At this point in history “Chernobyl” has become a byword for “man-made disaster of the worst variety.” Much of the accident’s potency as both cautionary tale and actual disaster derives from its underlying technology: nuclear. The power of the atom can generate energy that outstrips the capacity of coal by about two times, or flatten a city and its population in a flash, like at Hiroshima and Nagasaki in 1945. And while 1986’s Chernobyl reactor No. 4 meltdown didn’t cause nearly as many overall deaths as Hiroshima and Nagasaki’s quarter of a million, two people were killed in the explosion, 28 people died in the short-term from acute radiation sickness, and 6,000 were left with thyroid cancer.
But simple facts of death and disease aren’t the worst part of Chernobyl. The accident was “man-made,” which is another way to say “preventable.” Each and every point along the way to Chernobyl’s meltdown afforded a chance to steer things away from their ultimate, devastating end — from the initial development of the plant and design of its reactors all the way to the fire-suppression equipment available to first responders. Its RBMK reactors were inherently unstable, as their steam produced an excess of neutrons that hastened reactor No. 4’s meltdown. On top of this, safety measures in the plant’s construction proved lax, and operations on the day of the meltdown faulty. When scientists like Soviet chemist Valery Legasov tried to speak up about the facility’s flaws they were ignored. The worst part about Chernobyl is that it didn’t have to happen.
A faulty reactor design
Chernobyl was a disaster in the making right from the get-go thanks to some very poor reactor design decisions. Either out of vanity, a sense of competition with the West, or legitimate ignorance, the World Nuclear Association explains that Soviet scientists developed their own blueprint when building a device for Chernobyl dubbed RBMK: reaktor bolshoy moshchnosty kanalnys, or “high-power channel reactor.” Chernobyl had four such machines, built in 1977, 1978, 1981, and 1983. The last reactor — No. 4 — is the one that melted down in 1986.
RBMK reactors differ from others because of one key reason: They use water as a coolant and graphite as a moderator, rather than using water for both purposes. Moderators slow neutrons down, which makes fission more likely — the fission that generates energy. This makes RMBK reactors more powerful but less safe.
By contrast, non-RMBK reactors intentionally sacrifice power for safety. When their temperature rises and water boils into steam, the machine becomes less efficient at slowing down neutrons because steam is a worse moderator than water. This reduces the likelihood of fission and prevents nuclear reactors from overheating — even at the cost of reduced power.
According to the World Nuclear Association, RMBK cores therefore employ a “positive void coefficient” — positive in that power always increases. More steam produces more power that produces a higher temperature that produces more steam, etc. That’s what happened in Chernobyl’s reactor No. 4 until it exploded and caught fire.
Lax safety measures
RMBKs could prove disastrous even without any other risk factors. But lo and behold: Chernobyl’s builder’s employed shoddy craftsmanship that only made an impending catastrophe more likely. In an interview with Sotsialisticheskaya Industriya (per Nature), Chernobyl director Viktor Bryukhanov described how — under immense pressure from Soviet authorities — he had to intentionally cut corners to finish the project. If he didn’t play ball he’d lose his job. “It is not within the power of one man to overthrow a system of economic-management relationships,” he told the outlet.
Looking to those cut corners, Chernobyl used regular electric cables throughout the plant rather than cords coated in fire-resistant materials. The World Nuclear Association also says that the plant’s nuclear cores weren’t properly contained and consisted only of a concrete-lined chamber sandwiched between two steel plates — one on top weighing 1000 tons and another on the bottom. This is also not common practice in the West.
Meanwhile, Nature describes problems with Chernobyl’s failsafe measures, particularly when it came to the control rods in its reactors. Control rods help regulate the rate of fusion, and are subject to automation depending on the needs of the reactor. But, Chernobyl’s construction allowed employees to manually remove too many control rods at the same time, which impacted automatic shutdown procedures and worsened reactor No. 4’s meltdown. These measures were changed in later reactors to disallow employees from removing too many of the devices, but by then Chernobyl’s damage was done. In short, the plant had no “safety culture,” as the World Nuclear Association says.
