The staff at Tricastin were “slightly contaminated” by radioactive particles that escaped from a pipe at a reactor complex, an EDF spokeswoman said.
The company says sensors detected a rise in the radiation level while maintenance work was being carried out at a reactor that had been shut since 12 July.
The rise in radiation prompted 97 EDF and maintenance subcontractors to be evacuated and sent for medical tests.
“Seventy of them show low traces of radioelements, below one 40th of the authorised limit,” EDF said, adding that the incident would not affect people’s health or the environment.
“What concerns us is less the level of the people contaminated than the number of people contaminated,” EDF spokeswoman Caroline Muller told the Associated Press news agency.
Safety concerns
Two weeks ago, the authorities had to issue a ban on fishing and water sports in two local rivers after 30 cubic metres of liquid containing unenriched uranium leaked from a broken underground pipe onto the ground and into the water.
The environment minister has since ordered tests of all France’s nuclear power plants to ensure such leaks have not gone undetected elsewhere.
On Friday, energy company Areva said liquid containing slightly enriched uranium leaked at another of its sites in south-east France.
The same day, 15 EDF workers were exposed to what the company called “non-harmful” traces of radioactive elements at the Saint-Alban plant in the Alpine Isere region.
The incidents have raised questions about the state-run nuclear industry, at a time when some countries are considering nuclear energy because of the soaring price of oil, correspondents say.
France derives more than 75% of its electricity from its 59 nuclear power plants, and President Nicolas Sarkozy has recently announced plans to expand the nuclear programme.