French scientists are looking at the possibility of submerging small nuclear power plants deep underwater to supply low-cost energy to isolated countries or islands that cannot afford a major inland atomic plant.

France pioneered the mass development of nuclear power stations in the 1970s and now sees a possible use in the industry for technology adapted from nuclear submarines, a top engineer said.

A study will now look into whether standardized nuclear plants the size and shape of submarines, and much cheaper to install than regular plants, could safely operate in the sea and supply power to land via underwater cables.

State-controlled submarine builder DCNS will carry out two years of feasibility studies -- backed up by reactor maker Areva , nuclear power producer EDF and France's atomic body CEA -- to address pollution and security questions.

A first "Flexblue" unit with a capacity of 50 to 250 megawatts (MW) -- which compares with up to 1,650 MW that can be generated by a reactor on land -- could come on stream by end-2016.

"I am convinced this can be done," Andre Kolmayer, head of DCNS's civilian nuclear business unit, told Reuters.

"There are about 150 nuclear submarines roaming around the world today, so putting a nuclear plant underwater is not exactly a novelty," he said.

"DCNS has built nuclear submarines for 40 years, and we have put 18 in action. The technology we'll use for Flexblue will be carefully demilitarised, but it will evidently benefit from this experience," said the atomic engineer, who worked for nuclear reactor maker Areva for 25 years before joining DCNS in 2002.

DCNS plans to build a capsule-shaped unit 100 metres (328 feet) long, 12-15 metres in diameter and weighing 12,000 tonnes and moor it on the seabed at a depth of 100 metres.

"This is a cylindrical shape, but that is as close as it is to a submarine. There is no propulsion ... It will not go as deep as submarines. We won't have the same acoustic discretion, anti-radar quality or resistance to military shock," Kolmayer said.

The company aims to capitalise on renewed global interest in atomic power in the face of surging oil prices and growing concern over climate-warming carbon emissions from power plants.

"The facility's technology cannot be used for military purposes," said Kolmayer, who sees Flexblue as less vulnerable to terror attacks and natural disasters than plants on land.

He said security issues were at the heart of DCNS's studies. The water depth would protect the units against a plane crash, thunder or a tsunami, and a metal net would protect them by making a torpedo explode at a distance.

"Going that deep is not within the reach of everyone, so they (terror groups) would need to have quasi-military means," Kolmayer said, adding that should the unit be hit, a security option would mean the reactor compartment is flooded with water.

"WATER EXTINGUISHES EVERYTHING"

Kolmayer said an accident like the Chernobyl disaster in 1986 would not be possible in theory, although this would have to be backed up by DCNS's studies over the next two years.

"We are talking about a small reactor. If you plunge everything in the water, it cools down naturally. To have strong radioactive emanations, you need the reactor to go at a very high temperature and start melting ... but water extinguishes everything," he said.

Anti-nuclear groups such as "Sortir du Nucleaire" ("Phasing Out of the Nuclear Age") have described the project as "absurd".

"Radioactivity would spread even more quickly in the water than in the air, with even fewer means to control leaks," said Sortir du Nucleaire coordinator Anne-Laure Meladeck in Lyon.

The units would be installed in groups -- "a little like wind farms," said Kolmayer -- 5 to 15 km offshore.

DCNS said they could supply cities of about 100,000 inhabitants, or up to a million in emerging countries, via underwater cables and offer a standard, easy-to-assemble power production tool that is much cheaper than nuclear plants on land.

"The market is global and complementary to that of big nuclear plants. We are not aiming at the same market. We're aiming at emerging countries whose power network is too small to harbour a big nuclear power plant," said Kolmayer.

He estimated the global market for Flexblue at between 100 and 300 units, depending on the price, which DCNS puts anywhere from 100 million euros ($137.6 million) to 1 billion.

He cited Malta, Cyprus and Morocco as examples of typical markets DCNS would target, insisting it had received no mark of interest yet.

af.reuters.com