Russia Moves to Cut Off Ukraines Nuclear Power Plants

Russia hit critical electricity transmission facilities linked to nuclear power plants during its latest assault on Ukraine’s power grid on Thursday, the International Atomic Energy Agency reported. It was the third such attack in roughly as many months, heightening concerns among experts about the potential for a nuclear disaster.

The agency said that the Russian strikes had hit electrical substations crucial for Ukraine’s three operational nuclear plants to transmit and receive power. While no direct damage to reactors was reported, all of them reduced output as a precautionary measure and one was disconnected from the grid.

“Ukraine’s energy infrastructure is extremely fragile and vulnerable, putting nuclear safety at great risk,” Rafael Mariano Grossi, the head of the agency, the I.A.E.A., said in a statement released late Thursday.

Russia has targeted Ukraine’s energy infrastructure since the war’s first winter two years ago, in an effort to collapse its grid and make life miserable for its citizens. The attacks, frequent since the spring, have put added strain on the country, which is already facing a dire situation on the battlefield as its troops slowly but steadily cede ground to Russia.

In a sign of the difficulties, President Volodymyr Zelensky announced on Friday that he was replacing the commander of Ukraine’s ground forces, appointing Maj. Gen. Mykhailo Drapaty to succeed Lt. Gen. Oleksandr Pavliuk. General Pavliuk had been in the role since February, a period during which Ukraine lost hundreds of square miles of territory.

“The Ukrainian army needs internal changes to achieve our state’s goals in full,” Mr. Zelensky said in a statement, highlighting the need to increase the army’s combat capability and improve training.

Mr. Zelensky said Major General Drapaty had led the defense of Ukraine’s eastern Kharkiv region during a Russian spring offensive there, which didn’t yield major gains.

For a long time, Russia’s attack on the power grid focused on thermal and hydroelectric plants along with their transmission facilities, causing widespread blackouts across the country. Still, Ukraine’s grid did not collapse, mainly because much of its power generation relies on nuclear plants, which had been largely spared from air assaults.

Russia’s strategy of destroying substations connected to nuclear power plants is newer and appears intended to collapse Ukraine’s last major power generation capacity, experts say. The attacks against the substations began in late August, the I.A.E.A. reported.

The substations are essential because they distribute power from the reactors to the rest of the country. Ukraine’s three operational nuclear plants, a total of nine reactors, provide about two-thirds of the country’s power generation capacity today, according Shaun Burnie, a nuclear expert at Greenpeace Ukraine.

Two plants are in western Ukraine, in the Rivne and Khmelnytskyi regions, while another is farther south. A fourth nuclear plant, near the southern city of Zaporizhzhia, was captured by the Russian forces at the beginning of the war.

The substations also have a second, no less critical function: They deliver electricity to the nuclear plants that is needed to cool the reactors and spent fuel. “Loss of cooling function at one or more reactors would inevitably lead to nuclear fuel melt and large-scale radiological release,” Greenpeace warned in a note shared with The New York Times.

United Nations experts issued a similar warning in a statement released on Monday. They said that “further damage to Ukraine’s electricity system could lead to an electricity blackout which would increase the risk of operating nuclear reactors losing access to the grid for powering their safety systems.” Such an event, the statement said, could lead to a serious nuclear disaster.

The Ukrainian authorities have tried to highlight the new threat in recent months. President Volodymyr Zelensky told the United Nations General Assembly in September that Russia was planning potential catastrophic attacks on Ukraine’s “nuclear power plants and the infrastructure, aiming to disconnect the plants from the power grid.”

In response, the Ukrainian government agreed with the I.A.E.A. in September to deploy monitoring missions to substations linked to nuclear plants, to assess the damage and try to prevent further attacks. The agency visited seven substations this fall, documenting “extensive damage” and concluding that the grid’s ability “to provide a reliable off-site power supply” to nuclear plants had been “significantly reduced.”

The Ukrainian authorities would like the nuclear agency to deploy personnel frequently, or even permanently, to inspect the substations, hoping their presence might deter further Russian attacks. Greenpeace said in its note that “the Russian government needs the active support of the I.A.E.A. to support its global nuclear power ambitions and therefore cannot risk the safety of I.A.E.A. personnel in their ongoing efforts to destroy Ukraine’s electricity system.”

But so far, as highlighted by the U.N. experts, the agency has conducted only one monitoring mission, with no additional visits announced.

On Friday, Ukraine continued grappling with the aftermath of Russia’s large attack on its grid the day before. Ukrenergo, the national electricity operator, has introduced intermittent shutdowns nationwide to reduce strain on the system. Some areas, like the southern regions of Kherson and Mykolaiv, have also been mostly cut off from power because of the attacks, local officials said.

The Ukrainian authorities reported that Russia used cluster munitions — weapons that break apart in midair, scattering smaller bomblets over a wide area — to attack the grid. These munitions sometimes fail to detonate immediately, posing a lingering threat and hindering the work of workers sent to repair damaged facilities, who have to wait until the area is cleared of unexploded ordnance. Ukraine has also used cluster munitions in the war.

“The use of these cluster elements significantly complicates the work of our rescuers and power engineers in mitigating the damage, marking yet another vile escalation in Russia’s terrorist tactics,” Mr. Zelensky said on Thursday.

Despite the risks, some energy workers stay on site at the power plants during attacks to operate critical equipment. Oleksandr, the head of production management at a thermal power plant run by DTEK, Ukraine’s biggest private energy company, said he was at work during a recent attack.

“There were two of us working at the station’s central control point,” said Oleksandr, whose surname could not be disclosed for security reasons. “I managed to shout ‘Get down!’ to my colleague and instantly everything went dark: Dust rose, plaster flew. The explosion occurred in the turbine area 150 meters away just as we were falling to the floor.”

Yurii Shyvala contributed reporting.