1. Chapter 12 Nuclear Energy

2. 3-Person Teams (without moving unnecessarily)
Outline your group opinions on a whiteboard and be prepared to present you’re opinions to the class (and comment on other teams opinions)
Did the US make the best decision to develop nuclear power? Explain.
How would the US be different if we hadn’t chosen to develop nuclear power?
WWII, Potential Cheap Power, Profit, Avoid being bullied by nuclear countries.

3. 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

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

5. 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
What else changes in order to release this energy?
Mass is lost, it is converted to energy.

6. 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

7. 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
What particles or rays can be released? What are they? Alpha (Helium nucleus- 2P, 2N), Beta (electron from nucleus-Neutron changes to Proton), gamma rays (high frequency non-visible light)

8. Radioactive Isotope Half-lives
What is a half-life? The time for ½ the radioactive substance to change into a different material.

9. Nuclear Fission Nuclear Fuel Cycle
Power
Process
Waste Process
Nuclear Fission
Nuclear Fuel Cycle
processes involved in producing the fuel used in nuclear reactors and in disposing of radioactive (nuclear) wastes
The left column is the nuclear power process flow chart. The right column is the waste generation flow chart. Can you think of environmental impacts that might come from the right column?
Dashed arrows in flow chart have not been happening; how do you feel about that?

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

11. How Electricity is Produced
Reactor vessel is the orange structure, it is designed for containment. Primary circuit is orange (pressurized water to prevent steam), Secondary circuit is blue converts to steam and back (power production), the tertiary circuit removes heat from the second circuit.
Reactor vessel is the orange structure, it is designed for containment. Primary circuit is orange (pressurized water to prevent steam),
Secondary circuit is blue converts to steam and back (power production), the tertiary circuit removes heat from the second circuit.

12. Breeder Nuclear Fission
A type of nuclear fission in which non-fissionable U-238 is converted into fissionable Pu-239
What is the percentage of Uranium that is 238?
What is the percentage that is U235?
>99%, <1%

13. Compare the relative benefits of Conventional and Breeder Reactors.
Discuss and answer
Compare the relative benefits of Conventional and Breeder Reactors.
See next slide

14. Mr. H’s Thoughts Conventional:
Uses only 0.7% of the Uranium orelots of hazardous waste.
Breeders:
Uses >99% of the Uranium ore
Reactors are potentially highly explosive.
Produce lots more weapons grade Plutonium.
Produce more energy than conventional.
Allow recycling of waste from conventional reactors.

15. Whiteboard Question
How can Mixed Oxide Fuel (MOX) reactors play an important role in nuclear energy?

16. Mr. H’s Thoughts
Book discussion of MOX is sketchy, but MOX apparently:
doesn’t make weapons grade Plutonium.
can use weapons grade Plutonium and U235 to produce electric (and reduce radioactive waste and eliminate stockpiles of weapons grade Plutonium).

17. Whiteboard Question
In the Breeder Reaction, does U neutron = Pu239? Explain Now refer to Appendix 1, does your answer change?
Click to next slide

18. Breeder Nuclear Fission
A type of nuclear fission in which non-fissionable U-238 is converted into fissionable Pu-239
Where did the Proton come from to change Uranium into Plutonium?
Where did the Proton come from to change Uranium into Plutonium?

19. Pros and Cons of Nuclear Energy vs Coal
Pros: Less of an immediate environmental impact compared to fossil fuels, but nuclear has higher potential risks.
5 vs 5 overall

20. 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
Disaster potential

21. 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
Shut down costs can be substantial.

22. 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)
Japan

23. Three-Mile Island 1979- most serious reactor accident in US
50% meltdown of reactor core (close call)
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

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

25. Chornobyl Radiation spread was unpredictable
Radiation fallout was dumped unevenly
Death toll is 10, ,000
Firefighters gave lives.

26. 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
Several hundred metric tons of weapons grade plutonium worldwide, but just several kilogram would make a bomb.

27. Radioactive Waste Low-level radioactive waste (low radioactivity)-
Radioactive solids, liquids, or gasses that give off small amounts of ionizing radiation
High-level radioactive waste (high radioactivity)-
Radioactive solids, liquids, or gasses that give off large amounts of ionizing radiation

28. 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

29. Radioactive Waste Temporary storage solutions
In nuclear plant facility (require high security)
Under water storage
Above ground concrete and steel casks
Not intended for permanent storage.
Need approved permanent options soon.
Short half-life fission material tricks body into believing they are nutrients. They bioaccumulate.

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

31. Case-In-Point Yucca Mountain
40,000+ tons of high-level radioactive waste already exist. Before long we will have more stored in temporary locations than the “permanent site could hold”.
Transportation safety concerns.
2 dozen other countries store deep underground.
Concern about rising water table. After an earthquake in 1992, the water table rose only 1 meter (not considered serious by experts).
Obama killed the project early in first term.

32. Whiteboard Question
Should we use Yucca Mountain for long-term storage of high-level nuclear waste? If not, then what should be done?
Mr. H thinks we should finish and use Yucca Mountain, then investigate another site for the future. Doing nothing is the worst possible decision.

33. 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)

34. Is nuclear power used too much or not enough in the U.S.? Why?
Whiteboard Question
Is nuclear power used too much or not enough in the U.S.? Why? .

35. Catastrophic potential Waste is awful Renewable options available
Mr. H’s Thoughts
Overused
Expensive
Catastrophic potential
Waste is awful
Renewable options available
Mr. H thinks we should finish and use Yucca Mountain, then investigate another site for the future. Doing nothing is the worst possible decision.

36. Fusion
Fuel= isotopes of hydrogen

37. How do you slow or stop a fusion reaction once it starts?
Whiteboard Question
How do you slow or stop a fusion reaction once it starts?
.Turn off the supply of Tritium (not found in atmosphere)

38. 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