The operator of the crippled nuclear power plant leaking massive amounts of radiation in northern Japan announced a plan Sunday that would bring the crisis under control within six to nine months and allow some residents to return to their homes.

The phased road map for ending the crisis at the Fukushima Daiichi nuclear power plant, presented by Tokyo Electric Power Co. chairman Tsunehisa Katsumata at a news conference, included plans to cover the damaged reactor buildings to contain the radiation and eventually remove the nuclear fuel.

"We sincerely apologize for causing troubles," Katsumata said. "We are doing our utmost to prevent the crisis from further worsening."

Frustrations have been mounting over TEPCO's failure to resolve the nuclear crisis more than a month after a catastrophic earthquake and tsunami hit Japan on March 11, knocking out power and cooling systems at the Fukushima Daiichi complex.

"Well, this year is lost," said Kenji Matsueda, 49, who is living in an evacuation centre in Fukushima after being forced from his home 20 kilometres from the plant. "I have no idea what I will do. Nine months is a long time. And it could be longer. I don't think they really know."

Katsumata, who was hammered by questions over his management responsibility, told reporters he was considering stepping down because of the crisis.

"I feel very responsible," he said.

Katsumata said he was not sure when the tens of thousands who had been forced to flee their homes because of the crisis could go back, but Japanese Trade Minister Banri Kaieda said some could return home within six to nine months.

'We are very confident that Japan will recover, and will be a very strong economic and global player for years and decades to come.'—Hillary Clinton, U.S. secretary of state

"Of course, some people will be unable to return home, but we will keep everyone informed," he said, adding that the government hoped TEPCO could contain the radiation sooner than the schedule announced Sunday.

In the first three months of the plan, the company hopes to steadily reduce the level of leaking radiation, Katsumata said. Three to six months after that, it hopes to get the release of radioactive materials firmly under control.

The company is focusing on cooling the reactors and spent fuel pools, decontaminating water that has been contaminated by radiation, mitigating the release of radiation into the atmosphere and soil, and measuring and reducing the amount of radiation affecting the evacuation area, he said.

Kaieda said he hoped to see the process quickly "shift from the first aid phase to a systematic and stable phase."

Radiation levels spike again

Explosions, fires and other malfunctions have hindered efforts to repair the stricken plant and stem radiation leaks.

TEPCO vice-president Sakae Muto said Sunday the Unit 2 containment vessel at the plant was leaky and likely to have been damaged, but added that the spent fuel rods in the cooling pool in Unit 4 were confirmed not to have been damaged, which could have greatly complicated containment efforts.

Officials reported late Saturday that levels of radioactivity had again risen sharply in seawater near the plant, signalling the possibility of new leaks. Workers have been spraying massive amounts of water on the overheated reactors. Some of that water, contaminated with radiation, has leaked into the Pacific Ocean.

Plant officials said they plugged that leak on April 5 and radiation levels in the sea initially dropped. Authorities have insisted the radioactivity will dissipate and poses no immediate threat to sea creatures or people who might eat them. Most experts agree.

Regardless, plant workers on Saturday began dumping sandbags filled with sand and zeolite, a mineral that absorbs radioactive cesium, into the sea to combat the radiation leaks.

TEPCO said it planned to establish a system for recycling water contaminated by the radiation and removing salt from the seawater that has been used as an emergency cooling measure but that was also corroding the reactors.

Clinton reassures Japan

Also Sunday, during a visit to Tokyo, U.S. Secretary of State Hillary Clinton told Japanese Prime Minister Naoto Kan that the U.S. would stand by Japan.

"We are very confident that Japan will recover, and will be a very strong economic and global player for years and decades to come," Clinton said.

Kan thanked Clinton for U.S. help with the crises.

"We will never forget and we will keep in our memory that the U.S. has provided such robust support," said Kan, in comments suggesting the aid has helped soothe friction over an American military base in Okinawa that forced his predecessor, Yukio Hatoyama, to resign last year.

Relief operations mounted by American soldiers after the earthquake and tsunami helped show a new and welcome face for troops the Japanese have hosted, sometimes grudgingly, for decades. Roughly 20,000 U.S. troops were mobilized in Operation Tomodachi, or Friend, the biggest bilateral humanitarian mission the U.S. has conducted in Japan. The U.S. is also helping Japan cope with its nuclear crisis.

Kan has pledged to beef up disaster preparedness and make his top priority resolving the crisis at the Fukushima plant.