Flexblue, nuclear power from under the sea – too radical a solution?

martin cross By martin cross, 22nd Dec 2011 | Follow this author | RSS Feed | Short URL http://nut.bz/2mr9fg47/
Posted in Wikinut>Guides>Science>Energy

Flexblue is a submarine-style nuclear-powered generating plant designed for coastal and island communities whose recent unveiling by the DCNS group has sparked controversy.

DCNS unveils its new concept – Flexblue

The French government-owned group, DCNS, specializing in naval systems, has unveiled its latest solution to the problem of providing power to coastal and island communities: Flexblue.

This new concept calls for a complete nuclear power plant – nuclear reactor, steam turbine generator and the associated electrical systems – to be housed in a watertight cylinder anchored to the seabed offshore and supplying power via undersea cable to the local or national distribution network.

The reactor is an adaptation of a well-proven design of nuclear propulsion plant for submarines, revised for continuous power production. The self-contained unit consists of a cylindrical protective hull 100m (330 ft) long by 12-15m (40-50 ft) in diameter. Each unit weighs around 12,000 tons and must be transported by a purpose-built vessel. The units are designed to be anchored securely to an ultra-stable area of the seafloor some kilometres offshore in 60-100m (200-330 ft) of water. Submarine-style ballast tanks inside the unit are used to lower it into position and raise it subsequently for refuelling, maintenance and any necessary repairs.

The design is modular so that it can adapt to future developments and the units are rated for outputs of 50 to 250 MW. The units can be mass-produced in a factory and transported to the installation site rather than having to be built in situ and with a much shorter completion time of less than 2 years because of the lack of additional civil engineering and construction work. The cost per unit is estimated in the range of several hundred million Euros.

The Flexblue concept is ‘perfectly rational”

The above diagram shows the layout of a standard PWR nuclear reactor. In the case of a Flexblue unit, all the main elements would be contained within a single cylindrical hull, with only the power output cable and the cooling water inlet and outlet connections being outside the containment hull.

In his presentation of Flexblue, DCNS’s CEO, Patrick Bossier, hails the project as a major innovation in the global energy market based entirely on proven technologies, combined in a new way and drawing on the Group’s 40 years’ experience in nuclear engineering and century of experience in submarine design and construction. He lauds Flexblue as combining the very best of DCNS’s know-how in submarine engineering and marine environments to ensure performance, reliability, safety, durability and environmental protection.

The output of the unit is stated as providing sufficient capacity to supply a community of up to one million people, equivalent to "a city the size of Tangier or an island like Malta".

In terms of safety and environmental protection, Boissier claims that water is the best barrier against radiation and that the depth of water covering the unit would protect the unit from an aircraft falling from the sky (perhaps one of France’s major concerns regarding its land-based plants in the aftermath of 9/11.

Bruno Tertrais, a nuclear specialist and Head of Research at the Strategic Research Foundation, states that Flexblue is “a project that may appear crazy but, when analyzed carefully, is perfectly rational”. DNCS claims that the project would provide electricity at a competitive cost and the French electricity utility, EDF, and the nuclear industrial combine, AREVA, have already expressed interest.

In addition to the OTEC power plants whose feasibility DNCS is currently studying in several locations, Flexblue has been put forward as a means of resolving the power generation problems of scattered French territories in the Tropics (e.g. various Caribbean islands, Polynesia and La Réunion in the Indian Ocean). The first pilot plant, however, is proposed to be installed in the English Channel, off the Normandy coast near Flammanville, where there are already two nuclear reactors in operation and the new flagship EPR reactor under construction, providing easy access to the national; power distribution network, and the nuclear waste reprocessing plant at La Hague, making this France’s Nuclear Coast. The unit would be serviced and maintained from the nearby naval dockyards at Cherbourg.

This glowing presentation has done little to quell the concerns of the nuclear programme’s detractors.

