Radioactivity in the marine environment arises from both naturally occurring and man-made sources, and can be harmful to humans and non-human species. The major sources of discharges are shown in Figure 4.11. For this assessment we have used data on changes in radioactivity concentrations in the environment from national monitoring programmes and OSPAR periodic reports.

Generally we have found that radioactive discharges are strictly controlled, discharge levels have reduced and a strategy is in place to further reduce discharge levels in the future.

The aims of the OSPAR Radioactive Substances Strategy are to reduce radioactive discharges, emissions and losses, so that concentrations in the marine environment will eventually be near background values for naturally occurring radioactive substances and close to zero for artificially produced radionuclides. The revised UK Strategy for radioactive discharges, published in July 2009, sets out how the UK intends to achieve OSPAR’s interim objective that additional concentrations above historic levels are close to zero by 2020. This builds on the UK Strategy for radioactive discharges published in 2002, widening its scope to include aerial as well as liquid discharges from the decommissioning and operational activities of the nuclear and non-nuclear sectors. The Strategy reports on the progress that has been made on reducing discharges and concentrations to the marine environment since 2002 on a sectoral basis and sets projections and expected outcomes for radioactive discharges up to 2030, based on a set of environmental principles. Forecasts indicate the UK’s consistent progress with meeting the OSPAR commitments.

This strategy is having a noticeable effect, and inputs have fallen further since Charting Progress. The annual reports in the Radioactivity in Food and the Environment (RIFE) series confirm that radioactivity levels in UK waters currently pose no risk of harm to humans or wildlife.

Figure 4.12 Annual ⁹⁹Tc liquid discharge from Sellafield and concentrations in winkles, plaice and lobster collected near Sellafield.

With regard to specific radionuclides:

• Since 2005, technetium-99 (⁹⁹Tc) discharges from processes at Sellafield have fallen below 10 TBq per annum, and have met the end of 2006 target set in the UK Strategy for radioactive discharges (2002). Environmental concentrations of this radionuclide have also decreased significantly overall since 1995 (see Figure 4.12 for biota). Figure 4.13 shows the current distribution of ⁹⁹Tc in subtidal sediments of the Irish Sea. Note that the highest concentrations are in a patch of muddy sediments off Sellafield.
• Remobilisation of radionuclides from deeper sediment layers into surface sediments and overlying waters is now the principal source of caesium-137 (^137Cs) and plutonium in the Irish Sea. Increased concentrations of plutonium-239/240 (²³⁹,²⁴⁰Pu) in certain areas of the Irish Sea and Solway Firth suggest redistribution of historically contaminated sediments is an emerging factor for ²³⁹,²⁴⁰Pu.
• Polonium-210 (²¹⁰Po) was historically discharged by a phosphate processing plant near Whitehaven. The levels of ²¹⁰Po in seafood around Whitehaven have fallen to within the range of natural variability. ²¹⁰Po is responsible for ~50% of the radiation dose to seafood consumers around Sellafield, which remains well within the UK and EU annual dose limit of 1 mSv set to protect human health. Most of this dose is due to the legacy of earlier discharges. Current discharges from Sellafield are very low relative to their 1970s peak and continue to fall.
• Concentrations of tritium (³H) and carbon-14 (¹⁴C) in fish and molluscs near the radiopharmaceutical plant in Cardiff are decreasing, although tritium levels remain higher than elsewhere in coastal waters.
• The offshore oil and gas industry is responsible for a large proportion of the total alpha-emitting radioactivity entering UK waters, as a result of discharges of the ‘produced water’, which contains elevated levels of the naturally occurring radionuclides radium-226 (²²⁶Ra), radium-228 (²²⁸Ra) and lead-210 (²¹⁰Pb). However, discharges fell by about 25% between 2000 and 2006, and will continue to reduce in line with declining production of oil and gas.

There is evidence of radioactive particles on beaches around Sellafield and Dounreay. However, the beaches remain open at both locations as there is no risk to users of these beaches. For the protection of consumers, the harvesting of seafood in the vicinity of Dounreay was banned under FEPA in 1997. Monitoring programmes are in place at both Sellafield and Dounreay to locate and retrieve contaminated particles from the foreshores. At Dounreay, an offshore programme of particle recovery is also underway.

In a screening assessment, modelled dose rates in aquatic systems were below the threshold of 40 µGy/hr in all cases except near the Springfields nuclear fuel manufacturing site in Lancashire, where new discharge limits should ensure that, in the future, the dose rates do not exceed the threshold.