Chapter 12 Nuclear Energy

Overview of Chapter 12 o Introduction to Nuclear Power Atoms and radioactivity Atoms and radioactivity o Nuclear Fission o Pros and Cons of Nuclear Energy Cost of Nuclear Power Cost of Nuclear Power o Safety Issues at Power Plants Three Mile Island & Chornobyl Three Mile Island & Chornobyl Nuclear Weapons Nuclear Weapons o Radioactive Waste o Future of Nuclear Power

Introduction to Nuclear Energy o Nuclear energy Energy released by nuclear fission or fusion Energy released by nuclear fission or fusion o Nuclear fission Splitting of an atomic nucleus into two smaller fragments, accompanied by the release of a large amount of energy Splitting of an atomic nucleus into two smaller fragments, accompanied by the release of a large amount of energy o Nuclear fusion Joining of two lightweight atomic nuclei into a single, heavier nucleus, accompanied by the release of a large amount of energy Joining of two lightweight atomic nuclei into a single, heavier nucleus, accompanied by the release of a large amount of energy

Atoms and Radioactivity o Nucleus Comprised of protons (+) and neutrons (neutral) Comprised of protons (+) and neutrons (neutral) o Electrons (-) orbit around nucleus o Neutral atoms Same # of protons and electrons Same # of protons and electrons

Atoms and Radioactivity o Atomic mass Sum of the protons and neutrons in an atom Sum of the protons and neutrons in an atom o Atomic number Number of protons per atom Number of protons per atom Each element has its own atomic number Each element has its own atomic number o Isotope Usually an atom has an equal number of neutrons and protons Usually an atom has an equal number of neutrons and protons If the number of neutrons is greater than the number of protons = isotope If the number of neutrons is greater than the number of protons = isotope

Radioactive Isotope o Unstable isotope o Radioactive Decay Emission of energetic particles or rays from unstable atomic nuclei Emission of energetic particles or rays from unstable atomic nuclei o Example Uranium (U-235) decays over time to lead (Pb- 207) Uranium (U-235) decays over time to lead (Pb- 207) o Each isotope decays based on its own half- life

Radioactive Isotope Half-lives

Nuclear Fission o Nuclear Fuel Cycle processes involved in producing the fuel used in nuclear reactors and in disposing of radioactive (nuclear) wastes processes involved in producing the fuel used in nuclear reactors and in disposing of radioactive (nuclear) wastes

Nuclear Fission o U-235 is bombarded with neutrons o The nucleus absorbs neutrons o It becomes unstable and splits into 2 neutrons o 2-3 neutrons are emitted and bombard another U-235 atom o Chain reaction

How Electricity is Produced

Breeder Nuclear Fission o A type of nuclear fission in which non- fissionable U-238 is converted into fissionable Pu-239

Pros and Cons of Nuclear Energy o Pros Less of an immediate environmental impact compared to fossil fuels Less of an immediate environmental impact compared to fossil fuels

Pros and Cons of Nuclear Energy o Pros (continued) Carbon-free source of electricity- no greenhouse gases emitted Carbon-free source of electricity- no greenhouse gases emitted May be able to generate H-fuel May be able to generate H-fuel o Cons Generates radioactive waste Generates radioactive waste Many steps require fossil fuels (mining and disposal) Many steps require fossil fuels (mining and disposal) Expensive Expensive

Cost of Electricity from Nuclear Energy o Cost is very high o 20% of US electricity is from Nuclear Energy Affordable due to government subsidies Affordable due to government subsidies o Expensive to build nuclear power plants Long cost-recovery time Long cost-recovery time o Fixing technical and safety issues in existing plants is expensive

Safety Issues in Nuclear Power Plants o Meltdown At high temperatures the metal encasing the uranium fuel can melt, releasing radiation At high temperatures the metal encasing the uranium fuel can melt, releasing radiation o Probability of meltdown or other accident is low o Public perception is that nuclear power is not safe o Sites of major accidents: Three Mile Island Three Mile Island Chornobyl (Ukraine) Chornobyl (Ukraine)

Three-Mile Island o most serious reactor accident in US o 50% meltdown of reactor core Containment building kept radiation from escaping Containment building kept radiation from escaping No substantial environmental damage No substantial environmental damage No human casualties No human casualties o Elevated public apprehension of nuclear energy Led to cancellation of many new plants in US Led to cancellation of many new plants in US

Chornobyl o worst accident in history o 1 or 2 explosions destroyed the nuclear reactor Large amounts of radiation escaped into atmosphere Large amounts of radiation escaped into atmosphere o Spread across large portions of Europe

Chornobyl o Radiation spread was unpredictable o Radiation fallout was dumped unevenly o Death toll is 10, ,000

Nuclear Energy and Nuclear Weapons o 31 countries use nuclear energy to create electricity o These countries have access to spent fuel needed to make nuclear weapons o Safe storage and handling of these weapons is a concern

Radioactive Waste o Low-level radioactive waste- Radioactive solids, liquids, or gasses that give off small amounts of ionizing radiation Radioactive solids, liquids, or gasses that give off small amounts of ionizing radiation o High-level radioactive waste- Radioactive solids, liquids, or gasses that give off large amounts of ionizing radiation Radioactive solids, liquids, or gasses that give off large amounts of ionizing radiation

Radioactive Wastes o Long term solution to waste Deep geologic burial –Yucca Mountain Deep geologic burial –Yucca Mountain As of 2004, site must meet EPA million year standard (compared to previous 10,000 year standard) As of 2004, site must meet EPA million year standard (compared to previous 10,000 year standard) Possibilities: Possibilities: Above ground mausoleums Above ground mausoleums Arctic ice sheets Arctic ice sheets Beneath ocean floor Beneath ocean floor

Radioactive Waste o Temporary storage solutions In nuclear plant facility (require high security) In nuclear plant facility (require high security) Under water storage Under water storage Above ground concrete and steel casks Above ground concrete and steel casks o Need approved permanent options soon.

Case-In-Point Yucca Mountain o 70,000 tons of high- level radioactive waste o Tectonic issues have been identified

Decommissioning Nuclear Power Plants o Licensed to operate for 40 years Several have received 20-year extensions Several have received 20-year extensions o Power plants cannot be abandoned when they are shut down o Three solutions Storage Storage Entombment Entombment Decommissioning (dismantling) Decommissioning (dismantling)

Fusion o Fuel= isotopes of hydrogen

Fusion o Way of the future?? Produces no high-level waste Produces no high-level waste Fuel is hydrogen (plenty of it!) Fuel is hydrogen (plenty of it!) o Problems It takes very high temperatures (millions of degrees) to make atoms fuse It takes very high temperatures (millions of degrees) to make atoms fuse Confining the plasma after it is formed Confining the plasma after it is formed o Scientists have yet to be able to create energy from fusion