Unit 7 Nuclear Energy

1. Unit 7 Nuclear Energy http://www.youtube.com/watch?v=BUrhs3KwTJ4 http://www.youtube.com/watch?v=kamQlCpiIXI&feature=related http://www.youtube.com/watch?v=VJfIbBDR3e8&feature=related

2. Overview of Nuclear Energy Nuclear energy was once gushingly said to be “too cheap to meter” in the future (the meter and reading it would cost more than the electricity would sell for) • That isn’t close to happening 50 years later and is not likely now US commercial nuclear power began at Shippingport PA in 1957; Soviets began in 1954 Nuclear power supplied ~20% of US energy in 2005 Nuclear energy is cheap to the consumer; but heavily subsidized by the Federal Government (only taxpayers pay for that!) Great controversy (among some) about dangers and eventual doom from spent fuel Plants will likely be built again after none since 1978(?) Developing countries considering/building nuclear power

3. GammaRay 85 to 104 a.w. Clumping 89Kr 7.1 The Nuclear Fission Reaction 236U Fission 235U Neutron Fission occurs when uranium atom is “split” into atoms of lesser atomic weight plus emitted energy 130 to 149 a.w. Neutron Neutron GammaRay GammaRay n = 1.0086789Kr = 88.91660144Ba = 143.92000235U= 235.04394236U = 236.05261 235U143 144Ba 92 Neutrons n + 235U143 236U144  144Ba88 + 89Kr53 + 3n + 176.9 MeV 92 92 56 36

4. Sources, extraction, and preparation Found in Congo, Canada, US (CO, WY, UT, NM, etc.), Africa, Ukraine, and everywhere to some extent Uranium mining of ore US carnotite contains 238U, 99.28%; 235U, 0.71%; and 234U, 0.006% Uranium extraction Convert raw ore to uranium oxide (U3O8) or “yellowcake” ~$15.50/lb to $43.00 (2010) Convert that yellowcake to uranium hexafluoride gas Enrich the 235U from 0.7% up to 2% to 5% for power plants; 93% for weapons (lots of centrifuges [Iran has 6000] in series) Uranium fuel preparation Make uranium dioxide pellets (~0.4 inch diam x 0.4 inch long) Load the pellets end-to-end in a zirconium alloy tube Place tubes in assemblies for ease of handling and loading

5. Types of Reactors Major Reactor Categories: • Light Water Reactors (LWR) use H2O • Heavy Water Reactors (HWR) use D2O or deuterium oxide • Canadian CANDU (Canadian deuterium oxide) reactor • Boiling water reactors produce steam at top of the core area • Pressurized water reactors keep water from boiling • Mixed oxide (MOX) reactors contain both plutonium and uranium oxides (make from old warheads) • Breeder reactors produce additional radioactive fuel that may be used in conventional reactors (recyclable?) • Fusion Reactors (based upon hydrogen) 2H2 into helium, 1He4

6. Light Water Reactors Ordinary, but pure, deionized (noncorrosive) water is used as a fuel core coolant Some reactors have used liquid sodium metal as a “coolant” with a heat exchanger The coolant flows around the fuel elements and carries off the heat Heat exchangers prevent leakage of the radioactive water into the steam turbines The primary side water remains in liquid state due to high pressure If the water area vents and goes dry, the core can melt if the reaction isn’t stopped in time (the “China Syndrome)

7. St. Lucie Plant on Hutchinson Island FL • 1680 MW • Services much of Eastern Florida • Ocean water cooling exits to lagoon • On barrier island subject to hurricane wave overwash

8. Boiling Water Reactors (BWR) Boiling water reactors have part of the water as steam around the fuel The water acts as a moderator to slow the neutrons to fission the uranium, while the steam is less dense and doesn’t moderate well If overheating occurs, the steam pushes the water level lower, slows the reaction and protects the reactor

9. Pressurized Water Reactor (PWR) Water is under high pressure so it can’t flash into steam The reaction is modified entirely by the control rods

