7/30/2019 NUCLEAR FISION & FUSION
http://slidepdf.com/reader/full/nuclear-fision-fusion 1/13
Nuclear Fission & Fusion
7/30/2019 NUCLEAR FISION & FUSION
http://slidepdf.com/reader/full/nuclear-fision-fusion 2/13
History:
Hahn & Strassman (1939)
•Bombarded Uranium-235 samples with neutronsexpecting the Uranium-235 to capture neutrons
•Instead, the products showed different chemicalproperties that they could not explain
7/30/2019 NUCLEAR FISION & FUSION
http://slidepdf.com/reader/full/nuclear-fision-fusion 3/13
•Explained Hahn & Strassman results.
•Instead of heavier Uranium, it had splitinto smaller elements = Nuclear Fission
Meitner & Frisch
7/30/2019 NUCLEAR FISION & FUSION
http://slidepdf.com/reader/full/nuclear-fision-fusion 4/13
Nuclear Forces
1. Electric repulsion – ________ charge particlesrepel each other
same
2. Strong Nuclear Force – causes protons andneutrons to ________ each other
attract
•Stable Nuclei = strong nuclear force is ________ than repulsion force
greater
•Unstable Nuclei = strong nuclear force is ________ than repulsion force
oHave too many or too few neutrons in nucleus
oHave more than 83 protons in nucleus
oWill decay into a more stable nucleus
less
7/30/2019 NUCLEAR FISION & FUSION
http://slidepdf.com/reader/full/nuclear-fision-fusion 5/13
Nuclear Fission – splitting of
heavier nuclei into lighternuclei.
U235
92n
1
0Ba
137
56Xe
84
36n
1
0energy + +15 + +
How much energy? E=mc2
_______= _______ x (_____ _ _____)2 c=3.0x108 Energy mass speed of light
E=mc2 explains _____ _____ (total mass of
nucleus is less than sum of individual particles)
mass defect
7/30/2019 NUCLEAR FISION & FUSION
http://slidepdf.com/reader/full/nuclear-fision-fusion 6/13
7/30/2019 NUCLEAR FISION & FUSION
http://slidepdf.com/reader/full/nuclear-fision-fusion 7/13
Nuclear Chain Reactions:
•Nuclear fission releases more neutrons which trigger
more fission reactions
•The number of ________ released determines thesuccess of a chain reaction
neutrons
7/30/2019 NUCLEAR FISION & FUSION
http://slidepdf.com/reader/full/nuclear-fision-fusion 8/13
7/30/2019 NUCLEAR FISION & FUSION
http://slidepdf.com/reader/full/nuclear-fision-fusion 9/13
Applications of ControllingChain Reactions
Must have a minimum amount of radioactive isotope
to sustain a chain reaction =_________ _______
1. Atomic Bomb (fission bomb) – Triggering a chain reaction in
U-235 or Pu-239
CRITICAL MASS
2. Nuclear Power Plants – Convert heat energy from fissionchain reaction into __________.electricity
Control chain reaction with ________ _____ thatabsorb ________ emitted after fission reaction.
control rodsneutrons
7/30/2019 NUCLEAR FISION & FUSION
http://slidepdf.com/reader/full/nuclear-fision-fusion 10/13
Nuclear Fusion - Energy released whentwo light nuclei combine or fuse
•However, a large amount of energy isrequired to start a fusion reaction:
o Need this energy to overcome ________ forcesof protons. o Extremely high temperatures can provide start-upenergy.
repulsion
More energy in fusing hydrogen that fission of uranium
7/30/2019 NUCLEAR FISION & FUSION
http://slidepdf.com/reader/full/nuclear-fision-fusion 11/13
Nuclear Fusion
7/30/2019 NUCLEAR FISION & FUSION
http://slidepdf.com/reader/full/nuclear-fision-fusion 12/13
Stars energy is produced
through fusion reactions
Fusion occurs until Fe is
produced because lessenergy is released thanrequired to fuse Fe nuclei =
_____ ____ ____ Star burns out
7/30/2019 NUCLEAR FISION & FUSION
http://slidepdf.com/reader/full/nuclear-fision-fusion 13/13
Cold Fusion:
Efforts are beingmade to start andsustain a fusion
reaction at lowertemperatures, in
other words with alower amount ofinput energy
Top Related