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UK decommissioning offers the chance for a global lead

As one of the pioneers of nuclear energy, the UK’s technology and construction industries are now at the forefront of global nuclear decommissioning.

It is 52 years since the first plant using radioactive atoms to create energy was built on these shores at Calder Hall near Whitehaven, Cumbria.

The Nuclear Decommissioning Authority was formed by the Government in April 2005 under the Energy Act and oversees and manages the decommissioning and clean-up of 17 sites including Sellafield, Sizewell A and Hunterston A.

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“The UK led the world with its nuclear programme and as a consequence of this early involvement we now have the opportunity to lead the world in the decommissioning of redundant facilities,” consultant Scott Wilson’s head of nuclear engineering Nick Jones says.

The total cost of decommissioning the UK’s nuclear plants stands at about £73 billion, but according to a statement from the NDA earlier this year, this could increase.

How these costs are spread will depend on the lifetime of the decommissioning strategy.

Currently this stands at 100 years and at the moment around £2.8 billion is spent annually on projects.

Secretary of state for energy and climate change Mike O’Brien says that the funding includes a grant to aid the NDA’s commercial income.

“The Government is committed to meeting the costs of decommissioning the existing civil nuclear legacy sites by the NDA,” he said in the House of Commons earlier this month.

“Over time the contribution from commercial income will decline as the NDA’s operational units enter their decommissioning phase.

“The discounted lifetime cost of delivering the NDA’s decommissioning and clean up programme, which is expected to take over 100 years to complete, is estimated at £40.7 billion.”

Director of nuclear at Costain Paul Candle argues that the biggest challenge for the industry is to categorise the waste appropriately.

Then it needs to be retrieved, conditioned and put into interim storage. “It depends on the facility – all the jobs are unique. At Sellafield we need to take the used fuel out of the reactors and put it into a large volume of nitric acid,” he says.

“From there it gets put through an evaporative process where it is mixed with molten glass. The glass then effectively stores the radioactive waste.”

Costain has just completed the detailed design process for the facility that will house the evaporative process. Construction will cost £300 million and is expected to finish in 2013.

But there has been talk of leaving some sites idle for 80 years before decommissioning.

This is because by then short lifetime radioactive material in the deactivated core would have decayed to the point that human access to the reactor structure would be possible, easing dismantling work.

A shorter decommissioning strategy would require a fully robotic core dismantling technique.

But industry experts expect opportunities to emerge much sooner.

DECOMMISSIONING: OUT WITH OLD

The post-World War II structures at Sellafield are posing significant engineering challenges for the decommissioning team.

The group is led by Sellafield and supported by Amec, BNS Nuclear Services and consultant Scott Wilson.

One of the first jobs was the pile fuel cladding silo waste retrieval project, which aims to reduce the overall site hazard and deliver an efficient means of waste retrieval and storage.

The silo was constructed in the 1940s to store aluminium cladding stripped from the Windscale pile fuel elements.

Material was deposited through its roof and it now contains a large volume of low and medium active material.

The team developed a design where a high-level reinforced concrete platform will be constructed adjacent to the north elevation of the silo.

Large access holes will be remotely cored through the concrete of the silo and radiation shield doors fitted.

The retrieval of waste will also be a remote operation, with shielded steel modules ‘docking’ with the silo and retrieving waste with a telescopic boom.

The waste will be lowered to a ground level steel module where it will be packaged and then transported to the new ground level waste stores on the site.

Possibly the biggest challenge facing Scott Wilson’s structural engineers is to demonstrate that the concrete retrieval structure can be built and the steel modules lifted into place without threatening the safety of the silo or the adjacent plant, equipment and services.

All the proposals have been analysed by the entire decommissioning team to identify ‘what if’ scenarios at each stage of construction.

Kier is currently doing early work on site, where a piled raft foundation is under construction.

An Official Journal tender for the construction of the reinforced concrete retrieval platform structure is due to be released shortly with the module packages following in late 2009 or 2010.

SKILLS SHORTAGE

As with any other fledgling industry, the decommissioning sector could face a skills shortage if people are not trained.

At the start of the month the NDA launched its national skills and capability strategy to help develop a sustainable workforce.

Areas where shortages need to be addressed include programme management, safety case writing and radiological protection.

Higher education institutes will also be approached to develop new programmes such as nuclear engineering and decommissioning and environmental restoration.

Currently the NDA is working with universities in Manchester, Sheffield, Leeds, London, Central Lancashire and Strathclyde.

It also aims to work with its supply chain development team, education and training bodies as well as regional and local skills and employment boards.

“Collaboration is the key to this success,” chairman of the NDA Stephen Henwood says.

“We aim to develop a skills heritage that we can be proud of.”