Disclaimer: Copyright infringement is not intended.

Context:

• On April 26, 1986, Reactor 4 of the Chernobyl Nuclear Power Plant exploded, causing one of the worst nuclear disasters of all time. To date, scholars debate about who exactly was to blame.

The Chernobyl disaster

• The Chornobyl disaster began on 26 April 1986 with the explosion of the No. 4 reactor of the Chornobyl Nuclear Power Plant, near the city of Pripyat in the north of the Ukrainian SSR, close to the border with the Byelorussian SSR, in the Soviet Union.

What caused the Chornobyl accident?

• On April 26, 1986, the Number Four RBMK reactor at the nuclear power plant at Chernobyl, Ukraine, went out of control during a test at low power, leading to an explosion and fire that demolished the reactor building and released large amounts of radiation into the atmosphere.
• Safety measures were ignored, and the uranium fuel in the reactor overheated and melted through the protective barriers.
• RBMK reactors do not have what is known as a containment structure, a concrete and steel dome over the reactor itself designed to keep radiation inside the plant in the event of such an accident.
• Consequently, radioactive elements including plutonium, iodine, strontium, and cesium were scattered over a wide area.
• In addition, the graphite blocks used as a moderating material in the RBMK caught fire at high temperatures as air entered the reactor core, which contributed to the emission of radioactive materials into the environment.

Experts' view on causes:

• Experts say a big factor behind the disaster was the unusual and poor design of the reactor, known as RMBK, particularly its propensity to sudden power surges—as happened at Chornobyl.
• Unlike elsewhere outside the Soviet Union, there was no containment structure shielding the reactor to stop radioactivity from escaping.
• According to the World Nuclear Association, the accident was also due to "the violation of operating procedures and the absence of a safety culture".
• The aftermath was also poorly handled, with officials slow to evacuate locals and Moscow sending 600,000 "liquidators" with little or no protective gear to put out a fire that raged for 10 days.
• The first alarm was raised on April 28, 1986, not by Russia but by Sweden after it detected an unexplained rise in radiation levels. Soviet leader Mikhail Gorbachev did not admit the disaster had occurred until May 14.

Fatalities from disaster:

• According to the International Atomic Energy Agency, the initial explosion killed two workers, with 28 firemen and emergency clean-up workers dying within three months from Acute Radiation Sickness.
• In 2005, the UN predicted that around 4,000 people may eventually die due to radiation exposure.
• A 2006 World Health Organization study predicted 9,000 cancer-related fatalities in Ukraine, Belarus, and Russia as a result of the Chernobyl disaster.
• An area of roughly 2,600 sq km remains (permanently) out of bounds for human habitation, due to the radio-active contamination.
• The Chornobyl disaster is said to have released 400 times more radiation than the atomic bomb dropped on Hiroshima, Japan by the United States.

Who is to be blamed for the disaster?

• There is no consensus on who or what was to blame for the Chornobyl disaster.
• Lawyers and the chief designer of the reactor, N A Dollezhal, blamed the operators for failing to meet "production discipline."
• The Soviet Union emphasized human error as the cause of the disaster, rather than design or manufacturing flaws.
• Operators of the reactor did not agree with this version and believed their actions were by regulations.
• Some experts argued that inadequate human-machine interaction and design faults of the core and control system were the main causes of the accident.
• Most of the experts agree on one fact the explosion resulted from reckless decision-making and failure to follow proper guidelines by the reactor operators. Operators believed they always had access to a kill switch to stop reactor operation, but its design contributed to the explosion.

RBMK ●The RBMK (Russian: reaktor bolshoy moshchnosti kanalnyy, "high-power channel-type reactor") is a class of graphite-moderated nuclear power reactors designed and built by the Soviet Union. It is one of two reactor types to be developed in the Soviet Union in the 1970s. ●The name refers to its (unusual)design where, instead of a large steel pressure vessel surrounding the entire core, the core is surrounded by a cylindrical annular steel tank inside a concrete vault, and each fuel assembly is enclosed in an individual 8 cm (inner) diameter pipe (called a "technological channel"). The channels also contain the coolant and are surrounded by graphite. ●The RBMK is an early Generation II reactor and the oldest commercial reactor design still in wide operation, although reactor units of the first generation type have all been decommissioned.

Source:

Indian Express

PRACTICE QUESTION Q) Match the following: List -I List - II (a) Chernobyl disaster (i) Styrene (b) Bhopal tragedy (ii) Chlorofluoro substances (c) Ozone hole (iii) Radioactive substances smog (d)Vizag gas leak (iv) Methyl Isocyanate A (a) - (iv), (b) - (iii), (c) - (i), (d) - (ii) B (a) - (iii), (b) - (iv), (c) - (ii), (d) - (i) C (a) - (ii), (b) -(i), (c) - (iv), (d) - (iii) D (a) - (ii), (b) - (iv), (c) - (i), (d) - (iii) Answer: B Explanation: (a) Chernobyl disaster - (iii) Radioactive substances smog: The Chernobyl disaster, which occurred on April 26, 1986, in Ukraine, involved a catastrophic nuclear accident. The explosion released a significant amount of radioactive material into the atmosphere, causing widespread contamination. The term "radioactive substances smog" refers to the radioactive particles and gases that were dispersed into the air as a result of the explosion. (b) Bhopal tragedy - (iv) Methyl Isocyanate: The Bhopal tragedy, which occurred on December 2-3, 1984, in Bhopal, India, is one of the world's worst industrial disasters. It involved the release of toxic methyl isocyanate (MIC) gas from a pesticide plant owned by Union Carbide India Limited (UCIL). The gas leak resulted in thousands of deaths and long-term health effects for many survivors. (c) Ozone hole - (ii) Chlorofluoro substances: The term "ozone hole" refers to the depletion of the ozone layer, particularly over Antarctica. This depletion is primarily caused by the release of chlorofluorocarbon (CFC) compounds into the atmosphere. CFCs were commonly used in refrigerants, aerosol propellants, and solvents before their harmful effects on the ozone layer were recognized. (d) Vizag gas leak - (i) Styrene: The Vizag gas leak, also known as the LG Polymers gas leak, occurred on May 7, 2020, in Visakhapatnam, India. It involved the release of styrene gas from a polymer plant owned by LG Polymers. Styrene is a toxic chemical used in the production of polystyrene plastics and synthetic rubber. The gas leak led to several fatalities and caused injuries to many people in the surrounding areas.