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  1. 1. Chernobyl Accident by Sibel Tekmen April 1986
  2. 2. Chernobyl disaster <ul><ul><li>nuclear accident near town of Pripyat </li></ul></ul><ul><ul><li>April 26, 1986 </li></ul></ul><ul><ul><li>  Chernobyl Nuclear Power Plant </li></ul></ul><ul><ul><li>  Ukraine </li></ul></ul><ul><ul><li>  worst nuclear power plant accident in history </li></ul></ul><ul><ul><li>  only level 7 event on the International Nuclear Event Scale </li></ul></ul>
  3. 3. The Accident <ul><ul><li>01:23 a.m. </li></ul></ul><ul><ul><li>  reactor 4 suffered a power increase </li></ul></ul><ul><ul><li>  explosions in the core </li></ul></ul><ul><ul><li>dispersed large quantities of fuel and core materials into the atmosphere and ignited the combustible graphite moderator </li></ul></ul><ul><ul><li>the graphite moderator increased the emission of radioactive particles, carried by smoke </li></ul></ul><ul><ul><li>reactor had not been contained in any kind of hard containment vessel </li></ul></ul><ul><ul><li>during an experiment scheduled to test a potential safety emergency core cooling feature </li></ul></ul>
  4. 4. The Accident Cont. <ul><ul><li>No. 4 reactor exploded and released thirty to forty times the radioactivity of the atomic bombs dropped on Hiroshima and Nagasaki </li></ul></ul><ul><ul><li>world first learned of the nuclear accident from Sweden, where abnormal radiation levels were registered in nuclear facilities </li></ul></ul><ul><ul><li>  when attempt was made at the emergency shutdown, a more extreme power output occurred which led to the rupture of the vessels and explosions </li></ul></ul><ul><ul><li>exposed the graphic moderator of the reactor to air and they ignited, resulting in fire sent a plume of radioactive fallout into atmosphere and area </li></ul></ul><ul><ul><li>plume drifted over parts of the western Soviet Union, and also much of Europe </li></ul></ul>
  5. 5. Conditions Prior to the Accident <ul><ul><li>reactor was running at full power, slowly operators began to reduce the power </li></ul></ul><ul><ul><li>12 hours after, running at 50% power </li></ul></ul><ul><ul><li>  only one turbine needed for steam, so turbine #2 switched off </li></ul></ul><ul><ul><li>  under normal conditions, the test reactor would have been reduced to 30%, but Soviet electricity authorities refused to allow this because of the need for electricity elsewhere </li></ul></ul><ul><ul><li>  staff received permission to resume the reactor power reduction, but one operator made a mistake, instead of keeping power at 30%, he forgot to reset the controller, which caused the power to plummet to 1% </li></ul></ul><ul><ul><li>operator forced the reactor up to 7%, by removing all but 6 of the control rods-a violation and reactor was never built to operate at such ow power </li></ul></ul><ul><ul><li>instead of enabling the emergency shutdown, they disabled it because that would abort the test </li></ul></ul>
  6. 6. Afterwards <ul><ul><li>city of Pripyat was not immediately evacuated </li></ul></ul><ul><ul><li>  population of the Soviet was not informed of the incident until April 29 </li></ul></ul><ul><ul><li>only after learning from Sweden, did Soviet union admit that accident had occurred </li></ul></ul><ul><ul><li>authorities attempted to conceal the scale of accident </li></ul></ul><ul><ul><li>  gov. commitee was formed as announced to investigate the accident </li></ul></ul><ul><ul><li>  evacuation began on April 27, residents were to bring only what was necessary since the authorities said it would only be temporary and last approx. 3 days, as a result, residents left most of their belongings, which can still be found today </li></ul></ul>
  7. 7. Effects <ul><ul><li>fire in building and radiation led to 28deaths </li></ul></ul><ul><ul><li>International spread of radioactivity </li></ul></ul><ul><ul><li>Sweden </li></ul></ul><ul><ul><li>Finland </li></ul></ul><ul><ul><li>Belarus </li></ul></ul><ul><ul><li>Ukraine and Russia </li></ul></ul><ul><ul><li>spread by weather </li></ul></ul><ul><ul><li>237 people suffered acute radiation sickness, 31 died within firste three months </li></ul></ul><ul><ul><li>Radioactivity to environment </li></ul></ul><ul><ul><li>  health effects: cancer, birth defects, radiation poisoining </li></ul></ul>