Nuclear Reactors

1. Nuclear Reactors

2. Nuclear Reactors • Fission has been developed as an energy source to produce electricity in reactors • Within the reactors, controlled fission occurs • And we harness the heat from fission to create electricity

3. Diagram of a nuclear power plant.

4. Schematic of the reactor core. • Fuel rods – contained enriched uranium • Moderator – slows the neutrons down so the uranium fuel can capture them more efficiently • Control rods • Coolant –

5. So how do we control it? • Control rods: control the fission process with cadmium rods that absorb neutrons Enrico Fermisupervised construction of theworld's first nuclearreactor.

6. Schematic of the reactor core. • Fuel rods – • Moderator – • Control rods – absorb neutrons; regulate the power level of the reactor • Coolant – usually water; extracts the heat produced during fission

7. Diagram of a nuclear power plant.

8. The 4 bad parts of fission… • Reactor components • Uranium • Heat production • Nuclear waste You notes should include why these 4 things create disadvantages for getting all our energy from fission.

9. The bad part of Fission: 1. Reactor Components • The concentration of uranium is not great enough to allow an explosion • A failure in the cooling system can lead to temperatures high enough to melt the reactor core • This is called a “melt down”

10. Melt Down • A melt down was narrowly avoided at Three Mile Island (in Pennsylvania) in 1979 • A total melt down occurred at Chernobyl in the Soviet Union in 1986 • Reactor No. 4 at the power plant exploded releasing 30 to 40 more times radiation than the bombs dropped on Hiroshima and Nagasaki • The Soviet government didn’t own-up to the disaster until scientists in Sweden recorded high levels of nuclear fall-out • People are still not allowed in the area surrounding the power plant

11. Chernobyl Melt Down

12. The bad part of fission:2. Uranium • Discovered in 1789 • Not rare – more abundant than tin • Widely scattered on Earth in the crust • Most accessible deposits: • United States, Canada, South Africa, Australia • Used in small amounts as a coloring agent for glass and ceramics • Natural nuclear reactor existed in Gabon millions of years ago

13. The bad part of fission:2. Uranium • U-238 – radioactive, but not fissionable • U-235 – fissionable, but only 0.7% of natural uranium. • 3% U-235 needed for fuel rods. • Scientists “enrich” the uranium found in nature so that it contains 3% of U-235 • For atomic bombs, the amount of U-235 needed is 90%!

14. The bad part of fission:2. Uranium • Breeder reactors: change non-fissionable U-238 and convert it into fissionable Pu-239 while the reactor runs • Completed by bombarding U-238 with neutrons • Controversial • very toxic, poisonous, and flames in air

15. The bad part of Fission:3. The heat produced is pumped into water

16. The bad part of fission:4. Nuclear Waste • Most nuclear waste created over the last 50 years is in temporary storage • In 1982 the Nuclear Waste Policy Act was passed • Established a timetable for choosing and preparing sites deep underground for the disposal of radioactive materials • The current plan calls for the nuclear waste to be packaged in glass blocks that will be packed in corrosion-resistant metal and buried in a deep, stable rock formation • The hope is that the waste will be isolated until radioactivity decays to safe levels

17. 4. Nuclear Waste

18. 4. Nuclear Waste • In 1998, the Waste Isolation Pilot Plant in New Mexico was issued a license by the EPA to receive nuclear waste • Yucca Mountain has been studied as a site for 20 years for the high level waste generated at power plants