24 Nov 2022 10:27

Zaporozhye NPP reactors go into cold shutdown, heat supply stops

ROSTOV-ON-DON/MOSCOW/BERLIN. Nov 24 (Interfax) - Two reactor units of the Zaporozhye Nuclear Power Plant, which supplied heat to Energodar during hot shutdown, are going into cold shutdown on diesel generators as the power supply from Ukraine has stopped, advisor to the Rosenergoatom head Renat Karchaa told Interfax.

"Diesel generators are necessary for shifting from hot shutdown to cold shutdown and serving the power plant itself, because the plant needs a supply of power regardless," Karchaa said.

The power plant has stopped supplying heat to Energodar. "Radiators will cool down shortly. I believe they will be completely cold in a day or two," he said.

It is technically impossible to connect the power plant to Russian power grids for now, because Ukrainian shelling has smashed a number of outdoor switchgears near the Zaporozhye NPP.

"Until the outdoor switchgears are fixed, and repairs sometimes can't be made because of the shelling, it will be technically impossible to connect to Russian power grids," Karchaa said.

So, the plant will be powered by diesel generators after the complete shutdown of its reactor units. That will require huge amounts of fuel, but that is not a problem, Karchaa said.

The delivery of mobile boilers for supplying heat to Energodar was reported earlier.

The Ukrainian army resumed attacks on the Zaporozhye NPP on November 19 after a 45-day pause. The shelling did not damage the reactor units but hit auxiliary systems. Ukraine cut the power supply to the plant on November 23.

The Zaporozhye NPP is receiving power supply from emergency diesel generators, International Atomic Energy Agency (IAEA) Director General Rafael Grossi said.

"Ukraine's Zaporizhzhya Nuclear Power Plant has once again lost access to external electricity and is instead relying on its emergency diesel generators for the power it needs for reactor cooling and other essential nuclear safety and security functions," Grossi said in a statement published on the IAEA website.

Eight out of 20 diesel generators are now supplying the site with back-up electricity, while the other 12 generators are in stand-by mode, he said.

In the case of the Zaporozhye NPP, emergency diesel generators can provide back-up electricity at least for 10 days, Grossi said. 

Relatively safe

Any de-energization of the Zaporozhye Nuclear Power Plant reduces safety levels there, and it is only relatively safe while in cold status, Rosatom head Alexei Likhachev said, adding that power transmission lines must be repaired within days or the risk of an accident will increase.

"The thing is that any de-energization of the power plant increases its vulnerability and lowers its safety. Naturally, the Zaporozhye Power Plant has its own power supply system, which consists of 18 standard so-called Fukushima mobile generators and a stock of diesel fuel for about 17 days, which we will naturally be maintaining," Likhachev said.

"We can keep the plant relatively safe while it maintains cold status and is in cold shutdown. But, clearly, this measure also has vulnerabilities, especially when the plant, including its safety system, comes under direct, aimed fire," he said.

The optimal safety model is the sustainable operation of the power plant and the supply of electricity to consumers through heavy-duty transmission lines, Likhachev said.

"Practically every power transmission line has been destroyed and, unfortunately, the Ukrainian Armed Forces are preventing their repairs. Only one line, the Dnepropetrovsk one, which goes across the line of contact between forces and the Dnieper River, is relatively stable now," he said.

That line was also broken during the night, but has been fixed, Likhachev said.

"So, our task is, and I have discussed this with the IAEA director general, to begin repairs of power transmission lines, which go both to territory controlled by Ukraine and to Russian territory. The first and primary objective is to provide an alternative power supply to the plant irrespective of the hostilities. This task should be accomplished in the coming days," he said.

Or else, "the risk of an accident will increase," Likhachev said.

The Zaporozhye NPP is the largest nuclear power plant in Europe, operating six VVER-1000 reactor units. Only two units were recently operational in order to supply heat to Energodar.

The power plant has been declared the property of Russia, and the Zaporozhye NPP federal state unitary enterprise has been established. JSC Zaporozhye NPP Operator founded by Rosatom's Rosenergoatom is running the power plant.