1. Chapter 12 Nuclear Energy

2. Overview of Chapter 12 Introduction to Nuclear Power Nuclear Fission
Atoms and radioactivity
Nuclear Fission
Pros and Cons of Nuclear Energy
Cost of Nuclear Power
Safety Issues at Power Plants
Three Mile Island & Chornobyl
Nuclear Weapons
Radioactive Waste
Future of Nuclear Power

3. Introduction to Nuclear Energy
Energy released by nuclear fission or fusion
Nuclear fission
Splitting of an atomic nucleus into two smaller fragments, accompanied by the release of a large amount of energy
Nuclear fusion
Joining of two lightweight atomic nuclei into a single, heavier nucleus, accompanied by the release of a large amount of energy

4. Atoms and Radioactivity
Nucleus
Comprised of protons (+) and neutrons (neutral)
Electrons (-) orbit around nucleus
Neutral atoms
Same # of protons and electrons

5. Atoms and Radioactivity
Atomic mass
Sum of the protons and neutrons in an atom
Atomic number
Number of protons per atom
Each element has its own atomic number
Isotope
Usually an atom has an equal number of neutrons and protons
If the number of neutrons is greater than the number of protons = isotope

6. Radioactive Isotope Unstable isotope Radioactive Decay Example
Emission of energetic particles or rays from unstable atomic nuclei
Example
Uranium (U-235) decays over time to lead (Pb-207)
Each isotope decays based on its own half-life

7. Radioactive Isotope Half-lives

8. Nuclear Fission Nuclear Fuel Cycle
processes involved in producing the fuel used in nuclear reactors and in disposing of radioactive (nuclear) wastes

9. Nuclear Fission U-235 is bombarded with neutrons
The nucleus absorbs neutrons
It becomes unstable and splits into 2 neutrons
2-3 neutrons are emitted and bombard another U-235 atom
Chain reaction

10. How Electricity is Produced

11. Breeder Nuclear Fission
A type of nuclear fission in which non-fissionable U-238 is converted into fissionable Pu-239

12. Pros and Cons of Nuclear Energy
Less of an immediate environmental impact compared to fossil fuels

13. Pros and Cons of Nuclear Energy
Pros (continued)
Carbon-free source of electricity- no greenhouse gases emitted
May be able to generate H-fuel
Cons
Generates radioactive waste
Many steps require fossil fuels (mining and disposal)
Expensive

14. Cost of Electricity from Nuclear Energy
Cost is very high
20% of US electricity is from Nuclear Energy
Affordable due to government subsidies
Expensive to build nuclear power plants
Long cost-recovery time
Fixing technical and safety issues in existing plants is expensive

15. Safety Issues in Nuclear Power Plants
Meltdown
At high temperatures the metal encasing the uranium fuel can melt, releasing radiation
Probability of meltdown or other accident is low
Public perception is that nuclear power is not safe
Sites of major accidents:
Three Mile Island
Chornobyl (Ukraine)

16. Three-Mile Island 1979- most serious reactor accident in US
50% meltdown of reactor core
Containment building kept radiation from escaping
No substantial environmental damage
No human casualties
Elevated public apprehension of nuclear energy
Led to cancellation of many new plants in US

17. Chornobyl 1986- worst accident in history
1 or 2 explosions destroyed the nuclear reactor
Large amounts of radiation escaped into atmosphere
Spread across large portions of Europe

18. Chornobyl Radiation spread was unpredictable
Radiation fallout was dumped unevenly
Death toll is 10, ,000

19. Nuclear Energy and Nuclear Weapons
31 countries use nuclear energy to create electricity
These countries have access to spent fuel needed to make nuclear weapons
Safe storage and handling of these weapons is a concern

20. Radioactive Waste Low-level radioactive waste-
Radioactive solids, liquids, or gasses that give off small amounts of ionizing radiation
High-level radioactive waste-
Radioactive solids, liquids, or gasses that give off large amounts of ionizing radiation

21. Radioactive Wastes Long term solution to waste
Deep geologic burial –Yucca Mountain
As of 2004, site must meet EPA million year standard (compared to previous 10,000 year standard)
Possibilities:
Above ground mausoleums
Arctic ice sheets
Beneath ocean floor

22. Radioactive Waste Temporary storage solutions
In nuclear plant facility (require high security)
Under water storage
Above ground concrete and steel casks
Need approved permanent options soon.

23. Case-In-Point Yucca Mountain
70,000 tons of high-level radioactive waste
Tectonic issues have been identified

24. Decommissioning Nuclear Power Plants
Licensed to operate for 40 years
Several have received 20-year extensions
Power plants cannot be abandoned when they are shut down
Three solutions
Storage
Entombment
Decommissioning (dismantling)

25. Fusion
Fuel= isotopes of hydrogen

26. Fusion Way of the future?? Problems
Produces no high-level waste
Fuel is hydrogen (plenty of it!)
Problems
It takes very high temperatures (millions of degrees) to make atoms fuse
Confining the plasma after it is formed
Scientists have yet to be able to create energy from fusion