The explosion at the Reactor 4 Unit was the cause of the Chernobyl Nuclear Power Plant disaster. A large amount of radioactive material was expelled into the surroundings, along with a partial meltdown of the reactor core. The last few decades have seen a lot of international efforts to safely contain and decontaminate the site.
Russian forces have seized the site and the Zaporizhzhia nuclear power plant as part of the ongoing conflict in Ukraine. Ukrainian authorities reported a power loss at Chernobyl on March 9.
It is important to understand the potential impact of power isolation, despite reassurances by the International Atomic Energy Agency that there is no imminent safety threat.
When nuclear fuel is removed from the core of a reactor, it is redesignated as spent nuclear fuel and often treated as a waste product for disposal.
After being removed from the reactor core, fuel will continue to heat up. The spent fuel material at the Chernobyl site needs to be adequately and continuously cooled to prevent a release of radioactivity.
At Chernobyl, standard procedures to safely handle such material involve placing the fuel into water-filled ponds, which shield the near-field environment from radiation. Continuous circulation of fresh, cool water and a medium for heat transfer from the fuel to the water are provided by them.
The fuel will emit heat if the circulation is compromised. This can cause the surrounding water to evaporate, leaving nothing to absorb the radiation from the fuel. It would leak to the surroundings.
In the case of Chernobyl, the spent fuel material has been out of the reactor for an adequate period of time and does not require intensive cooling. The water could eventually be evaporated if the power is not restored. This could increase the risk for an increased radiation dose being taken by the remaining site workers.
The Reactor 4 Unit, which contains large quantities of a lava-like material, is the main risk.
This is highly radioactive and its eventual disposal presents a substantial scientific and engineering challenge. The New Safe Confinement structure needs the continued operation of radiation monitoring and ventilation systems to remain online.
Two out of six reactor are operating. The reactor that is currently shut down is luckily affected by the damaged power connection. It is difficult to get spare parts in the middle of a war.
We don't know how long the site will be without power despite assurances that there are on-site reserves of diesel fuel. There is no cause for alarm according to the IAEA. There is enough water in the spent fuel pools to avoid an accident. The water may not be gone for months.
The fighting in the region is making it difficult to fix the power connection problem.
It is difficult to get spare parts in the middle of a war because of the damaged power connection at Zaporizhzhia. The reactor is not an immediate safety risk because it is shut down. If power is cut to one of the operating reactor, this could lead to a meltdown.
Estimates of completion for the safe dismantling, decontamination and decommissioning of the Chernobyl site range into the late 2060s, despite the collective aim of the global engineering community. The latest events events pose a serious threat to the ongoing efforts to decommission.
The University ofSheffield has a PhD in Materials Science by Lewis Blackburn.
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