TOKYO (Reuters) - Following are main developments after a massive earthquake and tsunami devastated northeast Japan and crippled a nuclear power station, raising the risk of an uncontrolled radiation leak.
* New readings show a sharp rise in radioactive iodine in the sea off the Fukushima Daiichi nuclear power plant to 3,355 times the legal limit, according to the state nuclear safety agency. The agency plays down the impact, saying residents have left the area and fishing has stopped.
- French President Nicolas Sarkozy, who chairs the G20 and G8 blocs of nations, plans to visit Tokyo on Thursday. He will be the first foreign leader in Japan since the March 11 earthquake and tsunami that wrecked the nuclear plant.
France also flew in two experts from state-owned nuclear reactor maker Areva and its nuclear research body to assist Japan's heavily criticized plant operator Tokyo Electric Power Co (TEPCO).
* TEPCO says its chairman is now at the firm's helm after its president, barely seen since the crisis began, was taken to hospital suffering from high blood pressure and extreme dizziness.
National Strategy Minister Koichiro Gemba said on Tuesday that nationalisation of TEPCO, Asia's largest utility, was one option being considered.
* Japanese Prime Minister Naoto Kan and U.S. President Barack Obama agree that close cooperation is essential in handling the problems at the plant. The two leaders pledge to help people affected by the quake.
- On Tuesday, plutonium was found in soil in five places at the plant, heightening public alarm. TEPCO says traces of plutonium found were of level not harmful to human health. The nuclear safety agency said the discovery could mean the reactor's containment mechanism had been breached.
- The nuclear safety agency says the amount of plutonium detected near the plant is similar to that which would result from a nuclear test, but is not harmful to humans.
- Around 27,500 people dead or missing from the earthquake and tsunami.
- Some opposition lawmakers have criticized Prime Minister Naoto Kan for not widening the exclusion zone around the plant.
- PM Kan says the situation at the nuclear power station requires utmost vigilance. Workers resigned to a struggle of weeks or months to restart vital cooling systems.
- Environmental group Greenpeace says it has detected high levels of radiation outside the 20-km (12-mile) exclusion zone, but Japanese officials say levels away from the plant are not dangerous for humans. Experts say radiation in the Pacific will quickly dissipate.
- Estimated cost of damage from the earthquake and tsunami to top $300 billion, making it the world's costliest natural disaster. The 1995 Kobe quake cost $100 billion while Hurricane Katrina in 2005 caused $81 billion in damage.
(Tokyo bureau; Compiled by World Desk Asia)