(Bloomberg) — Ukraine powered down most of the remaining operational nuclear reactors under its control following a massive Russian missile and drone attack overnight.

Most read on Bloomberg

International Atomic Energy Agency staff stationed at Ukraine’s power plants said only two of the nine reactors were producing electricity at full capacity on Sunday. Production was reduced to between 40 and 90% of the capacity of other units, according to a statement from the UN nuclear watchdog.

“The country’s energy infrastructure is extremely vulnerable, which has a direct impact on nuclear safety and security,” said IAEA Director General Rafael Mariano Grossi. He added that inspectors are currently assessing the extent of the damage.

Russia launched one of its largest missile barrages against Ukraine on Sunday, as its neighbor’s full-scale invasion nears the 1,000-day mark. About 120 cruise, ballistic and aeroballistic missiles and 90 drones were fired by Kremlin forces operating from bombers and ships, the Ukrainian Air Force said.

An IAEA team based at the Khmelnytsky nuclear power plant reported hearing a loud explosion, while other teams stationed at the Rivne site reported that high-voltage power lines were unavailable. Both facilities are in western Ukraine.

Ukraine has warned that airstrikes on critical power substations could trigger an emergency situation at one of three operating nuclear power plants still under kyiv’s control.

Substations maintain stability by regulating high-voltage transmission on power grids. Unlike fossil fuel plants or renewable power plants, nuclear generation needs a constant flow of electricity to keep safety systems functioning. Without it, the fuel inside a reactor core risks overheating, which could lead to a dangerous release of radiation.

Ukraine has thousands of electricity substations. But what is at stake are ten crucial nodes linked to nuclear power plants, the destruction of which could plunge the country into darkness and cause a radiological emergency, Ukrainian Energy Minister German Galushchenko told Bloomberg News in an interview in September.

“IAEA teams visited seven substations – located outside nuclear power plants across the country – in September and October to assess the damage caused by the August attacks, and will assess whether further “The visits are necessary as a result of today’s military activities,” Grossi said on Sunday.

Most read from Bloomberg Businessweek

©2024 Bloomberg LP