Plutonium has been detected in soil samples taken from the Fukushima Daiichi nuclear power plant as radiation levels continue to hamper efforts to stabilise the troubled reactors.
The plant's operators TEPCO say the samples, taken at the plant on March 21 and 22, could have been discharged from nuclear fuel at the plant hit by the March earthquake and tsunami.
It is the first time TEPCO has confirmed the presence of plutonium outside of the reactors. Plutonium is more toxic than other radioactive materials such as iodine and caesium.
TEPCO said the amount recorded was equivalent to the fallout observed in Japan when atmospheric nuclear tests were conducted in the United States and Russia in the past.
"The detected plutonium from two samples out of five may be the direct result of the recent incident, considering their activity ratio of the plutonium isotopes," TEPCO said in a statement.
But the company was firmly playing down any cause for alarm.
"The density of detected plutonium is equivalent to the density in the soil under normal environmental conditions and therefore poses no major impact on human health."
The plant operator is analysing three further soil samples.
Hidehiko Nishiyama, a spokesman for the Japanese Nuclear and Industrial Safety Agency, told Kyodo News the detection of plutonium suggested "certain damage to fuel rods" and it is "deplorable" the toxic radioactive material was found despite various containment functions at the reactors.
Radiation levels at the plant continue to hamper efforts to bring the situation under control.
Yesterday morning TEPCO reported radiation levels in a pool in the basement of the basement of the unit 2 reactor's turbine building was 100,000 times higher than normal.
Radiation levels in a trench, which is connected to the basement pool, outside the unit 2 reactor exceeded 1,000 millisieverts per hour, Kyodo News reported.
TEPCO suspects the contaminated water has come from the reactor's core, where fuel rods have partially melted.
According to the Japanese National Institute of Radiological Science, exposure to 1,000 millisieverts per hour can cause nausea and fatigue in ten per cent of people.
Meanwhile, a visiting US chief nuclear industry regulator has expressed the view that the situation at the Fukushima plant "remains serious."
After meeting with senior officials of the Japanese government and TEPCO, US Nuclear Regulatory Commission Chairman Gregory Jaczko said that the "unprecedented challenge before us remains serious and our best experts remain fully engaged to help Japan address the situation".
While noting US atomic energy exports have been working closely with their Japanese counterparts, Jaczko also said, "I reconfirmed in my meetings that we are prepared to provide any assistance we can in the days to come."
- NZHERALD STAFF, AGENCIES, JIJI PRESS (JAPAN)