Though reports of a fire at Ukraine's Zaporizhzhia nuclear power plant are alarming, there's still a lot we don't know, nuclear weapons expert Jeffrey Lewis said Friday.
So far, radiation monitoring conditions — which were updated just a few minutes ago — look "normal," according to Lewis, director of the East Asia Nonproliferation Program at the James Martin Center for Nonproliferation Studies.
There are radiation detectors "all over the place," that would be able to pick up on any spikes in radiation, he said. "Reactors are big, sealed and concrete structures. They should not catch on fire. We don’t know what caused the fire."
Biggest fear: If a potential fire breaches the containment structure of the reactor, that's when it could get dangerous, Lewis said.
But there should be workers at the site 24/7, who could stop the reactor before the fire reached it, he added.
"The biggest fear would be if the containment zone would be damaged, let’s say, by a missile," he said.
James Acton, co-director of the Nuclear Policy Program at the Carnegie Endowment for International Peace, said the biggest concern was if the fire disrupted the reactors' cooling systems. If they can't cool themselves, the fuel inside could overheat and melt down.
"I’m sure the reactor has been shut off, but the fuel inside is still radioactive and still requires cooling. You have to keep the reactor cool for as long as the fuel is in. The reactor has to be kept continuously cool," he said.
If the cooling stopped, a meltdown could range from taking place in a few hours or days, depending on how radioactive the reactor is.