1. Chapter 9 Nuclear Radiation
9.6
Nuclear Fission and Fusion

2. Nuclear Fission In nuclear fission,
a large nucleus is bombarded with a small particle
the nucleus splits into smaller nuclei and several neutrons
large amounts of energy are released

3. Nuclear Fission When a neutron bombards 235U,
an unstable nucleus of 236U undergoes fission (splits)
the nucleus splits to release large amounts of energy
smaller nuclei are produced, such as Kr-91 and Ba-142
neutrons are also released to bombard more 235U nuclei

4. Nuclear Fission Diagram
1n U U Kr Ba n + energy

5. Nuclear Fission Chain Reaction
In a nuclear chain reaction, the fission of each U-235 atom produces three neutrons that cause the nuclear fission of more and more uranium-235 atoms.

6. Energy and Nuclear Fission
The total mass of the products in this reaction is slightly less than the mass of the starting materials. The missing mass has been converted into energy, consistent with the famous equation derived by Albert Einstein, E = mc2.
E is the energy released, m is the mass lost, and c is the speed of light, 3.0  108 m/s. Using this equation, a small amount of mass is multiplied by the speed of light squared, resulting in a large amount of energy.
Fission of 1 g U-235 produces same energy as 3 tons of coal.

7. Learning Check 1n + 235U 137Te + ?X + 2 1n + energy 0 92 52 ? 0
Supply the missing atomic symbol to complete the equation for the following nuclear fission reaction.
1n U Te + ?X n + energy ?

8. Solution 1n + 235U 137Te + 97Zr + 2 1n + energy 0 92 52 40 0
Supply the missing atomic symbol to complete the equation for the following nuclear fission reaction.
1n U Te Zr n + energy

9. Nuclear Power Plants In nuclear power plants,
fission is used to produce energy
control rods in the reactor absorb neutrons to slow and control the chain reactions of fission

10. Nuclear Fusion
Fusion
occurs at extremely high temperatures ( C)
combines small nuclei into larger nuclei
releases large amounts of energy
occurs continuously in the sun and stars
Hydrogen atoms combine in a fusion reactor at very high temperatures.

11. Learning Check
Indicate whether each of the following describes nuclear fission or nuclear fusion.
___ A. A nucleus splits.
___ B. Large amounts of energy are released.
___ C. Small nuclei form larger nuclei.
___ D. Hydrogen nuclei react.
___ E. Several neutrons are released.

12. Solution
Indicate whether each of the following is nuclear fission or nuclear fusion. nuclear fission A. A nucleus splits. nuclear fission and fusion B. Large amounts of energy are released. nuclear fusion C. Small nuclei form larger nuclei. nuclear fusion D. Hydrogen nuclei react. nuclear fission E. Several neutrons are released.

13. Nuclear Radiation – Concept Map