Thursday, April 7, 2011

Chernobyl and Japan Disasters

To fully understand what exactly happened in Chernobyl and Japan we first need to understand how Nuclear Reactors work.
A Nuclear Reactor is a system that contains and manages the sustained nuclear chain reactions (1). A nuclear reactor works by fuel and is made up of heavy atoms that divide when they absorb neutron. Then, it is placed into the reactor vessel along with a little neutron source. The neutron begins a chain reaction where every atom that divides releases more neutrons that cause other atoms to split. Each time an atom divides, it releases big amounts of energy in the form of heat. The heat is carried out of the reactor by coolant, and this coolant is generally water. Then the water heats up and goes off to a turbine to spin a generator.
To further understand what happened in Chernobyl and In Japan we have to know a few terms that have to do with a Nuclear Reactor/Reaction.
* Core: The core is part of the reactor that contains the nuclear fuel to generate most of the heat.
* Coolant: The coolant is the material that goes through the core. Its job is to transfer the heat from the fuel to the turbine.
* Turbine: The turbine converts heat from the coolant to electricity.
* Containment: The containment is the structure that splits the reactor from the environment.
* Cooling Towers: Cooling towers dispose the excess heat that are not able to convert into energy.
This is an Image of How a Nuclear Reactor System Works

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What Happened at Chernobyl?
On April 26, 1986 the worst disaster in nuclear history occurred in the station at Chernobyl, Ukraine. It is described as “one of the most frightening environmental disasters in the world (2). Chernobyl was a little known town in north central Ukraine on the Pripyiat River near the Belarus border. The failure of the system was caused by the attempt of technicians to install a security system and reactor number 4 caused much of the damage. The nuclear plant was made up of four graphite reactors. The world first learned of this accident from Sweden because the “radiation was detected at Swedish monitoring stations”.
The operators of the fourth unit were trying to do a controlled experiment by gradually allowing power into the reactor and the reactor was supposed to fall to low levels but it didn’t. The aim of the test was to monitor the dynamics of the graphite reactor with limited power flow. Twelve hours after power reduction was started the power had reached to 50 percent. Since only one turbine was needed to take in the decreased amount of steam plant 2 was turned off. Then the power had been reduced to 30 percent. During this time one of the operators had made a huge mistake. Instead of keeping power at 30 percent, the operator had forgotten to reset a controller, which caused the power to fall to 1 percent. Water had started to fill at the core, and xenon was building up in the reactor and the power was too low for the test. Then the operator’s added water to the reactor is and the reactor is heated by the nuclear reaction. The operator boosted the reactor to 7% by removing all but 6 of the control rods. Not only was this a violation of procedure but also the reactor was not constructed to operate at such low power. The operator failed to get the flow of water corrected and the reactor was continuing to be unstable. To avoid aborting the controlled experiment the operator disabled emergency shutdown procedures. By 01:22 am, when the operators thought they had the most stable conditions, they decided to start the test (3). The operator blocked automatic shutdown on low water level and the loss of both turbines because of a fear that a shutdown would abort the test and they would have to repeat tests. As soon as the test began the other turbines were shut down and the power in the reactor started to slowly increase because of the lessening in water flow caused by the turbine shutdown. The operator tried to initiate manual shut down but that lead to a fast power increase. In no time did the reactor reach 120 times its full power and all the radioactive fuel disintegrated and due to all the pressure the entire top shield of the reactor blew up. Then experts tried to throw radioactive material out into the atmosphere for 10 or more days. Also, multiple fires broke out on both inside and outside of the reactor plant. By 5:00 pm that same day the firemen had suffocated the flames. In the later days to come, about 5000 tons of materials were thrown into the reactor to extinguish burning graphite and to smother radiation release. To date, there is no evidence if the dumping of these materials actually achieved their goal. Recent data has shown only a fraction amount of these materials actually got into the well.

Picture From:,r:2,s:0
How did this affect the people of Chernobyl?
Due to this catastrophic accident, the people of Chernobyl were exposed to radiation “two times bigger than that created by the bombs dropped on Hiroshima and Nagasaki during World War Second”. 70 percent of the radiation is estimated to have fallen on Belarus and still 10 years later babies are being born with no arms, no eyes, no legs, only stumps for limbs and suffer from various other diseases. It is estimated that over 15 million people have been victimized by the disaster. It has also been estimated that eventually the accident will have more victims than World War II and it will cost over 60 Billion dollars to make these people healthy/normal. Approximately thirty-one lives were lost on the spot and approximately more than 600,000 people were involved with the aftermath. Hundreds of thousands of Ukrainians, Russians, and Belorussians had to abandon entire cities and settlements within the thirty-kilometer zone of extreme contamination (4). A lot of money has been spent and will continue to be spent to relocate neighborhoods and decontaminate the once rich farmlands.
What did the Soviet Union do to fix the problem?
The Soviet Union has designed several plans to cover the damaged reactors. The officials decided to close off the Chernobyl reactors with walls. After, the installation of the heavy steel and concrete walls, the protective walls were about 28 stories high and a steel roof was also added on. Despite all these efforts to keep people safe the sarcophagus is cracked and is slowly being demolished. Multiple sensors were placed to monitor levels of gamma radiation, neutron flux, temperature, heat flux, as well as the concentrations of hydrogen, carbon monoxide and water vapor in the air but much damage has already been done and it is too late to fix anything.
What Happened in Japan?
~In Japan, they had three reactors that exploded these reactors were reactors 1, 2, and 3. In these reactors the water was heated and later exposed rods. The exposure to the rods naturally caused the rods to overheat. Since there was no water to act as a coolant it caused the reactor to explode. Japan has tried to do many this to calm the reactors down. Since Japan is located near the water the have tried to get ocean water to act as a coolant to regulate the temperatures.

Picture From:,r:0,s:0

Picture From:,r:21,s:0&tx=98&ty=44&biw=1298&bih=553
Similarities between Japan and Chernobyl.
-Although Chernobyl's nuclear disaster was far more hazardous Japan and Chernobyl do share some similarities.
~ Japan assisted their citizens a lot more than Chernobyl did but evacuation was held in both places
~ Even though Japan is not as affected as Japan radiation was spread in both areas to the environments that surrounded the reactors
What were the Differences between Japan and Chernobyl?
There are many differences because Japan's nuclear reactor even wasn't as bad as Chernobyl's.
~The designs of the reactors were different in both Japan and Chernobyl.Physicist Alexander Sich said construction, both outside and inside the reactor, is fundamentally different (5). Chernobyl used graphite in their moderator. Japan used water in their moderator. Chernobyl therefore received a greater impact because graphite can very easily cause fires and explosions.
~Japan's reactors had a sturdy and heavy steel and concrete wall to protect the environment. Chernobyl did not have any sort of wall or containment around their reactor and there it caused the radiation in the environment to be deadly.
~Chernobyl's disaster was caused due to a controlled experiment. The event was solely caused by human error. Japan's disaster was caused by a natural disaster the tsunami and earthquake.
~Chernobyl's reactor' released much more radiation than Japans reactors.

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The control room at Chernobyl's Reactor No. 4 is shown here. Reactor design, wind patterns, communication and other factors can cause differences in the severity of nuclear accidents (6).
Should we be Concerned?
Yes, we should be concerned for the people dealing with these issues and should try to help them as best as we can but we should not be concerned with radiation issues in the the United states because Japan's radiation will not come around the U.S. Also, the people in Japan will not suffer as badly as the people in Chernobyl did because Japan had built a better reactor than the Soviets did.