TOKYO — Four out of six reactors at the Fukushima Daiichi nuclear plant were damaged beyond repair in Japan’s devastating earthquake and tsunami, the chairman of the Tokyo Electric Power Co. said Wednesday.

Chairman Tsunehisa Katsumata said he is taking over daily operations at Tokyo Electric, which owns the crippled plant, because company President Masataka Shimizu has been hospitalized for an illness brought on by stress.

Shimizu, 66, has been largely silent since the March 11 earthquake and tsunami sent the Daiichi plant on a path toward nuclear disaster. Officials said Wednesday that he was suffering from hypertension and dizziness.

As contamination levels spiked offshore, workers continued to endure soaring radiation levels as they worked to stave off a full-scale nuclear meltdown. Tokyo Electric’s stock prices have plummeted, and Japanese lawmakers debated this week whether to nationalize the utility, which is Asia’s largest electric power company.

Katsumata, appearing before reporters Wednesday for the first time since the earthquake, said the company would prefer to remain privately held.

He expressed his “deep apology” for the “grave accident” at the plant, and for the “anxiety, concern, and inconvenience caused to the society over the spread of radioactive substances to the atmosphere, water, and the impacts on crops and drinking water.”

He said that reactors No. 5 and 6 at the plant can still operate, but “we have no choice but to scrap” reactors 1 through 4.

It is not the first time that Katsumata has dealt with a nuclear emergency as a result of a natural disaster. He was president of Tokyo Electric in 2007, when an earthquake struck a company-run power plant in Niigata prefecture, spilling hundreds of barrels of nuclear waste. In the aftermath, Katsumata had to apologize publicly for underreporting the extent of the damage. He was eventually moved from managing the day-to-day operations of the company into the chairman’s role.

On Wednesday, officials said measurements of radioactive iodine in the sea outside the Daiichi plant had spiked a day earlier, amplifying fears about an uncontrolled leak of highly contaminated water from at least one of the damaged reactors.

Levels of Iodine-131 were 3,355 times the legal safety limit, up from the previous high of 1,850 times the limit that was recorded on Sunday, officials said. The water was sampled about 1,000 feet south of a wastewater outlet.

“Experts are trying to analyze the situation and looking at all possibilities,” said Japan’s chief cabinet secretary, Yukio Edano, in a televised news conference. “We are considering the worst-case scenario. ... If the radiation goes up and it affects health of people in the area, we will advise people immediately.”

Potential solutions for containing the hazardous materials include spraying a synthetic resin on the ground to slow or stop contamination from spreading to the sea, and dropping a cloth cover over the reactors. Hydrogen explosions blew off the roofs of two reactors and damaged a third; at least one reactor’s spent fuel pools are now exposed to the environment.

Hironobu Unesaki, professor of nuclear engineering at Kyoto University, said a cover could be an effective way to control gaseous emissions from the reactors. But he said a cover would likely not have an impact on the water leaking from a pipe or a compression chamber at the base of the reactor, as the company suspects is happening.

Workers made limited progress Wednesday in eliminating radioactive water from the cavernous turbine rooms next to the first three nuclear reactors.

Water in two of the buildings has not yet been drained, because nearby condenser tanks needed to receive the water are already full. It could take several days to empty their contents safely into another tank on-site.

In the room adjacent to the first reactor, workers were able to reduce knee-deep water to a depth of about eight inches. But work stalled because the condenser tank there became full. Government officials on Wednesday raised the possibility of using a tanker or large boat as a repository for the contaminated water.

Water-based radiation in the building outside the second reactor exceeds 1,000 milliseiverts per hour, or 100,000 times the level that would be found if the plant were operating normally.

Correspondent writer Andrew Higgins and special correspondents Tetsuya Kato and Akiko Yamamato contributed to this report. \

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