(CNN) — Russian soldiers occupied the Zaporizhzhia nuclear power plant, the largest in Europe, following fierce fighting near Ukrainian facilities that drew international condemnation and sparked fears of a possible nuclear incident.
Those concerns were quickly downplayed by experts, who warned against comparisons to the Chernobyl plant, where the world’s worst nuclear disaster occurred in 1986.
Modern plants are significantly safer than older ones like Chernobyl, they said. However, analysts expressed their horror that the violent Russian invasion of Ukraine has spread to nuclear facilities, a development with few recent similarities.
And the site’s operator and regulator have reported that the situation on the ground is “extremely tense and challenging,” according to the International Atomic Energy Organization (IAEA).
“No country besides Russia has fired on the reactors of an atomic power plant. The first time, the first time in history,” Ukrainian President Volodymyr Zelensky said in a facebook post.
The IAEA called for an end to the fighting around the facilities, and world leaders were quick to criticize Russia’s move.
No radioactive material was released from the plant, but it was a “close call,” Rafael Grossi, director general of the IAEA, told CNN’s Christiane Amanpour on Friday.
Following the Russian attack, “there was great concern whether the physical integrity of the nuclear power facility had been compromised, with the (…) possible risk that this entails,” Grossi said.
Grossi had earlier told reporters that what will happen next in Zaporizhzhia is “a situation that is very difficult to sustain, very fragile” as long as there is an active military operation and Russian forces are under control. “This is unprecedented,” he said. “Completely uncharted waters.”
What happened at the Zaporizhzhia NPP?
Reports of an attack on the facility surfaced Friday morning, with a video of the scene showing bursts of gunfire apparently directed at the Zaporizhzhia plant before dawn.
“The Russian army is firing from all sides at the Zaporizhzhia nuclear power plant, the largest nuclear power plant in Europe,” tweeted Ukrainian Foreign Minister Dmytro Kuleba.
A large number of Russian tanks and infantry “broke through the blockade” towards Enerhodar, a few kilometers from the Zaporizhzhia power plant, according to Grossi.
A Russian shell then hit a building inside the plant site, sparking a localized fire, but none of the reactors were nearby and they were not affected, the IAEA chief said.
In a Facebook post early Friday, Zelensky accused Russian troops of committing a “terrorist attack” by intentionally shooting at the power plant, which could put the lives of millions at risk.
“Russian tanks, equipped with thermal imaging, are shooting at the atomic blocks. They know what they are shooting at. They have been preparing for this (attack),” Zelensky said in the post, adding that “our guys hold the station of safe atomic energy.
In a statement Friday morning local time, the State Nuclear Regulatory Inspectorate (SNRI) confirmed that the Zaporizhzhia nuclear power plant in southeastern Ukraine was occupied by Russian military forces, but said officials remained in contact with plant management.
The plant’s six reactors remain intact, although auxiliary compartment buildings for Reactor Unit 1 have been damaged, the SNRI said in its statement. Four of the remaining units are cooling while one unit is providing power, according to the release.
Separately, Ukraine’s nuclear power operator Energoatom said that the “administrative building and the checkpoint at the station are under the control of the occupants.” He said staff are working on the power units to ensure their stable operation.
How dangerous was the attack?
Ukrainian officials were quick to sound the alarm about the possible implications of the attack. Foreign Minister Dmytro Kuleba said “if (the plant) explodes, it will be 10 times bigger than Chernobyl”, and Zelensky said such an incident would mean “the end of Europe”.
But experts were quick to emphasize that they did not believe a reactor could explode, pointing to fundamental differences between Chernobyl and the Zaporizhzhia plant.
The IAEA said Ukrainian authorities had reported background radiation levels as normal and the fire had not affected “essential” equipment. The plant did not sustain any critical damage in the attack, Andrii Tuz, a spokesman for the plant, told CNN on Friday.
“The design is very different from the Chernobyl reactor, which did not have a containment building and therefore, in my opinion, there is no real risk to the plant now that the reactors have been safely shut down,” he said. Mark Wenman, Reader in Nuclear Materials at Imperial College London, at the Science Media Center (SMC).
