Hazard reduction in action

The Windscale Advanced Gas-cooled Reactor (WAGR) became the first UK nuclear reactor to be fully decommissioned, with its outer shell left on the Sellafield site.

Built in the early 1960s, WAGR was a prototype for the second generation of reactors in the UK.

It closed in 1981 and since then has been in a programme of decommissioning which included the removal of its biological shield and pressure vessel.

The largest asbestos removal project in
Europe is currently being undertaken at
Chapelcross site in Scotland, where 3,000 tonnes of the insulation material are being stripped from the 16 heat exchangers. The former power station, near Annan, is also part-way through a programme to remove its 38,000 spent fuel rods.

Further south, meanwhile, another 2,300 tonnes of asbestos have been safely removed from Calder Hall, on the Sellafield site, which shares similar design features. The £26 million project, now complete, is believed to be the second largest of its kind in Europe.

Calder Hall was the first nuclear reactor in the world to supply electricity for domestic use and was opened by The Queen in 1956.

The station’s four reactors stopped electricity generation in 2003 and a programme to remove its 40,000 spent fuel rods is now under way.

50,000 tonnes of nuclear fuel – more than 5.5 million fuel elements – were manufactured for the UK’s first generation of nuclear power stations, the Magnox fleet.

The last fuel element was delivered to Wylfa power station in December 2011 and loaded into the reactors.

With 10 of the power stations now closed, more than five million of the fuel elements, around 90%, have been removed and sent to Sellafeld for reprocessing. When defuelling is complete, more than 99% of a site’s radioactivity is removed.

One of the UK’s most critical nuclear cleanup tasks was the destruction of a highly toxic liquid coolant left over from the early post-war experiments with fast breeder technology.

Dounreay was the only UK location to use sodium-potassium coolant, or NaK, in its fast breeder programme, which was eventually abandoned. Although NaK produced little waste during operations, it posed a serious chemical
and radiological hazard, combusting on contact with air or moisture. Most nuclear plants use pressurised water or gas as coolant.

After many years of research, development, innovation and trials, a £15 million purpose-built plant was constructed to address the unique
and complex decommissioning challenge.

Destruction of the last contaminated batches of NaK was achieved one year ahead of schedule and to higher environmental standards than once thought possible.

A significant hazard was reduced when a specially designed robot sealed a contaminated wall in one of Sellafield’s oldest cooling ponds.

Redundant pipework was also removed from the 60-year-old First Generation Magnox Storage Pond where high radiation levels prevent workforce access.

The space-age robotic arm uses software controls originally developed by NASA, and was only deployed after 80,000 hours of intensive practice in a full-scale mock-up of the facility to ensure that every eventuality had
been considered.

Magnox spent fuel, radioactive sludges,
various nuclear wastes and skips are currently stored in the open-air pond, where conditions have deteriorated over the decades and which is a priority decommissioning task for the UK.

For the first time in 50 years, fuel has been retrieved from the world’s largest open-air fuel pond.

The half-tonne of fuel was transferred from Sellafield’s Pile Fuel Storage Pond to a transport flask and exported to a modern facility, where it will be held pending final disposal.

Extensive preparatory work supported the achievement, which came five years earlier than expected and marks an important step towards decommissioning. The open-air pond
began operations in 1952 after a four-year construction period and processed 300 tonnes of Magnox fuel and 2,100 tonnes of fuel from the Windscale Piles. The goal is to remove all fuel by 2015 or even sooner.

Cleaning up nuclear sites

Ultimately, the NDA’s mission is about the long-term goal of restoring nuclear sites to a condition where they can be used for a different purpose.

Once the mission is complete, the strict
regulations covering nuclear sites can be removed and the land released for
re-development.

The level of restoration will depend on a site’s next prospective use, whether for industrial development, housing or back to nature.

Since the NDA was formed in 2005, a total of 77 hectares – almost 200 football pitches – have now successfully reached this stage.

A total of 322 buildings have been demolished at two of the UK’s earliest research centres, Harwell and Winfrith, since clean-up and decommissioning work started.

Among the facilities that have disappeared was GLEEP, the first reactor in western Europe which was built in 1946 and used for initial investigations into how to make a reactor work.

Another milestone was the demolition of the Zebra reactor, used purely for research, which closed in 1982 before undergoing a clean-up and decommissioning programme. The site has now been grassed over.

A new strategy for dealing with the UK’s low level radioactive waste (LLW) has increased recycling and yielded savings that are expected to reach more than £440 million by 2017.

