2. Mr. ShieldsRegents Chemistry U02 L05

3. Nuclear Fission Fission splitting large nuclei up into smaller more stable nuclei accompanied by the release of ENERGY 235U + 1n 142Ba + 91Kr + 3 1n 92 0 56 36 0 Energy Smaller nuclei are more stable because the Binding energy per nucleon increases.

4. Fission Why do nuclei Fission? Fission reactions release energy FusionRxnsReleaseenergy Ni-62 Fe-56 Reducing mass increases binding Energy above Mass # 50

5. 235U + 1n 142Ba + 91Kr + 3 1n 92 0 56 36 0 Once the uranium atom fissions by slamming it with one neutron, 3 more neutrons are released These three neutrons can now interact with 3 other uranium atoms etc. etc. etc.uraniumneutronFISSION

6. 235 U + 1 n 11 42 Ba + 91 Kr + 3 1 n + 1n -> 3n -> 9n -> 27n -> 81n -> 243n Chain Reaction Etc. until LOTS OF ENERGY! Uncontrolled release Of neutrons

7. Critical Mass If the sample is sufficient in size the released neutrons will cause other U-235 to fission exponentially. The amount necessary to sustain a chain reaction is called the CRITICAL MASS If a critical mass is present then … Released Energy So where does this energy come from??

8. CRITICAL MASS is necessary to sustain a chain reaction.

9. Detonating a nuclear device When these 2 subcritical pieces are joined together the mass becomes critical …. Detonation occurs

10. Indian Point Buchanan, NY Nuclear Power Plants

11. Production of power in a nuclear reactor

12. Nuclear Waste One of the problems society faces is what to do with Nuclear waste materials. Several industries are the main generators of this material - nuclear power industry - medical industry - Weapons industry - Research SO… WHAT DO WE DO WITH THIS MATERIAL???

13. Nuclear Waste Rememeber … the problem is - This material can be extremely radioactive thus dangerous to life thus dangerous to life - And the half-life of some of these materials can be thousands of years can be thousands of years So what do we do with it?

14. We are dealing with a time scale of the several thousand years that the nuclear waste would take to fully decompose. The unpredictability of climate changes over periods of thousands of yrs could threaten the geological and environmental stability that Yucca Mountain is currently prized for. Nuclear Waste

15. Medical Use of Radioactivity In the U.S… - 30 million people are hospitalized yearly - one in three are diagnosed or treated with nuclear medicine - Radionuclides are used in more than 11 million nuclear medicine procedures medicine procedures - Radionuclides are used in 100 million laboratory tests on body fluid and tissue specimens. on body fluid and tissue specimens.

16. Radionuclides used in Medicine To be useful as a radionuclide it must have a short half life and be readily expelled from the body. Technetium-99m Imaging can help diagnose bone infections in young children at the earliest possible stage and treatment of Brain tumors Cobalt-60 is used to treat cancer Iodine-123 widely used to diagnose thyroid disorders. Iron-59 used to image circulatory system And there are many other radioisotopes used in medicine. * * * * Know these radionuclides!

17. Radionuclides used for Dating Materials Carbon-14: Used for dating archeological finds (must have once been living) Carbon-14: Used for dating archeological finds (must have once been living) Half-life = 5260 yrs Half-life = 5260 yrs Uranium-238: Used to date the age of rocks or geological areas Uranium-238: Used to date the age of rocks or geological areas Half-life = 4.5 billion years Compares U-238 present to the amount of Pb-206 present. Remember the U-238 decay curve? Pb-206 is stable.

18. Nuclear Fusion Energy Fusion small nuclei combine to form larger nuclei 2H + 3H 4He + 1n + 1 1 2 0 Deuterium Tritium This is one example of a fusion rxn but other small nuclei also can also undergo fusion Requires High temperature and pressure to Overcome positive nuclear repulsion

19. Nuclear fusion in the sun. Last step of a multi-step process that can be represented by The overall equation: 4 1H  4He + 2 0e + E 1 2 -1 Overall equation for The fusion of H into He

20. The sun ‘s energy, as well as all other stars, create their energy using fusion Hydrogen is converted to Helium and then all the other Elements follow in kind. If the star then super nova’s all these Elements are dispersed into the universe. The Sun You might say We are all Children of the Stars!

21. Fusion Why do nuclei undergo Fusion? Fission reactions release energy FussionRxnsReleaseenergy Ni-62 Fe-56 Binding energy increases As we inc. mass to up to about 50

22. The H-Bomb A thermonuclear reaction. Min. temperature required for Detonation is 40 million degrees K. A nuclear bomb is need to detonate a hydrogen bomb to create both the necessary Temp and Pressure.