SHIZUOKA, Japan | Emergency crews Thursday turned to firetrucks, water cannons and helicopters dropping enormous loads of water, as they raced to cool dangerously overheated fuel rods and restore power to a smoldering nuclear power plant.
By nightfall, they were still unsure if they had succeeded in preventing a nuclear catastrophe that could spread more radiation from the stricken Fukushima plant in northeast Japan.
“We are doing all we can, as we pray for the situation to improve,” said Teruaki Kobayashi, an official at Tokyo Electric Power Co. (Tepco), which owns the Dai-ichi plant in Fukushima.
Tepco said it believed workers were making headway with efforts to complete an emergency power line to restart the plant’s own electric cooling systems, but the utility is not sure the cooling systems will still function. If they don’t, electricity won’t help.
A raging tsunami triggered by the 9.0 magnitude earthquake last week knocked out power at the plant. Without cooling systems, nuclear fuel rods overheated, explosions rocked several of the reactor units and radioactive gas escaped into the atmosphere.
Many Japanese have accused Tepco of withholding information about the extent of the damage to four of the nuclear reactors at the plant, about 150 miles northeast of Tokyo. But workers risking their lives to save their fellow citizens are growing tired of the criticism.
One worker turned to the Internet to appeal for understanding.
“Please stop attacking us,” Michiko Otsuki wrote on a blog on the popular Japanese social networking site Mixi.
Ms. Otsuki and her co-workers stayed at their job sites after the twin disasters created the nuclear power crisis.
“We carried on working to restore the reactors from where we were, right by the sea, with the realization that this could be certain death,” she said.
“The machine that cools the reactor is just by the ocean, and it was wrecked by the tsunami. Everyone worked desperately to try to restore it. Fighting fatigue and empty stomachs, we dragged ourselves back to work.”
To save their fellow citizens, Tepco workers are risking exposure to high levels of radiation that could cause cancer, she said.
“Everyone at the power plant is battling on, without running away. There are people working to protect all of you, even in exchange for their own lives,” Ms. Otsuki wrote.
“People have been blaming Tepco. But the staff of Tepco has refused to flee, and [we] continue to work even at the peril of their own lives. Please stop attacking us,” she said.
Japanese officials said they probably would continue dousing the reactor units with massive amounts of water for another day.
On Thursday, a Japanese military CH-47 Chinook helicopter dumped loads of 2,000 gallons of water on each pass over Unit 3, where nuclear fuel rods were exposed. They blasted the unit with another 9,000 gallons of water from high-pressured pumps on the firetrucks. Trucks with water cannons could not get close enough to the site because of high radiation levels.
U.S. and Japanese officials disagreed over conditions at the plant.
In Washington, the State Department urged Americans to leave Japan and offered voluntary evacuations to relatives of U.S. personnel in Tokyo, Yokohama and Nagoya.
President Obama visited the Japanese Embassy to sign a condolence book and reiterate the U.S. commitment to the Japanese people.
Gregory Kaczko, chairman of the Nuclear Regulatory Commission, warned Congress at a hearing Wednesday that he believes the Japanese government was downplaying the risks from the plant.
“We believe radiation levels are extremely high,” he said.
However, an official at the headquarters of the U.N. nuclear agency Thursday was more hopeful.
“It hasn’t gotten worse, which is positive. But it is still possible that it could get worse,” Graham Andrew of the International Atomic Energy Agency told reporters in Vienna, Austria. “We could say it’s reasonably stable at the moment, compared to yesterday.”
Also on Thursday, finance officials from the Group of Seven major industrialized countries agreed on a coordinated effort to weaken the Japanese yen, which has surged to record levels since the disaster.
A superstrong yen could cripple Japanese exports, further worsening the economic impact of the disaster that killed thousands and triggered an unfolding nuclear crisis.
The coordinated intervention in international currency markets would be the first by the G-7 countries since the fall of 2000, when the G-7 intervened in an effort to bolster the euro.
In a joint statement issued after emergency discussions, the G-7 officials said that the United States, Britain, Canada and the European Central Bank will join with Japan in a “concerted intervention” in currency markets Friday.
“We express our solidarity with the Japanese people in these difficult times, our readiness to provided needed cooperation and our confidence in the resilience of the Japanese economy and financial sector,” the G-7 finance officials said in their joint statement.
• This article is based in part on wire service reports.