vessels and pipes where liquors exist, ponds, storage cells for fuels and wastes and drums or containers.

The site is authorised by the Scottish Environment Protection Agency (SEPA) to discharge low-activity effluent to the sea. Conditions attached to this authorisation and other licences regulate how and when this happens.

The site itself imposes lower limits on each of the plants that produce effluent and applies constant downward pressure to keep discharges to the minimum necessary.

The operation, clean-out or decommissioning of these facilities can produce effluent contaminated with radioactivity. Areas of contaminated land also produce radioactive effluent as a result of contact with groundwater and rainwater flows

Effluent from facilities is abated at source - for example, filtration - where it is demonstrated this represents "best practicable means". Facilities where effluent may have higher activity levels can use ion exchange or other abatement technologies to clean up the effluent.

The effluent flows into a low-active drain that carries potentially contaminated liquid from all the facilities to a collection point known as the Low Level Liquid Effluent Treatment Plant (LLLETP).

This plant also receives potentially contaminated groundwater diverted from areas of contaminated land, the low level waste disposal pits, boreholes and the shaft. LLLETP also takes effluent from the neighbouring Vulcan site.

The treatment plant cost of £7.5 million to build and went "active" in 2003, allowing an old facility that did not meet modern standards to be taken out of service.

The treatment plant is designed to remove any solvents and suspended solids and neutralise its pH.

Once treated, the effluent is transferred to sea discharge tanks where samples are taken to measure its radioactivity and suitability for discharge. The effluent is sampled again during discharge to sea and these measurements are reported routinely to SEPA.

Discharges are allowed around the period of high tides. The effluent is carried in a pipeline in a subsea tunnel to a diffuser approximately 600 metres offshore, where it is dispersed in the sea.

It is a condition of the authorisation that the site measures the impact of these discharges. This is done by taking samplesof water and marine life. The results are reported routinely to SEPA and appear in the Radioactivity in Food and the Environment series of reports published annually by regulators. The results are also published on this website .