French company proposes offshore nuclear power

Building nuclear power stations underwater could help protect them from terrorist attacks, according to a French company hoping to do just that.

DCNS, the state-owned submarine-building and nuclear engineering firm, plans to conduct a validation study on its designs for a small subsea power plant for supplying coastal regions with electricity.

The Flexblue plant would sit on the seafloor at a depth of 60m to 100m, a few kilometres off shore, and have an electrical output of between 50MW and 250MW. By comparison Sizewell B power station in Suffolk has an output of almost 1200MW.

The power plant’s design makes Flexblue resistant to tsunamis, earthquakes or floods and its underwater position makes it less vulnerable to terrorist attacks, the company told The Engineer.

Andre Kolmayer, the company’s vice president for civil nuclear, said: ‘One challenge of the Flexblue concept is to bring together two worlds – nuclear energy and naval shipbuilding.’

With the exception of the long-standing cooperation in nuclear propulsion systems for DCNS-designed warships for the French Navy, the worlds of nuclear energy and shipbuilding have followed essentially parallel paths.

‘The idea of bringing these two worlds together is the result of our group’s determination to expand into the energy sector by exploiting its unique engineering expertise.’

The power plant would comprise a small nuclear reactor, a steam turbine-alternator set, an electrical plant and associated electrical equipment.

Power cables would carry electricity from the Flexblue plant to the coast and a system of ballast tanks would be used to raise or lower the plant during installation and for major maintenance, refuelling or dismantling.

The reactor design mirrors that of nuclear submarines in that it would attempt to prevent any contact between nuclear materials and the marine environment.

Three barriers, similar to those of existing reactors, would protect the reactor core from leaking – a fuel cladding, a reactor vessel and a hull.

Underwater submersion would provide a natural means of cooling the reactor, as well as enhancing security, and the only substance released into the environment would be the seawater used for cooling.

DCNS will conduct a technical and licensing design certification over the next two years in partnership with French nuclear energy commission CEA, nuclear conglomerate AREVA and energy company EDF.

If the design is validated, a prototype could be built by 2016.