What is the real risk of nuclear catastrophe in Ukraine?

The risk of an accident at the Zaporizhzhia nuclear power plant in southern Ukraine is more linked to a succession of equipment failures and errors – catalyzed by war – than to the possibility of a direct shot hitting a reactor. Despite this, the impact of a nuclear accident would be so high that the international community dramatically increased pressure this week on Russia, which controls the nuclear facility.

For the first time in history, a large nuclear power plant is in the middle of the battlefield in a high intensity war. It is the largest plant in Europe and is located in the city of Enerhodar, in the oblast (state) of Zaporizhzhia. It accounts for % of Ukraine’s electricity supply.

The complex was invaded by Russian forces on March 4 . The action ignited a fire in non-essential facilities and sparked a wave of international criticism. The takeover of the plant was part of a rapid advance by the Russian army that resulted in the capture of a large swath of southern Ukraine in the first week of the war.

The battlefront soon advanced northeastward, towards the city of Zaporizhzhia, capital of the oblast. Thus, the region of the plant, in occupied territory, began to enjoy relative tranquility.

Part of the approximately 10 ) 1,000 employees continued to operate the plant, but forced to do so by the Russians. It is now operating at minimum capacity, with only two of the six reactors operating, but continues to supply power to regions under the Ukrainian government’s control.

Even with the fighting taking place around

kilometers from the plant, the possibility of a missile hitting one of the six nuclear reactors has always terrified residents of the region. I witnessed this on the morning of 26 April, when the city of Zaporizhzia was bombed. Reports quickly spread across the region of people who saw cruise missiles fly over the plant. Panic spread through the city, but there was no damage to the nuclear facility.

However, reports of explosions at the plant reoccurred in August. A fire station and radiation measurement stations were destroyed. Russia and Ukraine blamed each other for the attacks.

These events began to occur after the start of a major Ukrainian counteroffensive to try to retake part of the Kherson oblast, which is about 180 kilometers southwest of Enerhodar, along the Dnipro River. Until then, the biggest fighting of the war had been concentrated in the north and east of the country.

At least 20 a thousand Russian fighters were redirected south with the aim of thwarting the Ukrainian counteroffensive. Russian artillery units were then positioned between the plant’s six reactors to fire primarily at the city of Nikopol or at Ukrainian troops attempting to cross the Dnipro River. In other words, the plant started to be used by Moscow as a kind of shield, allowing the Russians to fire freely without threat of counterattack.

Russia accused Ukraine of acts of terrorism, for supposedly shooting at the power plant. The Ukrainian authorities say they have evidence that the Russians were forging false attacks to try to blame the government of President Volodymyr Zelensky for facilitating a catastrophe.

According to the Ukrainians, a Russian film crew would have been caught staging a fake Ukrainian attack. The footage would be used in information warfare.

It is currently not possible to independently verify the correct version of these facts.

Actual risks to the plant

Russia and Ukraine are known to fight in the Zaporizhzhia region mainly using artillery fire. These include mortar and howitzer fire (which are types of cannons that fire grenades in a parabola trajectory) and rockets. These weapons can destroy armored vehicles and fortifications.

However, all nuclear reactors and pools of discarded radioactive material at the Zaporizhzhia plant are protected under concrete and steel structures about 1.2 meters in height. thickness. They are sufficient to withstand accidental artillery impacts from the collision of a large aircraft.

However, there is a possibility of radioactive leakage caused by failures in the nuclear fuel cooling systems.

The Enerhodar plant was built in the years of 1986 and uses VVER (pressurized water nuclear reactor) technology. According to engineer Dagoberto Lorenzetti, a specialist in nuclear energy, the system is similar to the technology used in Angra plants, in Brazil.

“The water in this type of reactor is, at the same time, an element moderator and refrigerant”, he stated.

This means that, as a moderator element, water is able to reduce to adequate levels the energy of the neutrons that are emitted in each uranium nuclear fission 235 This causes these neutrons to generate new nuclear reactions, creating a chain reaction and producing energy.

This energy heats up another hydraulic system. the water turns into steam and drives a turbine that generates electricity.

In addition, the water is also used to cool the reactors and a series of pools where the discarded nuclear fuel is placed. cooling system works from pumps powered by electricity.

