Radiation at new high after quake

Japan's Trade Minister Toshimitsu Motegi wears protective gear to inspect Fukushima storage tanks. Photo / AP

Japan must step up on the critical global issue, says nuclear expert

Radiation levels at Japan's stricken Fukushima nuclear plant have reached a new high after an earthquake off the country's east coast underlined the urgency of the crisis.

Readings at steel tanks used to store thousands of tonnes of radioactive water showed a 20 per cent rise to 2200 millisieverts per hour.

Experts say exposure to that level of radiation for more than two hours could prove fatal to a human.

The new high was at the same "hot spot" identified by the Nuclear Regulation Authority on Saturday, when the level stood at 1800 millisieverts.

"The radiation concentration was found in the H3 area of storage tanks, which are the same type of tanks that have leaked in the past," a spokesman for Tokyo Electric Power Co (Tepco), the plant operators, said.

"The reading of 2200 millisieverts was found about 5cm from the tank, but it had fallen to 40 millisieverts per hour 50cm from the tank," Tepco said.

The company was not able to find any leak in the tank.

Tepco said all its systems at the plant were functioning normally after Wednesday's earthquake of 6.9 magnitude struck about 400km beneath the surface of the seabed 580km south of Tokyo.

The tremor registered at level four on Japan's seven-point scale along the east coast of the country, including at the Fukushima plant, which was damaged by an earthquake and tsunami in March, 2011.

Tom Snitch, a senior professor at the University of Maryland who has more than 30 years' experience in nuclear issues, said the Japanese Government needed to take some very difficult decisions quickly.

"They need to address the real problems, the spent fuel rods in unit 4 and the leaking pressure vessels.

"All of this is really a political decision and not a technological issue. This is a critical global issue and Japan must step up."