Transcript Slide 1
Chernobyl David Gee March 3, 2010 What happened? Source: http://en.wikipedia.org/wiki/Chernobyl_disaster The nuclear power plant in Chernobyl had the biggest disaster in the history of nuclear power on April 26, 1986. There were 56 deaths attributed to this incident, and probably thousands of other deaths indirectly linked to it. This unfortunate event was the result of several unsafe practices; it demonstrates what not to do when running a nuclear power plant. Causes A test for the emergency core cooling system was planned, and it was necessary to reduce power output during that. BUT: Causes Another power plant went offline, so they delayed the test. Meanwhile the workers changed from day shift to night shift, and the new shift wasn’t as prepared to run the test. Control rods had been withdrawn and water flow had been increased to the limit. The night shift did not know about this. Causes • When the experiment ran, output decreased, so water flowed less… • generating more steam… • inhibiting water flow further… • generating even more steam… Causes • Liquid water is a moderator! • Power output increased steadily as a result. • Control rods were eventually inserted, but there was a design flaw: coolant was displaced before the neutron-absorbing material was inserted. • The reaction rate increased, and the power spiked. Causes The core overheated, and the control rods became stuck when blocked by fractured fuel rods. Source: http://www.world-nuclear.org/info/chernobyl/inf07.html Causes First a steam explosion occurred, then a second explosion of unknown cause, although it was likely a nuclear explosion from xenon radioisotopes. The core didn’t have a containment vessel. Graphite (which is combustible) and reactor fuel (which is radioactive) were ejected everywhere. Response The only available working dosimeter was for low-level radiation detection (0.001 röntgen per second). When the crew brought in another dosimeter later, which read much higher levels of radiation, they assumed the second dosimeter was defective and that the reactor was intact, despite reactor fuel and graphite lying around the building. Response A nuclear power plant in Sweden discovered increased radiation levels, but no cause could be found as everything was intact. Until Sweden reported this, the Soviet Union concealed that a disaster occurred, and when they finally issued an evacuation warning, they downplayed the severity of the situation. Source: http://en.wikipedia.org/wiki/Chernobyl_disaster Response Radioactive debris had to be removed. Even when wearing protective suits, workers could spend only 40 seconds on rooftops of nearby buildings. Eventually concrete was used to seal off the reactor and its radioactive contents. This has become known as the “sarcophagus”. Effects Nowadays there is an “Exclusion Zone” around Chernobyl. No one is allowed to live there. The pine forest in the area turned brown and died. Radioactivity accumulated in fish, to levels of about 0.1 to 60 kilobecquerel per kilogram. Source: http://blog.photos2view.com/blinky-the-three-eyed-fish.htm Effects However, groundwater was not affected. Most nucleotides decayed quickly, and the slowdecaying ones were adsorbed by the soil above before reaching water. Eventually wildlife, including rare species, flourished in the “exclusion zone”, despite the increased radiation levels. Effects There have been several health effects for humans. Anxiety has increased mental health problems. Acute radiation sickness has definitely been linked to Chernobyl. Down’s Syndrome, chromosomal aberrations, neural tube defects, and cancer have been correlated with this incident, but causation is still unclear. Source: http://www.world-nuclear.org/info/chernobyl/inf07.html Effects Nuclear power has had a negative connotation ever since the disaster at Chernobyl. Public fear increased, and as a result politicians in many countries have been hesitant to support nuclear, instead favoring fossil fuels. More stringent safety requirements have been established worldwide for running nuclear power plants. Summary The safety procedures executed before and after the disaster demonstrate what not to do when running a nuclear power plant or dealing with the aftermath of a crisis. The disaster at Chernobyl had widespread, devastating effects, including environmental damage, health problems, and death. References • World Nuclear Association, http://www.worldnuclear.org/info/chernobyl/inf07.html • “The Chernobyl Forum”, International Atomic Energy Agency, 2006 • “Chernobyl”, Institut de Radioprotection et de Sûreté Nucléaire, 2006