Construction News

Thu October 28 2021

Related Information

Nuclear Legacy

22 Nov 12 Hazardous, time consuming and expensive: nuclear decommissioning projects pose some of the greatest technical challenges, and opportunities, for contractors. Emma Crates reports.

Up until last month, the government’s aspirations for the future development of nuclear power in the UK were looking rocky. Last year’s Fukushima disaster in Japan had dampened enthusiasm across the sector. Hitachi's decision to buy the Horizon project from E.ON marks a change of mood, increasing the probability of new reactors appearing on the skyline soon. However, while energy suppliers agonise over whether this new generation of reactors will arrive in time, the toxic legacy of life-expired power stations requires immediate action. 

The UK was an early pioneer of this brave new technology, opening the world’s first commercial nuclear power station at Calder Hall in Cumbria in1956. At the time, little thought was given to what would happen after the facilities passed their useful working life. Six decades on, the Nuclear Decommissioning Authority (NDA), the public body responsible for cleaning and decommissioning civil nuclear sites, presides over a complicated legacy. Its portfolio of 19 sites stretches from Dounreay in Scotland to Winfrith in Dorset. Collectively the sites contain hundreds of structures contaminated with radioactive material, each posing a unique set of challenges. Working in the nuclear sector is not for the faint-hearted: it can take years of planning, preparation and testing before a single structure can be safely defueled, decommissioned and dismantled. The process is hazardous, costly and time consuming. Bespoke solutions are often required. 

But in the past few years parent body organisations (PBOs), appointed by the NDA to oversee the clean-up of individual sites, have put in place a series of strategic alliances and framework agreements that aim to capture industry expertise, benchmark best practice and safely accelerate decommissioning programmes by years, or even decades. 

With highly lucrative contracts on offer, and superior levels of technical expertise being demanded, multinational consortia dominate the bidding for this kind of work. The Babcock Dounreay Partnership (BDP), a joint venture between Babcock, CH2M Hill and URS, was appointed PBO for the decommissioning of the Dounreay nuclear plant in Caithness in April 2012. BDP’s contract is the first in the UK to take a decommissioning site through to completion. It will run until Dounrey reaches interim end state, sometime between 2022 and 2025. This is the point at which all buildings have been cleaned out or demolished and the radioactive waste is made safe for long-term storage or disposal. To meet this milestone, 180 structures have to be dismantled, 50 of which have had radioactive activity. BDP says that its plan, executed through site licence company Dounreay Site Restoration Ltd (DSRL) will reduce costs by more than £1bn to £1.6bn, and cut more than 10 years from the decommissioning plan. 

Sellafield in Cumbria has arguably the most complex nuclear legacy in the world, a mixture of military and civilian nuclear facilities packed into 6km2. Here around £500m is spent on decommissioning projects annually, and this figure is projected to rise to £700m. At Sellafield some 200 structures are contaminated by nuclear activity. But even though 100 decommissioning projects are already under way, timescales for full remediation of the site run to 2120 – more than 100 years away. 

To speed up the process, Sellafield Ltd, the site licence company owned by PBO Nuclear Management Partners (NMP), has started to implement a series of strategic alliances with a combined value of £9bn. The first framework agreement – The Design Services Alliance – was awarded in February: a £1.5bn contract to The Progressive Alliance (led by Babcock and URS) and AXIOM (a consortium of Amec, Jacobs, Mott McDonald and Assystem). It is expected to extend to15 years. A joint venture between Morgan Sindall and Arup has recently been named preferred bidder for the second framework, the £1.1bn Infrastructure Strategic Alliance (ISA). Sellafield Ltd expects to announce the preferred bidder for its Multi Discipline Site Wide Works framework agreement before

the end of 2012. Other collaborative-style initiatives in the pipeline include a contract for site-wide logistics, appointing a decommissioning technical programme partner and introducing a major project delivery strategy. 

