The Chernobyl nuclear disaster

On April 26, 1986, the Chernobyl Nuclear Power Plant in Ukraine (then part of the Soviet Union) erupted, resulting in what many believe to be the world’s greatest nuclear accident.

Even after many years of scientific inquiry and government investigation, many issues surrounding the Chernobyl disaster remain unresolved, particularly about the long-term health effects of the large radioactive release on people who were exposed.


According to the World Nuclear Association, the Chernobyl Nuclear Power Plant is located about 81 miles (130 kilometres) north of the Ukrainian capital, Kyiv, and about 12 miles (20 kilometres) south of the border with Belarus.

 It is composed of four reactors that were planned and constructed in the 1970s and 1980s. To provide cooling water for the reactor, a man-made reservoir around 8.5 square miles (22 square kilometres) in size and supplied by the Pripyat River was built.

Pripyat, created in 1970, was the closest town to the power plant, located little under 2 miles (3 kilometres) distant, and contained about 50,000 people in 1986. Chernobyl, a smaller and older town with a population of roughly 12,000 people, located about 9 miles (15 km) distant. The rest of the area was mostly farmland and forest.

Chernobyl vs. Fukushima Nuclear Disaster

The Chernobyl facility employed four Soviet-designed RBMK-1000 nuclear reactors, a design that is now widely acknowledged to be fundamentally defective. According to the World Nuclear Association, RBMK reactors were pressure tube designs that used enriched U-235 uranium dioxide fuel to heat water, generating steam that powers the reactors’ turbines and generates electricity.

According to the World Nuclear Association, water is also utilised in most nuclear reactors as a coolant and to regulate the reactivity of the nuclear core by eliminating excess heat and steam. The RBMK-1000, on the other hand, employed graphite to regulate the core’s reactivity and maintain a continuous nuclear reaction in the core.

As the nuclear core heated and created more steam bubbles, the core grew more reactive, not less, resulting in a positive-feedback loop known as a “positive-void coefficient” by engineers.


According to the United Nations Scientific Committee on the Effects of Atomic Radiation, the explosion happened on April 26, 1986, during a regular maintenance inspection (UNSCEAR). Operators intended to test the electrical systems when they shut off critical control systems, violating safety requirements. As a result, the reactor’s power and stability became dangerously unstable.

According to the Nuclear Energy Agency, Reactor 4 was shut down the day before to complete maintenance checks on safety systems during anticipated power shortages (NEA). While the exact origin of the explosions is still debated, it is widely assumed that the first was caused by an excess of steam and the second was impacted by hydrogen. The excess steam was produced by a drop in cooling water, which allowed steam to build up in the cooling pipes — the positive-void coefficient — resulting in an immense power surge that the operators were unable to shut down.

According to the NEA, the explosions happened at 1:23 a.m. on April 26, demolishing reactor 4 and igniting a raging fire. Radioactive fuel and nuclear components rained down on the region, and a fire spread from the building holding reactor 4 to surrounding structures. The blowing wind transported toxic fumes and dust, as well as fission products and the noble gas inventory of naturally occurring odourless and colourless gases.


The blasts killed two workers at the company, the first of numerous who died within hours of the catastrophe. As rescue crews worked furiously to put out the fires and radiation leaks, the death toll increased as plant workers succumbed to severe radiation illness over the next few days.

The original fire was put out by 5 a.m., but the subsequent graphite-fueled fire took 10 days and 250 firemen to put out, according to the NEA. Toxic pollutants, however, continued to be blasted into the atmosphere for an extra ten days. The majority of the radiation emitted by the failed nuclear reactor came from fission products such as iodine-131, cesium-134, and cesium-137. According to UNSCEAR, iodine-131 has a relatively short half-life of eight days, but it is rapidly inhaled through the air and tends to localise in the thyroid gland. Cesium isotopes have longer half-lives (cesium-137 has a half-life of 30 years) and pose a risk to the environment for many years after they are released into the environment.

