The company that runs the Thorp nuclear reprocessing plant admitted that it may have to close for a number of years owing to a series of technical problems.
The huge £1.8bn plant at Sellafield imports spent nuclear fuel from around the world and returns it to countries as new reactor fuel. But a series of catastrophic technical failures with associated equipment means Thorp could be mothballed at a cost of millions of pounds.
Under strict orders from the government's safety watchdog, the Nuclear Installations Inspectorate, the plant's operators, Sellafield Ltd, is expected to have little option but to mothball the reprocessing plant for at least four years.
Closure of Thorp for any length of time could cost the company and government hundreds of millions of pounds and embarrass the resurgent nuclear industry, which is embarking on an ambitious programme of new reactors for Britain. Thorp is contracted to reprocess more than 700 tonnes of spent nuclear fuel, most of it for Germany, which could sue if Sellafield does not return it on time.
A Sellafield Ltd spokesman said that a technical inquiry had been launched into options for the complex. He said: "Thorp is working well but one of the downstream plants that supplies Thorp has problems. At this stage we do not know what impact it will have. It is being assessed now. [It may mean] Sellafield does not have the normal capacity to deal with a high-level nuclear waste stream. Even if we do have the capacity, then Thorp may have to be closed down."
Yesterday nuclear critics urged Sellafield Ltd to close Thorp immediately. Martin Forwood, spokesman for Cumbrians Opposed to a Radioactive Environment (Core), said: "The crisis ... can only be bad news for Thorp, which already has a dreadful operational record. It would make sense to put this white elephant out of its misery permanently. The plug should be pulled on Thorp, preferably for good but at least for four or five years."
The problem involves three evaporator plants that serve Thorp. The two oldest have been running intermittently following repeated breakdowns, and the third has been closed after a rise in radioactivity levels was discovered. Work has started on a new £100m evaporator, but it is believed to be two years behind schedule and unlikely to open before 2013.
The latest technical hitches are embarrassing for the government, which hopes to use Sellafield as the centre of a huge British nuclear industry, with the Cumbrian coast expected to host a new enormous waste depository as well as possibly two new nuclear power stations.
Closure could also slow the decommissioning of other nuclear reactors in Britain. Revenue from Thorp was expected to provide much of the £70bn conservatively estimated to be needed to decommission Britain's reactors and clean up the environment after 50 years of nuclear power. Most first-generation UK reactors are expected to have closed within 10 years.
Evidence that drastic action may have to be taken on Thorp has been mounting for months. Recent reviews by Sellafield Ltd have assessed alternative options for the plant's future, including a moratorium on reprocessing and, as a second option, operating it for only part of the year.
Sellafield's problems have been compounded since the Nuclear Inspectorate put a legal limit on the amounts of highly radioactive liquid that can be stored at Sellafield. Yesterday, Sellafield Ltd said that stocks of high-level liquid waste had fallen "significantly" in recent months.
Construction of Thorp began in the 1970s and was completed in 1994. The £1.8bn plant went into operation in 1997 with the assurance from its then owners, British Nuclear Fuels Ltd, that it would reprocess 7,000 tonnes of spent fuel in its first 10 years of operation, two-thirds of the business coming from abroad.
To date, Thorp has completed about 6,000 tonnes of its initial order book and is now, largely as a result of the broken evaporators, limited to processing 200 tonnes a year - about a sixth of its original design capacity.