The wrongdoings in Zaporizhzhia


…and no, it is not what you are thinking

By Mr. Luca Romano, Founder and Mr. Fulvio Buzzi, Vice-admin, L’Avvocato dell’Atomo, Italy.

Luca Romano and Fulvio Buzzi, founder and vice-admin of the highly successful Avvocato dell’Atomo platform, share their insights on everything that went wrong in Zaporizhzhia.

During the night between the 3rd and the 4th of March of 2022, the Russian army seized control of the Enerhodar Nuclear Power Station, commonly known as Zaporizhzhia.

Since the first strike occurred, a lot of concerns were brought up by different people and authorities about possible nuclear safety issues. Ultimately, those concerns led to an inspection by the International Atomic Energy Agency (IAEA) in the late days of August, to assess the situation. Despite that, up until November 2022, shelling around the Nuclear Power Station continues, with Russia and Ukraine blaming each other (and footage suggesting Russia is responsible).

Despite international concerns, so far, no radiation leaks have been detected, and the claims of an imminent radiological disaster have been proven wrong.

So, where do all the concerns stem from?

A communication problem

An old saying goes as follows: “truth is the first victim in any war”. This holds true even in the 21st century: during the invasion of Ukraine, indeed, both sides twisted the facts about the risk of a nuclear accident, and while president Zelensky is certainly deserving support for his country, he was a major offender here, when he claimed that the seizure of Zaporizhzhia poses an existential threat to the whole of Europe.

While president Zelensky might have been legitimately worried and in good faith, this claim is false. The press also did not help.

Because the general public is mostly ignorant about the perils of ionizing radiation, let alone the safety systems of a nuclear power station, a delicate situation like the one in Zaporizhzhia requires responsible reporting, which mostly was not what happened. Several western media tilted towards scaremongering rather than seeking factual information from experts, with dangerous results: in Italy and Belgium drugstores had to deal with scared customers in search of Iodine tablets: those drugs have side effects and should not be taken without medical advice. Anxiety and panic attacks have also been recorded.

The reactors in Zaporizhzhia are nowhere similar to the ones in Chernobyl.

The Zaporizhzhia nuclear power station is home to six reactors, which together can provide a net electrical power output of 6 GW. All of the six reactors are VVER-1000, which is a completely different design than the RBMK, which figured in the Chernobyl disaster. RBMKs existed only in the soviet union and were the only water-cooled, graphite-moderated reactor ever built: they had some features that were interesting for the USSR establishment – cheap, easily scalable, able to produce weapon-grade Plutonium, and some known flaws, presence of flammable graphite in the core, lack of a proper containment building, and positive void coefficient.
VVER, on the other hand, are Pressurized Water Reactors (PWR from now on), which is a family of reactors with a proven record of safety that is widely adopted in a lot of western countries.

PWRs are safe. Very safe

The VVER has some engineering differences to the western design of PWRs, but the basic structure of the safety systems is comparable: they are designed to avoid and contain a nuclear accident. Starting from the core: if the fuel temperature increases, the molecules of which it is composed start vibrating; this agitation causes an increase in the absorption of neutrons and, consequently, a reduction in the power of the reactor. This phenomenon is called “negative fuel temperature coefficient” and it is the first intrinsic safety feature that comes into action. If the temperature continues to rise, the water eventually heats up and this leads to a reduction in the liquid density. Water in VVERs acts as a neutron moderator – it slows down the neutrons to speeds where fissions become more likely. If the density of water decreases, the ability to slow down the neutrons reduces, leading to a reduction in power: this phenomenon is called “negative coolant temperature coefficient”, and it is a second safety feature that activates naturally.

If the temperature continues to rise, water needs a space in which to expand. Here comes the pressurizer, which is a cylinder filled with 60% water and 40% steam. If the liquid level rises, the vapor is compressed and part of it condenses, reducing the pressure. If the temperature continues to increase, “cold” water is sprayed from the top. If the temperature and pressure increase beyond prescribed limits, an automatic valve opens, allowing steam to be discharged. Meanwhile, the amount of dissolved boron in the cooling water is increased automatically in order to boost neutron captures and reduce reactor power (Boron is an element that absorbs neutrons). 