Evacuations in Pripyat began on April 27, around 36 hours after the tragedy. Many residents were already complaining of vomiting, headaches, and other symptoms of radiation illness at the time. By May 14, officials had blocked off an 18-mile (30-kilometer) radius surrounding the facility, evacuating a further 116,000 people. . According to the World Nuclear Association, 220,000 more households will be urged to relocate to less hazardous places during the following few years.


According to the US Nuclear Regulatory Commission (NRC), 28 Chernobyl employees perished in the first four months after the catastrophe, including several courageous workers who knew they were exposing themselves to lethal amounts of radiation in order to protect the site against additional radioactive breaches. Because the predominant winds were from the south and east at the time of the disaster, much of the radioactive plume drifted northwest toward Belarus. Nonetheless, Soviet officials were sluggish to communicate information to the outside world about the magnitude of the calamity. However, when radiation levels raised concerns in Sweden three days later, experts were able to determine the approximate site of the nuclear accident based on radiation levels and wind directions, prompting Soviet officials to expose the entire nature of the situation, according to the UN.

According to the NRC, 31 persons died as a result of radiation exposure or other direct repercussions of the Chernobyl catastrophe within three months of the event. According to a 2018 UNSCEAR study, as many as 20,000 instances of thyroid cancer were discovered in individuals under the age of 18 in 1986 between 1991 and 2015. While there may be additional cancer cases among emergency responders, evacuees, and residents over the course of their lives, the known total incidence of cancer deaths and other health problems directly connected to Chernobyl’s radioactive release is lower than was previously predicted. According to an NRC report, “the bulk of the five million individuals residing in polluted regions… got relatively tiny radiation doses equivalent to natural background levels (0.1 rem per year).” “As of now, the data does not firmly link the event to radiation-induced increases in leukaemia or solid cancers other than thyroid cancer.”

According to some analysts, the unfounded fear of radiation exposure caused more pain than the real calamity. According to the World Nuclear Association, many doctors throughout Eastern Europe and the Soviet Union advised pregnant women to have abortions in order to avoid having children with birth defects or other disorders, even though the actual level of radiation exposure these women experienced was likely too low to cause any problems. According to the head of UNSCEAR, the United Nations produced a study on the impacts of the Chernobyl disaster in 2000 that was “full of baseless allegations that have no validity in scientific evaluations,” and was subsequently ignored by most authorities.


The trees in the adjacent forests were destroyed by significant amounts of radioactivity shortly after the Chernobyl radiation releases occurred. Because the dead trees developed a vivid ginger hue, this area became known as the “Red Forest.” According to the National Science Research Laboratory at Texas Tech University, the trees were finally destroyed and buried in ditches. According to the NRC, the damaged reactor was quickly enclosed in a concrete sarcophagus meant to confine the leftover radiation. However, there is ongoing scientific dispute over how effective this sarcophagus has been and will be in the future. After stabilising the old sarcophagus, development on the New Safe Confinement structure began in late 2006. According to World Nuclear News, the new building is 843 feet (257 metres) broad, 531 feet (162 metres) long, and 356 feet (108 metres) tall, and is planned to totally contain reactor 4 and its surrounding sarcophagus for at least the next 100 years.

According to World Nuclear News, despite the pollution of the site and the inherent hazards of running a reactor with significant design defects, the Chernobyl nuclear facility continued to operate to supply Ukraine’s electricity demands until its final reactor, reactor 3, was shut down in December 2000. Reactors 1 and 2 were decommissioned in 1991 and 1996, respectively. The site’s deactivation is planned to be finished by 2028.

The plant, the abandoned towns of Pripyat and Chernobyl, and the surrounding countryside form a 1,000-square-mile (2600-square-kilometer) “exclusion zone” that is off-limits to almost everyone save scientists and government officials. Despite the hazards, numerous residents returned to their houses soon after the accident, with some sharing their experiences with news organisations such as the BBC, CNN, and The Guardian. In 2011, Ukraine opened the region to tourists who wanted to view the disaster’s aftermath firsthand.