Presentation is loading. Please wait.

Presentation is loading. Please wait.

Nuclear Energy By: Elisa Fatila April 6, 2006.

Similar presentations


Presentation on theme: "Nuclear Energy By: Elisa Fatila April 6, 2006."— Presentation transcript:

1 Nuclear Energy By: Elisa Fatila April 6, 2006

2 The History of Nuclear Power
First reactor built operational in 1942 by Enrico Fermi1 First commercial reactor in Obininsk, USSR US Patent held by Enrico Fermi and Leo Szilard 1 Patent number 2,708,656 in 19551 235U and 239Pu fuels First tubes to carry UF6 were made of TEFLON Enrico Fermi 1. Argonne National Laboratory.

3 Uranium Uranium as abundant as Zn and Sn
Half-life 238U is 4.5 billion years 99.3% is 238U and ~ 0.7% 235U Show chart of abundance in different countries Where found in canada, Cameco corp. (Crown corp. since WWII) and Coegma, trade TSX $42, most situated in Northern Saskatchewan, pver half of production from Australia and Canada Uranium winning Figure 2: Reserves of uranium worldwide

4 Uranium as Fuel 1 lb of 235U = 1 million gallons of gasoline
Price of uranium ~$33/lb USD  All time high of $43/lb in 19792 Cost comes from labour and technology required for power plants and enrichment 2. Uranium stocks. World demand outreaching supply by 100 million lbs, now price is around $30/lb Briefing papers. Figure 1: The price of uranium in the US US$/lb U3O8 (2)

5 The Nuclear Fuel Cycle Mining and milling Fuel preparation
Energy production Spent fuel reprocessing Waste disposal General fuel cycle, explain from yellow cake to UO2 Pitchblende  U3O8  UF6  UO2

6 Chemical Conversion of UO2 to UF6
UO2 + 4HF  UF4 +2H2O 3UF4 +2ClF3  3UF6 + Cl2 Fluoridating agents: BrF5, F2 UF6 low vapour pressure Discuss why certain fluoridating agents used, discuss UF6, Riegel’s handbook of chemistry

7 Enrichment of UF6 UF6  gaseous diffusion  UO2 powder or
gas centrifuge Converted to UO2 by ammonium diuranate precipitation ~3% 235U suitable for most reactor types Pic of diffusion chambers, Graham’s law of effusion (mass related to flow velocity) Oak Ridge National Laboratory Review Figure : Gas centrifuge cascades at Ohio diffusion plant

8 Reactor Types Two major types: fast Slow (thermal) Breeder type
Light water Heavy water Neutron energies Pressurized water reactors Boiling water reactors Neutron = 2 MeV (fast)

9 Breeder Reactors 238U + 1n  239U + ν + e  239Np + ν + e  239Pu
Requires 15% - 30% enrichment Generate 239Pu as product Liquid metal (K, Na) as coolant Formation of 239Pu (β-emission) 238U + 1n  239U + ν + e  239Np + ν + e  239Pu Picture of reactor design, explain why coolant used, why governments do not like, discuss moderator, what makes a material a moderator, discuss corrosion, successive beta decays, tell how Pu was joke by Seaborg, coolant used because more effective at heat transfer

10 Heavy Water Reactors CANDU reactors
Heavy water acts as moderator and coolant Cost of D2O offset by lowered enrichment cost Heavy water more effective at moderating neutrons so less enriched U is required (2) Controlled substance Discuss price of D2O, discuss isotopic abundance, BEST MODERATORS ARE THOSE WHICH DO NOT ABSORB NEUTONS , Girldler-Sulphide process

11 Light Water Reactors Require about 3% - 5% enrichment
Light water as coolant and moderator Common and inexpensive pressurized or boiling water (1) US Pellets encased in Zr alloy Bonnie Anne Osif, Anthony Baratta, Thomas W Conkling TMI: 25 years later: The Three Mile Island Nuclear Accident and Its Impact The PWR transfers energy from the fuel to its intermediate heat exchanger to generate the steam that drives the turbine. Boiling water generates steam within reactor that goes directly to the turbine In boiling water steam goes directly to turbine, but it’s radioactive steam

12 Pebble Bed Reactors Researched in China and India Use 235U and 232Th
Generate more U than consumed Use inert gases as coolant (CO2, N2, Ar) Gasification of coal, He at 950 can convert the brown coal into gas,

13 232Th + n 223Th  233Pa + e + v  233U + e + v
Other Reactors Types Gas-cooled (fast or thermal) Thorium reactors absorbs slow neutrons 232Th + n 223Th  233Pa + e + v  233U + e + v 232Th relatively abundant Find out about MOX fuels, Nuclear Energy: Promise or Peril, C R Hill, Georges Ripka, A L Mechelnyk, B Van Der Zwaan Note that all reactors are closed systems: humorous exception mentioned, popular in 3rd world countries rich in Th: India

14 Important Reactor Components
Heavy Water Light Water Liquid Metal Pebble Bed Cladding Zr Mg-Al alloy Moderator D2O graphite N/A Control Rods Cd, B steel Cd, Hf Coolants H2O Na CO2, He Cladding, Zr use in tubes, zircalloy developed in Germany

15 Problems with Nuclear Energy
Terrorist concerns Disposal concerns (Yucca Mountain) Wastes produced at each step of fuel cycle Accidents (Three Mile Island, Chernobyl) Discuss neutron activation, discuss consideration of various states of matter and temperature of molten uranium, discuss fission products such as MONEY

16 Why Nuclear Energy Increasingly Important
Increase in populations in China and India Wildly fluctuating prices in oil New, safer technology Chronologically farther away from accidents

17 Conclusion Nuclear fuel cycle Economic effects Political fallout

18 Spent fuel Reprocessing
Resource poor Japan and France Cost comparison: ~$30/lb extract  $400/lb reprocess PUREX separation of 239Pu, 235U and fission products Sensitive and dangerous Kilograms of 239Pu criticality risk 7 M HNO3 TBP Irradiated fuel elements Solution of UO22+ Pu (IV) + fission products Inherent to fast breeder reactors FP PuO2 and UO2

19 Waste Disposal Classification of wastes:
Low level wastes: mill tailings High level wastes:


Download ppt "Nuclear Energy By: Elisa Fatila April 6, 2006."

Similar presentations


Ads by Google