“They have really lost it”

The anti-nuclear activist, Didier Anger, a former MEP for the Green Party, made no bones about his view of the concept: “They have really lost it. In the event of an accident, there is nothing worse than water, where radioactive pollution spreads like a chemical much faster than in the air. The whole of the Channel and potentially other seas would be contaminated or totally destroyed, depending on the severity of the accident and dispersion by currents. Furthermore, the sudden heat-up caused by the accident would create a tremendous, life-destroying, thermal shockwave.”

Other concerns

The design concept breaks one of the fundamental “laws” relating to the design of any electrical equipment for use in proximity to water. Water and electricity react, causing a major short-circuit and possible fire further down the power line. No design, therefore, should incorporate a water source above an electrical system. In the case of Flexblue, not only the generating plant but a nuclear reactor is immersed in water. Salt water is a highly corrosive medium and will quickly find the slightest weakness in any metal container. The submarine plant’s hull will require regular inspection for any potential water penetration.

The English Channel is not as seismically stable as might be envisaged. Between 1925 and 1927, Brittany and the Channel Islands were hit with three significant earthquakes ranging from 5.1 to 5.6 in magnitude. A few years later, the Dogger Bank was hit by a 6.1 magnitude quake. The proposed location for the pilot Flexblue unit may not be as stable as would be wished.

The English Channel is also one of the world’s major waterways and, although relatively sparsely populated on the French side, it is quite heavily populated on the British side. All along their length, both sides are popular holiday locations and support local fishing industries. The long and short-term impacts of any nuclear accident in this area would be tremendous, and could be further compounded by impact on the other nuclear plants in the area.

Unlike a small conventional power plant, nuclear or otherwise, Flexblue would bring little benefit to the local communities on the coastal strips or islands where they are being installed. The units would be manufactured in a French factory, transported in a special ship, installed by French technicians and maintained by only a handful of specialist personnel. There would be no employment created locally for construction workers or in the many local services that a long-lasting construction project would require. For job-starved coastal and island communities, this lack of jobs being created by the project may weigh heavily against its more universal acceptance.

Possible overriding arguments

Seven 250 MW Flexblue units would be equivalent in output to the EPR reactor currently under construction at Flamanville and would also be equivalent in cost to the original estimate for its construction and only half of its newly revised cost of over 6 billion Euros.

Given their relatively short production time, the units could also be on-stream earlier than the EPR reactor’s estimated completion date of 2016.

For EDF and the French government, faced with scheduled replacement of the present nuclear reactor pool at a rate of one per year from 2020 onwards, deploying quickly produced Flexblue units, at the very least in replacement of the coastal plants, may be considered a simple solution to the time pressures and potential supply problems they now face because of the construction failures encountered with the all-important EPR reactor at Flamanville.

The technology is essentially already proven and costs would be similar and may even be significantly reduced, especially if economies of scale can be achieved.

The above arguments and particularly the fact that the French government owns around 74% of the DCNS Group, Flexblue’s designers, may tip the scales in favour of a significant deployment of Flexblue units, regardless of any other considerations. This would result in a high number of units installed in the Channel and possibly the Bay of Biscay, significantly increasing the potential risk of an accident.

The opposition candidates for the French Presidency are less solidly committed to the nuclear programme than President Zarkovy. The outcome of the elections in 2012 may therefore have an impact on Flexblue’s future.

In the meantime, DCNS is planning to conduct further in-depth research over the next two years, in partnership with EDF and AREVA, and identify the industrial challenges faced in manufacturing the units.

DCNS has also released a video demonstrating a prototype of the Flexblue unit.


Channel Islands, Coastal Communities, Controversy, Electrical Power, Energy, English Channel, Flexblue, French Nuclear Energy Policy, Generation, Low-Carbon, Nuclear Installation, Nuclear Pilot Plant Installation, Nuclear Power Plant, Offshore, Power For Island Communities, Small Nuclear Reactors, Submarine, Underwater, Unit

Meet the author

author avatar martin cross
I am a technical translator and writer, a former chef and marketeer, currently disabled. I write articles on food,, travel, politics, religion and technology among other topics.

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