Our Course Review
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Nuclear fission Our course review Nuclear fusion Lasers: NIF/LLNL Nuclear weapons • We have two lectures after today: next Tuesday and Thursday. Manhattan Project 235 U • I promise to return graded papers, homework, and exams next 239 Pu Trinity Tuesday, March 5 (I am finally at home with no work travel this Hiroshima and Nagasaki weekend). Fusion weapons • Reading period begins Tuesday, March 12; exam on Tuesday, Example nuclear weapons March 19 at 7 pm. Exam will be open laptop or tablet, where you email to me your exam answers; otherwise, similar style to midterm exam. If you do not have a laptop or tablet, email me. • Writing assignment due March 11: a briefing paper to the President of the USA on a topic where some physics knowledge is required (see next slide). You are encouraged to email me about your proposed topic; I can give you a few suggestions and ideas. Nuclear fission Final paper due March 11 review Nuclear fusion Lasers: NIF/LLNL Nuclear weapons 8–12 page briefing paper, double-spaced, with citations. Submit through Manhattan Project 235 U SafeAssign. 239 Pu Trinity • Abstract (roughly half a page, summarizing your paper; use italic Hiroshima and Nagasaki font) Fusion weapons • Statement of problem Example nuclear weapons • Relevant information (the quality of the sources you use will be part of your grade) • Proposed action, including discussion of costs and benefits • Arguments against your proposed action, and your counter-arguments • Conclusion Nuclear fission Curve of binding energy review Here’s the curve of binding energy shown inverted, so that nuclei like to Nuclear fusion roll up the hill. Notice the “bumps” near magic numbers Lasers: NIF/LLNL 2 · [2; 8; 20; 28; 50; 82; 126]; these are analogous to closed electron shells Nuclear weapons Manhattan Project with atoms (i.e., noble gases). 235 U 239 Pu Trinity Hiroshima and Nagasaki Fusion weapons Example nuclear weapons This figure from Georgia State’s Hyperphysics web site Nuclear fission Nuclear fission review Nuclear fusion Lasers: NIF/LLNL Nuclear weapons Manhattan Project 235 U 239 Pu Trinity Hiroshima and Nagasaki Fusion weapons Example nuclear weapons (Wikipedia) Nuclear fission Nuclear waste disposal review • Nuclear waste is hot and Nuclear fusion nasty stuff (the scale at Lasers: NIF/LLNL left tops off at 104 TBq, Nuclear weapons or 104 · 1012 = 1016 Manhattan Project 235 U decays/sec). However, it’s 239 Pu Trinity compact and contained. Hiroshima and 137 Nagasaki Note how Cs with a Fusion weapons half life of 30 years Example nuclear dominates the activity at weapons first. • U.S. does not yet have an agreed-upon, operating permanent repository for high level waste. There are both technical questions (how do you guarantee containment for millions of years?) and political ones. Nuclear fission Passive reactors review Nuclear fusion Most reactors now in operation are based on 40 year old designs. New Lasers: NIF/LLNL designs feature passive (convective) cooling, and built-in backup water Nuclear weapons reservoirs: Manhattan Project 235 U 239 Pu Trinity Hiroshima and Nagasaki Fusion weapons Example nuclear weapons GE-Hitachi economic simplified boiling water reactor (ESBWR) Westinghouse Advanced Passive 600 MW (AP600) Nuclear fission The Oklo reactor review Nuclear fusion • At a uranium enrichment facility in France, uranium supplies were Lasers: NIF/LLNL found to have not 0.7202% 235U but 0.7171%. How could that be? Nuclear weapons Manhattan Project • Exploration of the site of uranium ore—the Oklo Mine in Gabon, 235 U Central Africa—revealed that some ores from the site had values as 239 Pu 235 Trinity low as 0.440% U! Hiroshima and Nagasaki • Conclusion: some induced fission took place due to high enough Fusion weapons uranium concentrations in the ground, with groundwater as a Example nuclear weapons moderator! Consistent with Nd and Ru isotope distributions. • This all happened about 2 billion years ago, when 235U concentrations were higher planet-wide (t1=2 = 700 million years). • Non-volatile fission products in the deposit have traveled only centimeters over 2 billion years. • See July 1976 and Nov. 2005 issues of Scientific American. Nuclear fission Producing electricity review Nuclear fusion Lasers: NIF/LLNL Nuclear weapons Manhattan Project Nuclear 235 U 19.27% 239 Natural gas Pu 2011 Sources of Electrical Power 24.79% Trinity (www.eia.gov) Hiroshima and Hydro Nagasaki 7.93% Fusion weapons Wind 2.92% Wood 0.90% Example nuclear Oil 0.69% weapons Coal 42.29% Geothermal 0.41% Other gases 0.27% Solar 0.04% Waste 0.48% Nuclear fission Electricity alternatives review Nuclear fusion Lasers: NIF/LLNL Nuclear weapons Manhattan Project 235 U 239 Pu • Trinity Hydroelectric power is great where it’s available::: Hiroshima and Nagasaki • Solar and wind power are both intermittent, and require significant Fusion weapons energy storage, and fossil fuel or nuclear power backup. Example nuclear weapons • Coal is the cheapest fossil fuel, but is the “dirtiest” in terms of CO2 output, production hazards (worker safety), environmental hazards (mountaintop