Chernobyl Essays (1237 words) - Nuclear Technology,

Chernobyl April 26th 1986 marked the date of the worst nuclear accident to ever occur. Chernobyl, a nuclear power plant in Russia was undergoing routine safety tests that envolved running the reactor on less then full power, followed by a standard shut down. At Chernobyls reactor number 4 a specific test was designed to show that a coasting turbine could produce enough power to pump coolant through the reactor core while waiting for electricity from diesel generators. During the test turbine feed valves were closed to initiate turbine coasting, and automatic control rods were withdrawn from the core. When the steam valves to the turbine close, the pressure in the reactor should go up causing the boiling point of the water to increase. This creates more water in the reactor, increasing cooling. During this test there was a problem with the feed water supply, so the increase in cooling water did not happen. What did happen was an uncontrolled increase in the steam pressure. The operator saw this and started to shut down the reaction by reinserting the control rods. The initial insertion of the control rods caused the reaction to concentrate in the bottom of the reactor. The reactor power rose well above its maximum capacity. Fuel pellets shattered, reacting with the cooling water, creating high pressure in the fuel containers. This surge in pressure caused the fuel containers to rupture. This led to two severe explosions, one a steam explosion, the other a rapid expansion of fuel vapor. The force of these explosions lifted the pile cap, allowing air to enter the reactor. The graphite used in the reactor construction caught on fire, ending a horrible and tragic sequence of events, but beginning another. Local firemen, unaware of the dangerous amounts of radiation, were called in to put out the fire. All of the firemen died, either a result of the fire, or from breathing radioactive debris. Unfortunately, their heroic attempts were useless, because the core of the reactor was exposed making the fire much to hot for water to cool. The first thing the Russians did was try to cover up the accident. This turned out to be impossible, considering the amounts of radioactive debris released into the air. Shortly after the accident a nuclear power plant in Sweden measured high amounts of radioactivity in their area, called the Russians to inquire if there had been an accident. The Russians shortly thereafter alerted the press, and evacuated towns surrounding Chernobyl. This of course wasnt their biggest problem. They needed to find the fuel that had escaped from the reactor in order to avoid another massive chain reaction. This was a huge problem due to the extreme amounts of radioactivity inside the sarcophagus. They didnt have the money for robots, so they sent in the Soviet Army. 3400 men were used on roof runs in which theyd go and collect samples from the roof of the reactor. During these missions soldiers could be subjected to 20 Rankins of radiation. Many people who have worked at Chernobyl have died from sudden heart failure. The Russian government denies that this has anything to do with their work at Chernobyl, but their have been too many deaths related to heart failure for it not to be. The next move was to find the fuel. Unlike American nuclear power plants that have their reactors over steel reinforced concrete the crazy Russians built their reactor on top of offices. Inside these offices radiation levels reach around 100 to 250 Rankins of radiation per hour. This means it would be impossible to ever work safely inside Chernobyl, unless of course you had a few hundred thousand years on your hands for the radioactivity to fall to safe levels. Unfortunately they didnt, they had to find the fuel before another chain reaction occurred, releasing more nuclear fallout into the environment. Throughout their early investigation they could find no clues to the whereabouts of the fuel. Finally, one cold December day in 1986, scientists came across a large highly radioactive mass approximately 2 meters across in size. Because of its unique shape they titled it the Elephants Foot. Their only dilemma was, what the heck is it? This problem