Sellafield says that many of these new contracts will follow the alliance model, which “is widely regarded as best practice in other industries and involves true collaborative arrangements between Sellafield Ltd and the delivery partners.” Magnox Ltd, which is responsible for the clean-up of 10 Magnox reactor sites, recently appointed a Costain and Balfour Beatty joint venture for its £288m Construction Infrastructure and Enablers strategic framework. The contract has the option of extending to 10 years and is expected to be worth up to £30m annually. Although every site has unique challenges, Magnox Ltd is striving to identify common elements that all its 10 sites share. 

The company launched a radical revision to its clean-up strategy, The Magnox Optimised Decommissioning programme (MODP), in October 2011. Specialist teams have been appointed to identify common challenges such as pond clean-up, asbestos removal and storage of intermediate level waste. These have now been grouped into strategic programmes. Work has also slowed on some sites while innovative practices and technology are trialled at Bradwell in Essex and Trawsfynydd in North Wales. Once the lessons from these two sites have been learned, the innovations will be rolled out to other Magnox projects. Magnox Ltd estimates that the MODP will save £1.3bn and cut a cumulative total of 34 years from the decommissioning programme, compared to the previous plan. 

be decommissioned by 2028. Further down the supply chain, multinationals are aligning themselves into strategic relationships to attract the highly lucrative subcontracts coming on stream. Multi-disciplinary consultant Atkins recently formed a joint venture with French-based nuclear specialist Areva to bid for tier two work on decommissioning and fuel management projects in the UK. But nuclear clients are keen to point out that there are still opportunities for smaller contractors in this busy sector. Babcock Dounreay Partnership says that around two-thirds of the site spend is down the supply chain. And commenting on the Morgan Sindall Arup JV at Sellafield, Nuclear Management Partners deputy managing director George Beveridge praised the partners for their “desire to work with our local supply chain to maximise opportunities through the ISA.“ 

Perhaps to reinforce this point, the NDA has launched a steering group to provide support for small and medium enterprises who would like to be part of the decommissioning supply chain. The steering group is supported by five regional groups and a series of joint events are being held with site licence companies. The next supplier event will be held in Bolton on 22 November 2012.

Sellafield: The Pile Fuel Cladding Silo

Related Information

At Sellafield, many of the most significant clean-up challenges are with the legacy ponds and silos that were used to prepare fuel for processing and to store waste. After more than five decades these facilities are weather-worn and deteriorating. Their safe defueling and dismantling has become an urgent priority. One of the most complex operations under preparation is the decommissioning

of the 21m-high pile fuel cladding silo, which houses six waste containers containing more than 3,200m3 of intermediate level radioactive waste. They also contain high levels of argon gas. While this is a critical path project, it must be carried out with absolute precision. The strategy is to drill six 2m x 3m holes into the north side of the silo. Access doors with gas-tight seals will be bolted to each aperture. Specially designed waste retrieval modules will then be bolted to the doors, similar to the way a capsule docks to a space station. The modules, designed by joint venture Bechtel Babcock Nuclear Solutions (BBNS) as part of a £150m contract, feature telescopic booms and grabs that will pick up the waste and rotate 180o to lower it into a module where it will be photographed and filmed, and basic radiological measures will be taken. The waste will then be transferred into 3m3 storage boxes and stored in an interim storage facility bolted onto the side of the silo. radioactive material, each posing a unique set of challenges. Working in the nuclear sector is not for the faint-hearted: it can take years of planning, preparation and testing before a single structure can be safely defueled, decommissioned and dismantled. The process is hazardous, costly and time consuming. Bespoke solutions are often required. But in the past few years parent body organisations (PBOs), appointed by the NDA to oversee the clean-up of individual sites, have put in place a series of strategic alliances and framework agreements that aim to capture industry expertise, benchmark best practice and safely accelerate decommissioning programmes by years, or even decades. With highly lucrative contracts on offer, and superior levels of technical expertise being demanded, multinational consortia dominate the bidding for this kind of work. The Babcock Dounreay Partnership (BDP), a joint venture between Babcock, CH2M Hill and URS, was appointed PBO for the decommissioning of the Dounreay nuclear plant in Caithness in April 2012. BDP’s contract is the first in the UK to take a decommissioning site through to completion. It will run until Dounreay

At present the project is still in development. After 20,000 man-hours, BBNS has completed the design of the gas-tight doors, and testing of the doors starts next June. The waste retrieval modules are still in design phase. Following extensive trials, three diamond-based cutting machines will be used to drill into the silo. The project team had considered stitch drilling 76 cores using a 300mm core drill, however this approach was abandoned because it was too technically challenging and problematic. “Diamond technology was selected because it offered the most reliable, powerful, and cost-effective machine suites suitable for the cutting processes,” says a Sellafield spokesperson.

