Transcript Chapter 19
Chapter 19 Nuclear Energy and the Environment Botkin and Keller Environmental Science 5e Nuclear Energy • Nuclear Energy – The energy of the atomic nucleus • Nuclear Fission – The splitting of the atomic nuclei • Nuclear Fusion – The fusing of atomic nuclei • Nuclear Reactors – Devises that produce controlled nuclear fission Botkin and Keller Environmental Science 5e Fission Reactors • As fission occurs, energy is released. • Major components of a fission reactor: • Core, control rods, coolant, reactor vessel • Burner Reactors: a type of nuclear reactor that consumes more fissionable material than it produces • Meltdown: a nuclear accident in which the nuclear fuel forms a molten mass that breaches the containment of the reactor, contaminating the outside environment with radioactivity. Botkin and Keller Environmental Science 5e Botkin and Keller Environmental Science 5e Botkin and Keller Environmental Science 5e Sustainability and Nuclear Power • Nuclear Radiation occurs when when a radioisotope spontaneously undergoes radioactive decay and changes into another isotope • 3 types of nuclear radiation: Alpha, Beta, Gamma • Breeder Reactor: – a type of nuclear reactor that utilizes between 40-70% of its nuclear fuel and converts fertile nuclei to fissile nuclei faster than the rate of fission – Produces nuclear fuels Botkin and Keller Environmental Science 5e Botkin and Keller Environmental Science 5e Botkin and Keller Environmental Science 5e Botkin and Keller Environmental Science 5e Nuclear Energy and the Environment • Nuclear Fuel Cycle: – the process involved in producing nuclear power from the mining and processing of uranium to controlled fission, the reprocessing of spent nuclear fuel, the decommissioning of power plants and the disposal of radioactive waste – Each part of the cycle is associated with different potential environmental problems Botkin and Keller Environmental Science 5e Botkin and Keller Environmental Science 5e Effects of Radioisotopes • Radioisotope: an isotope of a chemical element that spontaneously undergoes radioactive decay • Effect Environment in 2 Ways – Emitting radiation – Entering ecological food chains Botkin and Keller Environmental Science 5e Botkin and Keller Environmental Science 5e Botkin and Keller Environmental Science 5e Radiation Dose • Curie (Ci) unit of radioactivity – (equal to 37 billion nuclear transformations per second) • Becquerel (Bq) radioactive decay – (1 decay per second) • rads (rd) dose of radiation delivered by radioactivity • grays (Gy) same, but in SI units • Rems (rems) equivalent dose, normalized by radiation and tissue type • sieverts (Sv) same, but in SI units Botkin and Keller Environmental Science 5e Radiation and Health • LD-50 is about 5000 mSv (5 Sv) • 1000 – 2000 mSv: vomiting, fatigue, abortion of fetuses less than 2 months, temporary sterility • 50 mSv: maximum dose per year in industry – (30 times average natural background) • 1-5 mSv: maximum dose per year for public Botkin and Keller Environmental Science 5e Nuclear Power Plant Accidents • Three Mile Island (Harrisburg, PA) – Valve malfunction and human error – Partial core meltdown, • Chernobyl – – – – – Radiation in Sweden detected in power plant 4/28/86 Cooling system failed (human error) Top of building over reactor exploded. 30 km zone dose received 0.43 Sv Expected cases of leukemia, large numbers of thyroid cancer seen Botkin and Keller Environmental Science 5e Radioactive Waste Management • Low-Level Radioactive Waste – Waste materials that contain sufficiently low concentrations or quantities of radioactivity so as not to present a significant environment hazard if properly handled • Transuranic Waste – Radioactive waste consisting of human-made radioactive elements heavier than uranium – Contaminated clothing rags, tools, etc. • High-Level Radioactive Waste – Extremely toxic nuclear waste, such as spent fuel elements from commercial reactors. – How do we dispose of this waste material? Botkin and Keller Environmental Science 5e Botkin and Keller Environmental Science 5e