Every nuclear reactor is a balancing act, where fuel rods are carefully kept just close enough together to generate the heat needed to generate electricity, while being continually monitored to prevent overheating, which would melt the fuel. This requires continuous cooling and a highly trained staff. The reactors themselves are covered with a steel shell and a heavy layer of concrete, expressly designed to withstand projectiles and plane crashes, and meant to contain the heat of the fuel melting down in a disaster. The Chornobyl reactors lacked this level of protection, which led to the open-air release of radioactive material.
Ukraine has four operational nuclear facilities, including Zaporizhzhia, according to the IAEA’s Power Reactor Information System database. According to Joshua Pollack of the Middlebury Institute of International Studies at Monterey, there are at least two worrying scenarios that concern experts about nuclear power plants becoming engulfed in war zones:
• While reactors are very tough, their pools, containing used-but-still-hot fuel rods, aren’t. If a cooling pond is damaged and stops working, the water eventually boils off, and these fuel rods will catch on fire, spewing radioactive particles skyward. This was a major concern in the Fukushima disaster.
• If a reactor shuts down, loses access to outside power, and then loses its backup power, the coolant inside the reactor itself stops flowing. Shortly afterwards, the fuel catches on fire inside the reactor and releases hydrogen gas. “As we learned in Fukushima, this is quite dangerous,” Pollack said. In that disaster, hydrogen explosions blew the roofs off reactor buildings. That led to radioactive gas releases and massive evacuations.
There appear to be at least three explanations for Russian forces attacking Zaporizhzhia at this moment in its week-old invasion of Ukraine, said Melissa Hanham, an open-source intelligence specialist affiliated with the Center for International Security and Cooperation at Stanford University. The first is simply in the fog of war, the Russian invasion force is taking over every facility in its path, which led to the firefight at the plant. The second is a deliberate bid to control a high-risk site, similar to the takeover of Chornobyl at the outset of the invasion. The IAEA has complained about staff at Chornobyl not having relief in monitoring operations there. A third explanation suggested by Ukrainian officials is that Russia intends to control and cut off electricity to the country as part of its invasion plan.
“If it is under Russian control, you would ask for some confidence-building by allowing the IAEA to have access and regular communication with whoever is running it, presumably Ukrainian staff,” Hanham said.