Radioactive cooling fluid leaked at a French nuclear reactor Thursday following two small fires, but the spillage was safely collected in special tanks, officials said.

A reactor at the power plant in Penly on the English Channel near the port of Dieppe shut down automatically after two small fires broke out Thursday, the plant's operator EDF said.

Firefighters easily extinguished the blazes but a cooling pump was damaged, in turn causing a joint to leak radioactive water into collection tanks located inside the reactor building, EDF said.

The reactor continued to be cooled properly and teams were working to lower the water pressure, the company said.

EDF said the installation was secure, no one was injured, and there were "no consequences for the environment".

It was not clear what caused the fires but the French Nuclear Safety Authority (ASN) said firefighters had found small pools of burning oil but quickly extinguished the flames.

"These were pools of a few dozen square centimetres," said agency spokeswoman Evangelia Petit, adding the authority would make an inspection of the site Friday.

The ASN said in a statement that it had provisionally put the event at level 1 on the international INES scale, which classifies nuclear accidents at between 1 ("irregularity") and 7 ("major incident").

The agency said it was lifting the crisis situation that had been put in place on Thursday evening.

France generates 75 percent of its electricity from nuclear power and the future of the industry has become an issue in campaigns for the presidential election to be held in April and May.

France, the world's most nuclear-dependent country, operates 58 reactors and has been a leading international proponent of atomic energy.

But the country's reliance on nuclear power has been called into question since the Fukushima disaster in Japan, which prompted Germany to announce plans to shut all of its reactors by the end of 2022. (AFP)