What’s at risk in Chernobyl

The other three reactors continued to function, with the last of them shutting down in 2000. The radioactive fuel was removed from the reactor vessels and stored in another building on-site.


Wet storage for spent fuel rods

Wet storage for spent fuel rods

Wet storage for spent fuel rods

It was not until 2016, in a feat of engineering, that the unit 4 remains were covered with a massive structure weighing 36,000 tons.

But with war breaking out, Chernobyl has once again resurfaced in the headlines. First Russian forces occupied the nuclear plant, and then on March 9 they damaged a high-voltage line that connected the reactor site with the electricity grid.


Power lines to the former Chernobyl plant site

damaged

Power lines to the former Chernobyl plant site

damaged

Power lines to the former Chernobyl plant site

damaged

That’s important because when the reactors shut down two or three decades ago, they put more than 20,000 spent fuel rods in storage facilities that look like deep swimming pools. There were four of these pools whose walls and bottom are lined with corrosion-resistant steel and reinforced concrete.


INSIDE WET STORAGE FACILITY

INSIDE WET STORAGE FACILITY

INSIDE WET STORAGE FACILITY

The spent fuel is hot; each rod has a radioactive core surrounded by zirconium cladding, which can burn at hundreds of degrees Celsius. So the pools need pumps to circulate water and cool off the rods. That requires electricity from the grid.


Outer zirconium

metal casing

INSIDE DETAIL OF

SINGLE FUEL RED

Outer zirconium

metal casing

INSIDE DETAIL OF

SINGLE FUEL RED

Outer zirconium

metal casing

INSIDE DETAIL OF

SINGLE FUEL RED

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

But Ukrainian regulators from the State Nuclear Regulatory Inspectorate of Ukraine said March 9 that there was only enough fuel to last 48 hours. Petro Kotin, head of Energoatom, the state-owned enterprise that runs the country’s other 15 reactors, said that “at the Chernobyl nuclear power plant, the critical temperature can be reached in seven days if the generators are shut down.”

In that scenario, it’s possible for water in the pools to evaporate and the cladding on the spent fuel rods could be exposed to the air and catch fire.


INSIDE WET STORAGE FACILITY

INSIDE WET STORAGE FACILITY

INSIDE WET STORAGE FACILITY

That could release large amounts of cesium 137, a radioactive material that forced widespread evacuation of people who had been living anywhere near the Chernobyl site or the Fukushima area in Japan after the 2011 tsunami.

Chernobyl today, however, carries much less risk. US experts say that – barring any further damage from the fighting – the spent fuel rods could remain safely underwater for weeks, or even months. “The fuel rods have had a couple of decades to cool. So the cooling need is not that acute, ”said Edwin Lyman, director of nuclear power safety at the Union of Concerned Scientists.

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

“Most of the evidence suggests that if it’s just an interruption of the electrical cooling system, it would probably be weeks before the potential for the fuel to be uncovered,” Lyman said. “Roughly. And that would provide time for intervention either by restoring power to the pumps or refilling the pool. ”

US experts caution that reactors that are operating now, such as the Zaporizhzhia nuclear power plant, carry much greater risks because they run at higher temperatures.

Depending on the outcome of the war, the dangers posed by Chernobyl could be reduced even further. An American company has been hired to transfer the spent fuel into tall dry casks, large vessels surrounded by steel and concrete. But that transfer had only just started and will take years to complete.

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