Tokyo, March 29: Plutonium was detected in soil at five locations on the grounds of an earthquake- and tsunami-damaged nuclear power plant, heightening fears about radiation contamination from Japan’s worst nuclear crisis, news reports said Tuesday.
The levels of the radioactive substances from soil taken at the Fukushima Daiichi Nuclear Power Station a week ago do not pose a human health risk, said the operator of the plant, Tokyo Electric Power Co (TEPCO). They were equivalent to those that fell on Japan after past nuclear weapons test by other countries, the company said.
But the top government spokesman said the plutonium readings showed “the situation was very serious”. They also “reinforced the view that there was a partial melting of the spent fuel rods”, Chief Cabinet Secretary Yukio Edano said.
Japan’s Nuclear and Industrial Safety Agency said it was not certain which reactor the plutonium came from but added that TEPCO and the science ministry would reinforce monitoring of the environment beyond a 20-kilometre exclusion zone around the six-reactor plant as well as inside the complex, the Kyodo News agency reported.
Hidehiko Nishiyama, an agency spokesman, said the detection “underscored the gravity and the seriousness of the accident” and suggested “certain damage to fuel rods”.
The government said Monday that a partial meltdown of spent fuel rods caused high levels of radioactive materials detected in water in an adjacent turbine building of reactor number 2. Water had collected at the building after TEPCO, emergency services workers and the military doused the plant with water to cool its overheating reactors.
The water is “believed to have temporarily come into contact with fuel rods which have partially melted”, Edano said.
Nishiyama denied the possibility that the reactor 2 containment vessel, which protects against releases of radioactive materials, has cracks or holes, saying there was no data to suggest that. He said it was likely, rather, that radioactive water had leaked from pipes or valves.
Radiation levels above 1,000 millisieverts per hour were detected in water in a trench outside the same turbine building of reactor 2, TEPCO said Monday.
One end of the tunnel-like trench is located about 55 metres from the ocean with the surface of the water about 1 metre below its ground-level hole, Kyodo said.
Radiation-contaminated water has also been found in the adjacent turbine buildings of reactors 1, 3 and 4.
The limit of exposure to radiation for plant workers is 100 millisieverts per shift, but it has been raised to 250 millisieverts during the crisis triggered by the March 11 disaster.
The contamination has hampered work to restore power and cooling functions at the reactors to avert a potential disaster.
TEPCO was trying to clear the contaminated water to reduce the risk of more workers being exposed to radiation. Workers must access the overheating reactors to restore their key cooling systems.
On Thursday, three engineers working on the cable system at reactor 3 were exposed to radiation levels in water that were 10,000 times above normal.
International Atomic Energy Agency Director General Yukiya Amano said Monday that it would take more time to stabilise the situation at the Fukushima plant, 250 km north-east of Tokyo.
“The critical situation in Fukushima Daiichi has still not been overcome, and it takes some time to stabilise the reactors,” Amano said in Vienna.
The situation “continues to be very serious”, he said.
Visiting US Nuclear Regulatory Commission Chairman Gregory Jaczko agreed.
“The unprecedented challenge before us remains serious, and our best experts remain fully engaged to help Japan address the situation,” said Jaczko, who met officials of the government and TEPCO Monday.
The official death toll from the March 11 quake and tsunami stood at 11,004 Tuesday with 17,339 people listed as missing, Japan’s National Police Agency said.
–Agencies