The Chernobyl Tragedy
The Soviet Union sought out to Nuclear Energy as their primary power supply as it was cheaper and more efficient. As a result, the Chernobyl Power Plant was built in Ukraine near its capital city, Kiev. The power plant was responsible for supplying the major share of power to Kiev. Located 65 miles from Kiev, the Chernobyl Plant had four nuclear reactors which ran on radioactive fuel like Uranium and Plutonium to heat water and produce steam which in turn ran turbines to produce electricity.
On 26th April, 1986 at 1:24 AM (Moscow Time), reactor number 4 of the Chernobyl Power Plant exploded resulting in the world’s deadliest power plant explosion. Even till today, it is one of the only two recorded level 7 event on the International Nuclear Event Scale (the other being the Fukushima nuclear plant explosion in Japan in 2011 during the earthquake and Tsunami that had struck Japan). It claimed a few 30 to 50 lives at the time of explosion but was a result of the deaths of thousands of people due to the radioactive poisoning causing cancers and deformities in the surrounding cities. The nearest town to the plant, “Pripyat”, had to be evacuated and eventually locked down from Public access since it had become highly toxic with radiation. First we will understand how a nuclear reactor achieves its task of generating power and then analyse the events that had occurred which led to the meltdown at Chernobyl.
General Working of a Nuclear Reactor
Radioactive substances are highly unstable and can breakdown easily. Uranium atoms are excited when they are bombarded by neutrons. This disengages more neutrons from the Uranium atom. These new neutrons strike other Uranium atoms, and hence an event called a “Chain Reaction” occurs. During the breaking down of the Uranium atom by bombardment, an extremely high amount of energy is released. It is this energy which is utilized by the power plant to produce electrical energy. This heat is used to evaporate water and produce steam. Pressurized steam is used to rotate turbines which produce electricity. This is a highly efficient process and relatively cheaper than the traditional power plants which are run by coal.
Interesting Fact: 2 pounds of Uranium can produce the same amount of energy as 3300 tons of coal.
Uranium fuel rods are placed in a well-protected reactor core. They are surrounded by moderators which prevent static heat to build up. There are Control Rods which quite obvious from their name control the amount of chain reaction occurring. They can be placed in or removed from the reactor as per the power requirement. Water is pumped into the reactor core and is converted into steam. This steam is flown into the turbine chambers where the turbines rotate to produce electricity.
Sounds quite simple, doesn’t it? Well, it is not. It takes a good balance of water, control rods, turbine power generation and other factors to prevent the reactor from overheating. All these precautions are taken care of by engineers while constructing the nuclear reactors. Let us see what went wrong at Reactor Number 4 at the Chernobyl Power Plant.
What Went Wrong?
Let us start from April 25th, 1986. It was a normal day; there were no malfunctions in the reactor. It was working normally with no glitches at all. The more experienced and older scientists worked the day shift and left at night. The midnight shift was handedover to inexperienced and young engineers who were new to the Job. But they were very much qualified for the job.
- The midnight staff that operated the controls at reactor 4 during the disaster was inexperienced.
Suddenly they were in for a surprise test which was scheduled by higher officials. This test was to see if the turbines would continue to run on the backup generators even if the reactor would go cold. It was a test which was conducted before with inconclusive results. To conduct this test the automated safety features of the reactor had to be shut down.
- Automated safety features of the reactor had to be shut down.
There were two young engineers in charge of the critical controls, i.e., the control rods and water supply. The person in charge of the control rods had to bring down the power of the reactor gradually by adding in control rods (reactor number 4 had 211 control rods). Suddenly there was a sharp decline in the power output. At this point he removed a few control rods which made the reactor to come back to a runnable level. At this point the water supply man preps for the test which involves the stopping of the water flow. While preparing, he allowed excess water flow into the reactor which reduces the amount steam output due to which the turbines stop.
- The excess water flow by the control man causes the turbines to stop functioning.
This makes the control rods operator to remove more control rods. According to the reactor safety norms he is not supposed go below 26 control rods as it may be dangerous. But neglecting this he keeps a bare 6 rods in the reactor. This made the turbines to start working again. Remember that the test has not even begun!
- The control rods operator neglected the safety guidelines and kept only 6 rods in the reactor.
On 26th April, 1:24AM, when everything went back to normal, without anyone’s notice, the reactor was slowly heating up to a dangerous limit. The staff still sought to carry out the test. The Water supply operator stopped the turbines. This made the reactor to heat up to such an extent that the explosion caused a two ton lid to blow away into the sky.
- A lack of communication between the operators caused a miscalculated operation causing tons of radioactive material to blow into the sky.
Outcomes of the Event
In less than four minutes, the power plant fire fighters team rushed to the plant. They weren’t informed that it was a radioactive fire. A few hours later, the Kiev fire fighters had arrived to offer assistance. The fire was finally contained at about 6:35AM in the early morning. As a result 31 fire fighters died due to direct radioactive exposure.
The explosion caused a radioactive cloud to spread out in to the sky which went up to Japan on the east and America on the west. The soviet media first kept mum on the event. The US spy satellites on sensing unusual radioactive levels initially thought that the USSR had launched a nuclear missile (as it was the cold war during the period), alerting the intelligence agency. The neighbouring countries also noticing high levels of radiation in their areas started putting pressure on the Soviet Government, who finally came out with the news. The nearest town, Pripyat was shut down to public access, due to inhabitable levels of radiation. The damaged reactor continued to spew out radioactive material into the sky endangering the lives of the citizens. The Soviet government immediately ordered the army to seal off the reactor with concrete from top as well as the bottom. The United Nations later in 2000, with contributions started operations to seal off the Reactor completely and spray chemicals which absorbed most of the existing radiation. The reactor continued to operate with the remaining three reactors until 2000 when it was finally shut down due to increased deaths among workers.
The radiation that remained caused the deaths of tens of thousands of people in the surrounding areas of Kiev and local Ukraine. Mutations were caused by the radiation poisoning, crippling people and eventually killing them in a painful death. Many high officials were imprisoned following their irresponsible acts and the operators were exonerated in a hearing that took place after the investigation into this matter. It was and still remains the most horrible nuclear catastrophe that the world has ever seen.