What is at stake in Chernobyl

The other three reactors It continued to operate, with the last closed in 2000. The radioactive fuel was removed from the reactor vessels and stored in another building on the site.

It wasn’t until 2016, in an engineering feat, that Unit 4 . remained Covered With a huge chassis weighing 36,000 tons.

But with the outbreak of war, Chernobyl reappeared in the headlines. Russian forces occupied the nuclear plant first, and then on March 9 destroyed a high-voltage line connecting the reactor site to the power grid.

This is important because when the reactors closed two or three decades ago, they put more than 20,000 spent fuel rods in them. storage facilities Which resemble deep swimming pools. There were four such ponds, the walls and bottom of which were lined with corrosion-resistant steel and reinforced concrete.

The spent fuel is hot. Each rod has a radioactive core surrounded by a zirconium cladding, which can burn at hundreds of degrees Celsius. So the pools need pumps to circulate the water and cool the bars. This requires electricity from the network.

Without access to electricity, Chernobyl reactors turn into backup diesel generators.

But the Ukrainian regulators of the State Nuclear Energy Regulatory Inspectorate of Ukraine He said March 9 that there was only enough fuel for 48 hours. Petro Cotten, president of the state-owned Energoatom which operates 15 other reactors in the country, He said that “at the Chernobyl nuclear power plant, the critical temperature can be reached within seven days if the generators are shut down.”

In this scenario, the water in the ponds could evaporate and the cladding on the spent fuel rails could be exposed to the air and catch fire.

This could release large amounts of cesium-137, a radioactive substance that forced a large-scale evacuation of people who lived anywhere near the Chernobyl site or the Fukushima region of Japan after the 2011 tsunami.

But the dangers of Chernobyl today are much lower. US experts say that – barring any other damage from combat – spent fuel rods can remain safely underwater for weeks, or even months. “Fuel rods have two decades to cool off. So the need for cooling isn’t that severe,” said Edwin Lyman, director of nuclear energy safety at the Union of Concerned Scientists.

“The water covering the spent fuel must be cooled and any evaporation replaced, but even with the loss of cooling, it will take a long time … to be detected,” Frank N. Von Hippel, professor emeritus of science and global security at Princeton University, said in an email.

“Most of the evidence suggests that if it’s just an electrical cooling system outage, it will likely be weeks before the potential for fuel detection is detected,” Lyman said. “Cruelly. And that would free up time to step in by either putting power back into the pumps or refilling the pool.”

US experts warn that the reactors now operating like Zaporizhzhia nuclear power plantcarry much greater risks because they operate at higher temperatures.

Depending on the outcome of the war, the dangers posed by Chernobyl can be further reduced. An American company was contracted Transfer spent fuel to long dry drumsBig ships surrounded by steel and concrete. But this transfer was just beginning and would take years to complete.