removal, acid rain), health hazards (particulates, radioactivity). Nuclear fission Coal mining safety review Nuclear fusion Lasers: NIF/LLNL Nuclear weapons Manhattan Project 235 U 239 Pu Trinity Hiroshima and Nagasaki Fusion weapons Example nuclear weapons Nuclear fission Recent history review Nuclear fusion Lasers: NIF/LLNL Nuclear weapons Manhattan Project 235 U 239 Pu Trinity Hiroshima and Nagasaki Fusion weapons Example nuclear weapons Nuclear fission Mountaintop removal review Nuclear fusion Lasers: NIF/LLNL Nuclear weapons Manhattan Project 235 U 239 Pu Trinity Hiroshima and Nagasaki Fusion weapons Example nuclear weapons http://www.ohvec.org/galleries/mountaintop_removal/007/21.html Nuclear fission What to say about nuclear fission review Nuclear fusion power? Lasers: NIF/LLNL • Nuclear power produces electrical energy without significant Nuclear weapons release of CO2 into the atmosphere. This is of increasing Manhattan Project 235 significance in minimizing future global warming. U 239 Pu • Fraction of electricity generated from nuclear power varies from Trinity Hiroshima and country to country. US: 20%. France: 78%. Germany: 28%. Japan Nagasaki (pre-Fukushima): 26%. Fusion weapons • Reactors cannot explode like nuclear bombs. Water reactors shut Example nuclear weapons off with loss of coolant, though with much economic damage (Three Mile Island) and even radionuclide release (Fukushima). Graphite reactors can run away with much greater radiation release and destruction (Chernobyl). • In normal operation, nuclear power plants emit less radiation than coal-burning power plants! See McBride et al., Science 202, 1045 (1978), Table 4. Burning coal releases thorium which can be incorporated by plants (food chain) or inhaled along with coal combustion particulates. Estimated radiation dose from living near a coal plant: 0.32 mSv/year. For comparison, estimated dose from living near a pressurized water nuclear reactor: 0.13 mSv/year. Nuclear fission Nuclear fusion review Nuclear fusion Lasers: NIF/LLNL • From the curve of binding energy, if we can cause light nuclei to Nuclear weapons fuse we can release even more energy per nucleon. Manhattan Project • 235 U Requires high density and high kinetic energy(=temperature) to 239 Pu overcome the Coulomb barrier. Trinity Hiroshima and • Nagasaki Fusion products have a short half-life and thus don’t present a Fusion weapons long-term nuclear waste problem. However, all reactor materials Example nuclear get flooded with neutrons so just about everything is made weapons radioactive. • One approach: extreme heating of a fusion pellet using lasers (interial confinement fusion or ICF). • Another approach: magnetically confined plasma (magnetically confined fusion or MCF). • The challenges are daunting! “Fusion is thirty years away”—a statement made beginning in the 1950s. “Fusion is the energy source of the future, and always will be.” Nuclear fission The Lawson criterion review Required temperature/density combination for energy breakeven. See Nuclear fusion Lasers: NIF/LLNL also Serway Fig. 14-13. Nuclear weapons Manhattan Project 235 U 239 Pu Trinity Hiroshima and Nagasaki Fusion weapons Example nuclear weapons Nuclear fission TFTR at Princeton review Nuclear fusion Tokamak Fusion Test Reactor. Operated 1982–1997 at Princeton Lasers: NIF/LLNL University. Nuclear weapons Manhattan Project 235 U 239 Pu Trinity Hiroshima and Nagasaki Fusion weapons Example nuclear weapons Nuclear fission Joint European Torus review Nuclear fusion Lasers: NIF/LLNL Oxfordshire, UK, 1983–1999 with some continued operation. An inside Nuclear weapons view when “cold” and when operating: Manhattan Project 235 U 239 Pu Trinity Hiroshima and Nagasaki Fusion weapons Example nuclear weapons Nuclear fission ITER review Nuclear fusion Lasers: NIF/LLNL ITER: International Toka- Nuclear weapons mak Engineering Reactor Manhattan Project (France; $20B with USA 235 U share of $2B). Goal is 239 Pu Trinity to demonstrate methods Hiroshima and Nagasaki to extract energy, and to Fusion weapons perhaps reach momentary Example nuclear weapons “engineering” breakeven. As of 2009, the US had given a total of $27M to- wards ITER, or about 1/3 of the first-weekend ticket sales of the most recent Wolverine movie (NY Times, April 30, 2009). FY 2013: $178M. Nuclear fission Let’s go to Livermore review Nuclear fusion For the biggest, baddest laser around, let’s go to Livermore; it’s one of Lasers: NIF/LLNL the two nuclear weapons physics lab, along with Los Alamos in New Nuclear weapons Mexico. Manhattan Project 235 U 239 Pu Trinity Hiroshima and Nagasaki Fusion weapons Example nuclear weapons Nuclear fission Livermore lab review Nuclear fusion Lasers: NIF/LLNL Lawrence Livermore National Lab. NIF is at the upper right. Nuclear weapons Manhattan Project 235 U 239 Pu Trinity Hiroshima and Nagasaki Fusion weapons Example nuclear weapons Nuclear fission NIF: National Ignition Facility review Nuclear fusion Recently completed. Cost: $4.2B? Web site: Lasers: NIF/LLNL http://www.llnl.gov/nif/ Nuclear weapons 192 beams (3072 slab amplifiers), total energy of 1.8 MJ, pulse duration 14 Manhattan Project 3–20 nsec.