Botched systems operations
And so we come to the day of the disaster: April 26, 1986. Ironically, considering the aforementioned safety problems, Chernobyl’s reactor No. 4 melted down during a safety system test. The procedure was riddled with a chain reaction of bad luck and incautious decisions that might have been preventable even considering the plant’s design deficiencies. Those decisions started with a factor that proved more critical than it might have seemed: the time of day.
As the World Nuclear Association says, the safety test began on April 25 a little after 1:00 a.m. It involved shutting down reactor No. 4 and lowering its power along the way. But come 2:00 p.m., the plant had to maintain a power level of 1,600 MWt (megawatts thermal) to keep up with demands of the electric grid. So, the test was delayed and resumed late that night at a vulnerable point: a shift change. Meanwhile, the plant’s emergency core cooling system (ECCS) was isolated to continue the test. Though the decision didn’t significantly contribute to the accident, an available ECCS could have “reduced the impact slightly.”
For some unknown reason — likely human error — the operator let the system’s power fall below the allowed limits of 700 MWt. At 500 MWt the automatic regulating system kicked in, but power continued to fall, anyway. Thus began a complex game of switching water flows, removing control rods, closing valves, and seeing temperature and steam pressure spike and drop. A mere 11 seconds before the chief reactor control engineer’s final note at 1:24 a.m., the actuators in Chernobyl’s reactor four lost all power. Finally, the reactor blew.
Inadequate emergency response preparation
When Chernobyl’s reactor No. 4 blew in the early morning of April 26, 1986, 186 local firefighters raced to the scene. They weren’t exactly equipped with nuclear meltdown-fighting gear, but at no fault of their own. As the Nuclear Energy Agency explains, Chernobyl employed inadequate, inflexible emergency protocols that were not up to the task of dealing with the situation at hand. This means that even after the reactor blew, the extent of its disaster could have been mitigated had the right emergency response mechanisms been available.
Instead, as Coffee or Die explains, Chernobyl’s first responders showed up with no gas masks, no radiation suits, and wielding hoses used for spraying down any old local town fire. They arrived amazingly quickly — at 1:28 a.m., less than five minutes after the explosion — a testament to their readiness. But as they climbed onto the roof of reactor No. 4 to hurl water down onto the 3,600-degree Fahrenheit fire, they stood in the way of toxic smoke spewing 70 tons of uranium and 900 tons of graphite into the air. As The Washington Post reports, Chernobyl employee Yuri Andreyev reported seeing firefighters sink ankle-deep in melting asphalt, so hot were the flames.
As firefighters fought the blaze from the roof, Coffee or Die says that they were exposed to 20,000 roentgen equivalent man (rem) every hour — 45 to 50 times a lethal dose of radiation. Within a few weeks, 28 people were dead from acute radiation sickness.
Silenced scientists
At least one scientist tried speaking up Chernobyl’s faulty design, shoddy construction, and so forth: Valery Alekseevich Legasov. As ChernoblyX explains, Legasov was an award-winning chemist and first deputy director of the Kurchatov Institute of Atomic Energy, the institute that built the plant’s disastrous RMBK reactors. While he didn’t oversee reactor design directly, he was aware of its potential problems. And while it’s unlikely that he envisioned a catastrophic meltdown on par with what happened in 1986, he tried speaking up about improved safety measures for the reactors.
“I, as a chemist, was worried about the huge potential for chemical reactions in these devices,” Legasov said during a meeting at the USSR Academy of Sciences several years before Chernobyl blew. “There is a lot of graphite, a lot of zirconium and water.” In fact, he went one step further and pitched an improved form of shielding for the reactors, but his concerns were shot down. While we can’t say for certain, it stands to reason that those involved were afraid of retribution from Soviet authorities, same as Chernobyl director Viktor Bryukhanov told Sotsialisticheskaya Industriya.
After Chernobyl blew, Legasov went on to deliver a five-hour verbal report in Vienna in August that year regarding Chernobyl’s causes. Amongst other things, he confirmed what we’ve cited above: slipshod welding, pipework, and valves, RBMK channel failures, and more. It took until 1990 for the Soviet Union to accept responsibility for the whole, fully preventable Chernobyl disaster.
