The battle over a Ukrainian nuclear plant is over. The danger remains.

Russian troops took control of Ukraine’s Zaporizhzhia nuclear power complex last week after a battle that caused a fire but did not lead to a meltdown or any apparent leaks. But the situation is still dangerous.

The complex is the largest nuclear power plant in Europe, featuring six reactors installed between 1984 and 1995. In peaceful times, it provides about half of all Ukraine’s nuclear power, and about 20 percent of all its electricity from any source.

What happened?

By Friday, Russian forces had taken control of the power plant — a move that suggested the attack on the city had been carried out with the aim of capturing the facility.

What is the primary concern? Are we entering Chernobyl or Fukushima territory?

Almost certainly not. The design of the Zaporizhzhia reactors is fundamentally different from those at Chernobyl, and is considered much safer and easier to control. Furthermore, the reactors are nestled inside thick containment structures that are capable of withstanding significant shocks. At Fukushima, the meltdowns occurred because a tsunami disabled the backup diesel generators after the reactors themselves automatically shut down.

The fighting at Zaporizhzhia has reportedly stopped. Only one of the reactors is currently operating, at 60 percent capacity. Things would have to get substantially worse to produce a scenario where the reactors themselves are at risk: Further fighting would have to blow holes in the containment structures, several different backup systems would have to be damaged or destroyed, and external sources of power would have to fail.

Are there other risks beyond reactor meltdowns?

Is the danger over?

No. But the more time passes since the initial incident, the smaller the major risks get. Woods said that properly cooled reactors rapidly lose their leftover heat after shutdown, meaning even with some later catastrophe the risk of meltdowns drops. And of course, if the actual shelling and shooting have stopped, the risk of acute emergencies falls dramatically.

Who’s running the plant now?

“Are competent people in charge?” Woods asked. “Because if they’re in charge, everything’s going to be OK.”

Has there been any radiation leak at the plant?

Is this a sign that Russia is going after Ukraine’s power grid? What is Russia’s end game?

Whether the Russian capture of the ZNPP reflects a broader military strategy of controlling the nation’s nuclear power plants — and ultimately its power grid — remains unclear.

Wolfsthal pointed to one reason that Russia might want to control Ukraine’s nuclear plants. “Perhaps in Putin’s mind, he needed to seize Ukraine’s nuclear assets to back up his narrative that Ukraine was pursuing nuclear weapons,” he wrote. (IAEA inspections have shown no such nuclear weapons program existed in Ukraine).

Are electricity grids typical targets in war?

“It is not unprecedented that energy infrastructure has been attacked. In fact, from 2014-2018 there were ten attacks by pro-Russian separatists and others on energy infrastructure in Ukraine alone,” Anu Narayanan and Jonathan Welburn, experts at RAND corporation wrote in an email to Grid.

By taking over Zaporizhzhia, Russia now has control of one-fifth of Ukraine’s electricity generation. Before the invasion, Ukraine was preparing to connect its grid to neighboring European nations by 2023. For now, though, the grid is isolated, meaning Ukraine cannot easily access new power sources.

However, so far it appears Russia has opted for conventional weapons instead of hackers to exert control over Ukraine’s power system.

Are other power plants in Ukraine at risk?

Ukraine has three other nuclear power plants that are currently operational, which are concentrated in the western half of the country. It remains to be seen if Russia will try to target these facilities as well.