Radioactive contamination has been leaking into groundwater under Sellafield nuclear power station from 50-year-old tanks containing untreated nuclear waste, according to the Nuclear Installations Inspectorate.
An urgent investigation is under way to find out the extent of the leaks and how to control them.
Tests are continuing after the inspectorate revealed that Technetium-99, a by-product of reprocessing of spent nuclear fuel, was discovered in a borehole on the site as long ago as last November. It remains active for 200,000 years and is known to accumulate in the bodies of shellfish and lobsters.
The inspectorate said in a statement to the New Civil Engineer that the quantities so far found posed no public risk but further investigations were continuing.
Meanwhile, the European Parliament has heard contradictory views from scientific experts on the threat to health and the environment from Sellafield. At the start of a two-day hearing, some scientists cast doubt on the accuracy of a report commissioned by the parliament into Sellafield.
The report, commissioned by the parliament and conducted by the Paris-based WISE group, concluded that radioactive discharges from Sellafield could be responsible for high rates of childhood leukemia near the plant.
But Dr Ian Mitchell, a physicist from UCD, said the link could not be established with certainty.