A case study from Atkins

ITER, the International Thermonuclear Experimental Reactor, is a full-scale scientific experiment to demonstrate the feasibility of fusion power.

It is one of the most challenging and innovative scientific projects in the world today, involving parties representing over half of the world’s population. This project is the next step in demonstrating the scientific and technological feasibility of fusion power as a viable energy source to help meet mankind's future energy needs.

Working in a pan-European Joint Venture with Assystem, Iosis and Empresarios Agrupados, Atkins was retained by Fusion for Energy to provide the critical role of Architect Engineer on the ITER project in southern France. The Architect Engineer role is effectively that of the traditional Engineer; taking a Concept Design through Preliminary, Tender and Construction Designs while procuring and subsequently supervising the construction.

The project is being delivered to an 8 year programme by a tightly integrated team composed of 200 members of staff at the ITER site in Cadarache. 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.

Fig. 1 Site Plan

    
Fig. 2 ITER site in early 2010           Fig. 3 Impression of final facility

The technology required to contain and to manage a plasma at temperatures of up to 150 million °C, ten times the temperature at the core of our sun, is cutting edge with over thirty different contributing systems (PBS) from cryogenics to neutral beam heating, from vacuum to remote handling. 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 and includes the normal design basis events found on a nuclear project: seismic, aircraft impact, confinement through cracked concrete, shielding, shine (line-of-sight) and 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, to ensure coincident centroids of dynamic loads and restraint while also optimising the cost.

Fig. 4 Model of Seismic Isolation Pit   Fig. 5 Isolation Pit in construction

Fig. 6 Section through the Tokamak

The project poses huge engineering challenges. Over and above the usual nuclear design issues, to state that everything is “big” doesn’t really 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.

Fig. 7 Cut-away through the Assembly Hall and Tokamak

The main nuclear structures are founded in limestone rock; apparently sound but vulnerable to underlying solution features. 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 and is exacerbated by the need to hold to an ambitious programme and fixed budget. The facility is very 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 might successfully build something that might well affect the future of the entire planet.

Fig. 8 Catia image of process equipment in the Tokamak basement

Fig. 9 Catia image of process equipment in the Tokamak