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Fires in History: Chernobyl Nuclear Plant
On April 26, 1986, the Chernobyl Nuclear Power Plant disaster in the Ukraine would forever change the lives of millions of people. To this day, it is considered the worst nuclear accident in history.
• Date: April 26, 1986
• 1 of 2 level 7 events in history
• 500k workers contained the contamination
• 31 people died
• Thousands had radiation related illnesses
On April 26, 1986, Chernobyl Nuclear Power Plant was conducting an experiment for the fourth time. The plant had serious safety issues with cooling the core. Cooling pumps require electricity to cool a reactor after a SCRAM, in the event of a power grid failure. Chernobyl had two diesel generators that were supposed to support the backup for the cooling pumps. The requirement was that generators should get to 5.5MW in 15 seconds; however, this plant's generators took 60-75 seconds. It was a serious safety violation.
To solve this 1 minute gap, they attempted to use rotational energy from the steam turbine to generate enough electrical power to make up the time. Pre-experiment analysis showed that it should work. Unfortunately, plant personnel tested the theory three times. Three times they failed. They made some alterations and planned on a fourth attempt.
The day of the fourth experiment, Chernobyl got a call to postpone the test. A local power station went offline, and the power generation was needed to keep the area powered. They agreed, but continued to prepare for the experiment. They disabled the emergency core cooling system and did a few more procedures. Later in the day, they decided it was time to conduct the experiment.
The night shift was just about to leave when they were asked to prepare for the experiment. They rushed through procedures, rapidly reducing the power level even though it was supposed to be gradually reduced. The core power continued to reduce without operator action due to "reactor poisoning." The engineer accidentally inserted the control rods too far and it led to a near shut down of the reactor. As a result, the power spiked before falling to 5% of the minimum level safe for testing.
Alarms began to sound because the system was getting too hot. The engineers bypassed them. They continued with the experiment and it officially started at 1:23:04am. The diesel generators started; it was intended that the diesel generators would pick up the loads in less than a minute. The power for the main circulating pump was to be supplied by the turbine generator as it coasted down. However, as the momentum for the turbine generator decreased, so did the power it produced. In turn, the water flow decreased, and that caused bubbles in the core. At 1:23:40 the first explosion sounded. Three seconds later, a second explosion went off.
The final determination for the power plant explosion was deficient operating instruction and deficient design. Thirty-one people were killed and thousands were affected by the radiation. The aftermath of the disaster shows the terrible planning and safety procedures in place. The nearby city of Pripyat was not initially evacuated. Within hours of the explosion, dozens of people became ill. In the end, Belarus, Ukraine, Russia, Sweden, Finland, Austria, Norway, Bulgaria, Switzerland, Greece, Slovenia, Italy, and Mildova had nuclear contamination.
Over one million people have been affected by the radiation, which was 400 times the amount released in the atom bomb. 350 animals were born with major deformations within the first four years following the explosion, while there were only 3 reported in the five years prior the explosion. 237 people suffered Acute Radiation Sickness, and 31 died within the first three months. It is estimated that 4,000 people will die from cancer as a result of this event.