The last operating reactor at Ukraine’s six unit Zaporizhzhia NPP (unit 6) was shut down on 11 September. The plant, which was taken over by Russian forces in March had continued to operate despite constant shelling, which continued even after the International Atomic Energy Agency (IAEA) established a permanent presence there following an inspection visit on 1 September. The plant continues to be operated by its original Ukrainian staff while Russian nuclear utility Rosenergoatom has some experts at the plant and Russia’s national guard provides security protection.
Ukrainian nuclear utility Energoatom said it had disconnected unit 6 from the grid at 3:41 am and that "preparations are underway for its cooling and transfer to a cold state”. Unit 5 had been closed down on 8 September. The other four units had been closed for some time. After the shutdown of unit 6 was reported on Energoatom’s Telegram channel, the information was confirmed by a member of the main council of the (pro-Russian) Zaporozhye region administration, Vladimir Rogov, as well as by Rosenergoatom specialists.
Rogov told told RIA-Novosti that the decision to shut down unit 6 was made due to continued shelling of the plant by Ukraine and damage to the power lines. He said the constantly changing mode in which the reactors and turbines were forced to operate, because of the attacks, created the risk of an accident. He noted that the unit had already been operating at minimum capacity for several days before the shutdown.
The decision was taken after shelling damaged all of the power lines serving the plant, according to Renat Karchaa, an adviser to the head of Rosenergoatom. He said the shutdown of the reactor was carried out "in a soft mode". He told Interfax that a few days before the shutdown, it had worked at a minimum capacity (from 114 to 150MWe), supplying energy only to the station itself and the objects close to it.
"The shutdown of the last power unit of the Zaporizhzhia NPP is good news, an unnamed “expert in the field of nuclear energy, who built more than one nuclear power plant in the Soviet Union”, said in an interview with Moskovsky Komsomolets. He said Rosenergoatom at the plant had insisted on stopping the unit two weeks ago to lessen the risk of “negative events”.
“I'm not talking about a global catastrophe like the one caused by the Chernobyl accident," he said. “The maximum that can be caused by the bombing of the nuclear power plant is an increase in the background radiation within the exclusion zone is it were to destroy a container with spent nuclear fuel. We even worked out a variant involving a direct double hit of a projectile in the same container — the result will be similar.”
He explained why it was necessary to close the plant once its power lines had been destroyed. “It has nowhere to send its energy. When a reactor, turbine, or generator is running, the generated energy must flow somewhere. To date, all power transmission lines that supplied exclusively the territory of Ukraine (the share of the NPP accounted for 15% of electricity supplies), have been destroyed.
Once the reactor is stopped, the cooling process begins in order to "remove" the residual heat generation, he explained. He said there were more than enough resources at the plant to continue cooling the reactors. “These are diesel energy accumulators. There are three 5MWe diesels for each unit and two more large station diesels. They are already working, pumps are pumping water and feeding it to the reactor. The fuel supply is huge enough for several months.”
Earlier, on 9 September, IAEA Director General Rafael Mariano Grossi said he had learned from IAEA staff on the site “of the serious situation that developed last night at Zaporizhzhia Nuclear Power Plant (ZNPP)”.
The power infrastructure feeding the city of Energodar, home to the NPP’s operators and their families, has been destroyed by shelling of the switchyard at the city’s thermal power plant, leading to a complete power black-out in Energodar: no running water, no power, no sewage. “Given the increased and continued shelling, there is little likelihood of re-establishing reliable offsite power to the ZNPP, especially as the shelling continually and repeatedly damages the power infrastructure.”
As a result, the IAEA understands that the operator, having no longer confidence in the restoration of offsite power, is considering shutting down the only remaining operating reactor. The entire power plant would then be fully reliant on emergency diesel generators for ensuring vital nuclear safety and security functions. And as a consequence, the operator would not be able to re-start the reactors unless offsite power was reliably re-established. Furthermore, there are indications that, with the increasingly dire circumstances that the people of Energodar are facing, there is the significant risk of an impact on the availability of essential staff on site to continue to safely and securely operate the nuclear power plant.
“This is an unsustainable situation and is becoming increasingly precarious. Energodar has gone dark. The power plant has no offsite power. And we have seen that once infrastructure is repaired, it is damaged once again. This is completely unacceptable. It cannot stand,” Grossi said. “I therefore urgently call for the immediate cessation of all shelling in the entire area. Only this will ensure the security of operating staff and allow the durable restoration of power to Energodar and to the power plant. This dramatic development demonstrates the absolute imperative to establish a nuclear safety and security protection zone now.”