We are all familiar with the dropping of nuclear bombs on Japan’s Hiroshima and Nagasaki by the United States in 1945, which marked the end of World War II. However, this event was not the greatest nuclear disaster ever faced by humanity. While the bombings of Hiroshima and Nagasaki resulted in immediate and horrific devastation with estimated deaths ranging from 150,000 to 246,000, the Chornobyl disaster, which caused fewer immediate deaths, released approximately 400 times more radioactive material into the atmosphere, contaminating a vast area for decades to come. The severity of the disaster can be understood by the extent of radiation, as the radiation spread across entire Europe. It remains the worst and costliest nuclear disaster, with an estimated cost of USD 700 billion.
The Chernobyl disaster, which unfolded on April 26, 1986, at the No. 4 reactor of the Chernobyl Nuclear Power Plant, located near Pripyat, USSR (130 km from Kiev, now capital of Ukraine), remains a stark reminder of the catastrophic potential of nuclear technology gone awry. Join us as we unravel the layers of this tragedy.
How a Simulated Test Led to the Biggest Nuclear Disaster?
It was a pleasant day at Pripyat, a small area, near Chernobyl Town, situated 130 kilometers from what is now the capital of Ukraine (USSR at the time of the disaster). The chernobyl nuclear reactor consisted of 4 reactors. To evaluate the turbine generator’s capacity to supply emergency power to the reactor’s cooling water pumps in the case of an external power outage, a simulated test was scheduled in Reactor 4 at 14:15 hours on 25 April 1986. All the personnel of the day shift were briefed on the operating instructions for the test. Since power was required to meet the evening’s peak demand, the Kyiv electrical grid controller asked at 14:00 hours to delay further reduction of Chernobyl’s output.
As the day passed, the day shift was replaced by the evening shift. The Kyiv grid controller permitted the reactor shutdown to resume at 23:04. The evening shift left at midnight and the night shift takes over, which was less experienced. According to reports, they were not given a thorough explanation of the ongoing safety test’s details. The night shift had very little time to plan and carry out the experiment. Anatoly Dyatlov, the Chernobyl Nuclear Power Plant’s (ChNPP) deputy chief engineer, was present to supervise the test. According to the test plan, reactor power was gradually reduced to a thermal level of 700–1000 MW, and at 00:05 on April 26, an output of 720 MW was achieved. At 00:28, reactor power unexpectedly lowers to a dangerously low level (near zero). To combat this, operators commit several crucial mistakes, such as removing the majority of the control rods much beyond what is required as per safety regulations. As a result, the reactor core becomes extremely unstable.
At 01:00, after a few attempts, the operators succeeded in increasing the power to a level that was still far lower than what was intended for the test but was judged adequate by the shift supervisor to move forward. It is important to note that, according to the test protocol and as a result of previous operator decisions, several safety systems, such as the emergency core cooling system (ECCS) and automated shutdown mechanisms, continue to be deactivated. At 01:03, the test to determine how long the turbines would run and supply electricity to the water pumps in the case of an external power outage began. The 4th turbine generator was disconnected from the reactor.
At 01:23, the turbine’s coasting down begins, and the pumps powered by it start to reduce water flow to the reactor core. This leads to an increase in steam formation in the core. Due to the RBMK reactor’s positive void coefficient at low power, this increase in steam causes a rapid and uncontrolled surge in reactor power. The shift supervisor presses the AZ-5 (“Scram”) button, which should have fully inserted all control rods into the core, to request an emergency shutdown after noticing the power surge. However, their initial insertion enhanced reactivity in the lower portion of the core before the neutron-absorbing sections entered because of a design mistake in the control rods (graphite tips and void followers).
When there was a significant and quick rise in power, the emergency protection system’s power excursion rate signaled. The power continues to increase dramatically and surpasses 5300 MWt, which was significantly higher than its typical operating level of 3200 MWt. Because of the tremendous pressure and heat generated by the uncontrolled nuclear reaction, the fuel conduits ruptured. As a result, the generation of steam increases quickly. This rapid increase in steam is believed to had caused a steam explosion, as water vaporized quickly within the overheated reactor core. The explosion blew off the 1,000-ton concrete and steel cover of the reactor building and destroyed the reactor core.
At 01:23:52, a second, stronger explosion occured, most likely as a result of the buildup and detonation of hydrogen created by the reaction of superheated steam with the graphite moderator and the zirconium alloy cladding of the fuel rods. The reactor building was further destroyed, containment was broken, and flaming graphite and fuel particles were thrown into the surrounding region, causing numerous fires, including one on the turbine hall’s roof.
Chaos breaks out instantly. Workers find it difficult to understand what had transpired from the fire, debris, and increasing radiation levels. The immediate focus was on putting out the fires, especially the roof fires, without fully comprehending the massive outpouring of radioactive chemicals and the devastating damage to the reactor core.
The Reason behind Chernobyl Disaster
- Positive Void Coefficient: A dangerous feature of the RBMK reactor was its positive void coefficient. This implied that the nuclear reaction would increase rather than decrease if the coolant water in the reactor core boiled and formed steam voids (as a result of higher heat). Boiling should help slow down the reaction, which is the reverse of what is intended in a stable reactor.
