Are allegations that ZNPP could become a second Chernobyl justified?

When the russian army seized the Zaporizhzhya nuclear power plant in March, it was clear that they do not understand what the radiation hazard is and that the nuclear power plant is a nuclear facility. Since from the first day the buildings of the administrative sector were fired upon, part of the gym was destroyed, power units were fired at, and the flyover was damaged. Now it is getting worse again.

The power units of Zaporizhzhya NPP are quite safe when compared to russian power units of the same series, since Ukraine has introduced a number of measures to improve the safety of our power units since 2011. But they were designed back in the 70s of the last century and it was not assumed that the nuclear power plant would operate in the conditions of hostilities, war, occupation. They do not provide for any protective systems or mechanisms against shelling, and therefore damage to important systems can lead to negative consequences. ZNPP is connected to the energy system of Ukraine by four lines. Now three of them are not functioning due to damage.

It is important to understand that a nuclear power plant is not a thermal power plant, it does not work on the principle of a “kettle” - when you turn off the gas, the water stops boiling and everything stops. This is an object that requires long-term operation of systems to remove energy from the reactor core. If this system does not work, it can lead to a core meltdown, as happened at the Fukushima nuclear power plant. Such a scenario with melting of the reactor core is also possible at Zaporizhzhya NPP.

If hostilities continue at Zaporizhzhya NPP and the last line connecting Zaporizhzhya NPP to the energy system of Ukraine is damaged, then the only way to cool the power units will be the operation of standard systems powered by diesel generators. But the operating time of these diesel generators is limited by the amount of fuel they run on. There is enough fuel stored at the nuclear power plant, but not enough for a month. At the same time, it is not known whether the russian troops drained this diesel fuel or not. Within the light-version scenario: in the event of a damaged power line, complete power unit de-energization, if the personnel does not intervene, then in three hours the operating power unit can repeat the fate of Fukushima. If the information about the mining of power units is true, then the scenario could be much worse.

In addition to the six power units located at the Zaporizhzhya NPP site, there is also a spent nuclear fuel storage facility where fuel unloaded from the ZNPP spent fuel pools is stored. These are 170 containers, each container contains 24 assemblies, which is about 4,000 assemblies of spent nuclear fuel. This is about 2 thousand tons of uranium dioxide. This is more than the fuel in all six reactors of the station. Damage to all this can lead to very negative consequences, and the consequences depending on the situation, can be either one Fukushima, or six Fukushima or several Chernobyls.

We did not model it because it's a complex study that requires a lot of background information, with a lot of unknowns, from what exactly will be the impact on the reactor plant, what size of the warhead, or what will get activated, and ending with weather conditions. But those calculations that were performed earlier and were not related to military operations, but were carried out as part of the safety justification of power units, they showed that in the event of a complete blackout during a severe accident, if the containment fails, then the evacuation conditions will be met at fairly large distances.

It will be necessary to evacuate at least the population of Energodar and nearby cities. I assume that in the event of a blackout and damage to the containment, even at one power unit, a transboundary release of radiation pollution can occur, that is pollution of neighboring states, in particular Europe.

The reactor can be in a cold shutdown state indefinitely, if, of course, it is connected to the power supply. The power unit needs electricity to operate all its systems and mechanisms. Being in the “cold shutdown” state, the power unit has a much greater margin of time during which the personnel can eliminate an emergency, if one suddenly occurs, and prevent severe damage to the reactor core.

Such, in the event of loss of power supply to the power unit operating at power, the melting process can begin in three hours if nothing is done; if the reactor is in the “cold shutdown” state, then the personnel will have 57 hours to restore power. Therefore, a “cold shutdown” is safer than operating the reactor at full power. But the decision on “cold shutdown” should be made by the operating organization - NNEGC “Energoatom”.

There are no such recommendations in the world, because no one in the world thought that nuclear power plants would be an object of nuclear blackmail. But the staff has a number of documents that define actions in the event of an accident. There are instructions for the elimination of violations, accidents, guidelines for managing the design basis or severe accidents. The implementation of these instructions, in particular in the turbine hall, is very complicated, because there are occupying troops, putting pressure on the personnel, and people are constantly under stress. We observed in training, that the personnel can perform erroneous actions even without accidents. And when there are siren around you, the armed people with machine guns are standing by your side, the effectiveness of actions will be even less.

The only thing from the documents is an annex to the Geneva Convention of June 7, 1977, where one of the articles of this annex notes that nuclear power plants should not be the object of attack, even if they are military installations. That is, russia, in addition to some moral norms, violated the Geneva Convention to prevent the seizure of nuclear power plants. Therefore, in the future, humanity must develop a mechanism for influencing the aggressors, like russia, in order to make it impossible to repeat the scenario that is now taking place at Zaporizhzhya nuclear power plant.