Experts remain concerned about the safety of the Zaporizhzhia nuclear power plant as the war in Ukraine rages on. In the worst case, it could lead to a “disastrous chain of events,” power systems expert Victor M. Becerra told Newsweek.

Russian troops seized the plant—which is Europe’s largest—last March, shortly after the invasion of Ukraine began on February 24. Since then, the plant has repeatedly come under fire, triggering fears of nuclear disaster. Russian state media said Monday that fighting had intensified in the city, France24 reported.

The situation is particularly poignant given that Ukraine suffered the world’s worst nuclear disaster at the Chernobyl power plant in 1986. A disaster on the scale of Chernobyl occurring at Zaporizhzhia is unlikely, though, because well-designed plants such as Zaporizhzhia are built to withstand damage. But as the war rages on and Russian troops continue to advance into the city, concerns remain.

“Since March 3, 2022, there have been military hostilities in and around the Zaporizhzhia power plant,” said Becerra, a professor of power systems engineering at the University of Portsmouth. “The plant, currently controlled by Russian forces, has a total electrical power output of 5,700 MW, the largest in Europe.

Nuclear power plant at sunset
A stock photo shows a nuclear power plant. Concerns are continuing to mount over the Zaporizhzhia plant as fighting between Ukrainian and Russian forces intensifies in the area.

“The ongoing military conflict in the area has given rise to concerns by the international community, as repeated shelling has occurred since August 2022, some of which resulted in damage to buildings inside the complex.”

One of the largest concerns is that there could be a physical breach of the plant’s reactors. An artillery strike could damage the barriers that keep the radioactive material concealed, but the reactor is protected by a foot of steel.

“The conflict may compromise the security of the nuclear material stored in the complex,” Becerra said. “These spent fuel stores are more vulnerable than the reactor buildings. The reactor buildings are strong enough to withstand shelling.

“However, in the worst case, such as a direct missile strike on a reactor building, damage to the integrity of the plant may affect the cooling and emergency systems of the plant, which may lead to a disastrous chain of events that could result in the release of radioactivity into the environment.”

Becerra said the conflict has damaged the 750 kV transmission lines connecting the plant to the main electricity grid, resulting in some “critical power lines” going out of service.

“Under normal circumstances, these transmission lines transport electricity produced at the power plant but simultaneously provide power to essential services, including reactor cooling and emergency systems,” Becerra said. “These incidents have resulted in the temporary activation of emergency backup systems at the plant and increased safety risk should they fail.”

If the plant were to lose all electrical power, cooling systems could also stop working, potentially causing a meltdown.

“In [a meltdown] scenario, a reactor would be shut down and only generating of order of 1 percent of its normal power via “decay heat” [from radioactive products already previously built up in the fuel—actually also the reason why spent fuel is more dangerous to humans than fresh fuel],” Paul Norman, director of the Birmingham Centre for Nuclear Education and Research and professor of nuclear physics and nuclear energy at the University of Birmingham, previously told Newsweek.

But even in that situation, the overheated fuel would need to melt through the reactor’s vessel, and then seep through its walls, to pose a risk.

“This scenario is not like Chernobyl, where the bad/unstable design of the reactor caused it to internally explode, and it also lacked these thick protective layers that I mentioned—thus propelling a radioactive plume upwards which the winds could sweep around,” Norman said.

The scenario, however, would be similar to the 2011 nuclear disaster at the Fukushima plant in Japan, where a tsunami and earthquake caused systems in three reactors to fail and the cores to overheat, resulting in the world’s second-largest nuclear disaster.

More recent concerns surround the team of operators at the Ukraine plant, and how they are able to carry out maintenance to ensure its safety. Since Russian troops took hold of the area, the staff has remained in place.

“Even though all six reactors are currently shut down, there are worries about the potential effects on the ability of the much reduced and stressed team of operators to carry out essential repairs and maintenance at the plant, which may impact its safe operation,” Becerra said.

And although the International Atomic Energy Agency (IAEA) plans to establish a safe zone in the area, there are factors that are making it difficult to do. Rafael Grossi, head of the U.N. nuclear watchdog, said this month that discussing deals around a safe zone are becoming more difficult because of military involvement. Experts continue to stress the importance of establishing a safety zone.

“Although the causes of the Chernobyl disaster in 1986 are unlikely to be repeated in Zaporizhzhia, the scale of that disaster and its consequences are a stark reminder of why establishing a safety zone around the Zaporizhzhia nuclear plant is so important,” Becerra said.

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