All six reactor units of Ukraine's Zaporizhzhya Nuclear Power Plant (ZNPP) are now in cold shutdown for the first time since late 2022 after unit 4 reached this operational state early today, Director General Rafael Mariano Grossi of the International Atomic Energy Agency (IAEA) said.
In line with the ZNPP's plans, previously reported by the IAEA, the plant started transitioning unit 4 from hot to cold shutdown on Friday morning, a process that was completed at 7:30am today. It decided to take this step after the nearby town of Enerhodar - where most plant staff live - recently ended the winter heating season.
"I welcome this development which has been recommended by the Agency for some time, as it enhances the overall safety of the facility. The Agency will continue to closely follow the operational status of the Zaporizhzhya Nuclear Power Plant and provide technically viable alternatives in a context of rapid changes and challenges," Director General Grossi said.
The ZNPP stopped generating electricity for the national grid in September 2022, but it has kept at least one of its six units in hot shutdown since October 2022 to provide district heating as well as process steam for liquid waste treatment at the site.
After the plant earlier this year started operating four newly-installed diesel steam generators to produce steam for the treatment of such waste, as recommended by the IAEA, reactor unit 4 remained in hot shutdown primarily to help keep Enerhodar warm. The five other reactors were in cold shutdown, and have now been joined by unit 4.
When in cold shutdown, in case the heat removal is interrupted for any reason, there is an additional response margin of several days before the cooling of the nuclear fuel in the reactor might be challenged. The reactor also needs less cooling water than in hot shutdown, an issue that became more challenging after the destruction of the downstream Kakhovka dam in mid-2023.
Although the measure is positive for nuclear safety, the situation remains extremely fragile at a time when Europe's largest nuclear power plant is facing severe dangers, with several drone strikes targeting the facility over the past week.
"The decision to have all six units in cold shutdown is positive in itself, as the cooling down of the reactor provides an additional buffer in case of an accident. But it doesn't address the fundamental issue of a recent sharp deterioration of the situation at the plant. Without a doubt, nuclear safety and security at this major nuclear facility remains very precarious," Director General Grossi said.
The potential risks were underlined again this morning, when the team of the IAEA experts stationed at the site reported hearing sixteen rounds of outgoing artillery fire in less than half an hour - some at near distance, others further away but still clearly audible.
Ukraine's national regulator, the State Nuclear Regulatory Inspectorate of Ukraine (SNRIU), has previously issued regulatory orders to limit the operation of all six units of the ZNPP to a cold shutdown state.
