What are the risks of the 4th reactor unit at the ZNPP being transitioned to hot shutdown?

The National Nuclear Energy Generating Company "Energoatom" reported that the 4th reactor unit of the Zaporizhzhya Nuclear Power Plant was transitioned to hot shutdown pursuant to the order of the plant’s illegitimate management, thus violating the requirements of the license for operation. explains what it means and what threats it entails.

Before July 24, when the transition of the 4th reactor unit to hot shutdown was disclosed, reactor unit No. 5 had been in the same condition despite the demands of the State Nuclear Regulatory Inspectorate. However, Telegram channels of the invaders report that it was allegedly decided to transition the 5th unit to cold shutdown. Therefore, the 4th reactor unit will likely be in hot shutdown instead of the 5th unit.

What is hot shutdown of an NPP reactor unit, and how does it differ from cold shutdown?

Olena Pareniuk, a radiobiologist and senior research fellow at the Institute for Safety Problems of Nuclear Power Plants of the National Academy of Sciences of Ukraine, said earlier in an interview with that reactor units of the Zaporizhzhia NPP have been stopped and don’t generate power; hence, there’s no chain reaction that produces radioactive iodine. However, the expert added, the Russians can launch a reactor unit from hot shutdown in a matter of hours, and the chain reaction will start again.

A reactor unit in hot shutdown requires more cooling water, Olha Kosharna, an independent nuclear power expert, explained in an interview with , since the water that transfers heat from nuclear fuel assemblies is up to 275 °C (527 °F). In a reactor in cold shutdown, the water temperature is up to 70 °C (158 °F).

What are the risks of a reactor unit in hot shutdown?

"A reactor unit in hot shutdown can be launched to 1 percent of minimum capacity very quickly. It won’t generate power but will produce radionuclides, which can be dangerous in case of a nuclear accident: iodine-131, etc," Olha Kosharna explained. "The Russians understand that power generation at the Zaporizhzhia NPP is impossible without the Kakhovka reservoir. They have, in fact, lost the plant already. That’s why the reactor in hot shutdown is used for nothing but nuclear blackmail."

A statement posted by Energoatom also underscores that after the Russians blew up the Kakhovka dam and the Kakhovka reservoir shallowed, the supply of the Zaporizhzhia NPP with cooling water has been jeopardized, which makes it impossible to operate the plant in power generation mode. There’s no way the Russians don’t understand it.

Reactor unit No. 4 of the Zaporizhzhia NPP. Photo: Energoatom

Therefore, the purpose of transitioning the 4th reactor unit of the Zaporizhzhya Nuclear Power Plant to hot shutdown was to preserve the high degree of nuclear blackmail. In this situation, the risk of the Russians quickly launching the unit and causing an explosion with nuclear contamination cannot be ruled out. Another concern was added after International Atomic Energy Agency (IAEA) experts found anti-personnel mines on the periphery of the site of the Zaporizhzhya Nuclear Power Plant.