Overview: The United Nations General Assembly (UNGA) vide resolution 71/125 in 2016 designated April 26 as the International Chernobyl Disaster Remembrance Day. The resolution mentioned it was aimed at raising awareness on the long-term consequences of the disaster and strengthening coordination and cooperation to mitigate and minimise its consequences.
On April 26, 1986, a nuclear reactor at the Chernobyl Nuclear Power Plant in the erstwhile Soviet Union was subjected to improper testing at low-power, resulting in loss of control. The ensuing fire and explosion destroyed the building where the reactor was kept – releasing radiation into the atmosphere. The International Atomic Energy Agency (IAEA) explains that as safety measures were ignored, uranium fuel in the reactor overheated and melted through the protective barriers.
The radioactive elements released lasted in the air for about ten days, causing serious problems for populations in certain territories of present-day Belarus, Russia and Ukraine. According to the U.N., nearly 8.40 million people in the three countries were exposed to radiation. Two workers at the plant died immediately due to the explosion, with another 28 deaths in the following weeks as a result of the acute radiation syndrome.
The explosion explained
The World Nuclear Association says that the largest-ever uncontrolled radioactive release into the environment was the result of a “flawed” reactor design operated by “inadequately” trained personnel.
The Chernobyl plant is situated about 130 km north of Kyiv (Ukraine) and about 20 km south of the border with Belarus, housing four nuclear reactors of the RBMK-100 design. Designed by the erstwhile Soviet Union, the tube type reactor is equipped with individual fuel channels using graphite as a moderator and water as a coolant. The World Nuclear Association mentions that the combination is found in no other power reactor in the world. Unit 1 and 3 were constructed between 1970 and 1977 while units 3 and 4 were completed in 1983. The event took place at Unit 4.
A day before the disaster, prior to the routine shutdown, the crew wanted to determine how long the reactor could be cooled in the event of loss of power. The operators disabled the necessary automatic shutdown mechanisms before commencing the test. The peculiar design of the control rods (used for regulating fission inside a reactor) caused a dramatic power surge when inserted into the reactor. The heated fuel interacted with cooling water to create a fuel fragmentation (separation of fuel pellets into more than one piece), in turn, producing steam and increasing the pressure.
This pressure ruptured the unit and caused a steam explosion, releasing fission products into the atmosphere. Seconds later, another explosion threw out fragments from the fuel channels along with hot graphite.
What was the damage caused?
Much of the larger particles released got deposited in areas around the site as dust and debris. The lighter material, however, was carried by wind to territories in present day Belarus and Russia and, as per the World Nuclear Association, to some extent over Scandinavia and Europe. Further, the International Atomic Energy Agency (IAEA) in its report enumerating consequences of the disaster, said, “The deposition was highly heterogeneous; it was strongly influenced by rain when the contaminated air masses passed.”
The radiation also affected six firefighters who attended the initial fires on the roof of the turbine building.
According to IAEA’s report, open spaces in urban areas, particularly wet horizontal surfaces such as soil plots and lawns were most contaminated from the released particles. It adds the city of Pripyat, nearest to Chernobyl, and its surrounding could have been exposed to substantial external radiations, the effects of which was partially averted by the evacuation of the people. Some 3.50 lakh people were evacuated following the nuclear disaster with resettlement efforts ongoing. The World Nuclear Association states that the relocated workers and families at present live in a new town, Slavutich, which three km away from Pripyat and 30 km from the plant.
The deposition contaminated agricultural plants and affected the health of the animals consuming them. This contaminated milk, leading to an increased diagnosis of thyroid cancer, especially among children. The U.N. Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) in a report published in 2018 mentioned about 20,000 cases of thyroid cancers were diagnosed between 1991 and 2015 in patients 18 years or younger at the time.
In 1990, the UNGA adopted Resolution 45/190 calling for international cooperation to address and mitigate the consequences at the Chernobyl nuclear power plant. Additionally, the IAEA established an international framework for notification, exchange of information and seeking international assistance through the Convention on Early Notification of a Nuclear Accident and the Convention on Assistance in the Case of a Nuclear Accident or Radiological Emergency.
Is the plant still operational?
The plant is not operational now. The last reactor at the site was shut down in December 2000 and the phase of decommissioning began. This involves removing and disposing fuel and wastes, decontamination of the plant and areas around it, including radioactive soil and water. According to IAEA, thee decommissioning of the retired reactors is expected to take several decades and would be supervised by the Ukrainian Government. The nuclear regulatory body adds that people are allowed to visit the Chernobyl area, including the exclusion zone which is a 30 km radius surrounding the plant. Although the particulate matter still lingers, they are at tolerable exposure for limited periods of time. Erstwhile residents of the exclusion zone have also returned to their homes in areas with higher-than-normal radiation levels, it adds.
What happened to the plant recently?
Russian troops seized control of Chernobyl plant on February 24 at the onset of the conflict with Ukraine. IAEA Director General Mariano Grossi stressed on the importance of letting the nuclear facility operate safely and not being subjected to disruption. He reminded that any armed attack on and threat against nuclear facilities constituted a violation of the principles in the United Nations Charter, international law and statute of the Agency.
On April 1, it was informed that all Russian forces had left the facility. Further, there had been no staff rotation at the facility since March 20. Ukrainian state-enterprise Energoatom informed that Russian troops had dug trenches in the most contaminated parts of the exclusion zone at Chernobyl, as per BBC. It added there were unconfirmed reports stating that Russian troops subjected to radiation were being treated in Belarus.
As per the IAEA’s latest update on Monday, the Director General was to travel to Ukraine leading the organisation’s first assistance mission of safety, security and safeguards experts to the country. The team would deliver equipment, conduct radiological assessments and restore the safeguards monitoring systems.
