Tokyo -- Engineers will need up to nine months to fully shut down the damaged reactors at the Fukushima Daiichi nuclear power plant, the scene of the worst nuclear accident since Chernobyl, its owners announced Sunday.
It would take three months to bring down radiation levels and restore normal cooling systems at the plant, Tsunehisa Katsumata, the chairman of the Tokyo Electric Power Co., told reporters.
An additional three to six months would be needed before the reactors reach their cold shutdown point, he said.
The plan announced Sunday is the first timetable that Tokyo Electric has disclosed for reining in the crisis at Fukushima Daiichi, which was swamped by the tsunami that followed Japan's March 11 earthquake.
It comes five days after Japanese Prime Minister Naoto Kan called for Tokyo Electric to develop a timeline for bringing the disaster to an end.
The ultimate plan for the Fukushima Daiichi nuclear power plant involves the construction of a giant concrete box around all damaged reactors, according to the timeline. Design for the box should begin within nine months.
Also on Sunday, a top Japanese official headed to towns now slated for evacuation after safety officials warned of a possible new leak of radioactive water at the Fukushima Daiichi nuclear power plant.
Japan's Chief Cabinet Secretary Yukio Edano met with workers at the command center for efforts to stabilize reactors at Fukushima Daiichi on Sunday morning and held talks with the governor of Fukushima Prefecture.
After meeting with the governor, Yuhei Sato, Edano spoke to reporters.
"Ensuring people's livelihoods and security is our foremost priority," Edano said.
Edano also stopped in Minamisoma, a largely evacuated city in the outer belt of the 30-kilometer danger zone drawn around the plant, and in Iitate, a village outside the zone where elevated levels of fallout from the accident have been detected.
Both Minamisoma and Iitate are now scheduled to be evacuated in the coming weeks due to concerns about the long-term effects of radiation on their residents. Radiation levels recorded in both cities are not high enough to cause immediate health effects, but prolonged exposure could cause an increased risk of cancer, according to government data and reports from outside researchers.
Edano has been the government's top spokesman on the 5-week-old crisis at the plant, which was swamped by the tsunami that followed northern Japan's March 11 earthquake. The 14- to 15-meter (45- to 48-foot) wave knocked out the plant's coolant systems, causing the three reactors operating at the time to overheat.
The damage to the reactors and the resulting release of radioactivity led Japan's government to declare the situation a top-scale nuclear disaster last week, and experts from Japan's nuclear industry estimate the crisis could last another two to three months.
Workers at the plant are trying to drain thousands of tons of highly radioactive water from the flooded basements of the three reactor units. At the same time, workers are trying to pour tons of fresh water into the reactors and pools of still-energetic spent fuel to keep them cool.
Workers stopped a severe leak of contaminated water into the Pacific Ocean on April 6, but elevated levels of the short-lived nuclear waste iodine-131 recorded over the weekend could indicate a new problem, a Japanese safety official announced Saturday.
Iodine-131 has a radioactive half-life of eight days, and a more than fivefold increase in iodine concentrations in seawater behind the intake for the No. 2 reactor could be either from a fresh leak or from sediment stirred up while placing steel panels around the intakes, said Hidehiko Nishiyama, the top spokesman for Japan's Nuclear and Industrial Safety Agency.
"They will continue to monitor this carefully," Nishiyama said. "At this point, they have not visually found any leakage of any water into the ocean, and it is hard to check the conditions around No. 2 due to high radiation levels."
The iodine concentrations found were more than 6,500 times Japan's legal standards, up from 1,100 times on Thursday. But that number is far below the levels recorded when the earlier leak was spewing radioactive iodine into the ocean at 7.5 million times the limit. Authorities have built a silt and placed steel plates around the intake fence to corral the contamination since April 6.
They have also been dumping bags of an absorbent mineral into the water to limit the spread of radioactive cesium, another reactor waste.