The Chornobyl Nuclear Power Plant‘s Chornobyl corium clean-up remains one of the most technically demanding challenges in the history of nuclear engineering, and a new video documentary by That Chernobyl Guy lays out exactly why, tracing the decades-long struggle to understand and eventually remove a material that had never existed before the night of the accident.
A Material Nobody Had Ever Seen Before
Corium is what happens when a reactor core melts catastrophically. At the Chornobyl Nuclear Power Plant (ChNPP), the No. 4 reactor’s botched turbine spin-up test, combined with operators disabling all safeties, allowed the bottom core chain reaction to run unconstrained. The result was a massive steam explosion that flipped the biosafety lid clean off the RBMK reactor, while simultaneously melting the core material, which then burned its way down through the concrete beneath.
What pooled and solidified below was a previously unknown amalgamation: nuclear fuel, fuel rod cladding, and concrete all fused together under conditions no laboratory had ever replicated. Soviet scientists, confronted with something entirely outside their experience, initially struggled to characterise it at all. As the documentary details, researchers even had the material shot at in order to obtain samples, a measure of how difficult conventional sampling proved in the intensely radioactive environment.
The parallel with trinitite, the glassy material created by a US nuclear weapons test, is instructive. Both are amalgamations of ordinary materials transformed beyond recognition by extreme energy release. Corium, though, came in vastly greater quantities and in a location that humans could not safely approach for years.
The Elephant’s Foot and the Chornobyl Corium Clean-up Reality
The so-called Elephant’s Foot (the most photographed and discussed corium formation at ChNPP) became infamous for its supposedly lethal radioactivity. The documentary pushes back on that reputation. The Elephant’s Foot is, in reality, one of the least radioactively dangerous parts of the exposed corium, representing only a small fraction of the total mass inside the No. 4 reactor. Repeated sampling attempts, combined with internal degradation from radioactive decay and weathering in the years before any shelter was in place, have left it mostly reduced to slightly radioactive, rusty-looking dust.
The bulk of the corium, spread through the lower reaches of the destroyed reactor building, is a different proposition entirely. It is this material that engineers must eventually remove and dispose of safely, and the scale of the problem is hard to overstate.
The New Safe Confinement and What Comes Next
Before any retrieval can begin in earnest, the site needed to be stabilised. The structure built to achieve that is extraordinary in its own right. According to The Chernobyl Gallery, the New Safe Confinement (NSC) is the world’s largest mobile metal structure, slid into position over the ruined reactor. Bechtel notes that the NSC cost $1.7 billion to construct. The broader financial effort behind making Chornobyl manageable is even larger: the Chernobyl Shelter Fund, established in 1997, has received more than €1.5 billion from 45 donor countries, according to The Chernobyl Gallery.
The NSC does more than simply contain the site. Its internal cranes and robotic systems are the tools through which the actual corium retrieval is planned to be carried out. The documentary outlines the current thinking on how that retrieval might proceed: rather than attempting to navigate the destroyed corridors and staircases that stymied Soviet engineers during their 1980s sampling attempts, robots would cut into the sides of the reactor building directly. This approach might make it possible to remove most of the corium without repeating the access problems that made the early years so dangerous and so unproductive.
It is an approach shaped entirely by hard experience. The Chornobyl corium clean-up is not a problem that yields to blunt force; it is one that has demanded, and continues to demand, solutions that simply did not exist when the explosion happened. With the NSC now in place and robotic cutting methods under consideration, the work of final disposal is at least within the realm of the possible, though the scale of what remains inside No. 4 means the task is measured in decades, not years.
