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ITER: beyond the building

Atkins | 07 Apr 2016 | Comments

The dream form of energy – nuclear fusion – takes another step forward.

At a building site deep in the French countryside, the dream of clean, limitless energy is accelerating towards reality. Cadarache, 35 miles north east of Marseille, is home to the ITER site, which will be the biggest experimental nuclear fusion reactor in the world when it is complete.

“Fusion is almost a perfect form of energy: limitless, safe and clean,” says Dave Whitmore, director of nuclear projects with Atkins. “This project resonates with our vision to improve lives through nuclear energy and to take on the hardest technical challenges to help our clients deliver projects at an affordable cost.”

Since 2010, Atkins has been part of the evolution of the ITER site, providing architect engineer services as part of the Engage consortium, with Assystem, Egis and Empresarios Agrupados. This international collaboration stems from a contract signed between Fusion For Energy (F4E), the EU organisation managing Europe's contribution to ITER, and the Engage consortium for the architect engineer aspects of the project.

The work covers the design of the buildings and construction coordination. The scope of the project is vast: Atkins and its partners are delivering 39 buildings and associated infrastructure, including the 10,000-square metre complex that encloses the “tokamak” – the mammoth 23,000-tonne reactor at the heart of the experiment. It is the most complex machine on earth.

“We’re working on the tokamak right now,” says David Knoyle of Atkins, who heads the Nuclear Buildings team for Engage. “The work includes everything from the design of heavy cranes and nuclear shielding doors to cargo lifts for moving nuclear material safely around the building.”

ITER

 
 
 
 
 
 
 
 

Turning up the heat

ITER is engineering in its most extreme form. In order for fusion to take place, the temperature inside the tokamak must reach 150 million degrees centigrade – ten times hotter than the core of the sun. Triggering a nuclear fusion reaction – which is calculated to produce 500MW of thermal power – requires the injection of 50MW of heating power.

Designing for this environment demands special skills and the ability to unravel complex problems. Buildings need to safely accommodate a vast array of pipework and cables, as well as numerous embedments – thousands of plates pre-positioned in the walls, floors and ceilings, which act as fixing points for heavy equipment. Everything must be positioned with pinpoint precision before any concrete is poured.

This is a demanding task. At ITER, buildings and the equipment within them are intimately linked, but in some cases, buildings must be completed before the designs for the machines that will go inside them have been finalised. The tokamak reactor is a case in point. This will be housed in a vast reinforced concrete structure known as the bioshield. With a final height of 30 metres and massive walls up to 3.2 metres thick, there’s little chance to alter anything once the concrete has set.

“We know exactly what shape the tokamak will be, but designs for the services and pipework that lead into and out of it are still being finalised elsewhere,” explains Knoyle. “One of our skills as designers is to accommodate this uncertainty by providing options for the way pipes are routed through the building so the risk of conflict when the reactor is installed is minimised.”

Good design is not only about strength, economy and flexibility, but also buildability. Success hinges on designers and contractors working together at every stage. To eliminate potential construction snags, the team first built a mock-up of part of the bioshield structure.

“The mock-up gave us a good idea of how complicated it was to install the reinforcement detailing and allowed the contractor to put forward proposals for slight modifications,” says Knoyle. “It also allowed the contractor to do a trial run of some of the key embedments and to prove that the concrete mix would flow correctly between all the embedments and reinforcements.”

Arriving at the final design for the bioshield was by no means straightforward. The tokamak sits within a huge vacuum enclosure known as the cryostat – a stainless steel refrigeration chamber that weighs nearly 4,000 tonnes. Support for this is provided by the cryostat ring, a vital element which provides a mechanical interface between the cryostat, the tokamak and the building’s anti-seismic foundations.

The initial designs specified that the cryostat ring would be supported on a ring of steel columns. But just over a year into the project in 2011, the Fukushima disaster struck.

“Fukushima underlined the need for structures to be able to withstand the combination of multiple accidental events,” explains Gauthier Stiegler, civil engineer at Atkins. “Additional safety margins and new load combinations meant that the design had to be modified. This was a highly complex task.”

