Energy Systems & Climate Change

1. Energy Systems & Climate Change Thus. 5 Nov. 2009 Ch.7: Nuclear Dr. E.J. Zita (& Cheri Lucas Jennings) zita@evergreen.edu http://academic.evergreen.edu/curricular/energy/0910/home.htm

2. What’s happening today: • Questions? Announcements? • Ch.7: Nuclear • Brief Reports at 2:30 • 3:15 Seminar – finishing McKibben Responses due this week to Brief Reports:

3. Percent of electricity from nuclear

4. Nuclear-generating capacity

5. Fundamental Forces Gravity Electromagnetism Nuclear

6. Unification http://abyss.uoregon.edu/~js/cosmo/lectures/lec20.html

7. Discovery of the atomic nucleus1909 Rutherford

8. Nuclear strong force (vs. electric)

9. Isotopes

10. Isotopes Same number of protons = same chemistry Solve for m2

11. Nuclear binding energy

12. Nuclear binding energy E=Dmc2

13. Fission→ radioactive wasteFusion is safe, but works only in stars, so far

14. Magnetic confinement fusion

15. E=Dmc2: The nuclear difference Nuclear energy ~ 10 million x chemical energy 1 truckload Uranium/yr ~ 100 trainloads coal/wk E=Dmc2 really only applies to mass-energy transformations (not stretched rubber bands…)

16. Nuclear Fusion in the Sun: 4H  He + Dm

17. Fusion: 4H  He + Dm

18. Nuclear fission Heavy, unstable nuclei can fall apart naturally. Throwing neutrons at them can make them split faster: Neutron-induced fission (Lise Meitner)

19. Discovery of fission1938 Hahn + Strassmann  Meitner + Frisch

20. Nuclear chain reaction:critical mass ~ 30 lb for U235 ~ 30 tonnes coal

21. Controlled fission reaction: Moderator keeps neutron multiplication factor = 1 Moderator slows neutrons so they can fission U. Fast neutrons can’t do the job. Removal of graphite rods stops fission.

22. Atomic mass Ex.7.5 showed that using a 5 kW electric dryer (powered by a 33% efficient nuclear plant) for an hour produces N=1.2x1018 nuclei of 239Pu (plutonium). Mass per nucleon = mn = 1.67 x 10-27 kg The mass of each 239Pu nucleus = m = 239 mn = _____ Total 239Pu mass produced = M = N m = ______

23. Nuclear reactors • Light-Water reactors (LWR) need enriched U235 • (ordinary water  steam  turbine  electricity) • Boiling-water reactor (simple, 1/3 of LWRs) • Pressurized-water reactor (primary doesn’t boil) • Pro: Safety: loss of coolant = loss of moderator • Con: difficult to refuel • CANDU(Deuterated, or heavy water + natural U238) • Continuous refueling capability, easy to steal

25. More Nuclear reactors Graphite moderator Pro: continuous refueling capability Con: loss of coolant ≠ loss of moderator Chernobyl HTGR (High Temperature Gas-cooled Reactor) Pro: high safety Con: low performance Breeder reactors: first discuss beta decay…

26. Beta decay (weak force) n  p + e- + neutrino

27. Breeder reactors Rare U235 is fissile when hit with neutrons Common U238 can transmute  Pu contributes to fission power generation in old U reactors

28. Breeder reactors • Pro: • * use up common U238 • * operate at higher temperature (efficiency) • Con: • higher temperature, higher risk of nuclear accident • Liquid sodium coolant – flammable with air contact • Plutonium = potent bomb fuel • Critical mass ~ 5 kg (see Example 7.5) • Even France only uses one breeder.

29. Plutonium reprocessing(Union of Concerned Scientists: www.ucsusa.org) • Reprocessing would increase the risk of nuclear terrorism • Reprocessing would increase the ease of nuclear proliferation • Reprocessing would hurt U.S. nuclear waste management efforts • Reprocessing would be very expensive

30. Advanced reactor designs Standard LWR: coolant = moderator Advanced LWR: passive safety features Standardized design – easier to build Maximum nuclear efficiency: 36% Advanced HTGR: pebble-bed reactor pebbled fuel He gas coolant  heat exchanger  turbine Could burn Pu from old nuclear weapons Design efficiency 50% (not yet operational)

31. Nuclear power plants Pressure vessel limits Thigh and efficiency Otherwise, much like other power plants

32. Radioactivity Gamma rays: very high energy photons – zero mass (produced by excited nuclei) Alpha particles: very high mass (Helium nuclei) can have high or low kinetic energy If they penetrate matter, can do great damage. Most dangerous if ingested. Beta particles: electrons (or anti-electrons) Can have high or low kinetic energy Can slightly penetrate matter. (weak force)

33. Alpha decay Alpha particle = helium nucleus

34. Radioactivity Gamma decay Alpha decay

35. C14 from cosmic rays Cosmic rays excite N14→ decays to C14 Solar max: magnetic solar wind sweeps away cosmic rays → less *N14→ less C14 http://www.nuclearonline.org/newsletter/Oct05.htm

37. Lower recent C14 /C12 from fossil fuel burning Little Ice Age: low solar magnetic activity  more cosmic rays and C14 Evidence of anthropogenic source for greenhouse gases

39. Nuclear Policy • High subsidies supported growth in industry in decades past • Safety regulations plus major cost and schedule overruns made nuclear start-ups increasingly diffiult • 1979 Three Mile Island accident “seriously damaged public confidence in nuclear power” • US nuclear in decline – no new plants in 30 years • 1986 Chernobyl near-meltdown, major irradiation of local area, contamination spreading to lesser extent throughout USSR, Europe, Asia. Undetermined # of lives lost

40. Radioactive decay: l=decay rate

41. Half-life = T1/2

42. Half-life Solve for n and then t…

43. Measuring radiation Bequerel = 1 decay per second: but what kind of decay? How much energy? Curie = radioactivity of 1 g of 226Ra Consider effects on biological tissue: Rad = 0.01 J of radiation absorbed by 1 kg Also consider what kind of particles – alpha, beta, gamma? Most useful measure: Sv = Sievert = dose (in rad) * quality factor (QF)

44. Radiation quality factor (QF) Higher QF = more dangerous radiation TypeQF X and gamma rays ~ 1 Beta ~ 1 Fast protons 1 Slow neutrons ~ 3 Fast neutrons up to 10 Alpha particles and up to 20 heavy ions

45. Chernobyl: how many deaths? http://www.nirs.org/ch20/index.htm http://www.nirs.org/reactorwatch/accidents/accidentshome.htm

46. How many accidents unreported? http://www.iht.com/articles/2007/03/15/business/nuke.php

47. More Nuclear Policy Advocates call for nuclear renaissance because: • Technology is well-established • We know it can produce high-density electric power • Since we are not willing to give up quality of life dependent on high-density power, nuclear and hydro are the only current options • Hydro is essentially fully developed in countries like the US, and has ecological costs of its own • Vitrification can address waste issues

48. Waste disposal: Yucca Mountain? http://library.thinkquest.org/17940/texts/nuclear_waste_storage/nuclear_waste_storage.html

49. Waste disposal: Vitrification? http://environment.pnl.gov/brochures/WTP.pdf http://picturethis.pnl.gov/PictureT.nsf/All/3U2S5D?opendocument

50. UCS on nuclear • Need cheap, effective solutions to GW quickly • Nuclear power is not the “silver bullet” • Rapid major expansion of nuclear is not feasible • Nuclear security is a major concern • Research should continue, especially on nuclear waste issues