Russian assault on Chernobyl smashes nuclear safety assumptions
The attack on the nuclear power has sent reactor designers back to the drawing board
ByHelen Cahill4 June 2022 • 6:00am
A Russian soldier at the Chernobyl nuclear power plant in March
Nuclear reactors are designed to withstand plane crashes, core meltdowns and seismic shocks. But the nuclear industry has now woken up to a security threat it had not yet considered: war within a power plant’s walls.
Experts were shocked when the Chernobyl nuclear plant became a centre of fighting in Ukraine.
The plant was captured by Russian forces early in the war, raising fears of compounding the radioactive tragedy that unfolded on the site in 1986. The nuclear industry has now concluded that future sites will need to be reinforced to defend themselves against an invading force.
Professor Stephen Thomas, an energy policy expert at the University of Greenwich, says: “The assumption had been that conflicts would always studiously avoid any nuclear power plant and clearly that wasn’t the case in Ukraine. But then you had fighting within the site of Chernobyl.
“The more you think about these things the more it becomes clear that you have to do something about it. We are now at the very early stages with how things might change after Ukraine.”
Nuclear designs have been repeatedly ripped-up and redrawn in the wake of major plant failures and other events that pose a security threat.
The meltdown at Three Mile Island in Pennsylvania in 1979 saw future reactors fitted with more extensive cooling systems to keep the reactor core at a stable temperature.
The Chernobyl meltdown led to calls for the installation of so-called core-catchers that prevent nuclear reactors from sinking into the soil and contaminating the groundwater after a meltdown.
The Fukushima disaster highlighted the need for more reliable back-up power systems. The plant was rocked by a wave that surged over its external walls and flooded its reactors. The plant’s diesel back-up generators then failed to kick in and provide a cooling system for the core.
All of these disasters led to new regulatory standards for the industry, and experts are now discussing how to respond to the Ukraine conflict.
Dr Nikolaus Muellner, a nuclear expert at the University of Natural Resources and Life Sciences in Vienna, says his team is currently working with the Austrian military to assess whether Ukraine’s nuclear reactors can withstand attacks from the kinds of weapons employed by the Russian troops.
Russian army entered the Chernobyl nuclear powerplant in March CREDIT: EPN/Newscom/Avalon
He says: “Combat scenarios and war scenarios are not yet part of the design of a nuclear reactor.
“Our preliminary results suggest that if an attacker really wants to destroy a nuclear power plant – perhaps because it supplies a factory that builds weapons – then it’s really unlikely any possible reinforcement could be made to stop them. If you can’t keep your opponent’s military far enough away from a power plant, then the plant may well fail.”
But he says there are ways to reinforce power plants that become the centre for unplanned combat. He says the design for the VVER-1000 reactor could be replicated more widely as it has a so-called containment structure of reinforced concrete that sits around the nuclear core.
Muellner says: “This protects the primary system and the nuclear island of the power plant, and it is a very strong building structure that can withstand extremely high pressures. It is unlikely a combat group with artillery and grenades attacking such a containment would be able to penetrate this wall.”
He warns that other safety measures would also be required to protect the reactor’s support systems against shelling. Buildings around the back-up diesel generators would need to be reinforced so that they can take fire from artillery and hand grenades, and cooling systems and other temperature control measures for the reactor would also have to be properly protected.
Muellner says these additions can be hard to make after a plant has been constructed, and that reactors which don’t have these reinforcements could be vulnerable.
“The VVER 440 reactor design does not feature these protections, for example,” he says. “There’s just a reactor hall covered by a metal roof. Artillery shells could penetrate this roof and go down into the spent fuel pool directly in the reactor hall.
“You can’t retrofit a VVER 440 with a containment, you need to think about this when you start building a power plant and for other buildings this could be possible.”
The nuclear experts will now be putting pressure on companies to reconfigure the future designs for reactors.
National regulators will ultimately decide whether to formally demand a particular design from companies operating in their jurisdiction. But Muellner says the conflict will almost certainly put pressure on regulators in Poland, Hungary, Finland and the Czech Republic to make sure future plants can survive a military attack.
Regulators will start updating their design requirements after academics and other policy experts have had time to assess how nuclear structures should change in response to the Ukraine conflict.
The Office for Nuclear Regulation investigates the safety measures in place at a nuclear plant through its three-stage generic design assessment. The probe does not currently demand safety provisions in the event of conflict, but Professor Thomas says the assessments will likely be updated.
He warns the Rolls Royce designs for small modular reactors could be affected as even a smaller plant would be vulnerable to attack.
He says: “Sizewell C may well get through the gate before all this changes but I wouldn’t bet on any subsequent designs getting passed before new requirements are imposed.
“The fact that a small module reactor is that much smaller doesn’t mean it can’t do a huge amount of damage. We’ll get some idea on how that will be affected when the regulator gets stuck into assessing the Rolls Royce SMR.
“The regulator officially started looking at it in March, but they are at the very early stages. It’s not until the final stage that they would get stuck into those particular design elements. “