10. CANDU Reactor The Canadian heavy water (deuterium oxide, DO2) reactor can use unrefined uranium U238 as fuel Canada, Argentina, and Pakistan use this reactor type This avoids the expense of uranium enhancement, but deuterium oxide must be separated from ordinary water Deuterium occurs about once in 6500 molecules of water

11. Mixed Oxide Reactor

12. Pebble-bed; Breeder reactor Pebble-bed reactors use fuel/carbon/ceramic pellets sized like a billiard ball The balls can be pushed through pipes into the reactor on top and removed at the bottom, thus no shutdowns are required; refueling is continuous Breeder reactors produce more fissile fuel than they consume The US (under Pres. Carter’s administration) presently prohibits breeder reactors because of potential weapons that could be made President Bush was considering using breeder reactors; President Obama decided against them Without breeder reactors, uranium ore may be depleted in ~50 - 80 years

13. Fusion Reactors Hydrogen can be fused into helium yielding more energy than was required to create the fusion The Shiva machine (named after the multiple-armed Indian Goddess) has 20 lasers that simultaneously strike a small plastic shell containing deuterium oxide to create fusion Immense amounts of energy fire the 20 lasers simultaneously to cause a negligible amount of fusion energy Remember EROEI, where a high amount of energy must come out compared to what went in for the conversion to be useful, but this is the reverse so far

14. The Fuel Cycle and the Spent Fuel Problem Conventional reactors require 18-month refueling to remove 1/3 “spent” fuel and replace it with active fuel Spent fuel must be reprocessed to make more active fuel or be stored in isolation Newly removed fuel is lowered into water tanks to allow radioactivity to diminish safely with time ~2 years Intense radiation causes the blue luminescence of the Cherenkov Effect; thus I claim nuclear-generated hydrogen is “blue” (fossil=black, wind or sun=green) After several years, the fuel assemblies can be removed and placed in “casks” for dry storage on site or elsewhere A National Repository at Yucca Mountain, Nevada intended to receive fuel transported by train and truck Not many voters in the lowest population state, but one is Sen. Reid, the Democrat majority leader, who is blocking storage there This project is now dead (wasted effort and materials)

15. Spent Fuel Diversion & Nuclear Weapons “Now I am become death, the destroyer of worlds.“ Vishnu in Bhagavad Gita - Robert Oppenheimer at the Trinity Site In the USA, there is concern that nuclear material may be diverted to criminal or terrorist purposes Nuclear weapons Fission Two subcritical masses are pushed together to critical mass A surround of explosive detonates to compress the core to dense critical mass Fusion Atomic explosion initiates hydrogen fusion bomb Electromagnetic Pulse Weapon High altitude burst radiates EMP and damages electrical and electronic equipment by induced voltage overload Neutron Bomb Neutron pulse kills without building destruction [Jack Welch, GE] Contamination by “Dirty Bomb” Radioactive materials are spread by conventional explosive to cause terror and decontamination delays; more psychological effect

16. Reprocessing (Dilution) The US buys excess nuclear weapon warhead materials from Russia to reduce danger of “leakage” to terrorists Reprocesses (mixes) the plutonium with uranium spent fuel to form reusable fuel that would be hard to separate for future weapons use Reduces diversion or sale to terrorists or “evil-doers” They’ll buy from North Korea or Iran instead Now, the problem is not traditional weapons but the cheap “Dirty Bomb”; processing is stirring and mixing High explosive mixed with radioactive waste explodes to cast radioactive particles over a wide area The degree of radioactivity isn’t important (old radioactive gloves and such would do), since terrorists seek terror, not necessarily death and injury

17. Safety Record US plants have a good safety record The Three-Mile Island gas venting event caused disruption and evacuation, but no deaths or injuries Core breaching or meltdown would have made this a far worse event! Very close to that happening Chernobyl had a poor design that is not used in the US 31 died, and 35,000 (?) were predicted to have long term radiation poisoning; cities relocated Radioactivity released into the air was detected in Norway Safety inspectors must report to the highest level of organization; resident Federal inspectors must be present to check the commercial inspectors

