ZAPORIZHZHIA, Ukraine — The gravest risk to the embattled Zaporizhzhia Nuclear Power Plant is physical damage to equipment from shelling that could lead to a release of radiation, the director of the United Nations’ nuclear watchdog agency said Friday after a visit to the site.
Other risks abound, Rafael Mariano Grossi, the director general of the International Atomic Energy Agency, told reporters in Vienna, a day after inspecting the nuclear station in southern Ukraine. The plant has been repeatedly hit by artillery. Loss of external power to cool reactor cores and stress on the operating staff also pose dangers, he said.
“It is obvious there is a lot of fighting in general in this part of Ukraine,” Mr. Grossi said. “The military activity and operations are increasing in that part of the country, and this worries me a lot.”
Mr. Grossi said two United Nations experts would remain at the plant to provide independent assessments of its safety going forward.
Most of the damage from the war at the sprawling station, which is the largest nuclear plant in Europe, occurred during shelling in August, Mr. Grossi said, unless one considers the destruction from the battle in March when the Russian army captured the site.
The Zaporizhzhia plant, nestled in a gentle valley of farm fields in a once sleepy and provincial corner of Ukraine that is now a site of raging battles along a front line, became this year the first active nuclear plant to be caught in a combat zone in the history of civilian nuclear power.
Over all, not one of what the nuclear monitoring agency calls the seven pillars of nuclear safety, which include physical integrity, reliable external power and availability of spare parts, remains intact, Mr. Grossi said. The plant has six reactors and before the war provided 30 percent of Ukraine’s electricity.
But on some points the agency’s initial assessment was more optimistic than the picture painted by Ukrainian officials, who had said that engineers and other employees had been subjected to harsh interrogation and even torture, raising stress levels when they returned to work in reactor control rooms and in other critical jobs.
Mr. Grossi said he had spoken with the Ukrainian employees and that they had found a way to cooperate — what he called “cohabitation” — with the Russian soldiers and nuclear experts also at the site. “The plant continues to operate, and there is a professional modus vivendi, if I can put it that way,” he said.
Before the visit, Ukrainian officials had said the agency should discount anything employees at the plant said, arguing they are essentially hostages.
Mr. Grossi said the Ukrainian and Russian nuclear engineers had managed to “cope” in operating the site and that he was less worried about disruptions in regulatory oversight and supplies of spare parts, those these problems also loomed as risks. He spoke after he and a team of inspectors crossed a front line in Russia’s war in Ukraine to conduct an inspection. Their mission was delayed by artillery strikes on their planned route, part of a swirl of chaotic violence in and around the station.
Mr. Grossi said his assessment was bound to disappoint both sides for declining to place blame on one or another army for the shells hitting the plant.
“I don’t want to pretend what we are doing will end this terrible war or give back this plant to Ukraine,” he said. The mission was limited to gauging nuclear safety, something he said the two-man team remaining at the site would do.
“Now, when there is an allegation that something has happened at the plant, you can turn to us,” he said, rather than weighing the conflicting claims of Russia and Ukraine. “That’s the difference.” He said Russian soldiers had not blocked access to areas of the site he asked to visit.
Asked to compare the potential fallout from a radiation release at Zaporizhzhia with the fire and meltdown at the Chernobyl nuclear plant in 1986, which spread radiation around Europe in the world’s worst civilian nuclear accident, Mr. Grossi said designs of the two power stations are not comparable. Zaporizhzhia’s reactors have containment vessels to limit radiation release. But he said disruptions in external power to cool reactor cores could lead to a meltdown.
“It could be a big thing or a small thing, depending on the damage” from the fighting, he said.