Credit…David Guttenfelder for The New York Times

ZAPORIZHZHIA, Ukraine – Artillery fire resumed on Sunday from the direction of a nuclear power plant in southern Ukraine, with shells raining down on a town from which the Ukrainian army did not able to retaliate, for fear of causing a meltdown or releasing radiation to the plant.

Hours before the dams, there were reports that conditions were deteriorating inside and near the Zaporizhzhia nuclear power plant. The flight of civilians from the area accelerated on Saturday.

The plant is the first active nuclear power plant in a combat zone. Both the United States and the European Union have called for the formation of a demilitarized zone, as fighting in and around the plant and its active reactors and stored nuclear waste has been of particular concern.

Ukrainian President Volodymyr Zelensky said in his late-night address on Saturday that Russia used ‘nuclear blackmail’ at the plant, reiterating a Ukrainian analysis that Moscow was using it to slow down a Ukrainian counteroffensive against the city. of Kherson, occupied by Russia, where Russian conventional military defenses seem increasingly wobbly.

Contrary to the fears of some analysts when Moscow launched its invasion in February, the most pressing nuclear threat in the war in Ukraine now appears to be Russia damaging the civilian power plant, rather than deploying its own nuclear weapons. Russia says Ukrainian forces are bombing the plant.

Engineers say the meter-thick reinforced concrete containment structures protect the reactors from even direct hits. However, the international community became concerned that the bombardment could start a fire or cause other damage that would lead to a nuclear accident.

The complex’s six pressurized water reactors retain most radiation sources, reducing the risk. After the pressurized water reactors at Japan’s Fukushima nuclear power plant failed in 2011, Ukraine upgraded the Zaporizhzhia site to allow shutdown even after the loss of cooling water from outside the containment structures , Dmytro Gortenko, a former power plant engineer, said in an interview.

Ukraine’s military intelligence agency said on Saturday Russian artillery fire hit a pump, damaged a fire station and caused fires near the factory that could not be immediately extinguished due to the damage caused at the fire station.

In fields near the Russian-held town of Enerhodar, near the factory, long lines of cars carrying fleeing civilians formed on Saturday, according to social media posts and another former ISIS engineer. factory who stayed in touch with local residents.

“People are abandoning the city,” said the former engineer, who asked to be identified only by his first name, Oleksiy, for security reasons. Residents had been leaving for weeks, but the pace picked up after Saturday’s blockades and fires, he said.

Since Russia captured the plant in March, its military has controlled the facility, while Ukrainian engineers have continued to operate it.

Ukrainian employees are not fleeing but sending their families away, said Oleksiy, who left in June. Enerhodar was built for factory employees in Soviet times and had a population of around 50,000 before the war.

Ukraine has accused Russia of staging artillery attacks targeting Ukrainian towns across the Dnipro River from the factory from July as the Ukrainian counteroffensive in the south intensified. .

On Sunday morning Russian howitzers fired at the Ukrainian town of Nikopol, which sits across from a reservoir of the power plant, Yevheny Yetushenko, the Ukrainian military governor of the town, said in a post on Telegram.

The Ukrainian military said it had few options to retaliate. In July, he used a self-destructing drone to hit a Russian artillery launcher that was about 150 meters from one of the plant’s reactors.