Evaporators are used in the condensing of highly radioactive liquid. The fault in Evaporator B was found during routine checks on equipment linking Sellafield to the Thorp facility, which reprocesses spent nuclear fuel rods.

The high level waste streams from Thorp and Magnox Reprocessing are fed to storage tanks via evaporators that concentrate the waste liquid, reducing storage volumes and providing a feed stock to the Waste Vitrification Plant, Sellafield, Ltd, the site’s operator, said in a statement.
 
Evaporator B  – one of three evaporators serving the Sellafield facility’s reprocessing plant, was shut down last week. Staff at the plant discovered the fault on Monday. Evaporator C, Sellafield’s main evaporator is still operational.  

"During routine operations within one of the evaporators, the plant’s in-built detection system identified a slight rise in activity levels,” said Sellafield, Ltd.

"Plant operators acted quickly to shutdown the plant in a safe and controlled manner, demonstrating their disciplined professionalism.”

A new evaporator, at a cost of £100 million, is under construction, but unlikely to come online before 2013.

An investigation is being carried to discover why the evaporator showed increased levels of radioactivity. At issues in the investigation is determining the cause of a slight rise in the activity around Evaporator B’’s top coils and what impact the temporary closure of Evaporator B will have on Sellafield’s operations.

Machinery has now been wired to bypass the broken evaporator until the problem can be fixed.

Due to the age of the facilities and the nature of the liquor that they process, corrosion within the evaporators is not an unexpected issue,” said the Sellafield statement.

“Modifications to the evaporator were made some time ago to ensure that, in the event of raised levels of activity, the facility remained in a safe state.”

Bellona reaction
“This latest incident is another nail in the coffin for the Thorp facility,” said Nils Bøhmer, Bellona’s nuclear physicist and an expert on Sellafield. Bøhmer said that Sellafield is an old facility that is difficult to run.

“This incident shows exactly that – this is not a top notch facility but an old one that needs lots of maintenance,” he said.

Consequences for Thorp
In an unrelated incident last week, Thorp was under scrutiny after radioactive water was found to have been leaking for more than a year, the BBC, the International Atomic Energy Agency and Sellafield, Ltd. confirmed.

The current loss of Evaporator B will likely impact the output of the Thorp reprocessing unit – a factor that is also under investigation, said a spokesman from Britain’s Nuclear Decommissioning Authority (NDA), which owns. Sellafield, told Bellona Web in a telephone interview.

The NDA owns 11 aged nuclear sites in Britain and is charged with their decommissioning. Sellafield, as the birthplace of Britain’s nuclear weapons programme, which later became a civilian site, has been said to be the most complex site in the NDA’s portfolio.

The Thorp reprocessing facility chemically breaks down spent nuclear fuel into uranium, plutonium and radioactive waste. The waste is then turned into a glass form and stored until it can be disposed of.

Thorp was hit with a large incident in 2005 when 20 tonnes of plutonium and uranium dissolved in nitric acid leaked undetected into the reprocessing plant’s clarification cell for eight months until it was eventually discovered in April of that year.

That event was classified on the seven-point international Nuclear Event Scale (NES) as a “3” or “serious incident” – one step below a full-blown accident that would have contaminated the surrounding environment.

Will Thorp shut down?
One British media report in the Guardian –  which is historically somewhat hyperbolic about Sellafield –  indicated that plant officials have said that Thorp may now be shut down for years.

However spokesmen for the NDA, which owns the Sellafield site, and Sellafield Ltd., the site’s operator, contradicted that report in interviews with Bellona Web Tuesday.

“It is far too early to speculate on whether the Thorp facility will be shut down, and it would be irresponsible to do so,” the NDA spokesman, who requested he not be identified by name, told Bellona Web.
 
The scope of the investigation
Even after repairs are made to Evaporator B, it is still unclear whether Thorp will be able to keep up with its projected generating capacity, which will have a damaging effect on international nuclear reprocessing business for Britain, as well as British government plans to use Sellafield as the centre of a new British nuclear industry revival.

Officials had gone so far last August as to say Thorp’s engineered life expectancy could be prolonged by as long as five to 10 years to support this renaissance – but this would be hard to justify if the Evaporator issue is not solved.

The NDA spokesman said the Authority will work to reduce highly radioactive stocks that are reprocessed by Thorp, and will now be backing up, as well as keeping Sellafield’s Magnox fuel reprocessing facility working to keep Britain in reprocessed nuclear fuel. The Magnox facility is also opposed by Bellona.

Thorp is currently under contract to reprocess some 700 tons of spent fuel, most of it for Germany, and the country could sue if Sellafield does not return it on deadline.

Only after the probe is completed and the NDA and the British government have determined how the evaporator support matches with their priorities will any decisions be made about shutting down Thorp, said the NDA spokesman.

Sellafield Ltd. is also participating in the investigation.

"We are now working to complete our investigations and undertaking any necessary remedial work," said the company statement.   

Local environmentalists call for Thorp’s closure
Chairman of action group Cumbrians Opposed to a Radioactive Environment, Martin Forwood, called in a statement for Thorp to be shut down. He said today that the pile up of incidents,  “can only be bad news for Thorp, which already has a dreadful operational record. It would be kindness itself, and make the most sense, to put this white elephant out of its misery permanently,” his statement said.

“The plug should be pulled on Thorp, preferably for good but at least for four or five years.”