Nuclear power stations dump liquid radioactive waste - for example water containing the radionuclides tritium, caesium-137, plutonium-239 and strontium-90 - into the sea. The half-lives of some radionuclides are so long that they will persist at significant levels in the coastal environment for hundreds or thousands of years. Dumping radioactive waste puts it out of sight but the action of the sea and marine food chains returns it to our coast, and into our food. The Sellafield reprocessing plant provides the major input of radionuclides into the Irish Sea, and although the discharges are much lower now than in the 1970s, caesium-137 in seawater is replenished by re-mixing of sediments releasing the isotope back into the water. Radionuclides move through food chains; mussels and cockles sieve particles out of water and accumulate radionuclides in their bodies. Fish take in the radionuclides by eating contaminated molluscs. When contaminated seafoods are eaten in turn by a person, the radionuclides may be incorporated into the body tissues. Exposure of living tissues to radiation can cause cancer, as energy released by radioactivity damages the genetic material of cells.

So we know it is a bad idea to dump radioactive waste into the sea, but where can we dispose of it safely?

Movement of dumped radioactive isotopes through soils and rocks is poorly understood. The Dounreay prototype fast reactor on the Caithness coast is undergoing decommission but is dogged by problems of leakage of waste. Sand-sized radioactive particles are found regularly on Dounreay and Sandside beaches. The particles may be swarf from cutting aluminium cladding away from nuclear fuel that was dumped into a shaft. Scotland Against Nuclear Dumping (SAND) feels that the particles are dangerous, in spite of the National Radiological Protection Board’s assessment that ‘the particles have no discernible health effect’. The Committee on Medical Aspects of Radiation in the Environment (COMARE) suggested that particles may access the beach via movement of water through rock strata and upwelling of fresh water in the sea. COMARE recommended that divers should search for freshwater springs that are spreading the particles into coastal waters.

Currently the UK has 10,000 tonnes of solid long-lived radioactive waste in storage that could rise to 500,000 tonnes as old nuclear power stations are decommissioned. The Committee on Radioactive Waste Management (CoRWM) was set up by the government to look at options for safe storage of this waste. Unrealistic options such as flying radioactive waste out to space, embedding it in ice sheets, or burial in the sea bed, were discounted immediately. CoRWM provides opportunities for the public and stakeholder groups to take part in the consultation. The four short-listed options are interim storage, near-surface disposal for short-lived wastes and deep underground disposal or phased deep underground disposal that enables waste to be retrieved if necessary.

Recently Nirex, the nuclear waste agency, revealed 12 potential sites for radioactive waste dumps listed in the 1980s and 90s. They are all coastal, and some may be picked in future for deep underground disposal. However, as sea levels rise, coastal radioactive waste in dumps may leak as water penetrates or erosion occurs. Certainly, the dump for low level radioactive waste at Drigg in Cumbria, located 500m from the coast is identified as being at risk of leaking if the sea level rises.

The practice of pumping raw sewage into the sea is no longer justified as we have technology for cleaning the sewage before discharge into rivers and coastal waters. Some uses have even been found for sewage sludge. The problem of radioactive waste, one of the most dangerous categories of waste, appears not to have such a straightforward solution. Selecting coastal sites for long-term burial of radioactive waste may not be a realistic option as sea levels rise. CoRWM has a difficult task ahead.

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