French safety authorities Monday said they had cleared a reactor at a 33-year-old nuclear plant to go on functioning for another decade provided maintenance work is carried out.

The number one reactor at Fessenheim, France's oldest nuclear plant, "is suitable to be used for 10 more years on condition that a certain number of instructions are respected," Andre-Claude Lacoste, president of the nuclear safety agency ASN, told reporters.

The conditions include reinforcing the reactor's concrete foundation to ensure it is resistant to corium, a magma that forms when a reactor gets too hot.

The French energy firm EDF that runs the plant told AFP: "We will take into account the different instructions from the ASN for Fessenheim to function correctly."

The Fukishima nuclear plant disaster in Japan caused by an earthquake in March drove some countries, notably Germany, to reconsider the future of nuclear power.

France, which produces most of its electricity from its nuclear plants, has shown no signs of cutting back despite complaints from environmentalists about plants such as Fessenheim.