Radioactivity Inside You • Concerned about radioactivity in nature? • To keep things in perspective, consider that 0.01% of all potassium is radioactive K-40. • Potassium is an essential element in the human body. • If your body is about 1% K, this means a 70 kg • (150 pound) person contains around • 1x1021 atoms (that’s one billion trillion atoms) • of radioactive K-40.
Radiation and Risk:Perception and Reality 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Nuclear Power Motor Vehicles Handguns Smoking Motorcycles Alcoholic Beverages Private Aviation Police Work Pesticides Surgery Fire Fighting Large Construction Hunting Spray Cans Mountain Climbing 20 1 4 2 6 3 12 17 8 5 18 13 23 26 29 What the Experts Calculate Relative Risk What the General Public Perceives
Radiation and Risk:Perception and Reality 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 Bicycles Commercial Aviation Electric Power Swimming Contraceptives Skiing X-Rays High School and College Football Railroads Food Preservatives Food Coloring Power Mowers Prescription Antibiotics Home Appliances Vaccinations 15 16 9 10 11 30 7 27 19 14 21 28 24 22 25 What the Experts Calculate Relative Risk What the General Public Perceives
Extraterrestrial Radiationand Radioactivity • The primary source of cosmic radiation is from outside this solar system. • Cosmogenic radiation is an extraterrestrial form of radiation that is produced when the upper atmosphere of the earth interacts with incoming cosmic radiation. • The atmosphere and the earth’s magnetic field act as a shield against incoming radiation, reducing the amount of radiation that actually reaches the earth’s surface. • The higher you rise in altitude, the higher your dose from cosmic radiation.
Consumer Products and Radioactive Material • There are more sources of radiation in the consumer product category than in any other. • Television sets accelerate electrons to make the picture on the screen and in the process produce a few low energy x-rays. • Smoke detectors emit radiation that is easily stopped even by smoke, and in that way detect the presence of smoke. • Some more products or services: treatment of agricultural products, long lasting light bulbs, building materials, static eliminators in manufacturing, and luminous dials, among many others.
Can a Nuclear Power Plant undergo a Nuclear Explosion? • The answer is simply “No”, Why? • Nuclear power plants require slow neutrons, controlled reaction, and 3-5% enrichment of U-235, the rest is U - 238 ; • A nuclear weapon requires fast neutrons, uncontrolled reaction, and enrichment of 95% of U-235. • U- 235 constitutes only 0.7% of the naturally occurring uranium , i.e.., it is not abundant!
How Long Will Nuclear Waste Products Remain Radioactive? • Half-life: is the time required for the level of radioactivity to fall to one-half of its initial value. • U-238 4.5 billion y • Th-234 24 days • Po-214 0.00016 s • H-3 12.3 yrs • I-131 8 days • Sr-90 28.9 y • C-14 5730 y
How Will We Dispose of Nuclear Waste from Nuclear Plants? • This is probably one of the most nagging problems of nuclear energy; • - U.S had accumulated 306,000 cubic meters of high level waste (mostly liquid) from the defense program and 4626 cubic meters of spent fuel rods from nuclear power plants.
How Will We Dispose of Nuclear Waste from Nuclear Plants? • For example, the storage facility at Seabrook is a 34-foot deep steel-lined concrete pool in a secure building. It has the capacity to hold up to 25 years’ worth of waste. • In the U.S. we do not have a long-term storage facility for high level waste (HLW). This has become an obstacle to the use of nuclear energy.
Fig. 7.20 – Spent cooling rods from a nuclear power reactor in a cooling chamber.
How Will We Dispose of Nuclear Waste from Nuclear Plants? • In 1970, some states passed laws prohibiting the construction of any new nuclear power plants until the federal government demonstrates that radioactive waste can be disposed of safely and permanently. • DOE had contracted with electric utility companies to begin accepting spent fuels elements in 1998. But progress in preparing a national underground disposal site has been painfully slow!
How Will We Dispose of Nuclear Waste from Nuclear Plants? • Scientists agree on the following disposal method: • 1. encase the spent fuel elements in ceramics or glass, pack in metal canisters, bury them in deep (1000ft) repository in appropriate rock formation (no water), for 300-500 years. • 2. possible states identified for waste disposal are; Nevada, Texas, Washington, Utah, and Mississippi.
How Will We Dispose of Nuclear Waste from Nuclear Plants? • A five-year pilot project is underway in New Mexico where salt beds at 2150 ft below ground are being used for isolation of nuclear waste. • Tunnels are also being dug 1400 ft below Yucca mountains in Nevada. When completed in year 2003, the site will be the largest radioactive storage facility in the country, with a capacity of 63,500 tons of high level waste. It has been estimated that it would take 20 years to transport all the waste to the Nevada site.
Low level waste (LLW) • LLW is regulated by the policy of 1980 for Regional Compact. • Two commercial disposal site: • Barnwell, SC (70% waste) • Richland, WA (30% waste)
Nuclear power in the U.S. and Worldwide • Cost overruns, changing federal regulations, years of litigation, and public opposition have halted the construction of new fission power plants in the U.S. • All plants ordered since 1974 have been canceled. • At present, only four plants are either being built or in various stages of testing or start-up. • Currently, 108 nuclear plants are operating in the U.S.
Nuclear power in the U.S. and Worldwide • Globally, 17% of the electricity produced and consumed is generated from nuclear energy. In the U.S. alone, we generate 19.1% of our electricity from nuclear power. • Romania has no nuclear power plants. • France has 55 plants and generates 74.5% of its electricity from nuclear energy. • It is ironic that most of the world’s uranium comes from Africa, yet the great majority of the African countries do not use nuclear power!
Percent of electrical power generatedby nuclear reactors in selected countries, 1997 - Fig. 7.25
Risks and Benefits of Living with Nuclear Power • The following are deaths per year for 100-MW power plant: (*= coal) • routine occupational hazard (0.3-0.6) 2.7* • routine population hazard (0.03) 1.2-50* • catastrophic hazard (0.04) 0.5*