Disaster scenario

According to a re report by the NGO Greenpeace released in March of this year, in a hypothetical scenario, the fighting could destroy the electrical cables that bring energy from other sources into the nuclear plant. It is this energy that sustains the operation of the plant’s water pumps.

After the report was published, three of the four lines that supply the plant were damaged by bombing.

Thus, if the external energy is completely cut off, the entire water pump system of the plant would start to operate in an emergency, with electricity supplied by diesel generators that exist inside the complex.

Na In the event that a group of these generators fails and is not replaced quickly, there is the possibility of overheating the entire system.

Even before the war, part of these diesel generators already had problems due to lack of parts and maintenance, according to an investigation by 2020 by the Ukrainian regulatory agency.

To make matters worse, many technicians and plant personnel involved in the emergency response process may have difficulty reaching the site – due to fighting and restrictions imposed by troops russians. This could delay the emergency response.

In reactors, with partial vaporization or complete drying of the water, the nuclear chain reaction would be extinguished and the equipment would automatically shut down. However, even when turned off, both the reactors and the spent fuel pools still need cooling – to remove the heat generated by the decay of nuclear fission products.

In the scenario raised by the study, if the cooling completely stops, there is a chance of meltdown of one or more nuclear reactors.

“We would not have a catastrophe the size of Chernobyl (1986) , but even so, an accident with serious consequences could occur. This sequence of events is possible, but unlikely’, assessed Lorenzetti.

Another possibility, with a little more chance of occurring, is a fire in the pools of used nuclear material, due to lack of water . This event could cause the leakage of radioactive material into the atmosphere, even if the reactor’s protective structure has not been compromised.

In other words, the possibility of a nuclear accident in Zaporizhzhia depends on the occurrence of a series of successive factors rather than a single event. However, the level of stress to which the Ukrainian employees of the plant are subjected, under the control of the Russians, can facilitate the occurrence of accidents.

The organization Greenpeace also pointed out the possibility of flooding and consequent failure in the plant’s cooling systems in the event that nearby containment dikes on the Dnipro River are damaged by artillery fire.

The report also warned of a minor nuclear accident scenario, in which a firing a heavy weapon could lead to the destruction of part of the 160 concrete barrels that store spent nuclear fuel (less radioactive content) in a plant yard.

Diplomacy and energy

The completion of a nuclear accident in Zaporizhzhia would not be good for either Ukraine or Russia – even for war propaganda purposes. So far, the persistence of fighting in the region seems to be motivated by the belief, especially of the Russians, that the plant’s structure will withstand eventual miscalculations in military operations.

The Ukrainian government has accused Moscow of of wanting to redirect energy production from the Zaporizhzhia plant to the occupied territory. Russia denies this possibility. But, if it happens, it could create a scenario of energy shortages in Ukraine, due to the importance of the plant.

In theory, the country could be helped by neighbors, as its electricity grid was connected to the of the European Union at the beginning of the war, precisely to mitigate this type of risk. But Europe itself risks electricity shortages if Russia cuts off the supply of natural gas – which is used to power many power plants on the continent.

Moscow reported on Friday (19) which will interrupt supplies for three days for alleged maintenance work on the Nord Stream 1 pipeline.

The UN Secretary General, António Guterres, defended last week, with the support of the Ukrainian government, the creation of a demilitarized zone in Enerhodar. But the proposal was rejected by Putin.

On the other hand, in a conversation with French President Emmanuel Macron, the Russian said he would agree to the entry into the plant of a delegation from the International Atomic Energy Agency ( IAEA). The visit is scheduled for September and will be led by the head of the organ, Rafael Grossi.

He had said that any further escalation of violence in the region related to the six reactors at Zaporizhzhia “could lead to a nuclear accident severe with potentially serious consequences for human health and the environment in Ukraine and elsewhere.”

The UN has already managed to forge an agreement to resume grain exports in Ukraine and facilitate the flow of Russian production. The idea was to reduce the possibility of a world food crisis.

Now, Guterres says he believes that, with behind-the-scenes negotiations, it will be possible to reach an agreement to prevent a nuclear disaster that could affect a large part from Europe and even from Russia.

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