Japan's nuclear safety agency says radioactive iodine has been detected at more than 3,000 times the allowable level in the ocean near the crippled Fukushima nuclear plant.
Officials said Wednesday that the water sample, with the highest levels yet recorded, was collected about 300 meters from the Fukushima plant, which has been leaking radiation since its cooling systems were knocked out by a massive earthquake and tsunami on March 11.
Prime Minister Naoto Kan received a phone call Wednesday from U.S. President Barack Obama offering any help in dealing with the nuclear crisis and the natural disasters, which have now left more than 27,500 people dead or missing. A naval task force with more than 18,000 personnel is already assisting in relief efforts.
French President Nicolas Sarkozy is due in Tokyo Thursday to offer support. French nuclear experts are also assisting in the effort to halt radiation leaks and repair cooling systems for the plant's six nuclear reactors.
Japanese nuclear officials said they are working urgently to determine the exact cause of the spike in radioactive iodine in the seawater sample collected Tuesday, which registered 3,355 times the legal limit. They said the finding was a cause for concern but not an immediate threat to human health.
The nuclear plant's operator, the Tokyo Electric Power Company, announced Wednesday that company president Masataka Shimizu has been hospitalized with high blood pressure and that Chairman Tsunehiso Katsumata will take charge of the crisis.
Kan told parliament Tuesday that TEPCO had failed to make adequate preparations for the tsunami that knocked out vital cooling systems at the plant. The tidal wave is estimated to have been 12 meters high, more than twice the height the plant's seawall was designed to withstand.
Nuclear experts believe the plant suffered partial meltdowns of the nuclear fuel rods in the cores of three of the six reactors after the earthquake and tsunami disabled the primary and back-up cooling systems that keep the rods from overheating.
There are also fears that the containment chambers used to prevent radiation from escaping from the cores may have been damaged in at least two of the reactors. The latest evidence of that came Tuesday when technicians discovered low levels of plutonium matching that used in the number-three unit's fuel rods in soil samples outside the plant.
Plant workers meanwhile are laboring under primitive conditions and with inadequate food and sleep to remove water from the basements and adjoining service tunnels at three of the reactors. The water, which is at 1,000 times the normal radiation level at the Number 2 unit, was at one point threatening to spill into the nearby ocean but it was reported Wednesday to be coming down in the basement of one of the buildings.
Workers need to keep pumping water into the reactors to prevent the fuel rods from overheating, even as they need to remove the contaminated water so they can replace and repair pumps needed for normal cooling. In a worst-case scenario, the fuel rods could catch fire, spewing radiation, or melt through the floor of the reactors allowing their radiation to be widely distributed through the ground water system.
Radiation from the plant has already been detected in milk and vegetables from farms in the surrounding prefecture and at low levels in tap water in Tokyo and other cities. Very low levels have been detected in countries across Asia, Europe and North America. Tens of thousands of people have been evacuated from homes within 20 kilometers of the stricken plant.
Some information for this report was provided by AP, AFP and Reuters.