One of the six units at the Zaporizhzhia nuclear power station, whose location amid the hostilities in Ukraine has caused global concern, is being moved from hot to cold shutdown to find out why boron was detected in a cooling circuit.
The Zaporizhzhia plant, Europe’s biggest, was seized in March 2022 by Russian forces, soon after the start of their full-scale invasion. Russia and Ukraine have accused each other of shelling the site near the frontline and the International Atomic Energy Agency (IAEA) has said it is lucky that the war hasn’t caused an accident there.
The site in the town of Enerhodar has six water-cooled and water-moderated reactors containing Uranium 235, four of which are shut down. The other two have been in so-called hot shutdown mode to provide heating and steam for nuclear safety purposes on site, as well as heating for Enerhodar.
Unit 5 is being moved to cold shutdown, and there are no plans to bring another unit into hot shutdown to replace it, the IAEA said in a statement on November 21.
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“Emergency exercises are very important for nuclear safety, especially in these times of heightened risk caused by the conflict,” IAEA Director General Rafael Mariano Grossi said in the statement. One of the plant’s six reactors will remain in hot shutdown to produce steam and heating, he said.
Borated water is the main coolant and the IAEA said plant operators are investigating why boron was found in the secondary cooling circuit of the steam generators in the plant’s fifth unit. The boron concentration in the cooling circuit is below permitted limits and no radioactivity has been detected in the secondary cooling circuit, the IAEA said.
“Boron is used to help stop the nuclear chain reactions from starting up. It’s supposed to stay near in the pipes containing the core, so finding some of it away from there indicates a need to check on leaks,” Mark Nelson, founder of the Radiant Energy Fund and an adviser on nuclear energy, told Newsweek.
“There’s no meltdown danger here. If the plant were in operation, it would probably be shut down to check the equipment,” he said. “Because the reactors have been off for so long, over a year, everything becomes easier for the plant staff. In an operating reactor, things can happen fast. That’s not the case here.
“The lack of radiation detected implies the nuclear fuel remains in good condition. But even a detection of radiation wouldn’t necessarily indicate danger. Operating plants around the world routinely fix small leaks before returning to power.”
The cold shutdown was ordered after three 17.4 megawatt diesel boilers located off-site started operating last week, providing additional heating to Enerhodar.
This is despite the State Nuclear Regulatory Inspectorate of Ukraine ordering in June that all six units should be in cold shutdown. The IAEA wants the plant’s operators to find another source of steam generation.
Ukrainian historian Serhii Plokhy, author of Chernobyl: History of a Tragedy and Atoms and Ashes, previously told Newsweek that although the risks posed by the Zaporizhzhia plant being at the war’s frontline had subsided in recent months, as long as it is under Russian control “the danger is there.”
Grossi has welcomed the access the IAEA has been given to visit the site’s six main reactor control rooms to monitor compliance with UN-backed safety principles.
The IAEA also has teams at other Ukrainian nuclear plants, including at Chernobyl, which in 1986 was the scene of the world’s biggest nuclear catastrophe.
Newsweek has contacted the IAEA for comment.
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Newsweek is committed to challenging conventional wisdom and finding connections in the search for common ground.