This month, Sir Robert McAlpine, which is building the £8m reinforced concrete interim waste storage facility that bolts against the silo, completed the final major concrete pour for the structure. The pour for the roof slab involved pumping 240m3 of self compacting concrete into position over an 11 hour period. Construction on the waste retrieval facility is scheduled for completion next year.  Meanwhile, Clarke Chapman Group has won a £3m contract to build a special semi-goliath crane, which will transfer the boxes from the PFCS into the waste retrieval facility. The boxes will weigh up to 60 tonnes when full. Waste retrieval is expected to start around 2018.

Dounreay

At Dounreay a new low level waste disposal site is under construction. This will be a series of up to six underground concrete vaults to receive up to 240,000 tonnes of radioactive waste. Site closure contractor Dounreay Site Restoration Ltd (DSRL) has engaged Graham Construction to design and build the first two vaults.

Subcontractor CA Blackwell and blasting expert Rocklift have now removed 200,000m3 of rock through blasting and excavation, and construction of the first two vaults, which require 8,500m3 of concrete, is now under way. If all goes to plan, waste disposal is expected to begin in 2014. One major project coming onto the horizon at Dounreay is the decommissioning of a 65m-deep shaft and a nearby silo that hold intermediate level waste. This project, valued at between £80m and £100m, has been dubbed the world’s deepest nuclear clean-up. DSRL expects around 20 companies to be involved in the work. Planning permission is now being sought to start construction in 2013. 

Remotely Controlled Technology

The problem of working in areas that are too hazardous for humans to enter has long posed  challenges for nuclear decommissioning projects. This has given rise to a range of innovative equipment that would not be out of place in a James Bond movie. Remotely-operated miniature submarines have already been deployed at Sellafield and are being developed to survey fuel storage ponds. Sellafield is also providing funding for the development of an unmanned aerial vehicle that could fly into spaces due to be decommissioned, providing detailed scans and detecting radiation levels. Other emerging technology to receive financial support from Sellafield is the snake-arm robot, developed by Bristolbased company OC Robotics. This consists of a self-supporting robotic arm that can navigate around obstacles like a snake. A camera is attached to the tip of the arm, which can also accommodate a selection of tools including a laser cutting head, water jet, gripper and ultrasound equipment. “Using a different robot for each function is very expensive, so we’ve developed a general purpose tool kit,” says OC Robotics managing director Dr Rob Buckingham who developed the concept with co-founder Andrew Graham. He explains that when travelling horizontally the articulated arm can stretch to roughly 3m, but its reach could be extended to about 10m, if it were attached to a rigid pole. “Working vertically, we can reach much greater depths because we’re not fighting gravity,” he adds. 

Buckingham says that one of the advantages of the concept is that the arm is very simple: lightweight, with hollow metal joints connected by wire rope. “These are easily replaceable metal parts. The xpensive and delicate motors and electronics are kept outside the area of contamination,” he explains. The Snake Arm robot, which took 10 years to develop, is already causing a stir across other sectors such as aerospace and security. Currently two robots are working in operational nuclear power plants in Canada and Europe, and trials have been carried out for Sellafield and Areva to explore the robot’s decommissioning potential. 

Buckingham believes that part of the robot’s appeal is that it could identify and remove the most radioactive elements from confined spaces, making the area safe for humans to enter. Long term, it could lead to the more efficient and appropriate disposal of waste, saving both time and money. Exactly when and how clients such as Sellafield will start using the Snake Arm on decommissioning projects is not yet certain. “The nuclear industry moves very slowly. It takes a long time for new technology to get accepted,” says Buckingham.

Got a story? Email news@theconstructionindex.co.uk

MPU
MPU

Click here to view more construction news »