The Zaporizhzhia nuclear power plant is strategically critical for both sides in the Ukraine-Russia conflict. But in terms of nuclear safety, the current impasse is perilous.
It is the nearest large generator of electricity to the parts of Ukraine annexed by Russia, and Moscow wants factory power to control its territory there. He also expressed a desire to redirect power from Zaporizhzhia to Russian cities as well.
On the other hand, Ukraine cannot afford to lose this asset – Europe’s largest nuclear power station which once supplied 20% of its electricity – at a time when Russia has control over its civilian infrastructure.
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The site is currently operated by its Ukrainian-born staff, but is under Russian military control.
The situation is tense. The plant’s Ukrainian state operator, Energoatom, said Russia had just kidnapped Zaporizhzhia’s deputy director – which they say happened before Russian engineers took over. This comes weeks after the plant manager was kidnapped and released.
The bombing of the factory was a constant threat.
Landmines exploding around the plant’s perimeter have also been implicated in starting fires that have threatened reactors and crucial electrical connections that connect the plant to Ukraine’s national grid.
So what are the risks?
The Zaporizhzhia power plant consists of six pressurized water reactors. The sheer scale of the facility means that there are hundreds of tonnes of nuclear fuel in the reactors themselves and over 2,000 tonnes of spent fuel in storage ponds and a dry storage facility on the site.
They are of a relatively modern design, with safety features that make them much safer in an emergency than those involved in other civilian nuclear disasters like Chernobyl and Fukushima.
They are also much safer now than they were when the Ukraine invasion began. Under the supervision of the International Atomic Energy Agency (IAEA), which now has two observers stationed at the plant, the six reactors are in “cold shutdown”, their fuel slowly cooling inside the buildings reactors.
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The main permanent risk is a loss of power to the site. Even when shut down, cooling water must circulate around the reactor fuel to prevent it from melting. Storage ponds must also be completed to avoid overheating of spent fuel and potential release of radioactivity.
Impact of the bombardment
Just a few days ago, bombardments disconnected one of the last cables supplying the site with electricity. It was not the first time the complex had to switch to emergency diesel generators. All are currently operating, but the plant has only 10 days of diesel stored on site.
The other risk, of course, is the impact of bombing or missiles. Since the site was occupied by Russia in March, shells have pierced buildings immediately adjacent to the reactors themselves.
The reactors are a very thick stationary vessel, surrounded by a heavy concrete shell, so the direct risk to them is considered quite low. However, a fire or damage to safety systems such as emergency power can lead to overheating and melting of fuel.
If projectiles were to touch the fuel stored in the reactor buildings or in the outdoor basins, this could lead to the spreading of highly radioactive waste on the site. However, the fuel is not flammable, so the risk to the wider environment is likely to be low.
What’s the worst case scenario?
The worst case scenario would be a total loss of power, combined with damage to reactor buildings or safety systems. Highly implausible in peacetime, but entirely possible in the current conflict.
In this case, most international experts believe that things could get worse like in Fukushima in Japan in 2011. During this disaster, a power failure caused the nuclear fuel to overheat, the hydrogen gas thus produced then exploded, releasing high radioactive contamination in the atmosphere.
This event released radioactivity over a wide area, resulting in costly evacuation of people and many years of environmental cleanup.
Unlike Japan, Zaporizhzhia staff had time to prepare for the worst. But the only sure way to prevent this is to end the fighting around the factory.
International Atomic Energy Agency chief Rafael Grossi is now in Moscow to negotiate a safe zone for Zaporizhzhia – but with neither side currently willing to relinquish control, the zone remains an accident in waiting to happen.