- Design Flaw in the Control Rods: The control rods were made of graphite, which was supposed to slow down the nuclear reaction when inserted. However, when the operators attempted an emergency shutdown by inserting all of the control rods, the graphite tips actually increased reactivity in the bottom portion of the core before the neutron-absorbing parts could take effect. As a result, rather than the desired quick shutdown, there was a power surge.
- Low Power Instability: The RBMK reactor was inherently unstable when it operated at low power levels, which is what happened before the safety test.
- Lack of Containment Structure: In contrast to many nuclear power plants in the West, the Chernobyl reactors lacked a sturdy containment structure that would have stopped the radioactive materials from leaking in the case of a significant accident.
- Inadequately Planned and Performed Safety Test: The purpose of the safety test was to determine whether the turbine could supply electricity to the backup water pumps in the event of a power outage. However, the test procedure was rushed, poorly planned and not appropriately shared with safety staff.
- Disabling Safety Systems: Operators purposefully turned off important safety systems, such as the reactor’s automatic shutdown mechanisms and emergency core cooling system to perform the test under particular circumstances. As a result, the reactor became exceedingly vulnerable.
- Operating with Dangerously Low Power: Before the test, the reactor’s power level was far lower than anticipated. Despite the acknowledged instability of operating the RBMK at such little power, the operators proceeded anyway.
- Violation of Operating Procedures: Numerous operating procedures and safety regulations were disregarded in the lead-up to and during the test, including exceeding the allowed number of control rods withdrawn from the core.
- Lack of Knowledge and Training: It has been reported that the operating staff did not fully understand the hazardous low-power reactivity characteristics of the RBMK reactor or the potential consequences of their actions. Additionally, there was a weak “safety culture” in the Soviet nuclear industry during that period.
Action Taken Aftermath of Chernobyl Disatster
1. Initial Response And Secrecy: A combination of widespread mobilization, secrecy, and eventually a lack of proper planning and openness defined the Soviet Union’s leadership over the Chernobyl disaster response. The following summarizes how the USSR managed the situation:
- Delayed Announcement: Although the explosion happened on April 26, 1986, the Soviet leadership took a while to make public the extent of the catastrophe. Only 36 hours later did the evacuation of Pripyat, the closest city, start.
- Information Control: Attempts were made locally as well as internationally to minimize the accident’s seriousness. Early reports were vague, and it took some time for the full extent of the radiation leak to be revealed. This secrecy was consistent with the Soviet Union’s overall information control strategy.
- Propaganda: Despite the recognized risks of radiation exposure, the administration made an effort to preserve a sense of normalcy, even hosting May Day parades in Kyiv.
2. Mobilization of Liquidators:
- Massive Effort: The mobilization of hundreds of thousands of individuals, referred to as “liquidators,” from all around the Soviet Union was the main control strategy. The duty of limiting the tragedy fell to these people, who included miners, firefighters, troops, construction workers, and medical professionals.
- Risky Work: Liquidators put out fires, cleared radioactive debris, and built the first sarcophagus around the damaged reactor 4 in highly dangerous conditions, frequently without the proper protective equipment.
- High Radiation Doses: Numerous liquidators were exposed to high radiation doses, which in certain circumstances resulted in fatalities and serious health effects. Other stories indicate high exposure and linked mortality among the initial responders, despite a study on Estonian liquidators showing no conclusive long-term health problems attributable to radiation. Liquidator involvement estimates range from 200,000 in 1986–1987 to possibly 600,000 in total.
3. Containment Strategies:
- Helicopter Drops: In an effort to put out the fire and stop more hazardous material leaks, helicopters were utilized to drop sand, boron, clay, and lead onto the reactor core that was on fire in the immediate aftermath.
- Sarcophagus Construction: Within months, the “sarcophagus,” a temporary steel and concrete structure, was immediately built around the demolished reactor to hold the radioactive materials. This was completed under extreme time constraints and radiation exposure.
4. Evacuation and Exclusion Zone:
- Creation of Exclusion Zones: More than 100,000 people were evacuated when Soviet authorities created an initial 10-kilometer exclusion zone around the plant, which was eventually extended to 30 kilometers.
- Access Control: Only authorized personnel were allowed to enter the strictly regulated exclusion zone.
5. Medical Response:
- Centralized Care: The Soviet Union established a three-tiered medical response system, with first aid at the factory, emergency care at nearby hospitals, and final assessment and treatment in Moscow.
- Focus on Acute Radiation Syndrome: The initial medical reaction was centered on treating first responders and plant workers who had acute radiation sickness.
6. Restrictions & Criticism:
- Insufficient Readiness: In spite of its centralized governance, the Soviet Union lacked sufficient readiness for a catastrophe of this scale. There were issues with public communication, emergency preparation, and radiation protection.
- Design Flaws: The RBMK reactor design itself had inherent safety flaws that contributed to the accident.
- Long-Term Management: Decades later, international efforts were needed to construct the New Safe Confinement structure because the original sarcophagus was only a temporary fix and gradually decayed.
