Ukrainian nuclear plant, controlled by Russian forces, temporarily went off line

A MARTÍNEZ, HOST:

Conditions are deteriorating at a Ukrainian nuclear plant currently under Russian occupation.

RACHEL MARTIN, HOST:

Yeah. On Thursday, the world's atomic watchdog warned that the Zaporizhzhia nuclear plant lost power twice, disconnecting for the first time ever from the power grid entirely. It was all later restored, but it's still very troubling.

MARTÍNEZ: NPR's Geoff Brumfiel has been following all of this. Geoff, what's happening at the plant right now?

GEOFF BRUMFIEL, BYLINE: Well, honestly, there is still a lot we don't know. But what we're told by the International Atomic Energy Agency is that the plant lost power, as you said. It was enough to trigger emergency systems at two operating nuclear reactors there. Now, a power line has since been reconnected to the plant.

MARTÍNEZ: So what caused the power to go out?

BRUMFIEL: Satellite imagery has shown wildfires burning very close to the plant and its power lines in recent days. It seems reasonable to assume they may have played a role. Russian state media says those fires were started by Ukrainian shelling. Ukraine blames the Russians. But of course, there's no way to know for sure.

MARTÍNEZ: But help me understand why a nuclear power plant needs power from the outside.

BRUMFIEL: The plant produces power, of course, but it also takes power from the grid, just like any other industrial facility would. And that power runs safety systems. It runs radiation monitors. And maybe most importantly, it runs cooling for the reactor cores. And that cooling in this case is the really big thing because even after a nuclear reactor shuts down its core, the nuclear fuel remains physically really hot, and cooling water is required to prevent it from melting down. In a speech last night, Ukrainian President Zelenskyy said emergency diesel generators actually had to be turned on to keep that cooling water running. And that's really one of the very last line of defense.

MARTÍNEZ: Now, on a scale of 1 to 10, Geoff, I mean, how worried should we be?

BRUMFIEL: Well, I asked Ed Lyman this very question - he's a nuclear expert at the Union of Concerned Scientists - and he told me he's up into the sort of seven to eight range at this point.

MARTÍNEZ: OK.

BRUMFIEL: I mean, it's not great. The danger here is that the site loses power again, the backup systems don't work right, and one or more of the reactors goes into meltdown. This would probably look a lot more like the 2011 Fukushima nuclear accident, and we could see radiation spreading from Ukraine to parts of Europe, Russia, maybe even Turkey. It would depend on the weather. It's a scenario, I think it's safe to say, nobody really wants to see.

MARTÍNEZ: OK. Considering the worry level is around seven to eight, can anything be done to prevent this?

BRUMFIEL: Well, ideally, there'd be some kind of demilitarized zone around the plant, but the Russians aren't willing to give up control. In fact, they've appeared to move some of their vehicles and troops even closer to the reactors in recent weeks. And short of that, the IAEA wants to send international monitors to the plant. Ukrainian officials want that visit to happen as early as next week.

MARTÍNEZ: All right. That's NPR's Geoff Brumfiel. Thanks a lot.

BRUMFIEL: Thanks. Transcript provided by NPR, Copyright NPR.