The Energy Commission, Günther Oettinger, has revealed that "nearly all" of the EU's 145 nuclear reactors need improvements to help them withstand natural disasters.
He said that the results of tests carried out in the wake of the Fukushima disaster showed that the power plants were merely "satisfactory".
Speaking during the unveiling of the results on 4 October 2012, Mr Oettinger said no reactors needed to be shut down immediately, but that "major potential for improvements" was needed "almost everywhere".
He warned that the cost of improving nuclear safety could reach €25bn.
He was particularly critical that some improvements recommended following the 1979 Three Mile Island and the 1986 Chernobyl nuclear incidents had not been carried out.