Presentation on theme: "15-5 What Are the Advantages and Disadvantages of Nuclear Energy?"— Presentation transcript:
115-5 What Are the Advantages and Disadvantages of Nuclear Energy? Concept Nuclear power has a low environmental impact and a very low accident risk, but high costs, a low net energy yield, long-lived radioactive wastes, vulnerability to sabotage, and the potential for spreading nuclear weapons technology have limited its use.
2How Does a Nuclear Fission Reactor Work? (1) Controlled nuclear fission reaction in a reactorLight-water reactorsFueled by uranium ore and packed as pellets in fuel rods and fuel assembliesControl rods absorb neutronsWater is the usual coolantContainment shell around the core for protectionWater-filled pools or dry casks for storage of radioactive spent fuel rod assemblies
3Light-Water-Moderated and -Cooled Nuclear Power Plant with Water Reactor
4What Is the Nuclear Fuel Cycle? Mine the uraniumProcess the uranium to make the fuelUse it in the reactorSafely store the radioactive wasteDecommission the reactor
6What Happened to Nuclear Power? Slowest-growing energy source and expected to decline moreWhy?EconomicsPoor managementLow net yield of energy of the nuclear fuel cycleSafety concernsNeed for greater government subsidiesConcerns of transporting uranium
7Case Study: Worst Commercial Nuclear Power Plant Accident in the U.S. Three Mile IslandMarch 29, 1979Near Harrisburg, PA, U.S.Nuclear reactor lost its coolantLed to a partial uncovering and melting of the radioactive coreUnknown amounts of radioactivity escapedPeople fled the areaIncreased public concerns for safetyLed to improved safety regulations in the U.S.
8Case Study: Worst Nuclear Power Plant Accident in the World ChernobylApril 26, 1986In Chernobyl, UkraineSeries of explosions caused the roof of a reactor building to blow offPartial meltdown and fire for 10 daysHuge radioactive cloud spread over many countries and eventually the world350,000 people left their homesEffects on human health, water supply, and agriculture
9Trade-Offs: Conventional Nuclear Fuel Cycle, Advantages and Disadv
10Trade-Offs: Coal versus Nuclear to Produce Electricity
11Dealing with Radioactive Wastes Produced by Nuclear Power Is a Difficult Problem High-level radioactive wastesMust be stored safely for 10,000–240,000 yearsWhere to store itDeep burial: safest and cheapest optionWould any method of burial last long enough?There is still no facilityCan the harmful isotopes be changed into harmless isotopes?
12Case Study: Experts Disagree about What to Do with Radioactive Wastes in the U.S. 1985: plans in the U.S. to build a repository for high-level radioactive wastes in the Yucca Mountain desert region (Nevada)ProblemsCost: $58–100 billionLarge number of shipments to the site: protection from attack?Rock fracturesEarthquake zoneDecrease national securitySelf-Study
13What Do We Do with Worn-Out Nuclear Power Plants? Decommission or retire the power plantSome optionsDismantle the plant and safely store the radioactive materialsEnclose the plant behind a physical barrier with full-time security until a storage facility has been builtEnclose the plant in a tombMonitor this for thousands of years
14Can Nuclear Power Lessen Dependence on Imported Oil, Reduce Global Warming? Nuclear power plants: no CO2 emissionNuclear fuel cycle: emits CO2Opposing views on nuclear power and global warmingNuclear power advocates2003 study by MIT researchers2007: Oxford Research Group
15Will Nuclear Fusion Save Us? “Nuclear fusion is the power of the future and always will be”Still in the laboratory phase after 50 years of research and $34 billion dollars2006: U.S., China, Russia, Japan, South Korea, and European UnionWill build a large-scale experimental nuclear fusion reactor by 2040
16Experts Disagree about the Future of Nuclear Power Proponents of nuclear powerFund more research and developmentPilot-plant testing of potentially cheaper and safer reactorsTest breeder fission and nuclear fusionOpponents of nuclear powerFund rapid development of energy efficient and renewable energy resources
17Science Focus: Are New and Safer Nuclear Reactors the Answer? (1) Advanced light-water reactors (ALWR)Built-in passive safety featuresHigh-temperature-gas-cooled reactors (HTGC)Pebble bed modular reactor (PBMR)Pros: no need to shut down for refuelingConsBreeder nuclear fission reactorsSelf-Study
18Science Focus: Are New and Safer Nuclear Reactors the Answer? (2) New Generation nuclear reactors must satisfy these five criteriaSafe-runaway chain reaction is impossibleFuel can not be used for nuclear weaponsEasily disposed of fuelNuclear fuel cycle must generate a higher net energy yield than other alternative fuels, without huge government subsidiesEmit fewer greenhouse gases than other fuelsSelf-Study