Nuclear regulators in France, Britain and Finland said today they have told French nuclear giant Areva and its foreign partners to correct a safety design flaw on its latest-generation EPR reactor.

Any redesign could increase already costly delays in completing the first two of the reactors being built by Areva in France and Finland, and undermine French attempts to create a massive export market for its technology.

EPR reactors are currently being built in Finland, France and China and the certification process is underway in the United States, Areva said.

Launched in 1992, the European Pressurised Reactor was designed by French power giant EDF and German counterparts EON and RWE to be safer, more fuel efficient and generate less nuclear waste.

But the regulators said control systems used to operate the EPR reactor in normal conditions are too closely interconnected with the safety systems that would take over under extraordinary circumstances.

"Independence is important because, if a safety system provides protection against the failure of a control system, then they should not fail together," they said in a joint statement.

"The UK nuclear safety regulator HSE, the French nuclear regulator ASN and the Finnish nuclear regulator STUK, have asked the licensee and manufacturer to make improvements to the initial EPR design," they said.

"The licensees, and Areva, have agreed to make architectural changes to the initial EPR design which will be reviewed by the regulators. It is for the licensees and the manufacturer, Areva, to respond to its regulator's issues."