Russian forces shelled Europe’s largest nuclear plant early Friday, sparking a fire as they pressed their attack on a crucial energy-producing Ukrainian city and gained ground in their bid to cut off the country from the sea.
Leading nuclear authorities were concerned — but not panicked — about the damage to the power station. The assault triggered phone calls between Ukrainian President Volodymyr Zelenskyy and U.S. President Joe Biden and other world leaders. The U.S. Department of Energy activated its nuclear incident response team as a precaution.
What is a Nuclear Reactor?
Nuclear reactors are the heart of a nuclear power plant.
They contain and control nuclear chain reactions that produce heat through a physical process called fission. That heat is used to make steam that spins a turbine to create electricity.
With more than 440 commercial reactors worldwide, including 94 in the United States, nuclear power continues to be one of the largest sources of reliable carbon-free electricity available.
producing a steady supply of heat to boil water, drive steam turbines and thereby generate electricity.
How does a Nuclear Reactor Work?
The main job of a reactor is to house and control nuclear fission—a process where atoms split and release energy.
Reactors use uranium for nuclear fuel. The uranium is processed into small ceramic pellets and stacked together into sealed metal tubes called fuel rods. Typically more than 200 of these rods are bundled together to form a fuel assembly. A reactor core is typically made up of a couple hundred assemblies, depending on power level.
Inside the reactor vessel, the fuel rods are immersed in water which acts as both a coolant and moderator. The moderator helps slow down the neutrons produced by fission to sustain the chain reaction.
Control rods can then be inserted into the reactor core to reduce the reaction rate or withdrawn to increase it.
The heat created by fission turns the water into steam, which spins a turbine to produce carbon-free electricity.
Why Ukraine’s Zaporizhzhia Nuclear Plant is Very Important?
The Zaporizhzhia nuclear power plant, built between 1984 and 1995, is the largest nuclear power plant in Europe and the ninth largest in the world. It has six reactors, each generating 950MW, and a total output of 5,700MW, enough energy for roughly 4m homes.
In normal times it produces one-fifth of Ukraine’s electricity and almost half the energy generated by the country’s nuclear power facilities.
The plant is located in south-east Ukraine in Enerhodar on the banks of the Kakhovka reservoir on the Dnieper river. It is about 200km from the contested Donbas region and 550km south-east of Kyiv.
What Happened on Friday morning?
A fire broke out in a training building outside the plant in the early hours of Friday, after being shelled by Russian forces, Ukrainian authorities said.
What Happens if the Nuclear plant Loses Power?
The Ukrainians were in the process of taking the reactors offline to protect them. Only one of the six reactors operational at the power plant is now thought to be running.
However, reactors cannot just be turned off like conventional energy supplies. They must be cooled slowly over 30 hours, which requires a constant electricity supply to the plant.
A disruption to this energy supply – and therefore the cooling process – could also lead to radiation leakage.
This could happen if nuclear fuel exceeded its melting point and radioactive materials broke through the containment facilities.
Prof Claire Corkhill, a nuclear materials expert at University of Sheffield, says the worst-case scenario would be a loss of cooling similar to that at Japan’s Fukushima plant following the 2011 tsunami.
In that case a loss of power led to a loss of cooling, which caused a meltdown in three of its nuclear reactors.
What Happens Next?
Ukraine is heavily reliant on nuclear energy, with 15 reactors at four stations that provide about half the country’s electricity.
In the wake of the attack on Zaporizhzhia, U.S. President Joe Biden, British Prime Minister Boris Johnson and others called for an immediate end to the fighting there.
Ukraine is also home to the former Chernobyl nuclear plant, where radioactivity is still leaking, which was taken by Russian forces in the opening of the invasion after a fierce battle with the Ukrainian national guards protecting the decommissioned facility.
In an appeal to the IAEA for help earlier this week, Ukrainian officials said that Chernobyl staff have been held by the Russian military without rotation and are exhausted.
Grossi earlier this week appealed to Russia to let the Chernobyl staff “do their job safely and effectively.”
During fighting on the weekend, Russian fire also hit a radioactive waste disposal facility in Kyiv and a similar facility in Kharkiv.
Both contained low-level waste such as those produced through medical use, and no radioactive release has been reported, but Grossi said the incidents should serve as a warning.
“The two incidents highlight the risk that facilities with radioactive material may suffer damage during the armed conflict, with potentially severe consequences,” he said.
James Acton, the co-director of the Nuclear Policy Program at the Carnegie Endowment for International Peace, said the simple key to keeping the facilities safe was to immediately end any military operations around them.
“Under normal circumstances, the likelihood of a reactor losing power and of the emergency diesel generators being damaged and of not being repaired adequately quickly is very, very small,” Acton said.
“But in a war, all of these different failures that would have to happen for a reactor to become damaged and meltdown — the likelihood of all of those happening becomes much more likely than it does in peacetime.”
Mitsuru Fukuda, a professor at Nihon University in Tokyo and expert on crisis management and security, said the Zaporizhzhia attack raises broader questions for all countries.
“Many of us did not expect a respected country’s military would take such an outrageous step,” he said. ”Now that (Russian President Vladimir) Putin has done it, not only Ukraine but the international community, including Japan, should reevaluate the risk of having nuclear plants as potential wartime targets.”