Introduction
Throughout the world’s use of nuclear power, here have been several very significant accidents regarding radiation leakage. These disasters associate fear with the entire nuclear industry, and combined with the history of nuclear weapons destruction, can easily ruin the demand for nuclear energy expansion. The two relatively largest nuclear disasters to ever occur were in Chernobyl, Ukraine in 1986, and Fukushima, Japan in 2011. Both disasters called for immediate evacuation of the surrounding area due to extreme levels of radioactivity. By learning about what caused these accidents, we can be sure that mistakes are never repeated, and nuclear power does not harm any more people.
Chernobyl
The disaster at Chernobyl was undoubtedly the result of gross negligence in safety design and operation. The plant consisted of four light water reactors, with no external radiation containment structure. This design flaw is critical, because radiation can be contained well with the proper design. The accident was caused by a poorly designed control rod in the reactor. Operators had disabled the shut down function of the reactor the day before the accident, so when the power surge in the fuel rod occurred, resulting steam pressure caused the entire core to overload, and explode. This was followed by a second explosion, which scattered half of the reactor along with its graphite control rods, and highly radioactive fission fragments.
Two people were killed by these explosions, and 28 people were killed due to radiation exposure during emergency response actions. Those killed had been
exposed to levels up to 20,000 millisieverts (mSv). The natural dose of radiation for a person is about 2,5 mSv per year. These extreme dosages were caused by the fission fragments that were around the close proximity of the explosion site. However, lighter radioactive particles were released into the atmosphere and carried by wind. The closest town to Chernobyl, Pripyat, had to be immediately evacuated, and residents still received doses of 50 to 100 mSv. Ultimately, the accident created a 4,300 square kilometer zone unfit for residence, due to levels of radiation that would exceed the normal 2,5 mSv per year.
Fukushima
The Fukushima disaster introduces a whole new threat to nuclear energy: natural disasters. Exactly 5 years ago, on March 11th, 2011, a tsunami caused by an earthquake in Japan damaged the cooling process and power supply of the
Fukushima nuclear plant. The result was an overheating that caused 3 nuclear reactors to meltdown. Throughout several days there were a number of failures causing this meltdown, and a hydrogen explosion. This leaked radioactive fission fragments into the surrounding water, as well as dispersed lighter fragments into the air.
What is more unnerving about Fukushima is that it was not caused by design or operator negligence. The plant was designed to withstand earthquakes and even significant tsunamis, but the Fukushima tsunami still put the nuclear plants 5 meters below sea level, causing in the meltdowns and explosion. Not only did the tsunami disable the reactors, but it also disabled people’s ability to respond effectively. Radiation monitoring could no longer be used, so the plumes of radioactive clouds could not be tracked to notify locals to evacuate. This is why in the course of days the prime minister’s evacuation order from the proximity expanded from an initial 2km to 20 km. Nobody was killed due to radiation exposure, but some workers have been exposed to as much as 250 mSv during the disaster, and have to be closely monitored. Still today the area of Fukushima is under reconstruction, and many people are still living in government subsidized housing. Hopefully, an unnerving situation such as this never causes us to lose control of our nuclear reactors, because if natural disasters remain a threat to nuclear reactors, nuclear reactor will be considered a threat to health and safety.
Works Cited
“Chernobyl Accident 1986.” Chernobyl. World Nuclear Association, n.d. Web. 11 Mar. 2016.
“What Happened?” Fukushima on the Globe. N.p., n.d. Web. 11 Mar.2016