The Chernobyl disaster took place at a plant using Soviet-era graphite-moderated RBMK reactors. But the Zaporizhzhia facility uses a pressurized water reactor known as the VVER model.
“The VVER design is inherently safer and more secure than the Chernobyl RBMK systems,” explained Jon Wolfsthal, Senior Principal at Global Zero and former Senior Director for Arms Control and Nonproliferation at the National Security Council, on Twitter on Friday.
A VVER reactor cannot “‘escape itself’ as the RBMK could,” Malcolm Grimston, an honorary senior fellow at the Imperial Center for Energy Policy and Technology in London, told the SMC.
But even if a reactor explosion were highly unlikely, other incidents could occur as a result of bombings or fires at the site.
“It’s really the electrical and plumbing that you’re worried about,” Joseph Cirincione, distinguished fellow at the Quincy Institute for Responsible Statecraft, told CNN on Friday.
Electricity at the Fukushima plant in Japan was cut off during the nuclear disaster there in 2011, while the reactors remained intact. “That meant you could no longer pump cooling water through the reactors or through the cooling ponds,” Cirincione said.
“I don’t think we’re out of the woods yet. We have to make sure the Russians who are taking over know what they’re doing,” he added.
Grossi, the director general of the IAEA, told CNN on Friday: “What I am saying to (Russia) and everyone is that the utmost restraint must be exercised in and around these types of facilities. Because, knowingly or not , you can get into a disaster very quickly, and that’s why we’re so concerned.”
How safe are modern nuclear facilities?
Differences in design and safety standards mean that the possibility of an on-site nuclear reactor exploding and causing disaster is not of concern to nuclear experts.
They noted that the threat would be greater if a nuclear reactor were to come under a targeted and sustained attack with the intention of causing a nuclear incident, which was not the case in Zaporizhzhia and would make little sense given the proximity of Russia’s major cities to all nuclear power plants. from Ukraine.
The pressure vessel of a modern reactor “is very robust and can withstand considerable damage from phenomena such as earthquakes and, to some extent, kinetic impacts,” Robin Grimes, professor of materials physics at Imperial College London, told SMC.
Six power units generate between 40 and 42 billion kWh of electricity at the Zaporizhzhia Nuclear Power Plant.
“It is not designed to withstand” attacks with explosive weapons, he added. “It seems unlikely to me that such an impact would result in a Chernobyl-like nuclear event (but) this has never been proven and is not impossible.”
“It is therefore astounding and reckless in the extreme that shells have been fired near a nuclear power plant,” he said. “Even if they weren’t targeting the nuclear plant, artillery is notoriously inaccurate in wartime.”
How many nuclear power plants does Ukraine have?
Ukraine relies heavily on nuclear power. The Zaporizhzhia plant contains six of the country’s 15 nuclear power reactors, according to the International Atomic Energy Agency (IAEA), and the facility alone accounts for a fifth of Ukraine’s average annual electricity output, according to Energoatom, Ukraine’s nuclear power operator.
That makes their occupation by Russian forces very significant; if the plant were to stop working it would severely affect the energy supply for millions of Ukrainians.
In total, Ukraine has four nuclear plants: two, including Zaporizhzhia, in the south of the country, and two more in the northwest, in regions that Russian troops have not occupied.
Those do not include the closed plant of Chernobyl, in the north of the country, which was occupied by Russian forces on the first day of their invasion of Ukraine. According to Mykhailo Podolyak, a Ukrainian presidential adviser, control of the Chernobyl zone was lost after a “fierce battle”.
More than 90 operational staff at the Chernobyl power plant were taken hostage by Russian forces after they occupied the plant, Ukraine’s ambassador to the United States Oksana Markarova said.
The Chernobyl plant was closed after the 1986 disaster and has been inside an exclusion zone ever since, but construction and reclamation efforts have continued at the site to reduce the risk of future radiation leaks.