Photo: EPA
The country's independent radiation watchdog sounded the alarm today after the incident – the fourth such scare in a fortnight.
Electricité de France workers were exposed to radioactive particles on Wednesday that escaped from a pipe at a nuclear reactor at the Tricastin complex.
Experts said that the latest incident involved the highest number of workers to be collectively contaminated in French nuclear history.
Tricastin, which houses four reactors, suffered another leak earlier this month at a separate treatment facility when 74kg of liquid containing unenriched uranium was spilled.
Authorities have just lifted a fishing and water sports ban in two nearby rivers.
Areva, the nuclear group whose subsidiary was allegedly responsible for the first leak, admitted that security needed revamping in France.
Wednesday's incident occurred in Tricastin's reactor number four, which had been shut down for refuelling.
The EDF employees, who were exposed to dust containing radioactive Cobalt 58, were sent to the sick bay and then home awaiting tests, while a probe has been launched into what went wrong.
EDF said that the contamination was slight - a dose smaller than one 40th of the annual regulation limit. However, the independent radioactivity research and information commission, Criirad, warned EDF and other nuclear power operators against any playing down of such incidents.
The annual radiation limit was, it said, "not the level from which risk begins but the maximum acceptable level".
If all of France's 274,000 nuclear workers received the maximum dose, some 219 would die from radiation-linked cancer, it warned.
However, other experts pointed out that those who take a head-to-toe x-ray receive just as much radiation and that natural uranium emissions, such as in the mountains of Iran, can be much higher.
One CGT union representative at Tricastin alleged that reduced maintenance time as part of EDF's profitability drive and the increasing use of sub-contracted workers threatened to compromise security.
A spokesman for EDF said: “We spend 1.5 billion euros a year on ensuring our plants are in optimum condition.
“Safety is our top priority over and above providing electricity to the network. Since our power stations were set up, 80 per cent of maintenance operations on reactors that have been temporarily turned off are carried out by external contractors.
“They are the most competent to maintain and repair specific parts of the reactor, some of which they have taken part in building.”
Two other "minor" leaks occurred last Friday. One was at a nuclear fuel plant in Romans-sur-Isere, south-east France, and another at the Saint-Alban plant - also in the Alpine Isere region – in which 15 EDF workers were exposed to "non-harmful" traces of radioactive elements.
The negative publicity around the Tricastin site has led local winegrowers to launch proceedings to change the name of their local appellation, currently Tricastin AOC.
"It's only a question of image as nuclear and food don't mix very well in consumers' minds", said the appellation's president, Henri Bour.
He said he tried to get the nuclear operators to change the name of the site a few years ago, but they "didn't understand our move, doubtless not wanting to admit that the nuclear industry's image is perhaps not perfect".
Last week, the French ecology minister Jean-Louis Borloo said he wanted to carry out tests on the ground water near all reactors and assess the state of waste storage sites.
With 58 reactors, France has the second largest nuclear power network after the United States and the facilities generate more than 80 percent of its electricity.
President Nicolas Sarkozy has been touring the world in recent months promoting France's nuclear prowess and its new generation of EPR reactors.
On July 7 and again on July 23, there were accidental leaks at the Tricastin Nuclear Power Center in France, which  is a collection of sites in four different communes: Saint-Paul-Trois-Châteaux and Pierrelatte in Drôme, and Bollène and Lapalud in Vaucluse.

Along with two other minor incidents on July 18, it has prompted the Commission for Independent Research and Information on Radioactivity (Criirad) to order a review of security and safety. Already last week, Environment Minister Jean-Louis Borloo said the ground water near all reactors should be tested and the state of waste storage sites assessed.
Cooling towers at Tricastin Nuclear Power Center 
In the latest incident, a hundred workers were exposed to radiation. They all work for Électricité de France (EDF), which runs the Tricastin facilities with Areva. This marks the largest number of workers to be collectively contaminated in French nuclear history.

The leak was at reactor number four, which was shut for refuelling. Workers were exposed to Cobalt 58 dust which escaped while maintenance work was being carried out. Sensors noticed a rise in the level of radiation and the workers were then evacuated.

"Seventy of them show low traces of radioelements, below one fortieth of the authorized limit," EDF said. A spokesperson later raised the number to 97 people. Criirad warned, however, that the limit was "not the level from which risk begins but the maximum acceptable level."

"We have an alarm system which is meant to protect the staff from contamination via the atmosphere,” said Tricastin director Alain Peckre. "If a problem is detected, the alarms go off, our security procedures swing into place and everyone is evacuated from the building."

A union representative from Confédération générale du travail (CGT) alleged that EDF was reducing maintenance and increasingly using sub-contractors, putting workers at risk in exchange for profitability.

"We spend 1.5 billion euros a year on ensuring our plants are in optimum condition," countered an EDF spokesperson. "Safety is our top priority over and above providing electricity to the network. Since our power stations were set up, 80 per cent of maintenance operations on reactors that have been temporarily turned off are carried out by external contractors. They are the most competent to maintain and repair specific parts of the reactor, some of which they have taken part in building."

The previous incident, on July 8, involved a 74kg spill of liquid containing unenriched uranium. Thirty cubic metres of water overflowed while a tank was being emptied. Subsequent test showed that contamination may have occurred for years.

Local wine growers Coteaux du Tricastin AOC have already become concerned about the negative association with "Tricastin" and have begun considering changing the name of their Appellation d'origine contrôlée (AOC).

"It's only a question of image as nuclear and food don't mix very well in consumers' minds," said the AOC's president, Henri Bour, to ''The Daily Telegraph''. Nuclear authorities "didn't understand our move, doubtless not wanting to admit that the nuclear industry's image is perhaps not perfect," he added.

"Nuclear was progress and we wanted that. We thought people were competent. Now we ask, were there previous incidents we weren't told about?" said local resident Roger Eymard to ''The Guardian''.

Autorité de sûreté nucléaire (ASN), a nuclear safety authority, has already criticised Areva for its handling of the first incident. ASN complained of poor communication with authorities and unsatisfactory security measures and operational procedures.

The leaks have occurred just as President Nicolas Sarkozy has been promoting the European Pressurized Reactor (EPR) as a solution to rising energy costs and global warming.

France has the second largest nuclear power network in the world and generates over 80% of its electricity through nuclear power.