The 2010 strategy focuses on reducing levels of waste generated, more recycling and new, more sustainable waste solutions. An additional goal is to preserve space in the UK’s only repository for LLW, the Low Level Waste Repository (LLWR) near Drigg, Cumbria.

Last year, 3,915 tonnes of metal were recycled, exceeding targets, and 571 cubic metres of waste were sent for combustion treatment, while the first-ever consignment of very low
level waste from a nuclear facility was sent to a specially authorised conventional landfill site.

Together with other measures,18 years worth of capacity have been saved at the repository in Cumbria. LLW does not normally require special shielding
during transport or handling.

Innovation in everything we do

More than £130 million is expected to be saved by adopting a radical change in how intermediate level waste (ILW) is managed at Magnox sites.

The original strategy was to build large, highly engineered stores at each site to house the packaged waste while the deep underground permanent facility is developed over the coming decades. However, Magnox has now begun to use small, robust cast-iron containers which provide radiation shielding and can be
bought individually, then used as required.

The process of evaluating GNS Yellow Boxes, which need only a weatherproof building and can be disposed of directly to the underground facility, was launched four years ago and required approval from the nuclear regulators.

Well-qualified, skilled staff are a fundamental requirement for decommissioning, and the NDA and its sites are actively involved in support
measures for a wide range of initiatives.

Hundreds of talented young people are entering the decommissioning workforce through apprentice schemes that provide on-the-job training and first-class qualifications.

Across the NDA estate, around 400 are at various stages of training, with 150 taken on each year at a cost of more than £8 million annually.

On another level, a pioneering
nucleargraduates© scheme was launched three years ago, with support from across the nuclear industry, to develop leadership skills for graduates from a wide range of disciplines,
including both sciences and humanities, via onsite training both in the UK and overseas.

Investment in skills training also covers training and research establishments, with investments totalling almost more than £30 million for colleges in England, Scotland and Wales, together with a world-class research facility in Cumbria.

With a hugely complex and diverse set of decommissioning challenges, one key area of focus is research and development (R&D).

Approximately £100 million is spent across all sites each year on R&D to develop technological solutions that enable safer and more effective decommissioning, while providing value to the UK taxpayer.

Recent successes include the pioneering
use of a treatment that destroys radioactive oil, robotic machinery that operates under water, laser cutting techniques that leave only small amounts of debris and software that
analyses the composition of radioactive waste more accurately.

Support is provided through various
mechanisms including site work programmes, direct funding to specific projects in the supply chain, bursaries to research students and jointly with academic institutions and partner organisations.

Making progress on challenges from the past

A new approach at the former Magnox power stations is set to remove a total of 34 years from the decommissioning process and save more than £1.3 billion.

The Magnox Optimised Decommissioning Programme (MODP) introduces a ‘lead and learn’ principle, where resources are concentrated on two of the 10 sites, enabling potential solutions to be comprehensively trialled and tested before being applied elsewhere.

Bradwell and Trawsfynydd sites will enter the dormant ‘care and maintenance’ phase much earlier than originally planned, leaving just the
reactor buildings and a waste storage facility on site. The lessons learned will enable more effective and coherent decommissioning at the remaining eight sites. 

Construction has started on a vital structure that will enable waste to be removed from a historic Sellafield storage facility, known as the Pile Fuel Cladding Silo.

Built in the 1960s, the Silo has six tall
chambers arranged side by side and was used to store the outer metallic parts – cladding – of irradiated fuel elements from the Windscale Pile Reactors. It is a priority risk and hazard reduction project on the site.

The Waste Retrieval Facility is a reinforced concrete super-structure that will be built alongside the silos and house a range of equipment to retrieve the contents. It is due for completion in December 2012.

For the second year running, another of
Sellafield’s oldest storage silos has exceeded its target for transferring highly active liquor to a treatment plant.
The Magnox Swarf Storage Silo has 22 wet silos which hold metal shavings and debris from operations to remove the cladding from Magnox fuel.

Since 2010, over 540 cubic metres of liquor has been transferred to the treatment plant. The facility contains high levels of radioactivity and is located in a congested area of the site, presenting unique challenges for
decommissioning.

"Massive strides have been made in the approach to
decommissioning. The NDA and its partners acknowledge
the importance of the task in continuing to provide
confidence that the nuclear legacy is being safely addressed.

As the number one priority, we remain totally focused
on reducing the risks associated with hazards across the
estate, particularly at Sellafield which accounts for half of
the budget and where many of the historic facilities require
remedial work before decommissioning can begin.”

John Clarke
NDA Chief Executive

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