In Zaporizhia, Ukraine, Europe’s largest nuclear power plant is at the center of fighting with Russia, and the risk is such that iodine pills have been distributed to the local population to protect them from possible radioactive fumes .
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If the worst fears – such as the explosion of the power station, comparable to the Chernobyl event in 1986 – seem to have been dismissed, the situation is worrying. Professor Guy Marleau, who has been teaching nuclear engineering for more than 30 years at Polytechnique Montréal, analyzes two possible scenarios.
The current situation
“The situation is very worrying,” comments Professor Guy Marleau straight away. But an explosion of the power plant as a result of a bombardment is unlikely, since this type of power plant is very well protected. “The concrete reinforcement can withstand the crash of an airplane,” says Mr. Marleau.
He explains that the staff in office is of Ukrainian nationality, while the new occupant is Russian. This is an exceptional situation where enemy nations must work together. “It increases tensions,” he says.
An international nuclear security team arrived on site on Tuesday and is carrying out checks. A routine operation in normal times, but which takes a particular turn in times of war.
Delegates from a dozen countries are due to check the status of the six reactors, five of which have been shut down in recent weeks.
Just a few days ago, the plant had to resort to emergency diesel generators due to a lack of power supply.
Faced with the imminence of the danger, the authorities distributed iodine pills to the population around Zaporijjia. Why?
“Iodine lodges very quickly in the thyroid. When you give stable iodine, it saturates the gland,” says Professor Marleau.
It is better that this iodine be stable rather than radioactive. If the place is taken, the radioactive iodine will not be absorbed by the body. The risk of cancer decreases.
1. The pessimistic scenario
Situation evoked: the war gets bogged down and the power plant is cut off from its electrical supply.
“We have 90 minutes!” summarizes Professor Marleau when asked about what would happen if a nuclear reactor ceased to be cooled by a pumping system. In the minutes following an overheating, radioactive leaks could occur in the sky of Ukraine.
Any nuclear power plant must be constantly cooled by a large quantity of water, much like the cooling system of our car engines. Otherwise, overheating can melt the fuel.
This is what happened in Fukushima, Japan, when a tsunami cut off the electricity supply. Paradoxically, the plant was flooded, but the pumps were broken, which was fatal for the fuel tubes.
Without cooling, the uranium pieces at the heart of the six reactors can reach 2000 degrees. Result: they melt and fall to the bottom of the boiler.
This heat vaporizes the cooling water and increases the pressure in the reactor. “There are emergency systems planned to avoid this, points out the expert. Valves are opened to release the pressure. Unfortunately, radioactive fumes escape with the water vapour.
The radioactive cloud can spread to Ukraine, Russia, Romania and possibly Switzerland and Hungary depending on the direction and strength of the winds.
2. The optimistic scenario
Situation evoked: the war ends within a few weeks and the Russians leave the territory.
Ukrainian personnel regain full control of the plant.
The plant’s six reactors must be safely inspected by qualified observers.
It is still in good working order and can be restarted safely.
“The effects can still be controlled,” says Guy Marleau, who points out that this type of plant, which meets about a quarter of the Ukrainian population’s electricity needs, is very reliable in terms of security.
That said, human error remains possible in a situation where the tensions are extreme.
According to New York Times, many nuclear experts believe that a buffer zone should be established around the plant. It would be a completely demilitarized zone within a radius of 30 kilometers around Zaporijjia.