Risks of de-energizing the Chernobyl nuclear power plant

Yesterday (9.03) the Chernobyl nuclear power plant was de-energized due to power line damage [1]. As I said earlier, commenting on what is happening around Ukraine’s nuclear facilities now, the most dangerous facility in the Chernobyl zone is the spent nuclear fuel storage facility (SNF) with 20,000 fuel assemblies. And the potential emergency scenario is conditionally Fukushima. When the release of radiation began due to overheating of the fuel, the cooling of which was disrupted due to the blackout of the station. But how realistic is this scenario?

HOJAT-1 is a wet fuel storage facility for the first 3 units of the station (here good video with footage from there). In fact, these are several large pools in which spent assemblies are placed. They release heat even many years after being unloaded from the reactor. However, this fuel is more than 22 years old, since the station’s last reactor was loaded in 2000. Therefore, the heat generated by the fuel is not so great.

Wet storage HOJAT 1
Wet storage HOJAT 1

Fuel of this age can also be stored dry. For example, for this purpose, the ISF-2 storage facility has already been built, where the fuel is placed in special dry ventilated containers. However, few assemblies have been moved there yet. Most of them are still in HOJAT-1.

Dry storage facility HOJAT 2

The International Atomic Energy Agency has been briefed on the situation. According to the organization, the volume of the pool and the age of the fuel are such that cooling can be sufficient even without electricity, so the situation “not safety critical”:

In 2012, the Chernobyl nuclear power plant held post-Fukushima stress tests, which showed that in the event of a de-energization of the ISF, the maximum temperature of the pool will not exceed 70 degrees, and in this form, without destruction, the fuel can stand for up to 2 months. Screen:

In addition, the station also has diesel generators, so that for some time it can theoretically work without an external energy source.

However, blackout is a loss of control. Lack of information (fire safety sensors, background radiation levels, etc.), pumps, filters, etc. – everything will be cut off. These are risks. If it happens that the staff will not be able to notice problems and quickly respond to them without power supply.

Another more important risk is that the same shift has been working at the station for two weeks now, since February 24, when the Russian military entered the territory of the station. People work seven days a week, under constant stress, they are responsible for the safety of such an object. Now also in a blackout emergency. That’s how it is describes IAEA.

And whether they will be able to normally start all backup systems in such a situation, restore the equipment to working capacity and control the safe state of the facility is a big question. The cause of the blackout is also questionable. Has she been eliminated? Is there a recovery going on? Are there fights going on? Unknown.

So there is apparently no risk of destruction of the storage facility and the fuel in it due to a blackout. But the very fact of such incidents in the situation of the capture of the station and exhausted personnel does not guarantee that all this will not eventually turn into something more dangerous and new accidents will not happen there.

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