Fission and Fusion

Fission releases energy produced in a nuclear reactor.  Fusion is the energy of the stars and the reason our sun burns bright.  Learn more here.

Fission and Fusion Learning Targets

  • Understand the difference between fission and fusion using a model
  • Be able to recognize fission, fusion, alpha decay, beta decay, or gamma decay in an example

Nuclear Fission

During nuclear fission, neutrons bombard heavy nuclei splitting them forming two smaller atoms.

The mass of product particles is slightly less than the mass of the reactant.  This mass is converted into energy which can be calculated using Albert Einstein’s famous equation E=mc2.  Energy released equals the mass lost times the speed of light squared.

In our animation, neutrons bombard heavy U-235 splitting into Ba-142, Kr-91, and three neutrons.  The neutrons released continue to create fission reactions with U-235.

A spontaneous reaction that will continue as long as there is a critical mass of U-235 to split.

Critical mass is minimum mass of fissionable material required for a chain reaction.  The fissionable material in our animation is Uranium-235.

Fission reactions are done in in a reactor to contain the extreme amounts of energy produced.  A nuclear bomb is the result of this reaction in an unrestrained environment.

Nuclear Fusion

Nuclear fusion is the combination of small nuclei into larger nuclei which releases large amounts of energy.

  • Nuclear fusion can release up to 10 times more energy than nuclear fission.  Nuclear fusion occurs naturally and is the source of energy in our sun and other stars.
  • In the fusion reaction, two smaller Hydrogen atoms are fused together to form a larger Helium and a neutron is released.
  • Nuclear fusion requires high temperatures, which is readily available in a star.  We currently have not discovered a way to maintain temperatures required to sustain nuclear fusion without vaporizing the container of the fusion reaction.  Today many are scientists are researching ways to create nuclear fusion under sustainable conditions.
  • As of 2020, research is ongoing at companies like Lockheed Martin to create unlimited energy through fusion.  Current nuclear technology only allows the use nuclear fission as an energy source.

Practice Questions

Answer the following nuclear decay or reaction questions related to alpha decay, beta decay, gamma decay, fission, or fusion.

 

1. Which nuclear decay or reaction does the following formula represent?

Reaction 1

Beta Decay

The atomic number of the element increases by one as a neutron releases a beta particle and becomes a proton

2. Which nuclear decay or reaction does the following formula represent?

Reaction 6

Gamma Decay

Energy released as a gamma particle with no mass.  The product is the same as the reactant but at a lower energy state.

3. Which nuclear decay or reaction does the following formula represent?

Reaction 4

Nuclear Fission

Uranium-235 splits to become two smaller molecules

4. Which nuclear decay or reaction does the following formula represent?

Reaction 2

Alpha Decay

An alpha particle, a helium-4 nucleus, is released from a single reactant

5. Which nuclear decay or reaction does the following formula represent?

Reaction 3

Fusion

Two smaller hydrogen molecules are fused together to form a larger Helium

6. Which nuclear decay or reaction does the following formula represent?

Alpha Decay

A helium nucleus (He-4) is released from a single reactant

7. What type of reaction creates the energy of stars?

Fusion

Forcing two Hydrogen atoms together to form a helium

8. What type of reaction produces energy of nuclear reactors in the year 2020?

Fission

Splitting a larger unstable molecule

9. What type of reaction releases an electron as a neutron becomes a proton?

Beta Decay

The electron is called a beta particle when this happens

10. What type of radioactive decay releases energy only?

Gamma Decay

A gamma ray is a burst of energy but the reactant maintains its elemental composition during the reaction.

11. Which reaction would produce more energy per reaction, fission or fusion?

Fusion

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