Nuclear security specialist on potential terrorist attack at ZNPP

Dmytro Gumenyuk, head of the safety analysis department of the State Scientific and Technical Center for Nuclear and Radiation Safety, details how exactly the enemy could damage the Zaporizhzhya NPP and the main dangers it would pose.

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The announcement by Ukrainian President Volodymyr Zelenskyy on June 22 that Russia is prepared to carry out a terrorist act at the occupied Zaporizhzhya nuclear power plant (ZNPP) caused a great resonance in the country. One of the first organizations to respond was the State Scientific and Technical Center for Nuclear and Radiation Safety, which released its own statement saying that should such an incident occur, people should not begin taking iodine pills. This was very timely, because many Ukrainians had already begun buying potassium iodide tablets and even just iodine in pharmacies throughout the country.

To find out more, NV spoke to Dmytro Gumenyuk, head of the Center's security analysis department.

NV: Your institution claims that there is no real threat of radioactive iodine entering the body in the event of an accident at the ZNPP, as the plant’s reactors have been stopped. What in fact are the threats posed by the facility today and the presence of Russian forces there? What dangers the reactors of ZNPP pose, and what problems could arise in the event of an explosion?

Gumenyuk: Our center said in a statement not to take potassium iodide tablets or other iodine-containing tablets. Why? Because their main task is to prevent iodine from accumulating in the body. But there are many other radionuclides in the reactor core that have a longer half-life. An incident even at a shutdown reactor would still cause the release of radioactive products into the environment. That is, there will be radioactive contamination. Therefore, the fact that you do not need to take potassium iodide does not mean that there cannot be a radiation emergency.

What could happen at the plant? It's hard to predict here, because we don't know what's in the minds of these monkeys with grenades. What are they planning to do? There are many scenarios. Theoretically, we can consider these as the most likely ones:

Read also: What will happen if Russia blows up the Zaporizhzhya Nuclear Power Plant

1)     The loss of water from the cooling pond due to the destruction and leakage of water from the Kakhovka reservoir. If there is no water in the cooling pond, and there are no additional actions to replenish the spray pools or systems that cool the equipment that removes heat from the nuclear fuel, it will begin to heat up, and may end up damaged or melted.

2)     They somehow damage the line that connects the Zaporizhzhya station to the Ukrainian power grid, meaning that there would be no power for safety systems. It would have to be provided exclusively by generators, which can also fail, and which have a limited amount of fuel. We also don't know if there is a supply of fuel for the generators, or if they (the Russians) have already consumed it or poured it into their tanks and armored vehicles. Usually, the plant operator keeps a minimum fuel reserve enough for 10 days, during which time fuel is delivered, but this is not how the station is designed to operate, and there is a possibility that diesel generators could fail during prolonged operation, or that fuel will run out. In the event of a loss of power supply to the systems that cool the reactor core, they will stop working, and, accordingly, the reactor will be in meltdown.

In general, one can say to some extent that it would be an incident like the one at Fukushima. The significant difference is that at Fukushima, the incident happened while the reactor was running, but here the reactors have been in shut down for almost nine months, some since the beginning of the full-scale invasion. In this case, the fuel is releasing very little heat, so you need only a bit of water to cool it. All these processes will be stretched for a long time. This is, in short, what could happen at the power plant.

Read also: Situation at Zaporizhzhya NPP serious but stable, says UN nuclear chief

NV: It's not just about spent nuclear fuel, is it?

Gumenyuk: No, not only about that. In all six reactors, there is fuel inside which no one has taken out. Moreover, there is also spent nuclear fuel stored in spent fuel pods. Inside the building in which the reactor is located, there is such a large tank in which cartridges with spent nuclear fuel are stored. This fuel also needs to be cooled.

There are systems that are designed to cool nuclear fuel for a long time, both in the reactor and in the spent fuel pool, but two main things are needed for this. One is electricity, and the other is cooling water. If there is no electricity or cooling water, then additional steps must be taken to prevent the heating-up of nuclear fuel.

