Week Three - Weebly



Week ThreeRadioactive Wolves PBS Student Worksheet to Accompany PBS Nature 2011 1. Explain how access to the exclusion zone is restricted and protected. 2. How has the radioactive fallout from the Chernobyl accident worked its way through the food web? 3. Scientists are shown measuring radiation from moose bones leftover from a wolf kill. How radioactive are the bones? 4. When do the scientists working in the exclusion zone need to wear all of their protective gear? 5. Who were the “liquidators”? 6. Explain how wolves can be used as a biological indicator of the overall health of the ecosystem. 7. What human activity had the biggest impact on the wolf populations before Chernobyl? 8. Explain how these ecological changes have reversed since humans abandoned the exclusion zone. 9. One of the scientists is shown gathering hair samples from an uncontaminated wolf den. Why would these samples be useful in studying animal life in the exclusion zone? 10. Pripyat was a large city built mainly to provide a home for all of the employees of the Chernobyl nuclear plant. Describe what it looks like now. 11. Why are the wolves so drawn to the abandoned buildings? 12. What other species is used as an indicator, besides wolves? 13. Why are laboratory rats kept and studied in the exclusion zone? 14. What is the percentage of door mice born with genetic abnormalities? How does this compare with normal levels? 15. Why are the catfish in the contaminated cooling pond so large? a. How radioactive are the fish bones? b. Are any of the fish in the exclusion zone safe for human consumption? 16. Why are the large oak trees so important for storks? Where are they found? 17. How are wolves actually slowing the return of the Pripyat marshes in the south part of the exclusion zone? 18. How many wolves were estimated to be living in the exclusion zone? How does this compare to the control area? Discussion Questions 19. Overall, do you think the Chernobyl accident has actually been ecologically beneficial for the ecosystems within the exclusion zone? Which do you think is more damaging or dangerous to the biodiversity – the contamination from the radioactive fallout, or the presence of a large human population? Justify your answer. 20. Imagine that you are trapped within the exclusion zone. As you hike your way out, you begin to feel hungry. Using what you know about bio magnification, which food source would be the safest? Explain how you know. a. Mushrooms, fruit, and berries b. Moose or deer meat. c. Wolf meat. d. Eagle meat. 21. If your school and surrounding area were to be suddenly abandoned, how do you think nature would reclaim it? What ecosystem was present before it was built on? Would it return to its original state? How long would it take? What animal or plant populations would increase? Would you expect any species to actually decline without humans?Chernobyl Nuclear Power Plant On April 26, 1986, a sudden surge of power during a reactor systems test destroyed Unit 4 of the nuclear power station at Chernobyl, Ukraine, in the former Soviet Union. The accident and the fire that followed released massive amounts of radioactive material into the environment. Emergency crews responding to the accident used helicopters to pour sand and boron on the reactor debris. The sand was to stop the fire and additional releases of radioactive material; the boron was to prevent additional nuclear reactions. A few weeks after the accident, the crews completely covered the damaged unit in a temporary concrete structure, called the “sarcophagus,” to limit further release of radioactive material. The Soviet government also cut down and buried about a square mile of pine forest near the plant to reduce radioactive contamination at and near the site. Chernobyl’s three other reactors were subsequently restarted but all eventually shut down for good, with the last reactor closing in 1999. The Soviet nuclear power authorities presented their initial accident report to an International Atomic Energy Agency meeting in Vienna, Austria, in August 1986. After the accident, officials closed off the area within 30 kilometers (18 miles) of the plant, except for persons with official business at the plant and those people evaluating and dealing with the consequences of the accident and operating the undamaged reactors. The Soviet (and later on, Russian) government evacuated about 115,000 people from the most heavily contaminated areas in 1986, and another 220,000 people in subsequent years (Source: UNSCEAR 2008, pg. 53). Health Effects from the Accident The Chernobyl accident's severe radiation effects killed 28 of the site's 600 workers in the first four months after the event. Another 106 workers received high enough doses to cause acute radiation sickness. Two workers died within hours of the reactor explosion from non-radiological causes. Another 200,000 cleanup workers in 1986 and 1987 received doses of between 1 and 100 rem (The average annual radiation dose for a U.S. citizen is about .6 rem). Chernobyl cleanup activities eventually required about 600,000 workers, although only a small fraction of these workers were exposed to elevated levels of radiation. Government agencies continue to monitor cleanup and recovery workers' health. (Backgrounder, 2014,).Week ThreeThree Mile Island The most serious nuclear reactor accident to date in the United States occurred at 4 a.m. on March 28, 1979, at the Three Mile Island nuclear power plant outside Middletown, Pennsylvania. Operator errors in dealing with a pump that had shut down caused the Unit 2 pressurized-water reactor to lose coolant and overheat. The temperature of the reactor core then rose to the point at which some of the zirconium-alloy fuel cladding failed, fuel itself partially melted, and cladding reacted with steam to produce bubbles of vapor and hydrogen, which then escaped into the reactor building, along with fission products from the reactor core. As a result of the failure to close a backup valve that could be operated manually, coolant was not restored to the reactor core until more than six hours after the accident, by which time enough hydrogen had accumulated in the building to pose the treat of a low-level explosion. The building had been designed to seal automatically in the event of a pressure rise, but no rise occurred, and four hours were allowed to elapse before the building was sealed, during which time radioactive gases escaped into the atmosphere. Within three hours after the first sign of trouble, elevated radiation levels were detected by monitors in the reactor auxiliary building. A site emergency was declared, and officials enlisted the aid of local, state, and federal emergency personnel. The presence of a large hydrogen bubble in the reactor vessel prompted widespread fear that the reactor might explode, a concern that experts failed to allay although they knew it to be a misapprehension. Adding to the fear, dosimeter readings made in a helicopter three hundred feet above the auxiliary building's ventilation stack were misinterpreted by officials to signify elevated ground levels of radiation, prompting the governor of Pennsylvania to recommend the evacuation of all pregnant women and preschool children residing within five miles of the plant, who then complied. Although large amounts of radiation were released, the resulting exposure of the public was relatively slight, resulting mainly from xenon-133 that was present in the gaseous plume. The largest dose of radiation any member of the public may have received is estimated to have been smaller than his or her annual dose from natural background irradiation, and the average dose to those living within fifty miles of the reactor is estimated to have been 40 to 50 times smaller than that. Because of the small magnitude of the doses that were received, no demonstrable injuries from the radiation were expected, nor have any actually been observed. Nevertheless, the legacy of fear and resentment left by the accident has adversely affected the well-being of those living nearby, and it has heightened negative attitudes toward nuclear energy.Upton, A., 2002, Encyclopedia of Public Health Upton, Arthur C.. "Three Mile Island." Encyclopedia of Public Health. 2002. . (January 6, 2015). ................
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