- Health Consequence: Long-term health consequences on the impacted populace and the liquidators are still being researched and discussed, with increased cases of thyroid cancer in children being a well-documented consequence.
Casualties: Immediate & Longterm
1. Immediate Casualties:
- First Explosion: Two plant employees were killed immediately by the explosion in Reactor No. 4.
- Acute Radiation Syndrome (ARS): 134 plant employees and emergency personnel were diagnosed with Acute Radiation Syndrome (ARS) as a result of high radiation exposures in the immediate aftermath. Within the first three months after the tragedy, 28 of the people who contracted ARS passed away. This includes firefighters and plant workers who received extremely high doses while trying to contain the emergency.
- The Chopper Crash: During cleanup efforts on October 2, 1986, four crew members on a Mi-8 helicopter perished. Their task was to dump radiation-absorbing materials onto the damaged Reactor No. 4, most likely a mixture of decontaminating acetate.
2. Long-Term Casualties and Health Effects of Chernobyl Disaster:
- Thyroid Cancer: The higher incidence of thyroid cancer is a notable and well-established long-term effect of Chernobyl disaster, especially for individuals who were children and teenagers at the time of the accident. About 6,000 cases had been reported by 2005, and the number was growing. Even while thyroid cancer is frequently curable, only a tiny number of cases—roughly 15 by 2005—have resulted in death. Ingestion of radioactive iodine-131, which tainted milk and food in the early weeks following the accident, is the main cause of the elevated risk.
- Liquidators: About 600,000 “liquidators” participated in the post-disaster cleanup operations, many of whom were exposed to high levels of radioactivity. While some organizations reject these high numbers, arguing that it is difficult to pinpoint particular causes of death decades later, others assert that the cleanup is responsible for thousands of liquidator deaths. Research on liquidators has revealed that those exposed to larger dosages had a statistically significant relative risk of solid cancer incidence and mortality in some cohorts, as well as a higher incidence of leukemia and cataracts.
- General Public: Radiation doses were relatively low on average for the general public in the most affected areas (Belarus, Russia, and Ukraine), although there were widespread psychological effects such as anxiety and poor perceived health, the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) estimates that fewer than 100 deaths have resulted from the fallout, aside from thyroid cancer. There is less clear evidence of a significant increase in overall cancer incidence or mortality rates, other than thyroid cancer. One World Health Organization’s study in 2006 projected approximately 9,000 deaths from cancer-related causes in the affected countries.
- Other Health Concerns: According to certain research, cleaning workers may be at long-term risk for leukemia, heart disease, and cataracts. However, there is still little proof that radiation exposure actually causes higher rates of non-cancerous illnesses or other solid cancers in the general population. There is no proof that birth abnormalities have increased or fertility has declined in the impacted areas.
Heroes of the Chernobyl
Firefighters like Vasily Ignatenko, who were among the first to respond to the fires despite their lack of awareness of the threat posed by the radiation, were among the immediate heroes of Chernobyl. Employees at the plant, including Oleksandr Akimov and Leonid Toptunov, remained on duty in an attempt to control the escalating circumstances. Engineers Boris Baranov, Valeri Bezpalov, and Alexei Ananenko were among the hundreds of thousands of volunteers who famously risked their lives to remove radioactive water from beneath the reactor. Along with innumerable others, these individuals made remarkable sacrifices to lessen the impact of the calamity.
Present Day Chernobyl
It has been 29 years since the biggest nuclear disaster in human history, the Chernobyl Exclusion Zone 30 KM radius area is still a high radiation area. Even though wildlife has flourished in the absence of human interference, the haunting remnants of the catastrophe persist, most notably the “Elephant’s Foot.” The remnants of the destroyed reactor still pose a serious risk because of this highly radioactive mass of corium, which is a solidified lava-like mixture of melted nuclear fuel, concrete, and metal.
Some radioactive isotopes that were released into the atmosphere are still there, but that are safe for limited time exposure. The Ukrainian government designated a portion of the exclusion zone as the Chernobyl Radiation and Environmental Biosphere Reserve in 2016. Also, there are now many “dark tourists” visiting Chernobyl and the deserted city of Pripyat.
Conclusion
The world was forever changed by the Chernobyl accident, a terrifying example of the possible repercussions of technical hubris and structural flaws. In addition to the immediate destruction and terrible death toll, it revealed nuclear power’s vulnerabilities and the long-term implications of similar disasters for people and the environment. Chernobyl was a sobering reminder of how crucial safety, transparency, and international collaboration are when handling technologies that impact the world. The exclusion zone is nevertheless a powerful reminder of a catastrophe that continues to influence how we view risk and accountability in the nuclear age, even after decades have gone by.
Call to Action
The tale of Chernobyl serves as a potent reminder. What lessons does this catastrophe teach you? You can email us at www.techgiraffe@yahoo.com or leave your thoughts in the comment section below. Let’s talk about the long-term effects and make sure that history doesn’t happen again. Your insights are important! Thanks again for visiting TechGiraffe.
Source of information: World Nuclear Association, United States Nuclear Regulatory Commission, United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) and Wikipedia