18. Three Mile Island, PA Unit 2 still closed and defueled Cemented in to seal it

19. Boric Acid Problem near Toledo, OH Boric acid (moderator) leaks were found under insulation; now fixed

20. Conflicts and Controversy Basic “Anti-Nuc”, “Anti-war” ideology drives protesters who have a separate progressive/liberal/leftist agenda Hiroshima and Nagasaki bombings ended World War II with less loss of life than continuing the war Anti-war activists attack nuclear energy and food preservation radiation for civilian use (Mulberry, Florida) Yucca Mt., NV attacked for seismic activity, heat, not good enough for 250,000 years storage of isotopes Possibly future generations might recover the waste and change the storage in 1000 years? Safe or not? By what scoring? Who decides? Obama did, and stopped the project by executive order

21. Advantages Low-cost electricity due to Gov’t subsidies, services, & insurance Provides “baseload” constant power to carry most of the load Clean power without air pollution (no CO2?) Requires highly paid work force (job votes) Source of local taxation revenue Advantages and Disadvantages • Disadvantages • Potential for radiation leakage and health effects • Possible terrorist target • Useful just as threat • Apparent cheap power retards renewable energy development • What to do with the spent fuel?

22. Degree of Nuclear Use Nuclear plants provide so much energy (~20%) that they cannot be discontinued quickly; replacement power would be required first at high cost Nuclear power primarily has a political problem and is opposed by strident antinuclear activists/protesters Condo owner organizations next to St. Lucie Plant spoke in favor of relicensing citing “Good Neighbor”! US nuclear plant construction likely to start again since population growth demands more energy, and natural gas prices will be higher in the future

23. US nuclear reactors are near user load centers Note reactors in Pres. Obama’s home state of Illinois

24. Shutdown Scenario for “Anti-Nucs” Why not close down reactors right now? ! ? Likely scenario that would follow: Utilities warn public to cut energy use 20% immediately! Public ignores warning; consumes as usual Nuclear generators are taken off the Grid by law on stop date Immediate Grid overload occurs (~20% of energy missing) Electricity outages occur simultaneously across the entire country, not just as in the past Northeast states disruptions Electric lighting, communication, refrigeration, trains, elevators, traffic lights, gas pumps, oxygen generators, etc. fail to operate Back-up diesel generators use up reserve fuel in days Civilization as we know it drops back to the 1700s, but without the appropriate conveniences they were using back then As widespread hunger spreads, pillaging mobs kill for food (and TVs), while soldiers shoot looters by thousands So should we shut off nuclear reactors immediately?

25. Future Trends in Nuclear Energy Older plants (>40 years) must seek relicensing from the NRC to continue operation Standardized plant designs speed construction and increase safety; use additional reactor units as needed Nuclear energy will increase in the less-developed countries in order to have long-term energy Some countries may desire to create nuclear weapons at the same time; e.g., North Korea, Iran? Fusion reactors may become useful in the future but years of research have only yielded less energy than was put in to the process --- I like our fusion sun!

26. Future Trends in Nuclear Energy (Con’t) ITER (Latin for “The Way”, I T E Reactor) Produce 0.5 GW for 400 seconds! Fuse deuterium and tritium to make H2 and emit a neutron Seven countries researching fusion energy Tokamak accelerator Goal is >10 units of energy out for each unit in Perhaps demo ready between 2030 to 2035 http://www.iter.org/default.aspx

27. Conclusion Nuclear plants provide a significant 20% of US energy Some antinuclear organizations want all plants closed right now and vocally oppose them Nuclear energy provides too much energy to readily close them without a substitute (~1600 MW/plant) Nuclear energy may be a transitional approach from fission plants to fusion plants some far away day Nuclear plants likely will be built again since population growth demands more energy, natural gas prices will be higher in the future, and fossil fuel plants pollute Wind energy is the closest renewable, since major hydro is difficult (see China’s Three Gorges Dam)

28. Questions?

29. THE END