Plutonium levels at Fukushima at 'background' level - France
Plutonium at the Fukushima nuclear plant, reported by Japanese authorities on Monday, is present only at "background levels," a French nuclear watchdog said on Tuesday.
Out of five sites where plant operator TEPCO said plutonium was found, two indicate "isotopes which appear to be connected to the accident itself," said Marie-Pierre Comets, a senior official at the Nuclear Safety Authority (ASN).
Plutonium is one of the most toxic substances known, although its main danger comes not from being in close proximity to its radiation but through inhalation or ingestion, say experts.
Just a dozen milligrammes of plutonium, when inhaled at one time, is lethal for a human, according to tests on lab animals cited by France's Institute for Radiological Protection and Nuclear Safety (IRSN).
Comets said, though, that "in terms of the quantities of plutonium detected on the site, we are still talking in terms of background levels," or very minor concentrations that are a global legacy of atmospheric nuclear bomb tests.
Olivier Gupta, deputy director general of the ASN, said the agency had yet to receive "a more detailed analysis of the precise composition" of the plutonium found at Fukushima.
"However, the data confirms previous hypothesis of severe damage to the fuel" inside the reactors, he said.
The plutonium, he said, could have come from mixed oxide fuel, a blend of plutonium and uranium, that had been used in the No. 3 reactor, or as a byproduct of burning uranium in the No. 1 and No. 2 reactors.
On Monday, Tokyo Electric Power Co. (TEPCO) said plutonium was found at five spots within the crippled facility, but not at levels that were a hazard to health.
The level of plutonium was similar to that detected in Japan after neighbouring countries such as North Korea and China conducted nuclear experiments, TEPCO said.
Japan's Nuclear and Industrial Safety Agency said it was unclear which reactor the plutonium came from.
© 2011 AFP