By Linda Pentz Gunter
After 36 years the nuclear site is again in danger
For 36 years things had been quiet at Chornobyl. Not uneventful. Not safe. But no one was warning of “another Chornobyl” until Russian forces took over the site on February 24 of this year.
Russia’s invasion of Ukraine first took their troops through the Chornobyl Exclusion Zone, where they rolled armored vehicles across radioactive terrain, also trampled by foot soldiers who kicked up radioactive dust, raising the radiation levels in the area.
As the Russians arrived at the Chornobyl nuclear site, it quickly became apparent that their troops were unprotected against radiation exposure and indeed many were even unaware of where they were or what Chornobyl represented. We later learned that they had dug trenches in the highly radioactive Red Forest, and even camped there.
Supposed to last just 100 years, that still inadequate timeframe was thrown into jeopardy as a reported firefight broke out prior to the Russian takeover. Fears arose that the shocks and vibrations of repeated shelling and artillery fire could cause the NSC to crack or crumble.
Housed inside the NSC is the destroyed Unit 4 as well as 200 metric tonnes of uranium, plutonium, irradiated dust, solid and liquid fuel, and a molten slurry of uranium fuel rods, zirconium cladding, graphite control rods, and melted sand.
The fuel lump from Unit 4, sitting inaccessible on a basement floor, remains unstable. In May 2021, there was a sudden and baffling escalation of activity there and a rise in neutrons, evoking fears of a chain reaction or even another explosion.
All of these volatile fuels and waste inventories still depend on cooling pumps to keep them cool. And those cooling pumps depend on power.
However, not everything at the site is within the NSC.
Units 1, 2 and 3 are not yet fully decommissioned and likely won’t be until at least 2064. Even though their fuel has been cooling for 20 years, it cannot go indefinitely without power. And managing it necessitates skilled, and unharried, personnel.
Loss of power threatens the ISF-1 spent nuclear fuel pool where much of the waste fuel is still stored. As nuclear engineer, Dave Lochbaum, described it in an email, “If forced cooling is lost, the decay heat will warm the water until it boils or until the heat dissipated by convective and conduction allows equilibrium to be established at a higher, but not boiling, point.
“If the pool boils, the spent fuel remains sufficiently cooled until the water level drops below the top of the fuel assemblies.”
At that point, however, adds Union of Concerned Scientists physicist, Ed Lyman, “a serious condition in the ISF-1 spent nuclear fuel pool” could occur. “However, because the spent fuel has cooled for a couple of decades there would be many days to intervene before the spent fuel was exposed.”
At the time of the invasion, workers at the site had been engaged in moving the full radioactive waste inventory from all 4 of the Chornobyl reactors, from the common fuel pool to the ISF-2 facility where it will be dismantled and put into long-term storage casks. It is unclear whether this operation was halted, but likely so.
Fire also remains a significant risk at the site. The massive 2020 wildfire that reached the perimeter of the Chornobyl plant site, occurred in April, well before the dry season. Military combat clearly invites the risk of igniting a lethal fire.
Indeed, the entire region, known as the Chornobyl Exclusion Zone, is a tinderbox. As Dr. Tim Mousseau and his research team discovered, dead wood and leaf litter on the forest floors is not decaying properly, likely because the microbes and other organisms that drive the process of decay are reduced or gone due to their own prolonged exposure to radiation.
As leaf litter and organic matter build up, the risk of ignition increases. There have been several hundred fires in the Zone already, sometimes, incomprehensibly, deliberately started. The explosions of war fighting could spark another. Indeed, stories did emerge about fires during the Russian occupation, their origin unclear.
But even without military attacks or destruction of the site, it was still at risk, especially when offsite power was lost, twice, raising fears of a potential catastrophe if emergency on-site power — consisting of diesel generators — did not work or ran out of fuel. Later reports revealed that plant workers had taken to stealing Russian fuel to keep those generators running.