If this is not sufficient, the automatic emergency stop of the reactor happens. This is called “SCRAM” and consists in the insertion of all the control rods, which cause an immediate shutdown. SCRAM can be caused by several situations: temperature or pressure change in the reactor, change in neutron flux, loss of coolant, and so on…

Decay heat removal is guaranteed even in most extreme conditions

Once the reactor is shut down, the radioactive fission products continue to decay, generating heat: even if the energy released decreases over time (after one hour is already at 1% of full power), it is still enough to melt the core and therefore it is necessary to keep cooling the reactor. If the electricity grid is running, there are no problems, but if the plant remains isolated because of lack of “off-site” power, there are several backup sources of power: in case one or more of the reactors are running, those can be reconfigured “on the spot” to power not just their own cooling systems, but also the ones of the reactors that are in stand-by mode. Zaporizhzhia is also connected to a small coal-fired plant. If none of these options is available, the emergency diesel generators come into operation.

The last barrier: the containment building

Even if all these safety systems are compromised and the core melts down, possibly escaping the reactor vessel through corrosion, the whole primary circuit is confined inside the containment building.
The containment building is more than a meter thick, with foundations of two and a half meters and with a secondary containment building outside. The containment buildings are designed to withstand the impact of aircrafts and missiles – which is why a simple conventional artillery shell going astray cannot cause severe consequences.

“Even if all these safety systems are compromised and the core melts down, possibly escaping the reactor vessel through corrosion, the whole primary circuit is confined inside the containment building”

What if it is not enough?

Let us assume for a moment that all of the aforementioned features are not enough. Maybe they have been deliberately sabotaged or maybe an intense battle causes multiple damages to several key safety components. What would happen then? There would be radiation leaking into the environment, but compared to previous radiological events, we are now much more prepared to face such an emergency.
First of all, it must be remembered that all large nuclear power plants are built far away from big cities, and according to the scientists of the American Nuclear Society and Nature, even if a core meltdown occurred, radiological consequences farther than 30 km from the plant would be extremely unlikely. 

Several measures can also be taken to ensure the safety of people and prevent the radiation leak to have consequences on human health: relocation, iodine tablets distribution, monitoring of dietary products (such as milk and vegetables) and so on.

Even if such measures were disrupted or could not be carried on properly because of the war, the consequences on human health would amount, in the worst-case scenario, to a few hundred extra cancer cases, which would take decades to manifest.

Big effort, small pay-off

If you read up until this point, you should have realized that causing a deliberate nuclear accident is not that easy and not that big of a gain if you are fighting a war. Intentionally causing a meltdown would turn any perpetrator into a war criminal, and they would still have a lot of work to do to affect human health.


This should not be a surprise: the Fukushima accident could only happen after a magnitude 9 earthquake followed by a 15 mt. high tsunami and will cause a grand total of zero radiation-related deaths, according to UNSCEAR.
However, so far, we only described the actual physical consequences of a possible disruption in Zaporizhzhia. Psychological effects, on the other hand, could easily turn a minor radiological event into a Europe-wide disaster, if panic is allowed to spread and people are not informed correctly.
And so it all goes back to responsible reporting.

About the Authors:

Luca Romano is MS in theoretical physics and obtained a Postgraduate master’s in science communication and journalism. Since 2020 he is in charge of the project “L’Avvocato dell’Atomo”, which grew to be one of the biggest advocacy and education projects about nuclear technologies and nuclear power.

Fulvio Buzzi is MS in energy engineering and currently working towards his Ph.D. in mechanical engineering. He started his university career hoping to save the world with renewables, only to realize, by studying, that nuclear technologies cannot be foregone. Since September 2020 he’s vice-admin of the project “L’Avvocato dell’Atomo”, hoping to educate the public to take his same journey.

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