Radioactive leak closes Thorp reprocessing plant at Sellafield

Reprosseseringsanlegget Thorp i Sellafield.
Foto: BNFL

Publish date: May 9, 2005

Written by: Charles Digges

A highly radioactive mixture of plutonium and uranium fuel that was dissolved in concentrated nitric acid leaked through a fractured pipe into an enormous steel chamber late last month, forcing the closure of Sellafield’s Thorp reprocessing plant by UK nuclear authorities, British nuclear officials confirmed Monday.

They were also quick to emphasise that the leak posed no danger to the public or the workers of the plant and that no excess radiation has been measured above the site.

The toxic leakage contains some 20 tonnes spent of uranium and plutonium fuel, making the chamber so radioactive at the moment that it is impossible to enter. The problem was discovered on April 18 in the plant’s Feed Clarification Cell, which holds dissolver solution while tests are carried out. Authorites held a local media briefing on the event on April 23, but it was driven into the international limelight in the May 9 issue of the London Guardian.

Bellona’s Nils Bøhmer said: “This incident shows that the Sellafield efforts need pressure from Norwegian officials so the complex can be safely decommissioned..”

He added that “Bellona will continue to follow Sellafield and to pressure British authorities and nuclear operators to ensure that there are no future releases from the site.”

Bellona’s president, Fredric Hauge, said: “We have indicated to the authorities that this work must not stop now. The government and the Environmental department declined very late, like last year, Bellona’s application for Kr. 700,000 to continue this competence-building around Sellafield."

Hauge added that the Norwegian government has let the Sellafield problem twist in the wind since the environmental victory that reduced radioactive Techitium-99 (Tc-99) emissions from Sellafield to 2 percent of their previous annual releases. “After a permanent cleansing of Tc-99 was introduced, there has been a deafening silence from the Norwegian Authorities, even though Bellona has reminded them time and again that Sellafield is still a big problem.”

“In addition is the scandal that Norwegian authorities continue to give research support to Norway’s Halden Reactor. Norway is the one country in the north that engages in atomic research. Each year, the Norwegian state gives Kr. 30m for atomic research at Halden. Of this, Kr. 20m is spent on fuel technologies including MOX research. To develop MOX requires reprocessing and that requires Thorp,” said a frustrated Hauge.

A UK nuclear official, who asked to remain anonymous, said it had not been determined how long the pipe—which is part of a two pipe system—had been leaking the some 83 cubic meters of fluid onto the floor of the chamber.

The official said that the current assumed cause for the incident, following an initial investigation, is that a manufacturer’s welding error was responsible for the leakage, but no final conclusions have been reached. Another scenario is that the pipe itself contained a rupture. The source added that the chamber holding the leakage is designed to hold hundreds more square meters of leaked liquid safely.

He also said that an environmentally safe solution for removing the fluid from the floor of the chamber would be arrived at within the next two weeks and that Sellafield site managers are working “in full co-operation with environmental and government authorities” who he indicated are receiving daily updates on the situation.

The leakage was unanticipated, certainly, but it is minor in terms of what the chamber can safely hold without endangering workers or the public,” he said in a telephone interview.

Public and plant workers safe
The discovery of the leakage was made after an April 18 camera inspection of the cell, which is a stainless steel and totally secure environment, and designed to withstand such pipe failures.

Officials have emphasised that the leak poses no threat to the public or to the workforce of at Sellafield. Safety regulators have been informed and investigations are underway to find out what has happened and what needs to be done before operations can resume at Thorp. Recovering the liquids and fixing the pipes will likely take months and may require special robots to be built and sophisticated engineering techniques devised to repair the £2.1 billion Thorp plant.

Barry Snelson, managing director of British Nuclear Group, Sellafield, the management company formed to run the Sellafield site on behalf of the NDA, said in a statement that he had asked for the front end of the plants reprocessing operations, including shearing, to be closed down.

"Safety monitoring has confirmed no abnormal activity in the air and there has been no impact on our workforce or the environment,” he said. "Let me reassure people that plant is in a safe and stable state."

Financial losses
Nonetheless, the incident is likely to be a financial blow for both nuclear clean-up efforts and customer reprocessing contracts from foreign customers, such as Germany, as the income from the Thorp reprocessing facility is estimated by the Guardian to be in excess of £1m a day, though British Nuclear Group officials called this figure speculative. Thorp-generated money was then to be diverted to the NDA’s UK-wide estimated annual clean-up budget of £2 billion, £560m of which was expected to come from the Thorp plant.

The loss of funding from the Thorp plant toward nuclear clean-up efforts in the UK will fall on UK taxpayers.

There are as yet no calculations available as to how much this will set back budgeted clean-up funding at Sellafield in particular, said the UK nuclear official who wished to remain unnamed. But dealing with the aftermath of the leak will add to Sellafield’s current decommissioning efforts.

The Thorp plant separates out uranium and plutonium from
spent fuel. Its critics also say it is uneconomical because it has never operated to its design capacity since it opened in 1994, and is years behind schedule in fulfilling international reprocessing orders.

This has made some customers bristle and the British Nuclear Group is embroiled in a court case with one of its customers, the German owners of the Brokdorf power station, which is withholding fees of £2,772 a day for storage of spent fuel, claiming it should have been reprocessed years ago.

In 12 years, Thorp has reprocessed 5,644 tonnes of fuel from its first 10-year target of 7,000 tonnes. Last year it failed to reach its target of 725 tonnes, achieving only 590.

The clean-up effort will spearheaded by the newly-formed National Decommissioning Authority (NDA), which took over ownership of UK’s main nuclear sites, including Sellafield and Dounrey, from British Nuclear Fuels (BNFL). The NDA has budgeted £2.2 billion for clean up this year. The lost revenue from the Thorp Plant, NDA officials told Bellona Web on Monday, would “obviously” set back clean-up plans.

On Friday the British Nuclear Group held a meeting with the government safety regulator, the Nuclear Installations Inspectorate (NII), to discuss how to recover the material and repair the pipe, UK nuclear officials said. The company has to get the inspectors’ approval before proceeding.

The problem at the plant was first noticed on April 18 when operators could not account for all the spent fuel that had been dissolved in nitric acid. It was supposed to be travelling through the plant to be measured and separated into uranium, plutonium and waste products in a series of centrifuges. The plant’s remote cameras that scan its interior found the leak.

Although most of the material is uranium, the fuel contains about 200 kilograms of plutonium, enough to make some 20 nuclear weapons, and must be recovered and accounted for to conform to international safeguards aimed at preventing nuclear materials falling into the wrong hands. The liquid will have to be siphoned off and stored until the plant can be repaired, said the nuclear source who wished to remain anonymous.

The company has set up a board of inquiry to find out how the leak occurred. The NII will set up a separate investigation and has the power to prosecute if correct procedures have not been followed.