A reactor vessel may be damaged, raising the possibility that radiation from uranium-plutonium mix may be released.
TOKYO - Japan's effort to contain the crisis at the Fukushima Daiichi nuclear plant suffered a setback, an official said on Friday, citing evidence that the reactor vessel of the No. 3 unit had been damaged.
The development, described by Hidehiko Nishiyama, deputy director-general of the Japan Nuclear and Industrial Safety Agency, raises the possibility that radiation from the MOX fuel in the reactor -- a combination of uranium and plutonium -- could be released.
Nishiyama said the authorities believe that a breach might have occurred in the vessel, which houses the nuclear fuel. One sign of that took place on Thursday as three workers, who were trying to connect an electrical cable to an injection pump, were injured when they stepped into water that was found to be 10,000 times more radioactive than normal in a reactor.
The No. 3 unit, the only one of the six reactors at the site that uses the MOX fuel, was damaged by a hydrogen explosion on March 14. Workers have been seeking to keep it cool by it with spraying seawater, while the containment effort has focused on trying to restart the reactor cooling system.
The Japanese government also said Friday that it will help people who wish to leave the area around the crippled Fukushima Daiichi Nuclear Power Plant, a sign that efforts to reassure frightened residents have failed to convince people to stay.
The developments came a day after shops across Tokyo began rationing goods -- milk, toilet paper, rice and water -- as a run on bottled water coupled with delivery disruptions left shelves bare. The unusual sights of scarcity in one of the world's richest, most modern capitals came a day after city officials reported that radioactive iodine in the water supply for Tokyo and five neighboring prefectures measured more than twice the level considered safe for babies.
Tests showed the levels in the city's water fell to acceptable limits for infants, but they continued to be up in the neighboring prefectures of Chiba and Saitama and a city in a third prefecture. The government there warned families in 11 cities in Chiba not to give infants tap water. "The high level of iodine was due to the nuclear disaster," said water safety official Kyoji Narita. "There is no question about it."
The problem is not likely to end soon; nuclear workers will have to keep venting radioactive gases from the damaged reactors, adding to the plume of emissions carried by winds and dispersed by rain. Radiation has been found in raw milk, seawater and 11 kinds of vegetables, including broccoli, cauliflower and turnips, grown in areas around the plant.
Yukio Edano, the chief cabinet secretary, said the three injured workers had sustained radiation burns to their legs while dragging an electrical cable through contaminated water in an effort to restore a crucial pump at reactor No. 3 in the crippled Fukushima Daiichi Nuclear Power Station. The workers were burned as contaminated water poured over the tops of their low boots, soaking their feet and ankles, Asahi Shimbun newspaper reported.
Linda Gunter, a spokeswoman for Tokyo Electric Power, said Friday that two workers would remain hospitalized and under observation. The third man had been wearing higher boots and had not gotten his legs wet; he will take a rest day and return to work, she said.
The company said workers had managed to restore lighting in the central control room of reactor No. 1, a key step toward restarting its cooling system.
The Associated Press contributed to this report.