The Zaporizhzhia Nuclear Power Plant in southern Ukraine briefly moved to emergency generators on Thursday after Russian shelling cut its external power supply, prompting the top director of the United Nations’ nuclear watchdog to disparage the international community for failing to secure the complex.
The nuclear plant, which is the largest in Europe, and the only one to ever be in the middle of active fighting, has now been forced to resort to its emergency diesel generators six times since Russia launched its full-scale invasion of Ukraine a year ago, according to the U.N.’s top nuclear official, Rafael Mariano Grossi.
“Each time, we are rolling a dice,” Mr. Grossi said on Thursday, “and if we allow this to continue time after time, then one day our luck will run out.”
“I am astonished by the complacency,” added Mr. Grossi, the director general of the International Atomic Energy Agency.
Later in the day, Ukraine’s national electric utility, Ukrenergo, said that the plant had been reconnected to the power grid after 11 hours.
The State of the War
The European Atomic Energy Community — whose membership is composed of E.U. nations but which lies outside the authority of the European Parliament — and 49 countries made a joint appeal to the I.A.E.A., saying that Russia should leave the Zaporizhzhia nuclear plant, according to the Ukrainian prime minister, Denys Shmyhal. “Nuclear terrorism and Russian blackmail must be stopped,” Mr. Shmyhal said on Twitter as he saluted the appeal.
The dangers of being at the center of a war zone, including repeatedly moving to emergency power, pose a serious risk of nuclear catastrophe, experts say. Here’s a closer look at why.
‘Offline’ nuclear plants still need power.
Even through all of the reactors at the Zaporizhzhia plant have been shut down, the equipment that cools their nuclear cores and spent fuel rods needs a constant source of power. If the cooling is interrupted, the heat from the nuclear material could melt through its containment, spewing radiation.
The site is running out of diesel fuel.
It’s important that a nuclear plant remains connected to an external power source, either the power grid or a backup.
The Zaporizhzhia plant’s emergency generators are powered by diesel fuel, but there is only so much on site. When the generators were activated after the shelling on Thursday, there was enough fuel to keep the generators going for 15 days, according to a statement from the I.A.E.A. And the plant is near a very active front line.
“The concern is that it’s difficult to get diesel to that part of the battlefield to refill the generators to make sure the power stays on,” said Amy J. Nelson, the Rubenstein Fellow in the foreign policy program at the Brookings Institution and a nuclear security expert.
During the previous periods when the plant was disconnected from external power, engineers raced to make repairs before the diesel fuel ran out. International nuclear inspectors have called the situation unsustainable and precarious.
The war presents other meltdown risks.
Although the plant was designed to account for risks from natural disasters, plane crashes and the like, no nuclear facility has ever before been at the center of active fighting.
Experts have a multitude of concerns. “It’s fire,” Ms. Nelson said. “It’s explosions from pressure building up.”
She noted that fuel rods could become corroded and cause a nuclear accident.
Any of these issues could disrupt power. Nuclear reactions produce heat that is channeled into steam to produce electricity, and any disturbance to the cooling process could cause a meltdown. Ms. Nelson referred to the events in Japan, in 2011, when an earthquake set off a tsunami that damaged the Fukushima nuclear complex, causing meltdowns.
“The temperature in the reactor increased so much that the corrosion was accelerated and caused a leakage of fuel,” she said.
If a power transformer is hit by shelling, that raises the risk of a fire. And cooling failures short of a meltdown could create pressure that might lead to an explosion.
