| MARCOULE, France
MARCOULE, France A worker was killed in an explosion at a French nuclear waste site on Monday, but officials said there was no radioactive leak and the authorities quickly declared the emergency over.
Four people were also injured, one with serious burns, in the blast at the Centraco site, owned by French power utility EDF and adjacent to the Marcoule nuclear research center on the river Rhone near the southern city of Orange.
The area no longer houses nuclear reactors. But supervisory bodies opened inquiries into the incident, which dented EDF's share price. In the wake of this year's Fukushima disaster in Japan, it was also likely to provide further arguments for opponents of France's heavy reliance on nuclear energy.
EDF, which a regulator said had improved safety at the site since being criticized in 2008, said the blast was contained within a furnace that was used to melt down scrap metal, from nuclear plants, which emitted only low levels of radiation.
"There was an explosion at the Marcoule site at 1306 (1106 GMT) causing one death and injuring four," an EDF spokeswoman said. "We don't know the cause."
Later, an executive from the plant operator, EDF subsidiary Socodei, called it a "classic industrial accident" which would most likely be classified as Level 1 on the seven-point international scale of nuclear incidents.
France's ASN nuclear safety watchdog declared the incident over but has launched an inquiry. The International Atomic Energy Agency, was seeking information from France and activated its incident and emergency center.
Data on previous fatal accidents at French nuclear plants were not available but officials said they could not recall one.
Police cordons kept onlookers away on Monday. Journalists saw police and other emergency vehicles at the site. There was no obvious sign of damage or smoke.
Local emergency services said there were no traces of radiation on the four people injured: "The risk of fire is over and there is no radioactive or chemical contamination of either the interior or exterior of the site," a rescue worker said.
Police also said there was no contamination outside the Centraco complex, which has been in operation since 1999.
Employing some 350 people, it melts down scrap metal such as valves and pumps used in nuclear plants and burns combustible waste in an incinerator, according to Centraco's website.
France, which draws 75 percent of its electricity from nuclear plants, is carrying out stress tests on its 58 reactors in the aftermath of the Fukushima disaster, when the Japanese nuclear site was damaged in an earthquake and tsunami.
Kash Burchett, European energy analyst at IHS Energy, noted a poll in June found 77 of French voters opposed to building new nuclear plants. But she said trade unions, as well as businesses facing higher fuel costs, would be unlikely to accept any move by a future government to curb investment in nuclear power.
"Even if a government of any hue were to attempt to slow investment into new nuclear facilities, let alone phase out existing capacity ahead of schedule, they would come up against the powerful, militant French unions," she said.
"Equally, the loss of nuclear power would increase energy costs substantially for households and businesses alike."
In its 2010 annual report, the ASN said that in 2008 it identified some weak spots in the Centraco site that prompted it to ask for an action plan to improve safety. It said the situation had improved since then at the site.
Malcolm Sperrin, director of Medical Physics and Clinical Engineering at the Royal Berkshire Hospital in Reading, England said: "It is unlikely that there will be significant, or any, releases of radiation into the wider environment but this will need to be confirmed in the next few hours or days."
(Additional reporting by Marion Douet, Mathilde Cru and Muriel Boselli in Paris and Kate Kelland in London and Scott DiSavino in New York; Writing by Catherine Bremer; Editing by Alastair Macdonald)