Known Nuclides

Nuclear Fission

Fission products

Nuclear Reactors (LWR’s) Boiling water reactor (BWR) Pressurized water reactor (PWR) 66% of US reactors are this type

American Nuclear Plants

Radioactive wastes

Nuclear Waste depots

Yucca Mountain

Nuclear Plants world wide

Nuclear Fusion The reaction shown is the easiest to use, but D-D is also possible and is what we discussed in class, simply because it is easier to get the fuel and the math is a bit easier. 2*M D = amu vs. 3 He + p = ( ) amu + ~2MeV or 3 H + n = ( ) amu + ~3MeV NOTE: 3 He and p are stable 3 H has a half-life of 12 years, n of 15 minutes. This process produces no long-lived radioactivity directly, unlike fission.

ITER Proposed 500MW Fusion test Facility. First plasma expected “International Thermonuclear Experimental Reactor”

Inertial confinement

Review for Final Exam Exam will have roughly 28 questions (i.e. slightly longer than previous exams, but you have much more time). Roughly half of the questions will cover material discussed since exam II, the rest will be roughly equally split between material covered on exam I and exam II Cover page will be on ONCOURSE some time next week.

Exam Review: Electricity Action of a battery, the concept of EMF Ohm’s law and power: V=IR P= IV Parallel and series circuits Faraday’s law and the generation of electricity Transformers The electric power grid: Generation, transmission, distribution

Summary of wind power Power available is roughly: –P=2.8x10 -4 D 2 v 3 kW (D in m, V in m/s) i.e. you get much more power at higher wind speeds with larger turbines 3-blade turbines are more efficient than multi- blade, but the latter work at lower wind speeds. At higher wind speeds you need to “feather” the blades to avoid overloading the generator and gears. Typical power turbines can produce MW You still find people question having even this form of generator near where they live!

Provide a source of DC electric power where the EMF is provided by absorbed light Need to absorb the light –Anti-reflective coating + multiple layers Need to get the electrons out into the circuit (low resistance and recombination) –Low disorder helps with both (hence crystal is more efficient than amorphous) Record efficiency of 42.8% was announced in July 2007 (U. Delaware/Dupont). Crystalline Si: highest efficiency (typically 15-25%), poorer coverage, bulk material but only the surface contributes, expensive (e.g. NASA). Amorphous Si: lower efficiency (5-13%), less stable (can degrade when exposed to sunlight). Synopsis of Solar Cells

Chemical energy is converted directly to (DC) electrical energy. Similar to battery, but there is an input fuel, you’re not limited to an “on-board” chemical supply. Need electrodes, electrolyte, probably catalysts at the electrodes, and perhaps a reformer. Different types have different chemistry, electrolyte, operating temperatures, efficiencies, size, and robustness (etc.) Synopsis of Fuel Cells

Alkaline Acid –High efficiency (up to 60%), small, pure H 2 fuel, very sensitive –Used by NASA (very expensive, so only they can afford it) Molten Carbonate –High efficiency (up to 60%), high temp operation (600C), bulky, robust –Used in back-up generation/ Combined Heat/Power (CHP) modes (Fuel Cell Energy) Polymer Electrolyte Membrane (PEM) –Lower temp operation (<100C), sensitive catalysts/ reformers needed, compact, lower efficiency (35%??) –Leading candidate for transportation (Ballard) Solid Oxide Fuel Cells –Highest efficiency (70%), very high-T operation (1000C) –Still in development, not yet commercially viable Synopsis of Fuel Cells

Nuclear Energy Binding energy of nuclei are MUCH LARGER than that of moelcules –E=mc 2 Radioactivity –Comes from both the primary reactions (especially in fission) and activation by the neutrons released in the reactions (both). –Half life, decay modes, health hazards Fission: –Split a large nucleus into smaller nuclei PLUS 2 or 3 neutrons after absorption of a SLOW neutron. –Energy release on the order of 0.74MeV/amu of fuel –Lots of such plants exist throughout the world, but there are problems Expensive to build (especially in the US) Safety issues

Nuclear Energy (cont.) Waste from nuclear power: –Spent fuel and decommissioned parts are both radioactive –Short-term issue (proliferation concerns) as well as long-term Fusion: –Combine two light nuclei (typically isotopes of hydrogen) into one (typically He) with release of energy ~0.84MeV/amu (and neutron(s)). –Fuel “waste” is much easier to deal with (less active, shorter half-lives) –Decommissioning may be even a bigger problem than with fission