Global: Cold shutdown reduces risk of disaster at Zaporizhzhia nuclear plant – but combat around spent fuel still poses a threat
- Sep 13, 2022 2:54 pm GMT
Source: The Conversation –
Energoatom, operator of the
The Conversation asked
What does it mean to have a nuclear reactor in cold shutdown?
The fission reaction that generates heat in a nuclear power plant is produced by positioning a number of uranium fuel rods in close proximity. Shutting down a nuclear reactor involves inserting control rods between the fuel rods to stop the fission reaction.
The reactor is then in cooldown mode as the temperature decreases. According to the
When the reactor is operating, it requires cooling to absorb the heat and keep the fuel rods from melting together, which would set off a catastrophic chain reaction. When a reactor is in cold shutdown, it no longer needs the same level of circulation.
How does being in cold shutdown improve the plant’s safety?
The shutdown has removed a huge element of risk. The Zaporizhzhia nuclear power plant is a pressurized water reactor. These reactors need constant cooling, and the cooling pumps are gigantic, powerful, electricity-guzzling machines.
Cold shutdown is the state in which you do not need to constantly run the primary cooling pumps at the same level to circulate the cooling water in the primary cooling loop. The
And by shutting down reactor No. 6, the plant operators can be relieved of a considerable amount of their workload monitoring the reactors amid the ongoing uncertainties around the site. This substantially reduced the potential for human error.
The operators’ jobs is likely to be much less demanding and stressful now than before. However, they still need to constantly monitor the status of the shut down reactors and the spent fuel pools.
What are the risks to the spent fuel at the plant?
The plant still needs a reliable source of electricity to cool the six huge spent fuel pools that are inside the containment structures and to remove residual heat from the shutdown reactors. The cooling pumps for the spent fuel pools need much less electricity than the cooling pumps on the reactor’s primary and secondary loops, and the spent fuel cooling system could tolerate a brief electricity outage.
One more important factor is that the spent fuel storage racks in the spent fuel pools at the Zaporizhzhia nuclear power plant were compacted to increase capacity, according to a 2017 Ukrainian government report to the
There is also a dry spent fuel storage facility at the plant. Dry spent fuel storage involves packing spent fuel rods into massive cylinders, or casks, which require no water or other coolants. The casks are designed to keep the fuel rods contained for at least 50 years. However, the casks are not under the containment structures at the plant, and, though they were designed to withstand being crashed into by airliner, it’s not clear whether artillery shelling and aerial bombardment, particularly repeated attacks, could crack open the casks and release radiation into the grounds of the plant.
The closest analogy to this scenario could be a terrorist attack that, according to a seminal study by the
Next steps from the
IAEA and UN
Establishing a protection zone requires negotiations and approvals at the highest political and military levels in
– ref. Cold shutdown reduces risk of disaster at Zaporizhzhia nuclear plant – but combat around spent fuel still poses a threat – https://theconversation.com/cold-shutdown-reduces-risk-of-disaster-at-zaporizhzhia-nuclear-plant-but-combat-around-spent-fuel-still-poses-a-threat-190516
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