Chernobyl Nuclear Power Plant Disaster

 Chernobyl Nuclear Power Plant Disaster

 

Introduction 

The year 1986 marks the unfortunate happening of the Chernobyl Nuclear Disaster, making it probably one of the darkest years in the history of Mankind. A nuclear reactor in a power plant went out of control causing a big explosion, the impact of which was spread across Europe. The impact was so high that the United Kingdom even witnessed Radioactive Rain. But what exactly happened that led to all these catastrophic consequences? Who is responsible for this disaster that

cost the Soviet Union $235 Billion? We are going to explain  the Chernobyl Nuclear Disaster of 1986 in detail  in this blog.

The process of the nuclear reaction  

Firstly, we need to know how this “Nuclear” thing works. Nuclear reactors' core consists of fuel rods, control rods, and moderators. Fuel rods cause reactions, while control rods absorb neutrons. Moderators like graphite blocks speed up reactions by reducing neutron energy and increasing collision chances. Water is commonly used in nuclear plants, but in Chernobyl RBMK 1000 reactors, graphite blocks were used. 

History of Chernobyl Nuclear Power Plant   

The Soviet Union made significant investments in nuclear power plants after World War II, including the Chernobyl Nuclear Power Plant. The facility was one of the most cutting-edge in the Soviet Union in the early 1970s which was 16 km away from the city named Chernobyl. It had four RBMK 1000 reactors, and it went into operation in 1977, 1981, and 1983. One thousand megawatts of power may be produced by each reactor, meeting 10% of Ukraine's electrical needs. An important investment in the nation's nuclear energy infrastructure was the Chernobyl Plant. Electricity generation typically involves a rotating wheel with kinetic energy. Hydroelectricity uses water to create energy, while wind energy generates energy by rotating turbines. Thermal power plants use coal to generate electricity, and nuclear energy uses steam to move wheels. However, water must be heated first, and constant water supply is essential to prevent overheating in reactors. The Chernobyl plant relies on water from a man-made water reserve and a nearby river for a consistent supply. In case of a power cut, backup diesel generators provide uninterrupted electricity to the pumps. However, starting these generators takes 1 or 2 minutes, requiring an additional power source within those 1-2 minutes.  

 

 

26th April 

The Chernobyl reactor builders suggested sourcing the electricity for these crucial 1-2 minutes from the nuclear reactor itself, as steam from the turbines would power the plants even after a shutdown. So, on 26 April, they were testing this. If there was a power cut, would the turbines be able to produce enough electricity to power the water pumps? This test was run earlier as well, but this test was never successful in reactor number 4. The workers hoped that the test would be successful that ill-fated night. One day before this, on 25th April, they had tried to conduct a test, but it couldn't be carried out. And so, the test was delayed by a day. The workers working in this plant didn't even get full sleep. At 11:10 PM on 25th April, they began the preparations for this test. Workers tested a nuclear power plant, aiming to reduce its output from 1,600 MW to 700 MW. Xenon poisoning caused a drop in electricity, prompting the removal of control rods. However, only 8 rods were removed, violating safety protocols. The reaction accelerated exponentially, causing shockwaves and a negative feedback loop. Workers executed an emergency stop, highlighting the need for more efficient nuclear reactions. 

Explosion 

At 01:23 AM, the emergency button was pressed, causing the control rods to be reinserted into the reactor to slow down the reaction. This was a design flaw in the reactor, as the control rods were made of graphite, which was used as a moderator in the reaction instead of water. The main part of the control rod was made of Boron Carbide, which slows down the reaction by absorbing neutrons. The tip of the control rods was made of graphite, which speeded up the reaction. When the button was pressed, the remaining control rods were inserted, causing a blast, which infinitely sped up the already speeding reaction. The reactor's power generation reached 33,000 MW, with the first blast occurring 6 to 8 seconds after the emergency button was pressed. 

Exploded reactor no 4

Effects of Explosion 

The reactor experienced a massive explosion, melting its core and causing a powerful blast that blew the 1,000-tonne lid into the air. The radioactive material spread through the atmosphere, with the second blast attributed to the burning graphite in the reactor. Two people were killed, and the amount of harmful radioactive material released was equivalent to 400 Hiroshima atomic bombs. This disaster is considered the World's Worst Nuclear Disaster. The radiation affected not only Ukraine but Europe, Spain, and Sweden, causing radioactive rain in the UK, radioactive dust in cows' milk, and thousands of children developing thyroid cancer. The reactor contained over 100 radioactive elements and 5% Uranium fuel, with 192 tonnes of Uranium fuel in the reactor. 

 

 current situation of Chernobyl

Controlling the situation 

Firefighters were called to control the fire caused by graphite, which took over 10 days to extinguish. They used helicopters to reduce radiation spread, but one crashed, killing four. Around 28 firefighters died within a few months. The reactor was producing high heat, causing a crack in the base and a water tank filled with radioactive water. Someone had to drain the water, risking his own life. 

 

Volunteers 

Three men named Boris, Alexei, and Valeri, dived into a water tank in 1986 to find valves for draining the water. The explosion could have killed millions and made Europe uninhabitable for 500,000 years. Fortunately, all three divers survived, and the Soviet Union sent 200,000 liquidators to clean up the radioactive waste. The Soviet Union's efforts were crucial in preventing further contamination. 

 

 Nuclear Waste Container 

 

Conclusion 

The Soviet Union attempted to cover up the nuclear explosion, but the high levels of radioactivity reached Sweden, forcing the Soviet authorities to disclose the disaster to the public. On April 28, 1986, the Soviet Union admitted the disaster, leading to a 30-km exclusion zone around the nuclear power plant. A concrete and metal made structure was built to contain the radioactive waste. Nature took over the Chernobyl Nuclear Power Plant site over time. 

 

 

 

Author's Bio: Md Shahriar Kibria Fahim was born in Sunamganj on October 1st, 2001. He completed his JSC as well as SSC from Govt Jubilee High School, Sunamganj and HSC from Jalalabad Cantonment  School and College, Sylhet. He is currently a student of Computer Science and Engineering at BRAC University. He loves to play cricket and spend time with  his friends.