Russia Moves to Cut Off Ukraine’s 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.