CNN Wire Staff
Tokyo (CNN) - Efforts to cool one of the reactors at a quake-damaged Japanese nuclear power plant have been "somewhat effective" since authorities turned helicopters, fire trucks and police water cannon on the facility, its owner said early Friday.
Japanese military helicopters dumped tons of water on the No. 3 reactor housing, including its spent fuel pool, at the Fukushima Daiichi plant until after midnight Thursday, the Tokyo Electric Power Company reported. Earlier, fire and police trucks turned their hoses on the No. 3 reactor housing for more than an hour, TEPCO reported, and the subsequent steam and lowered radioactivity levels indicated progress.
Experts believe that boiling steam rising from that pool, which contains at least partially exposed fuel rods, may be releasing radiation into the atmosphere.
In Vienna, Austria, a senior official of the International Atomic Energy Agency told reporters the situation remains serious, but there had been "no significant worsening" Thursday.
The damage to the nuclear reactors at Fukushima Daiichi has raised the specter of a multiple nuclear meltdown - the nightmare scenario more common in movies than in reality in which fuel rods cannot be cooled and the reactor's core melts. In the worst-case scenario, the fuel can spill out of the damaged containment unit and spread radioactivity and cancer-causing isotopes through the air and water.
Radiation levels at the plant dipped Thursday evening, but remained high after spiking Thursday morning to nearly 3.8 millisieverts per hour - more than a typical resident of a developed country receives in a year. But Japan's Nuclear and Industrial Safety Agency said 17 of 18 workers checked Thursday morning tested normal, and the one who received a higher dose of radiation required no medical treatment.
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