Chernobyl Sydney Curley

What is Chernobyl? Chernobyl Nuclear Power Plant in the Ukrainian Soviet Socialist Republic (then part of the Soviet Union, now in Ukraine). A nuclear accident on April 26th, 1986. The result of a flawed reactor design that was operated with poorly trained personnel.

About the reactors Chernobyl had 4 nuclear reactors of the RBMK-100 design. Thermal Reactor that burns uranium dioxide fuel. By thermal it is meant that the neutrons that are emitted by the atoms going through fission must be slowed down to low (thermal) energies so that they can cause more fissions. The heat that is generated in this process is carried away by the coolant which is ordinary water. This heat is used to make steam which is then used to drive turbo-generators to make electricity. The rate of the reaction is controlled by inserting control rods into the core. The large amounts of radiation produced under normal operation are contained within the core by heavy concrete and steel shielding.

The Test Before a routine shut down on April 25th, 1986 the reactor crew at Chernobyl 4 prepared for a test. The test was to determine whether cooling of the core could continue to be ensured in the event of a loss of power. This test was tried the previous year but it didn’t work because the power from the turbines ran down too fast.

Why did it happen? There was not proper communication between the team in charge of the test and the personnel in charge of the safety of the nuclear reactor. Insufficient safety precautions were included in the test and the operating personnel were not alerted to the nuclear safety implications of the electrical test and its potential danger.

What went wrong? For this test, the reactor should have been stabilized at about 700-1000 MWt (megawatt thermal) before shutdown, but the power fell to about 30 MWt. Many of the control rods were withdrawn in efforts to increase the power to the level originally planned for the test. The reactor was stabilized at about 200 MWt and it was decided that the test would be carried out at this power level.

BOOM! The reactor began to overheat and the water coolant turned into steam. At this point there only 6 control rods remained and the minimum safe operating number was 30. The emergency shutdown button was pressed. With power 100 times normal the fuel pellets began to explode cracking the fuel channels. After the explosions the reactor’s dome shaped top blew off and the contents started to erupt out.

Fire As air was sucked into the reactor, it ignited carbon monoxide gas, and cause a fire that burned for nine days. Unlike how most countries have their reactors, this one was not housed in a concrete shell for protection, as a result the building suffered severe damage and large amounts of radioactive debris escaped in the atmosphere. Firefighters were on the roof of the reactor fighting the fire while helicopters dropped sand and lead into in an effort to stop the radiation.

Radioactivity The many fires from this accident was the main release of radioactivity. A total of about 1.4 x 1018 Bq (an amount = to 1,000 Hiroshima bombs) was released and over half of it was from biologically-inert noble gases. It’s estimated that all of the xenon gas, half of the iodine and caesium, and at least 5% of the remaining radioactive material (had 192 tons of fuel) in the reactor core was released.

Radioactivity con’t Scientists have estimated how much fuel was blown into the atmosphere and into the reactor but their numbers leave 10-50 tons unaccounted for There are 3 situations raised to explain the missing fuel: The fuel was released in the explosion. It spewed out in the fire after the explosion. Its is burring deep in the rubble of the reactor.

Contamination It contaminated 23% of Belarus, some parts of Russia and Ukraine, regions of Poland, the Czech Republic, Scandinavia and southern Germany. 36 hours after the disaster, highly increased doses of atmospheric radioactivity were measured in Germany, Switzerland, the Czech Republic and even as far as Scandinavia. Due to rain and wind currents. 70% of radioactivity came down in Belarus, 15% in Ukraine and Russia and the other 15% dispersed over the rest of the world.

Cleanup They needed to get this site cleaned up immediately so the remaining 3 reactor could be restarted. 200,000 people came from all over the Soviet Union to help.(between 1986-1987) Most received high doses of radiation, 100 millisieverts (mSv), roughly 20,000 received 250 mSv, and a few received 500 mSv. Radiation doses on the first day, after the fire was put out, ranged up to 20,000 mSv. Later the number of people helping jumped to 600,000 most of which got low radiation quantities.

Vehicle Graveyard Cleanup involved helicopters dumping tons and tons of concrete on top of the melting-down reactor. All of the vehicles used during the cleanup became irradiated and there is now a "vehicle graveyard“ containing irradiated helicopters, tanks, and trucks used during the cleanup.

Cover Up Sweden, Denmark , Norway and Finland were detecting extremely high radiation levels and they couldn’t find where it was coming from. They finally figured out that the radiation was carried there by the prevailing winds from the USSR. The Soviets denied it until it was clear that something happened.

Issues Concrete cover (sarcophagus) was built around the #4 Chernobyl reactor to keep more radiation from spreading. It was supposedly built to last hundreds of years, but is not in good shape. Engineering report says that it is full of holes and an earthquake of 6 or higher on the Richter scale. It is estimated that an earthquake like that will hit the Chernobyl region once every hundred years.

Effects of Chernobyl Disaster Chernobyl shows just how bad the effects of a nuclear disaster are Groundwater radiation was almost at an unsafe level all over Russia. Many other countries were effected when clouds of radioactive smoke traveled to their country by prevailing winds and then fell and caused them radiation problems.

Deaths Only one person was killed on site and another died in the hospital shortly after because of the injuries from the explosion. The radiation doses from the first day caused 28 deaths. Reports show that 60,000 people have died from diseases caused by the radiation doses they received from the Chernobyl disaster.

Health 270,000 cancers and 93,000 fatal cancer cases caused by Chernobyl. Ongoing health impacts of Chernobyl damaging immune and endocrine systems. leading to accelerated ageing. cardiovascular and blood illnesses. psychological illnesses. chromosomal aberrations and an increase in fetal deformations.

Bibliography http://eightiesclub.tripod.com/id304.htm http://library.thinkquest.org/3426/data/chernobyl-today/index.html http://chernobyl-disaster.com/ghost-town-pripyat.php