The solution was to replace the steel columns with a concrete crown incorporating a ring of buttresses to provide extra support and spread the loads more evenly through the structure. Atkins was able to draw on its engineering know-how from other fields – including expertise in pre-stressed concrete design provided by the firm’s bridge experts – to support the feasibility studies and detailed design.

“On a project of this sort, you have to be flexible,” emphasises Stiegler. “You have to accept that, although you have been working on something for six months, you might have to go back and change the designs in response to new information. This capability is vital in a first-of-a-kind project such as ITER because it’s evolving as research develops.”

Atkins’ role at ITER is also evolving as work moves from design into construction: “Now that we have contractors on site digging and pouring concrete, the focus is on making sure that everything is kept on schedule and that contractors have all the information they need to get the job done safely,” says Knoyle.

To ensure construction proceeds according to plan, Engage has introduced building delivery managers and leads to supervise and coordinate work across the multiple contractors. One place in which expert supervision is proving invaluable is in the delivery of the huge Assembly Building. This vast, custom-made workshop is where the reactor and vacuum vessel will be pre-assembled ready for installation in the neighbouring Tokamak Complex.

“There are three principal contractors involved with that,” says Knoyle. “The role of the building delivery lead is to focus on making sure all the interfaces are achieved. The remit is to make sure that designs are delivered on schedule so that the contractors can complete their work and the building can be handed over to the client on time.”

Expanding horizons

Atkins has always worked closely with its partners and it is working closely with the world’s leading nuclear companies such as Areva and China General Nuclear Power Group (CGN) on a range of opportunities in the UK and globally, including ITER.

Atkins, Areva, CGN and another of Atkins’ close collaborators, the construction management specialist, Mace, have formed the Helios consortium to bid for the role of construction managing agent (CMA) at ITER.

“We’re investing in this because we see fusion as something we can bring real value to,” says Whitmore.

The CMA will support ITER in the appointment of contractors and in managing the installation and commissioning work needed to prepare the plant for full-scale fusion experiments. The mix of partners in the consortium reflects Atkins’ strategic commitment to forging stronger links with nuclear companies in countries such as France and China.

Atkins’ deep involvement at ITER underlines the company’s commitment to nuclear energy. The firm is active in the global nuclear arena in areas including nuclear safety, regulatory compliance and licensing in the United States, advising the nuclear energy programme in the United Arab Emirates and design work on nuclear new build projects in the UK, including Hinkley Point C. Atkins recently announced plans to acquire EnergySolutions’ Projects, Products and Technology (PP&T) business to extend its reach even further into the specialist decommissioning and waste management technology arena.

Atkins has deep roots in the nuclear industry. The company’s involvement stretches back to 1954 with its work to support the UK’s nuclear research establishments. Atkins provided design and construction management for the world’s first commercial nuclear power station at Berkeley in the UK, completed in 1955.

Today, more than 60 years later, Atkins’ experts are working on decommissioning the same plant – highlighting the company’s ability to provide services throughout the nuclear life cycle.

The company is expanding its nuclear capabilities to meet global demand for nuclear new build. Finding ways to reduce risk and make programmes more affordable is a priority. One way is to adopt a systems engineering approach including BIM (building information modelling) right from the start of major projects. This makes it possible for multidisciplinary teams anywhere in the world to work together on a single, shared design model that incorporates every detail.

While this approach is currently a rarity in the nuclear field – as it is in most other areas of construction – Atkins has already done it: “We’re not just preaching, we’re actually doing it,” stresses Whitmore.

In the case of the silos direct-encapsulation plant project at Sellafield in the UK, Atkins and its joint venture partners Areva (France) and Mace (UK) created a systems engineering infrastructure with integrated electronic tools.

“This was the first nuclear project on the cloud,” notes Whitmore. “We went through the mobilisation of that project and actually got these tools working. We know how to do it.”

“Our commitment to the digital agenda and our ability to apply systems engineering approaches with a clear governance focus means we have a lot to bring to ITER,” says Whitmore. “This goes beyond the buildings: it’s about bringing systems engineering to the heart of the project – to the tokamak itself.”


Pictures: Credit © MatthieuCOLIN.com © ITER Organization, http://www.iter.org/