5 Nov (NucNet): Work at the International Thermonuclear Experimental Reactor (Iter) at the Cadarache nuclear site in southern France is about to enter a new phase after it was announced yesterday that the concrete basemat that will support the tokamak complex has been completed.
Fusion for Energy (F4E), the organisation responsible for managing Europe’s contribution to the project, said workers have now started to frame out the lower walls of the seven-storey structure that will house the biggest fusion machine in the world, and the start of concrete pouring is “imminent”.
Completion of the basemat marks the conclusion of work that started in August 2010 and represented an investment of around €100 million for F4E.
The basemat construction was carried out by a group of companies led by GTM Sud of France under the supervision of F4E and the ‘Engage’ consortium consisting of Assystem, Atkins, Empresarios Agrupados and Egis.
From August 2010 to August 2014, workers excavated a 17-metre-deep seismic pit, created a ground-level basemat and retaining walls, installed 493 seismic columns and pads, and poured the foundation slab.
The basemat will be able to support more than 400,000 tonnes of building infrastructure and equipment, including the Iter machine, which alone will weigh 23,000 tonnes.
The basemat is far more complex that it seems, F4E said. It has a surface of 9,600 square metres and a thickness of 1.5m of reinforced concrete consisting of four successive layers – two of 50cm, one of 30cm and one of 20cm.
F4E said the design and validation process have been “extremely challenging” because the basemat will be the floor of the tokamak building that will house the machine and shield it. For this reason it is has been subjected to heavy scrutiny from the French nuclear regulator.
Construction of the tokamak complex is now the responsibility of a French-Spanish consortium VFR under a €300 million contract awarded by F4E in December 2012. The consortium includes French companies Vinci Construction Grands Projets, Razel-Bec, Dodin Campenon Bernard, Campenon Bernard Sud-Est, GTM Sud and Chantiers Modernes Sud, and the Spanish company Ferrovial Agroman.
The complex will be 80m tall, 120m long and 80m wide. It will require 16,000 tonnes of steel rebars and 150,000 cubic metres of concrete.
Iter is intended to demonstrate the scientific and technological feasibility of fusion power. It will be the world’s largest experimental fusion facility. Fusion is the process which powers the sun and the stars. When light atomic nuclei fuse together to form heavier ones, a large amount of energy is released.
The Iter project is a first-of-a-kind global collaboration. Europe will contribute 45 percent of its construction costs, while the other six members to the venture (China, India, Japan, South Korea, Russia and the US), will contribute equally to the rest. The total cost of the project has been estimated at EUR 15 billion.