These scenarios were previously analyzed by the plant’s operator, even before the war. An accident with loss of power supply or cooling water was considered in detail after the accident at the Fukushima nuclear power plant. Additional power units were purchased and equipped with mobile systems and mobile diesel generators which can be connected to the reactor so that the systems can partially work. Mobile motor pumps that can be connected to the equipment, or to the system that cools the fuel in the spent fuel pool, or to those systems that cool the fuel in the reactor.

An incident with a loss of power supply or loss of cooling water was considered. There are additional systems that can allow it to be controlled. But we do not know what orders these terrorists have. Will they give permission to turn on the generators, turn on the pumps, and all the rest? It very much depends on what orders this criminal occupying power will give.

NV: If, as you say, nuclear fuel starts to heat up and gets into the environment, what types of pollution are we talking about? How strong might this pollution be?

Gumenyuk: This will very much depend on how long it lasts. What are the conditions? There could be an incident in one of the reactors, or all six, or in the spent fuel pool, or at six spent fuel pools. But the leaked emissions will be liquid, especially if there is a breach of the protective containment frame (the room in which the reactor is located), as well as aerosol and gaseous emissions. How much pollution there is will also depend on the weather conditions. Unfortunately, in a telephone conversation without detailed analysis, I will not undertake to provide you with forecasts and comments so as to neither horrify nor unreasonably reassure readers. But there would be a threat of radioactive contamination.

Depending on the direction of the wind, weather conditions, and the magnitude of the release, this pollution could either be localized in a small area, or it could be transferred to larger areas.

NV: In addition to nuclear fuel, what other types of pollution or other substances can enter the environment in the event of an incident?

Gumenyuk: At this power plant, the main threat is nuclear fuel. But there is also a storage facility for spent nuclear fuel on site. Containers of it are stored in these large concrete barrels. Their energy release is small, as the concrete offers protection. Under normal conditions, they do not affect the environment and the population in any way. But, again, these animals (Russian troops) could damage them, and this could also be a source of radioactive contamination. In this case, depending on the weather conditions, damaged or spilled fuel could be subsumed in water. This pollution could enter the groundwater or evaporate. But due to the fact that the fuel is stored for quite a long time, the amount of radioactive products there has decreased. It would be, in terms of the magnitude of the release, perhaps less than in the event of an accident at a reactor or in the spent fuel pool.

Read also: Ukraine has been “shadow-banned” over the Kakhovka disaster - opinion

NV: Can we imagine what sort of area such a disaster would contaminate?

Gumenyuk: I'm not ready to scare people now... You see, an analysis of radiation consequences, as well as protocols for protecting the population, are determined, formed, and refined immediately after an accident occurs. Until then, it is very wrong to say that at best it will be this, or at worst it will be that, because these words will be misinterpreted. Still, I would emphasize that if the staff has the ability, they know what to do, and they have systems that can prevent an accident from occurring. It should be said that there is a chance that there will be no accident even if the cooling pond is damaged or power supply is lost.

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NV: What do all these threats mean for the population, and under what scenarios might questions of immediate evacuation arise?

Gumenyuk: Decisions on evacuation, shelter, and restrictions on being outside would be made by the competent authority, namely, if I am not mistaken, the State Emergency Service, based on the results of an assessment of the current state, as well as a forecast of the development of the radiation situation. It is wrong to say now that the population needs to be evacuated, because everything will essentially depend on what happens there. The population needs to listen to the recommendations of the competent authorities, namely the State Emergency Service and the Hydrometeorological Center. They model the movement of radioactive substances and pollution. There is also the State Inspectorate for Nuclear Regulation, which is also a competent body, and has an information crisis center that works 24/7 in case of an accident. It analyzes the current situation, makes forecasts, and provides this information in the form of press releases, including for the media.

Read also: No need to take iodine in case of Russian terrorist act at Zaporizhzhya NPP — scientists

The media, by using information from these authorities, can convey this information to the population, especially those who, unfortunately, are located in the occupied territories. It is definitely not necessary to speculate now, or especially to run out for potassium iodide tablets.

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