Takahiro Monma feeds his son at an evacuation center in Yamagata. The Monma… (Carolyn Cole / Los Angeles…)
The nuclear crisis in Japan could last for weeks, the chairman of the U.S. Nuclear Regulatory Commission said Thursday.
Still, officials are not concerned about harmful radiation levels coming to the United States.
The main challenge at Japan's Fukushima Daiichi nuclear power plant is getting more water to cool the stricken nuclear reactors and spent-fuel pool. When no cooling occurs, it is possible for dangerous levels of radiation to be emitted.
Photos: Crisis continues in Japan
"This is something that will likely take some time to work through, possibly weeks, as eventually you remove the majority of the heat from the reactors and the spent-fuel pools. It's something that will be ongoing for some time," said Gregory Jaczko, chairman of the Nuclear Regulatory Commission, which is an independent agency that regulates U.S. commercial nuclear power plants.
The agency has advised that U.S. citizens be evacuated if they are within 50 miles of the Fukushima Daiichi nuclear power complex. That recommendation was broader than the Japanese government's, which told its citizens to evacuate if they were less than 12 miles away from the plant.
Jaczko said there was no radiation threat to the United States.
"The basic physics and basic science really tells us that there can't be any risk or harm to anyone here in the United States, or Hawaii, or any of the other [U.S.] territories," Jaczko told reporters at a press briefing at the White House.
Deputy Energy Secretary Daniel Poneman alluded to the fast-paced series of events at the nuclear power plant. "The facts on the ground are genuinely complex. They are genuinely confusing," Poneman said.
Eleven American nuclear experts are in Japan assisting officials there with the crisis.
Related: CSPAN video of press conference