NewsNuclear power plant expert on Zaporizhia: "A second Chernobyl...

Nuclear power plant expert on Zaporizhia: "A second Chernobyl is definitely not threatening us"

Created: 09/20/2022, 4:55 p.m

The Zaporizhia nuclear power plant scares many people. The nuclear power plant expert Sören Kliem explains in an interview why we are not threatened by a nuclear catastrophe.

Berlin – The situation around the Zaporizhia nuclear power plant in eastern Ukraine, which is occupied by Russian troops, remains tense. The International Atomic Energy Agency (IAEA) has been on site with staff since the beginning of September. In a press release a few days ago, she announced that the power supply was now secured for the time being, but that the situation remained “sensitive”. Meanwhile, Ukraine reported a Russian rocket attack on the southern Ukraine nuclear plant, about 300 kilometers south of Kyiv, on Monday night.

Nuclear power plants in the middle of a contested war zone scare many people in this country too. Quite a few fear a nuclear catastrophe comparable to that of Chernobyl in 1986. We discussed this scenario with Dr. Spoke to Sören Kliem, head of the reactor safety department at the Helmholtz Center Dresden-Rossendorf. In an interview with BuzzFeed News Germany from IPPEN.MEDIA, the nuclear technician explains why military shelling is not problematic per se and why he doesn’t even see the alleged mistreatment of Zaporizhia’s staff as a serious security problem.

Mr. Kliem, the Zaporizhia nuclear power plant is still occupied by the Russians and is in the middle of a war zone. How high do you estimate the risk of a serious incident?

The worst possible accident for this type of reactor would be a core meltdown similar to that at Fukushima in 2011. This can happen if one of the reactors that has been shut down is no longer adequately cooled. However, many safety devices would have to fail for this. Whether or not there is a release of radioactivity depends on the course of the core meltdown. I rate the probability of a core meltdown as low.

Can there be an explosion in Zaporizhia like in Fukushima?

First of all, one has to state that the explosion in Fukushima had nothing to do with the core meltdown itself. It happened outside the reactor vessel. A meltdown doesn’t necessarily have to result in an explosion either. It is an accumulation of molten radioactive material in the lower part of a nuclear reactor. I am assuming that there will not be any explosions in Zaporizhia, as was the case in Fukushima, even in the event of an internal accident. The situation is different, of course, when there is an attack from outside.

Should there actually be a meltdown in Zaporizhia, will we face a second Chernobyl?

We are definitely not threatened by a second Chernobyl, because we are dealing with a different type of reactor at the Zaporizhia nuclear plant. Chernobyl was a reactor with structural safety deficiencies that led to an explosion and subsequent fire inside the reactor. This fire transported the released radioactive substances kilometers into the atmosphere, which carried radioactive clouds all the way to us in Central Europe.

Something like that can’t happen in Zaporizhia?

no The fuel rods there are sealed by a containment, similar to the German nuclear power plants. This is a 50 meter high concrete shell that encloses the entire reactor and allows nothing to escape. Even if the reactor core were to melt, no radioactivity would escape.


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Ein russischer Soldat schiebt Wache vor einem Reaktorblock des Atomkraftwerks Saporischschja in der Ostukraine (Mai 2022).
Europe’s largest nuclear power plant in Zaporizhia, Ukraine, has been occupied by Russian troops since early March. Here a Russian soldier can be seen in front of the first of a total of six reactor blocks. © Andrey Borodulin/afp

“The reactor itself does not have to be shelled for a core meltdown to occur”

So, can it be said that Zaporizhia NPP is a safe nuclear power plant? Comparable to the German systems?

The German nuclear power plants are among the safest in the world. The Russian reactors built in Soviet times are very similar to their German counterparts in terms of design and the whole safety concept, because they are very similar reactors. Also, the Zaporizhia reactors are only three to five years older than the last three German reactors still in operation, which went online in 1988 and 1989.

Can military fire also lead to a core meltdown in Zaporizhia? In its most recent announcement, the IAEA states that rocket hits continue to occur “in the wider vicinity” of the nuclear power plant.

Depends on the scenario. If, for example, a rocket hit the reactor and damaged the containment, i.e. the concrete protective cover, that would of course be serious damage. However, that does not mean that the reactor core with the fuel rods themselves would be damaged. The problem is that the fuel rods have to be cooled even when they are switched off. This requires a constant power supply, for which you first have to access the external power supply.

What happens if this external power supply is lost due to a power failure?

Electricity is then generated internally with diesel generators. If this secondary power supply infrastructure is also destroyed and the cooling of the fuel rods is interrupted, a core meltdown could theoretically occur. So the reactor itself does not have to be shot at.

So, at worst, a shortage of diesel for the power-generating diesel generators could lead to a meltdown?

The Zaporizhia NPP, Europe’s largest nuclear power plant, consists of a total of six reactors and each reactor has its own safety system. So if, in an emergency, one of the reactors that was shut down did run out of diesel, you could still fall back on the diesel supplies from the other five reactors.

At the Zaporizhia nuclear power plant, the personnel work under Russian occupation and it must be assumed that they will be harassed. Is there a risk that a core meltdown can also be triggered by human error, for example because the staff is under high stress?

There is definitely a much higher potential for error for people who have to work under the stress of war. But I think it’s impossible that a core meltdown can be triggered by a stress-related incorrect switching. In the event of a serious mistake, the reactor scrambles and the cooling of the fuel rods begins automatically. If these automated safety precautions all work, there will be no meltdown.

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