Fukushima radiation leak twice Tepco estimate

Japan's Nuclear Satety Agency has annoucned that the amount of radiation released by the Fukushima Daiichi nuclear power plant in the days after the 11 March tsunami could have been more than double that originally estimated by Tokyo Electric Power (Tepco), the plant's operator.

The agency said molten nuclear fuel dropped to the bottom of the pressure vessel in the No 1 reactor within five hours of the accident, 10 hours earlier than previously thought. It also speculates that that the meltdown in another reactor had been faster than initially estimated.

According to the latest estimates, 770,000 terabequerels - about 20 percent as much as the official estimate for Chernobyl - of radiation seeped from the plant in the week after the tsunami, more than double the initial estimate of 370,000.

These revelations have raised fears that the situation at the plant, where fuel in three reactors suffered meltdown, is more serious than government officials have acknowledged. At the end of last week, radiation levels inside the reactor #1 had risen to 4,000 millisieverts per hour, the highest atmospheric reading inside the plant since the disaster.

In a possible sign that the contamination is more widespread than previously thought, a university researcher said at the weekend a small amount of plutonium had been identified a mile from the front gate of the Fukushima plant - the first time it has been found outside the plant.

However, Masayoshi Yamamoto, a professor at Kanazawa University, said the level of plutonium in the sample was lower than average levels observed in Japan after nuclear weapons tests conducted overseas.

Last week, a fact-finding team from the International Atomic Energy Agency criticised Tepco for failing to acknowledge the risk to the plant from a tsunami, despite warnings from government experts and its own scientists.