Introduction to Nuclear Fission and Fusion

Basics• Two types of nuclear reactions:– Fission– Fusion

• Both types involve interactions between the nuclei of atoms

• Both produce energy

• Both are very different from chemical reactions

Basics• In chemical reactions, two laws

apply:– Law of Conservation of Energy• Energy cannot be created or

destroyed, it can only change forms

– Law of Conservation of Matter• Matter cannot be created or

destroyed, it can only change forms

Basics• In nuclear reactions, matter and energy are

two forms of the same thing

Matter Energy ‘destroyed’ nuclear reaction ‘created’

• This relationship is shown with a relatively well-known equation . . .

Basics

E = mc2

• E = energy (measured in joules)• m = mass (measured in kilograms)• c = speed of light (measured in meters per second) – The Universal Constant: 300,000,000 m/s– Or is it . . .

Basics

E = mc2

• E = mc2 tells us that a very small amount of matter can be converted to a very large amount of energy

• For example:– 1 paper clip (~0.3 oz) = 1 Hiroshima-sized atomic

bomb (18 Kilotons)– Other examples

Nuclear Fission: What is it?• Splitting an atomic nucleus

• Releases smaller atomic nuclei, neutrons, and energy

• Uses large, unstable atoms like Uranium

• Happens on earth in bombs and nuclear power plants

Nuclear Fission: How does it work?

Fission1. U-235 nucleus bombarded with neutrons

2. Nucleus becomes unstable and splits

3. Split releases other atoms, 2 neutrons, and energy

4. Each neutron splits another U-235 atom and a nuclear chain reaction begins

U-235 + 1 N Kr-92 + Ba-142 + Energy + 2 N

Nuclear Fission: How does it work?

Nuclear Fusion: What is it?• Forcing atomic nuclei together

• Releases larger atomic nuclei, neutrons, and energy

• Uses small elements like Hydrogen

• Happens on earth (bombs only) and in stars

Nuclear Fusion: How does it work?

Fusion (on Earth)1. Two small atoms are forced

together using extreme energy

2. Nuclei fuse, release tremendous amounts of energy

3. Energy forces other nuclei to fuse and a chain reaction begins

4. Only possible in uncontrolled situations

Nuclear Fusion: How does it work?

Fusion (in stars)1. Two Hydrogen atoms are forced together by the extreme gravity

of the star2. The Hydrogen fuse to form Helium and release tremendous

amounts of energy3. Hydrogen fuel and the mass of the star keep the reaction going