Constructing the International Thermonuclear Experimental Reactor

The International Thermonuclear Experimental Reactor (ITER) is a full-scale scientific experiment to show the feasibility of fusion power. Discover how Atkins' engineers are delivering technology that must overcome temperatures 10 times that of the sun's core.

Thermonuclear power plant
Thermonuclear power plant

The project

The ITER project, located in Cadarache, Southern France, is the next step in demonstrating the technological feasibility of fusion power as a viable energy source. It is one of the most challenging and innovative scientific projects in the world today.

Retained by Fusion for Energy to provide the role of architect engineer, Atkins is part of a pan European effort. This joint venture includes Assystem, Iosis and Empresarios Agrupados. The architect engineer's role is that of the traditional engineer. It involves taking a concept design through preliminary, tender and construction designs while procuring and then supervising the construction.

An integrated team of 200 staff is delivering the project to an 8 year programme. When completed, the site will extend over 42 hectares and comprise over 40 buildings including the Tokamak complex where fusion experiments will begin in November 2020.

Cutting edge technology

The project will involves cutting edge technology. Plasma will reach temperatures of up to 150million °C, ten times the temperature at the core of the sun. Over thirty different contributing systems (PBS) from cryogenics to neutral beam heating, from vacuum to remote handling will be in use to contain and manage it. These various PBS are being designed all around the world demanding close liaison and integration with our building and infrastructure design. This co-ordination is achieved through a suite of three-dimensional, object-oriented Catia models with strict protocols for their development and approval.

At the heart of the project is the Tokamak building containing the fusion reactor. This reinforced concrete, six-storey concrete structure will be 74 metres high (13 metres below the platform level and 61 metres above) and in plan, the size of two football pitches.

The facility is designed to current, post-Fukushima, standards. It includes the normal design basis events found on a nuclear project:

  • Seismic
  • Aircraft impact
  • Confinement through cracked concrete
  • Shielding, shine (line-of-sight)
  • Stringent EMC protection

The facility, weighing circa 365,000 tonnes, is supported on 493 seismic isolation bearings within the seismic isolation pit. The bearings have been carefully distributed to:

  • Minimise variations in bearing loads
  • Ensure coincident centroids of dynamic loads and restraint
  • Optimise the cost

Overcoming challenges

The project poses huge engineering challenges. Over and above the usual nuclear design issues, to state that everything is "big" doesn't do it justice. The Assembly Hall, illustrated below, is a steel portal shed used to assemble reactor components.

We are familiar with steel portals, except this one is 60m high and carries a 1500t crane in its roof. The fusion process plant and equipment is also large and cannot always be broken down into constituent components. This in turn requires that the structures maintain post-construction access routes inevitably passing through significant load-bearing walls and floor slabs. Interruption of such primary load paths has a direct impact upon the location and loading of the seismic bearings.

The main nuclear structures are founded in limestone rock. These are apparently sound but vulnerable to underlying solution features. An extensive geological survey was carried out to identify and remediate such cavities including boreholes, ground penetrating radar and micro-gravity investigations. In addition, a FLAC, finite difference ground continuum model was made to investigate the sensitivity of the structure to potential residual discontinuities.

The integration of nascent, developing technologies with the building and infrastructure calls for significant co-operation and co-ordination. This is made harder by the number of systems and their origin spread all over the world. The need to hold to an ambitious programme and fixed budget adds further complexity.

The facility is congested with space at an absolute premium. To address this fundamental issue, we have assembled a multi-national, multi-discipline team of engineers on site in Cadarache. While there are differences in language and cultures, it is reassuring to see that there is a common language of "engineering"; striving to work together, finding solutions so that we build something that might well affect the future of the entire planet.

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