The situation at the captured Zaporizhzhia nuclear plant in Ukraine just got way more dangerous

The looming nightmare of a nuclear plant disaster in a war zone moved closer to reality on Thursday, with the temporary cutoff of a last external cooling power line to the reactors at Ukraine’s largest power plant.

The plant — which Russian forces captured in March — lost its connection to Ukraine’s power grid at least twice on Thursday, the International Atomic Energy Agency (IAEA) said in a statement.

“Almost every day there is a new incident at or near the Zaporizhzhia Nuclear Power Plant. We can’t afford to lose any more time,” said IAEA Director General Rafael Mariano Grossi. A bipartisan group of former U.S. nuclear safety officials on Thursday also sent a letter to the White House asking for President Joe Biden to throw his weight behind a demand for an IAEA inspection of the plant, the Wall Street Journal reported.

Fears over a slow-motion nuclear disaster unfolding at the Zaporizhzhia plant have only grown in recent weeks amid regular reports of shelling of the site. Fires broke out Thursday in the ash pits of a nearby coal plant, according to Ukraine’s energy agency. Russia captured the nuclear plant after a dangerous firefight on March 3 seen worldwide on security cameras.

With two of its six reactors still operating, run by Ukrainian technicians under extreme duress including reported killings and disappearances, the plant has lost three of its four external power lines as well as taken damage to lab and chemistry facilities. The fourth line was the one reported lost and then reconnected on Thursday, an occurrence that led to the plant being cut off from Ukraine’s power grid, which the plant had been supplying with electricity throughout the war.

“Basically it’s not possible for us to fully perform our duties,” a Ukrainian worker at the plant told Grid, speaking on the condition of anonymity. Russian soldiers have moved into workshops, cafeterias and other facilities at the plant, the worker said. Plant staff and Ukrainian soldiers were tortured after the seizure of the plant, they said, some having their ears cut off. The remaining staff were searched and treated as prisoners, with communication handled through the plant’s management, also unable to work at full capacity and under control of personnel from Rosatom, the Russian atomic energy agency.

Nuclear power plants rely on external power lines to run their cooling systems, making initial reports of the fourth line loss alarming. The plant does have backup on-site generators, but those depend on diesel fuel to keep running. The loss of external power and backup generators led to the 2011 Fukushima Daiichi nuclear disaster in Japan, where observers fear a wartime version of that scenario — lost external power, then backup generators running out of fuel and finally a loss of reactor cooling that leads to calamity — could happen at Zaporizhzhia. More than 100,000 people were evacuated from a 19-mile-wide zone in the 2011 disaster. The diesel generators could run for five days if needed, according to the plant worker, but only if the Russians let them operate.

“The situation is fragile. And not knowing the actual situation at the plant, I can’t have any confidence in the reliability or the duration of the backup power supplies,” said Ed Lyman, director of nuclear power safety with the Union of Concerned Scientists. “But a disaster won’t be inevitable unless there is a complete loss of power to an operating reactor for a number of hours, and we aren’t there yet.”

Although Russia and Ukraine have both agreed to allow IAEA inspectors to visit the plant to assess its safety, negotiations are reportedly stuck on how the inspectors will arrive at the plant with Russia wanting them to come through the occupied Crimean Peninsula, which Ukraine rejects. Grossi said in his statement he hoped to send inspectors to the site within days.

“The Russians are clearly playing chicken with the international community on this,” said Miles Pomper, a senior fellow at the James Martin Center for Nonproliferation Studies of the Monterey Institute of International Studies. Russia could defuse the danger at Zaporizhzhia by acceding to a United Nations suggestion of a demilitarized zone around the plant and by doing a controlled shutdown of the working reactors allowing them to cool over days and weeks. Though the latter would add to Ukraine’s misery by causing electricity shortages, he added, “it would at least avoid a nuclear accident.”

Russia may have the end goal of disconnecting the plant from Ukraine’s power grid and connecting it to the one in occupied Crimea, said Pomper: “This may be what the Russians are really after.”

While the Rosatom personnel are aware of radiation dangers at the plant, the Russian military personnel there are not and regularly violate safety rules, according to the worker there.

“The Rosatom people are here mainly for the optics. They are unable to stop or reason with the military, for example, to tell them not to enter the premises, where they come in and search for weapons,” they said. “Those Russians have sometimes entered areas where one should not stay for more than 10 minutes and stayed there five times longer.”

In a shutdown, nuclear reactors do not immediately cool off, and they still need active maintenance to safely halt operation and store their fuel. A shutdown of Zaporizhzhia’s reactors would increase the immediate time window for interventions if cooling power is lost at the plant, from days to eventually a week or more, added Lyman. “But that assumes that there is no damage to the plant itself.”

Kseniia Lisnycha contributed reporting. Thanks to Lillian Barkley for copy editing this article.