Why the world is worried about a nuclear disaster in Ukraine

The world’s nuclear watchdog is visiting Ukraine’s Zaporizhzhia nuclear power plant this week amid fears sparked by shelling around the plant.
Rafael Grossi, director-general of the International Atomic Energy Agency (IAEA), warned last month that military action around the plant poses a “very real risk of nuclear catastrophe”.
Experts say the effects of such a disaster could lead to radiation leaks that would affect local communities but would most likely not result in a global catastrophe.
So what is at stake for Ukraine and the world if Russia’s war leads to nuclear catastrophe?
“The type of shelling we’re seeing shouldn’t have a significant impact on the reactors. The way it’s being done now, which you know is occasional shelling,” said Jonathan Cobb, senior communications manager at the World Nuclear Association.
According to the World Nuclear Association, Ukraine has 15 nuclear reactors that generate half of its electricity. Six of these reactors are located at the Zaporizhzhia plant.
The Zaporizhia plant has been under Russian control since the early days of its invasion of Ukraine, although Ukrainian workers still operate the plant.
The facility – the largest nuclear power plant in Europe – is right on the front line of fighting between Russian and Ukrainian forces.
The IAEA visit comes days after Ukraine warned of “new shelling”. In a statement released on Aug. 28, the IAEA said the shelling hit the area of the plant’s “two special buildings,” which house facilities such as water treatment plants, equipment repair shops and waste disposal facilities.
All measurements of radioactivity at the site were within normal ranges and there was “no evidence of a hydrogen leak”.
Jacopo Buongiorno, a professor of nuclear engineering at the Massachusetts Institute of Technology, said that nuclear power plants must be continuously cooled, which means there must be a way to dissipate the heat generated by nuclear fuel. When the plant is connected to the electricity grid of Ukraine, cooling is provided by water pumps fed from the electricity grid.
If not, the plants have backup diesel generators that can provide that power.
“In a well-functioning peacetime nuclear power plant, all these layers of protection and barriers are there. They work perfectly,” said Buongiorno. “And now there’s no indication they’re not working well, either.”
In history, there have only been two major nuclear reactor-related accidents. The first was Chernobyl in 1986, when a reactor went out of control during a test and exploded.
Recently, in March 2011, Japan was hit by a severe earthquake followed by a tsunami, causing a power outage at the Fukushima Daiichi Plant. The current caused the cooling systems in three reactors to fail and the core to overheat.
Experts say the worst-case scenario at Zaporizhia would be more like Fukushima than Chernobyl.
Fighting between Russians and Ukrainians could disrupt the reactors’ cooling mechanism, which could lead to the core overheating and melting – often referred to as a meltdown.
But getting to a meltdown would require a major event, experts say, because the reactors themselves are protected by two-meter-thick concrete containment vessels.
“At least in theory, even if there were a direct hit, there would be at least some protection,” said Mitchel Wallerstein, a nonresident senior fellow with the Chicago Council.
The biggest concern in such a scenario is for the local population living in the area.
The Ukrainian government has reportedly started distributing potassium iodide tablets, which prevent inhaled or ingested radioactive iodine from being absorbed by the thyroid — a gland in the neck that produces hormones that help regulate the body’s many functions, including its metabolism Valuation. Radiation exposure can increase the risk of thyroid cancer.
The European Union even announced on Wednesday that it is donating 5.5 million of these tablets at the request of the Ukrainian government.
Despite the temporary protection of the Zaporizhzhia Holding, experts see great value in the IAEA’s visit.
All but five of the 14 inspectors had left the plant on Thursday, along with Grossi, with the remainder scheduled to leave on Saturday.
There, the team will assess the safety of the facility and evaluate safety precautions and nuclear material surveillance equipment, as well as inspect the Ukrainian workers at the facility.
“These workers have essentially been operating the plant in the occupied territory for six months,” Cobb said. “And there have been reports – so far unconfirmed … of the poor treatment of workers by Russian forces there.”
Olli Heinonen, a former IAEA deputy director general who is now a fellow at the Stimson Center, said the agency is there to gather evidence and records of how the reactors have been operated over the past few months.
“I would expect this to take four or five days,” Heinonen said. “If it’s shorter then I think they’ll come back with less information and I’m sure Mr. Grossi won’t agree with that. But on the other hand they are in the hands of the occupying power.”
In a video posted to TwitterGrossi said the agency will establish a “permanent presence” at the plant, which experts say would be a valuable step.
“Just reporting on conditions would be a very valuable service. Maintaining that protective role and as an independent United Nations presence there that could report as well as possible on how the workforce was treated by Russian forces on the ground,” Cobb said.
“That would be a very meaningful and valuable role for them to perform.”
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