France, with its far-flung island communities in Oceania, the Caribbean and the Indian ocean, has been constantly battling with the problem of supplying power to these regions. Now, the French state-owned marine and naval engineering group, DCNS, has come up with a potential solution based on the French government’ favorite energy source, nuclear power.
The Flexblue Undersea Nuclear Power Plant Concept
DCNS has drawn on its long experience of producing nuclear submarines to develop a mini nuclear power plant for location off-shore. The well-proven nuclear propulsion unit used in submarines has been de-militarized and adapted for continuous power production.
The Flexblue concept calls for a complete nuclear power plant to be housed in a watertight cylinder, which is then anchored to the seabed in a suitable location in much the same way as an off-shore oil rig. Undersea cables then connected to the unit would supply power via undersea cable to the local or national distribution network.
The diagram shows the layout of a standard PWR pressurized water nuclear reactor. In the case of a Flexblue unit, not just the reactor unit containment shell but all the main elements, including the turbine, generator, pumps and condenser, would be housed in an overall containment unit, a single cylindrical hull, with only the power output cable and the cooling water inlet and outlet connections being outside the hull.
The hull also draws on submarine technology and is 330 feet long by 40-50 feet in diameter (100m long x 12/15m diameter). The complete unit weighs around 12000 tons and must be transported and lowered into place by a special purpose-built vessel. Ballast tanks are used to lower the units and raise them for maintenance purposes. Flexblue units are designed to be located on the seabed some miles out to sea in 200-330 feet (60-100m) of water. As with all nuclear installations, the site must be ultra-stable tectonically.
A video presentation of the Flexblue concept is available here.
Advantages of the Flexblue Concept
Unlike existing land-based nuclear power plants, which must be built in situ, Flexblue units can be mass-produced in a factory and take much less time to manufacture because no major civil engineering is required beyond any necessary preparation of the proposed site, which can be performed in tandem with the separate production of the nuclear power unit. Flexblue units can normally be manufactured in less than two years.
The design is modular so can be readily adapted and geared for rated outputs of 50 to 250 MW. The cost per unit is estimated in the range of several hundred million Euros, rather than the billions that a land-based power plant can cost.
DCNS claims that the output from a Flexblue unit would be sufficient to provide the electrical power requirements of communities with up to one million inhabitants, equivalent to "a city the size of Tangier or an island like Malta". This would make them a viable option for several of France’s island territories throughout the world. The energy cost is calculated as being similar to that from land-based power plants.
A concern since 9/11 has been that of an aircraft impacting on a nuclear plant’s reactor, causing a breach. The depth of water is thought to provide sufficient protection and also mitigates against terrorist interference with external components such as the pumps feeding the coolant water into the reactor unit. Water is also regarded as one of the best barriers against radiation.
Disadvantages of the Flexblue Unit
Despite its capability of offering tailored electrical power to smaller coastal and island communities, which may be expensive and/or difficult to reach with power supplied from land-based plants because of the long distribution lines required, Flexblue remains a nuclear power plant, with all that that entails.
Nuclear fuel must be brought in to replace that being consumed and the spent rods must be removed from the site and reprocessed or disposed of safely. Routine maintenance is also required. For both these activities, the unit must be raised from its anchorage on the seabed and then lowered back into place (or deep-sea divers could be use din the case of blocked intakes or fouled water inlet filters. The supply and maintenance logistics are likely to prove costly and complicated.
The unit represents a piece of high technology in a lower technology environment. A technical presence may be required for maintenance and administrative purposes – this would represent a significant additional cost to be absorbed by the consumer – or there could be long delays in restoration of power in the event of a breakdown.
Since the power plant is brought in as a pre-manufactured unit and little raw construction work is required, the benefit in terms of job creation in job-starved communities will be very low.
Although water may be considered a good radiation barrier, any breach in the undersea containment vessel would contaminate the marine environment over a wide area. The local fishing industry, potentially the community’s primary food source, would be compromised and local beaches could become polluted, damaging the local tourist industry. These considerations alone are likely to cause local authorities to seek a less drastic, less hi-tech solution to their power supply problems.
Current Take-up of Flexblue Technology
To date, no interest has come from France’s island and coastal communities outside the French mainland. The French state electricity utility, EDF, and the nuclear industrial combine, AREVA, however, have both expressed keen interest.
Since the flagship new nuclear EPR reactor at Flamanville has suffered a setback and will not commence electricity production now for at least another four years and replacement of France’s aging nuclear reactors (with the new EPR technology) is scheduled to commence by the end of the decade, France’s nuclear power supply industry may find itself in a bind. Quickly produced offshore power plants could offer a means of meeting demand while the current woes with the new EPR technology are resolved.
It has been proposed therefore that the first commercial Flexblue plant should be sited off France’s Nuclear Coast where it can be serviced easily from Cherbourg. The area already houses two nuclear reactors at Flamanville (plus the new EPR reactor under construction) and the nuclear reprocessing plant at La Hague.
A good logistical case can no doubt be made by France for locating a submarine nuclear power plant in this area but when regarded from a slightly more international perspective, severe concerns arise.
Counter Arguments to the Proposed Site of the Pilot Flexblue Unit
The proposed site borders the English Channel, one of the world’s busiest waterways, is close to the British Channel Islands and faces Britain’s long South Coast. Any breach in a Flexblue unit’s hull could contaminate a wide, densely populated area.
It is far from unknown, even in this age of GPS and radar, for ships to be lost in this region. A Flexblue unit may not be affected by a plane falling from the sky but may well be breached by a sinking ship. Furthermore, if a terrorist attack by plane has been a concern, unmanned submarine vessels can be damaged by external explosive devices such as limpet mines attached unobserved.
The area of the English Channel is also far from being ultra-stable tectonically. Three earthquakes in excess of magnitude 5.0 occurred near the Channel Islands in the 1920s and a magnitude 6.0 quake hit the Dogger Bank in the Channel. Small earthquakes regularly hit Britain.
A location in the Bay of Biscay, serviced from the French naval port of Brest, would certainly bear investigation as a potential Flexblue site. Two nuclear reactors, a nuclear reprocessing plant and a third reactor to a new, untried design under construction downwind from Britain’s South-East region and just a cross a short stretch of water from Britain’s populous South Coast already constitute significant cause for concern regarding any potential nuclear accident. The location of an undersea nuclear power plant in the area would only raise the potential risk of nuclear contamination.
Martin Cross - A translator, former chef and marketeer, currently disabled. I write articles on food,, travel, politics, religion and technology.
