90 minutes from a radioactive leak in Zaporizhia: see the possible scenarios

&90 minutes from a radioactive leak in Zaporizhia: see the possible scenarios

BET À DAY

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 it from any radioactive fumes.

If the worst fears – such as the explosion of the power plant, 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 at Polytechnique Montréal for more than 30 years, 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 a plane,” says Mr. Marleau. 

He explains that the staff on duty 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 wartime. 

&90 minutes from a radioactive leak in Zaporizhia: see possible scenarios

&90 minutes from a radioactive leak in Zaporizhia: see possible scenarios

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Delegates from a dozen countries are due to check on the status of the six reactors, five of which have been shut down in recent weeks.  

A few Within days, the plant had to resort to emergency diesel generators due to lack of power.  

Faced with the imminence of the danger, the authorities distributed emergency pills iodine to the population around Zaporizhia. Why?

“Iodine lodges very quickly in the thyroid. When we 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. Within minutes of overheating, radioactive leaks could occur in the skies of Ukraine.

Any nuclear power plant must be constantly cooled by a large amount of water, much like the cooling system of our car engines. Otherwise, overheating may 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 failed, which was fatal for the fuel tubes. 

Without cooling, the uranium pieces at the heart of the six reactors can reach the 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 the strength of the winds.  

2. The optimistic scenario

Situation mentioned: the war ends in a few weeks and the Russians leave the territory.  

Ukrainian personnel regain full control of the plant.  

The plant's six reactors are to be safely inspected by observers qualified.  

It is still in good working order and can be safely restarted. 

“The effects can still be monitored,” says Guy Marleau, who specifies that this type of power plant, which meets about a quarter of the electricity needs of the Ukrainian population, is very reliable in terms of security. 

That said, the human error remains possible in a situation of extreme tensions. 

According to the New York Times, many nuclear experts believe that a buffer zone should be established around the power plant. This would be a fully demilitarized zone within a radius of 30 kilometers around Zaporizhia.