A British expert on nuclear technology has criticised controversial plans to build a long-term storage facility for spent fuel rods in northern Switzerland.
The site had been earmarked for use by the Swiss authorities, which have been searching for waste disposal areas for radioactive material for more than three decades.
John Large said he was sceptical whether the site at Benken, near the German border, was safe in the long run.
Large is advising a group of anti-nuclear activists from Switzerland who commissioned a report on a feasibility study by Nagra.
He called on the organisation charged with the disposal of nuclear waste, Nagra, to examine more sustainable storage facilities.
Large said many questions remained unresolved, and the clay layer at the planned site under the village of Benken, north of the city of Zurich, was rather thin.
He warned against the planned use of steel canisters for the disposal of the waste. His criticism is in line with a statement by a government advisory committee.
The British expert - who helped recover the sunken Russian submarine, Kursk, from the Barents Sea in 2001 - added that Nagra had failed to consider options for interim storage sites and had not looked into safety aspects during the transport of nuclear waste.
He also accused Nagra of underestimating the threat of terrorist attacks on a final repository.
However, the Federal Nuclear Safety Inspectorate (HSK) dismissed the allegation, saying that, for obvious reasons, it had not made its anti-terrorist strategy public.
A spokesman for Nagra described Large's report as a list of commonplace statements.
The Swiss authorities have been searching for a long-term storage site for radioactive waste for more than 30 years. It is expected to take another 25 years before construction work on a permanent storage facility gets underway.
In a local vote in 2002, citizens threw out plans for a repository at Wellenberg in central Switzerland.
However, under a law passed last year, Switzerland's nuclear power plants are no longer able to ship their waste to France and Britain for reprocessing.
The law also rules out local referendums against a storage sites. A cabinet decision on such an issue can only be challenged in a nationwide referendum.
swissinfo with agencies
Under a 2005 law nuclear power plants are no longer allowed to send spent fuel rods abroad for reprocessing or disposal.
Over the past 30 years the authorities have been searching for suitable long-term storage for highly radioactive nuclear waste.
Proposals to shut down Switzerland's nuclear power plants were rejected in a nationwide vote in 2003.
Switzerland has five nuclear power reactors.
They are expected to have produced 8,000 cubic metres of spent fuel after their 50-year operating period.
The first nuclear plant - in Beznau - went online in 1969.
About 40% of Switzerland electricity comes from nuclear energy.
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