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The Helicopters of Chernobyl

30 years after the explosion that triggered the largest nuclear disaster in history, we take a look at the role helicopters played in the disaster response effort at Chernobyl


By Stefano Silvestri



On a clear day in Pripyat, Russia on the 26th of April 1986, the city, home to 14,000 at the time, was founded in 1970 to house the workers of the Chernobyl Nuclear Power Plant. One of the untold stories of the Chernobyl disaster, is one that details the roles that helicopters played in stemming the radioactive material spread that could have had worldwide consequences.

It was to be an experiment like hundreds of others, a test of a turbo-generator in the nuclear plant at Chernobyl. But something went wrong on that one particular shift in the plant that turned into a chain reaction that changed the world, destroyed whole generations, and forever changed the very concept of nuclear energy.

The immediate aftermath of the Chernobyl disaster made infamous the so called “liquidators”, thousands of people, including soldiers and technicians sent into the still smoldering Central in an attempt to extinguish the raging fire of graphite.



THE HELICOPTERS OF CHERNOBYL

36 hours into the disaster it was decided to utilize helicopters to assist in stemming the radioactive matter pouring into the atmosphere. Helicopters were sent from Siberia 4,000 kilometers from Chernobyl to dump hundreds of tons of sand, lead, clay and boron directly on the remnants of the exposed reactor at the Chernobyl plant. The mission was simple for the helicopters: close the nuclear wound exposed in the initial explosion.

In time, the exposed reactor would be enclosed by a sarco****us of concrete that would later be rebuilt with reinforced steel to prevent the leakage of radiation and prevent any potential flare ups from the still smoldering radioactive material inside.

The response to the disaster required many different helicopter types. In all, five helicopter types were used in the response to Chernobyl: the Mi-2 Hoplite, Mi-6 Hook, Mi-8 Hip, Mi-24R Hind and the largest helicopter in the world, the Mi-26 Halo. In addition to initial fire prevention tasks, the aircraft were also used in support of the “liquidators” operations to complete construction of the concrete sarco****us used to initially contain the radioactive material. Each helicopter had a specific task during the crisis response. The versatile Mi-2 was employed to conduct radiation measurements from the air, the Mi-6, capable of lifting 12 tons, was used to deploy extinguishing material over the reactor core, the Mi-8 was used in support of the technicians on the ground.

The Mi- 24R, designed as an attack helicopter, was instead used for radiological tasks. The front machine gun replaced by a dosimeter that conducted radiation monitoring and was used in a surveillance capacity to designate safe routes for workers on the ground. On the first day of operations at Chernobyl, pilots and crew completed 96 missions, doubling that effort in the next 24 hours. By April 28, 1986, two days after the initial explosion at Chernobyl, operational escalation had become reality as did the dangers posed to the air crews of the helicopters. To shelter from radiation, crews were using some of the lead destined to be released over the damaged reactor core to cover and protect the platforms where the aircraft were housed. An idea born out of desperation, ingenuity and practicality. The crews were able to decrease the lethality of exposure with this method by almost two and a half times.




The Mi-26 was able to stay the longest periods over the exposed reactor to drop retardant loads with 100% accuracy

The heaviest work at Chernobyl was completed by the Mi-26, the largest helicopter in the world. The reasons behind using this helicopter at the time were obvious due to its size and lifting ability, but the Mi-26 was also the only aircraft capable of withstanding the extreme heat and radiation over the exposed reactor core. The Mi-26 was also the only helicopter equipped with a system for monitoring the release of extinguishing compounds, using cameras to greatly increase the accuracy of dropping the material precisely and considerably decreasing the number of flights needed to deploy material.

Unlike the Mi-6, the Mi-26 was also able to remain hovering over the crater containing the exposed radioactive core longer. The Mi-26 had a 100% on target success rate dropping its retardant material on target during the response. Double the amount of material dropped by other fixed wing assets used in the crisis response.



THE Mi-8 CRASH

The missions that had the most risk associated with them were completed in the first two weeks of the Chernobyl disaster. But later in the response and recovery effort, the crew of one of the Mi-8 was to pay the ultimate price. “Before the accident there were huge cranes around the reactor. After the explosion, some of these were literally hanging in the void without support” recalled Colonel Oleg Chichcov years after the disaster. Chichcov was at the time of the explosion at Chernobyl a Mi-26 helicopter instructor that was dispatched as part of the response effort. “I had been assigned to a mission area, but I refused until the cranes had been made safe.” After Chichcov’s refusal, one of the Mi-8 crews on scene was asked to complete the mission, accepting it and ultimately, never returning.

All occupants of the helicopter were killed in the crash, which was recorded on video, yet not seen until the relaxation of censorship after the fall of the Soviet Union. Helicopters continued to fly at Chernobyl until the end of 1986, completing what would become known as the most unprecedented fire season in the history of mankind. Fighting a seemingly endless fire that refused many attempts to extinguish it. For the aircraft that fought to save Russia from nuclear contamination, the outcome was bleak. All of the helicopters used in the initial two weeks were so contaminated by radioactive material that they were forced to be grounded, never to fly again. The helicopters were stored along with other contaminated vehicles in a remote location, stored until being destroyed years after the disaster.

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Originally Posted By awilll⏩

Strong radiation does a number on electronics. The particles have enough energy that if they impact molecules in a semiconductor, they ionize the material (liberate electrons from their parent atoms). This can cause a variety of effects.

At low levels, it causes "soft errors". The sudden liberation of charged particles causes circuits to misbehave and interpret what should be a digital "0" as a "1" (or vice versa). This can cause temporary misbehavior, or flip bits in memory.

At more extreme levels, it can damage thin insulators (and their interfaces with the semiconductor) and cause permanent paths of electrical "leakage" (current flows where it shouldn't). These "hard errors" can render circuits inoperative.

It is somewhat possible to mitigate these issues, but if the radiation is really strong, it's almost impossible to do with something small like a robot. They simply can't carry the amount of shielding that would be required.

At really, really strong radiation levels, the bonds in metals can be damaged, causing the metal to become brittle and weaker than it should be.