Chernobyl Accident

(This blog is replacing the Pandora’s Promise blog that I could not access the video for.)

In April 1986, a result of a flawed Soviet reactor design combined with ineffectively trained personnel responsible for operation and the lack of any safety culture, caused the Chernobyl accident in Ukraine. On the 25^th of April the personnel at Chernobyl 4 reactor started preparing for a test to determine how long turbines would spin and supply power to the main circulating pumps. This test was conducted a year prior but was unsuccessful due to the power from the turbine rapidly was depleted.

There were a series of operation steps that took place, which put the reactor in an extremely unstable condition. The planned procedure included shutting off the reactor’s emergency core cooling system that was responsible for supplying water for cooling the core in an emergency. As the process continued, the power at which the reactor was operating was less then the minimum operating reactivity margin, which is a violation. The operator made a poor decision and the process was continued. At this point, any efforts that could have been made to increase the power were disturbed by xenon poisoning, reduced coolant void, and graphite cool down.

The power excursion rate emergency protection system signals came on when power started to rise and exceeded the required level. This caused fuel elements to rupture that led to increased steam generation, which then further increased the power level. There was a rupture of several fuel channels that increased the pressure inside of the reactor that caused the reactor support plate to become detached and jammed the control rods. While the channel pipes were rupturing, more steam had been generated as a result of the lack of pressure of the reactor cooling circuit.

At this point there were two explosions. The first one was the initial steam explosion and second was a result of the build-up of hydrogen due to steam reactions. As stated by the World-Nuclear Organization, “Fuel, moderator, and structural materials were ejected, starting a number of fires, and the destroyed core was exposed to the atmosphere. One worker, whose body was never recovered, was killed in the explosions, and a second worker died in hospital a few hours later as a result of injuries received in the explosions.”

There was a massive immediate impact to the environment after the accident. At the time, this accident was named as the largest uncontrolled radioactive released into the environment for any civilian operation. For about 10 days, large amounts of radioactive substances were released into the air, which caused a social and economic disruption in Ukraine.

With the task of cleaning up the radioactivity of the site, about 200,000 people were recruited from the Soviet Union. These people received high doses of radiation, and later about 400,000 more people were called in to help and received lower does of radiation. About 116,000 residents were evacuated and later about 1,000 relocated back to the area unofficially.

Human health has been affected by the Chernobyl accident. Whether people were exposed to radiation directly fro the radioactive cloud or the radioactive materials deposited on the ground and were consumed through contaminated food there was a high level of contamination. Children’s thyroids were heavily exposed to radioactive iodine, which caused serious health concerns. 28 emergency workers died from acute radiation syndrome, 15 patients died from thyroid cancer, and it is estimated that 4,000 died from cancers caused by Chernobyl.

The main lesson learned from the Chernobyl accident is reactor safety. There have been modifications made in reactors currently operating. Following Chernobyl, the International Atomic Energy Agency brought together engineers to focus on safety improvements. According to the Chernobyl Forum report, about seven million people received or are eligible for benefits as “Chernobyl victims.”

Works Cited

"Chernobyl Nuclear Accident." Scientific Facts on  the. N.p., n.d. Web. 30 Oct. 2013. <http://www.greenfacts.org/en/chernobyl/index.htm>.

"Chernobyl fuel transfer milestone." Chernobyl. N.p., n.d. Web. 30 Oct. 2013. <http://www.world-nuclear.org/info/Safety-and-Security/Safety-of-Plants/Chernobyl-Accident/#.UnE3HRaRPFJ>.

"History of Chernobyl Disaster." ICRIN > Home >. N.p., n.d. Web. 30 Oct. 2013. <http://www.chernobyl.info/Default.aspx?tabid=274>.