Reactor 4 at Chernobyl presents one of the planet’s most hostile environments. Beyond the inherent physical dangers, the ruins are intensely radioactive, cast in perpetual darkness, and encased within a deteriorating concrete sarcophagus. This structure, in turn, is now overarched by the New Safe Confinement.
Despite these formidable obstacles, it remains critical for scientists to ascertain the current conditions within. This crucial undertaking falls to Anatoly Doroshenko, a young scientist affiliated with the Institute for Safety Problems of Nuclear Power Plants (ISPNPP). His work involves what might be considered the most perilous job globally: venturing deep into the reactor’s dilapidated core to collect readings and samples. His proximity to the remnants of the core can be as close as 8 meters, a feat he undertakes perhaps as frequently as once a month.
Doroshenko, speaking beside a scale model of the Chernobyl facility at the institute’s laboratory within the exclusion zone, dismisses the notion of fear. “It’s not scary,” he states. “I prepared for it for a considerable duration. One simply needs to achieve a mental state that allows for acceptance of the task and its inherent necessity.”
He elaborates on the unique sensation associated with such work. “It is indeed a peculiar feeling. I believe it can be likened to the triumph of conquering Everest, venturing into the vastness of space, or exploring the ocean floor. A distinct surge of adrenaline is invariably present.”
Each expedition into the reactor requires the completion of specific tasks within a limited timeframe. This imposes a demand for a careful balance between speed and meticulousness. “You must thoroughly understand your objectives and the path you will take,” Doroshenko advises. He reiterates the importance of self-control, almost as a personal mantra. “You must maintain control of yourself.”
“The awareness that everything is contaminated is paramount. When you touch any surface, you must know precisely what that surface is, to avoid contaminating your clothing or yourself,” he explains. “The core principle is to be fully cognizant of your planned actions, as the safe duration for occupancy is limited. While the desire to perform the work is strong, and the urge to observe something remarkable is present, this is not a sightseeing tour. You are engaged in critical work, therefore a clear understanding of all necessary actions must reside in your mind.”
Doroshenko’s protective gear varies based on the area’s radiation levels. In less hazardous zones, he wears a hat, protective gloves, and a respirator. For areas with higher contamination, he adds a full-body suit to shield against dust, or even a secondary polythene suit. Lead aprons are also available, but their weight and bulk significantly impede movement through the confined and intricate spaces within the reactor.
As a younger scientist, he accompanied an older colleague to the main circulation pumps. These pumps were integral to reactor 4’s cooling system and played a role in the chain of events leading to the 1986 disaster. “It serves as a critically important site to observe, and it is widely recognized,” he notes. “We have been examining the extensive damage caused by the explosion.”
“Our primary defense is knowledge, not the protective suits,” emphasizes researcher Olena Pareniuk from ISPNPP. “Anatoly is among our key personnel. He appears fatigued and somewhat subdued, as we all do, but his performance is excellent. We have a limited number of young individuals proficient in dosimetry measurements.”
Viktor Krasnov, the acting director for science at ISPNPP and Doroshenko’s superior, states that numerous generations of scientists have entered the reactor since 1986 to conduct measurements and deploy sensors. Within, they encounter cramped conditions, pipes filled with radioactive water, and substantial formations of corium. Corium, a molten mixture of fuel, concrete, and metal, formed under the extreme temperatures of 2500°C following the disaster, has flowed and solidified throughout the ruins, creating distinctive, unusual shapes.
“The earliest individuals who actually entered the facility coined informal names for the various formations encountered: the elephant’s foot, the cat’s house, the dog’s house, the octopus beam, the mammoth beam,” Krasnov recalls. “The interior is entirely devastated, rendering all pathways exceptionally challenging to navigate.”
The potential risks are nearly innumerable. One such danger is the 2200-tonne Upper Biological Shield, formerly positioned atop reactor 4 and now referred to as Elena. It was dislodged during the explosion, landing at a 15-degree angle, supported by debris. Its potential collapse could destabilize the precarious ruins and unleash vast quantities of radioactive dust.
A more enduring risk, underscoring the necessity for consistent, precise readings, stems from intermittent surges in nuclear activity. The exact location of all fuel material within the reactor remains unknown, and this material occasionally becomes active.
When uranium or plutonium fuel undergoes radioactive decay, it emits neutrons. These neutrons can initiate a fission reaction if they are absorbed by another radioactive nucleus. However, significant volumes of water can impede these neutrons, preventing their capture. In the immediate aftermath of the disaster, the sarcophagus maintained dry conditions inside the reactor, leading to a neutron spike.
Subsequently, the presence of water increased. This was partly due to numerous holes in the concrete shelter allowing ingress for birds and weather, which raised humidity levels and consequently reduced neutron flux. “Currently, with the New Safe Confinement installed, humidity is lower. Consequently, we anticipate the potential for incidents and require advance knowledge,” Krasnov notes. This necessity highlights the critical importance of Doroshenko’s continued expeditions into the reactor to gain a clearer understanding of the prevailing conditions.
Despite the stringent safety protocols observed at Chernobyl, the act of entering an exploded reactor will never be entirely without peril. “I am aware of the risks,” Doroshenko acknowledges. “Consequently, I remain concerned about my health, as a lapse in this concern could lead to errors. While I cannot predict future health complications, I understand that adherence to radiation safety standards can mitigate these risks.”