Nuclear Fission and FusionUMA LAD

PHY 3305: MODERN PHYSICS

DECEMBER 2, 2014

Outline • Fission and fusion will be defined.

• Examples of fission and fusion will be discussed.

• Modern day applications of these reactions will be discussed.

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Nuclear Reaction• Occurs when a nucleus collides with another particle

• Example: uranium- 235 decays into barium and krypton

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Total Energy released:Q= (mi – mf)c2

Nuclear Fission• Nucleus breaks down into many parts

• Releases kinetic energy

• Many isotopes decay through induced fission

• Number of protons and neutrons affects the amount of energy released

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Fig. 1. Uranium Fission. “Mousetrap Reactor.” SMU Physics and Astronomy Demonstrations. 2014. Web. 25 Nov. 2014.

Chain Reactions• Each fission reaction will cause other fission reactions to occur.

• Critical assembly: ensures that a reaction can sustain itself

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The energy released during a chain reaction:Ej = E0kj

Fission Reactor• Uranium-235 is used as the fuel• Control rods absorb neutrons

• Neutrons produced from each generation become slower

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Pressure Water Reactor

Fig. 2. A Light-Water Nuclear Fission Reactor for the Production of Electric Power. Digital image. ”Applied Nuclear Chemistry.” UC Davis Chemwiki. UC Davis, n.d. Web. 20 Nov. 2014. 

Nuclear Fusion• Nuclei combine to form heaver nuclei

• Mass decreases

• Kinetic energy increases

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Lawson Criterion• For fusion to occur:• High temperatures are necessary

• Reaction must be held:

• For a certain amount of time

• A certain density of ions

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Proton-Proton Cycle

• End result: helium

• Energy source of the Sun

Fig. 3. Fission in the Sun. “Proton- Proton Chain Reaction.” Wikipedia. Wikimedia Foundation Inc., 2006. Web. 25 Nov. 2014.

Fusion in Relation to Stars• Carbon Cycle• Uses carbon as a catalyst

• Results in helium

• Occurs when a star has a high temperature

• Stellar Collapse- Star collapses into a white dwarf• Energy production from fusion no longer matches the gravitational

attraction

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Fusion Reactors• Difficult to use as a power source

• Requires extreme conditions

• Ways to confine nuclei• Magnetic confinement

• Inertial confinement

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Conclusion• Fission - nucleus breaking down into many parts.

• Fusion - nuclei combining to form heaver nuclei.

• Chain reaction - one reaction triggers many other reactions.

• Fission reactors are used to produce energy.

• Proton-proton cycle is composed of multiple fusion reactions.

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SourcesHarris, Randy. Modern Physics. 2nd ed. San Francisco: Pearson, 2008. 503-513. Print.

Herrmann, Mark. “Plasma Physics: A promising advance in nuclear fusion.” Nature 506 (2014):

302-303. Web. 17 Nov. 2014.

Nave, Rod. "Nuclear Fusion." HyperPhysics. Web. 11 Nov. 2014. <http://hyperphysics.phy-astr.

gsu.edu/hbase/nucene/fission.html#c1>.

Reed, Cameron B. “Neutrons as Party Animals: An Analogy for Understanding Heavy-Element

Fissility.” The Physics Teacher 50 (2012): 544-545. Web. 17 Nov. 2014.

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