7.3 Nuclear Reacti ons•Nuclear Fission•Nuclear Fusion•Induced Nuclear Reaction•Chain Reaction•CANDU Reactors

By Jenny Lee

• NUCLEAR FISSION is the splitting of a more massive nucleus into two less massive nuclei, subatomic particles, and energy.

• Heavy nuclei tend to be unstable, and to increase stability, they split into atoms with lighter nuclei. (FISSION)

Fission is accompanied by a very large release of energy. Fission produces up to 5 neutrons, but 3 is common.

Nuclear Fission

※U-235 absorbs the neutron and becomes highly unstable. Then it produces 3 neutrons and continues the process.

• CHAIN REACTION is an ongoing process in which one reaction initiates the next reaction. – A nucleus will split an atom, and the atom will produce other

neutrons which will continue the process.

• It can be controlled by materials that absorb neutrons.

Chain Reacti on

※ U-235 absorbs the nucleus and produces two other neutrons. This process continues, and continues the chain reaction.

http://www.youtube.com/watch?v=ekx6gz_s5VM

Video : Nuclear Fission

1. What is the ongoing process in which one reaction initiates the next reaction?

a. Continued Reactionb. Cause and Effect Reactionc. Chain Reaction

2. Why does nuclear fission occur?a. To increase stabilityb. To decrease stability

3. Fission is accompanied by a very large release of _______.a. Gamma Raysb. Energyc. Alpha particles

Quiz

1. C) Chain Reaction2. A) To increase stability3. B) Energy

Answers :

Nuclear Reacti ons•NUCLEAR REACTIONS are those that involve a change in an atom’s nucleus. •Nuclear Reaction is a process in which an atom’s nucleus changes by gaining or releasing particles or energy.•A nuclear reaction can release all three types of subatomic particles, including gamma rays.•Small change in mass = large change in energy.

•INDUCED (FORCED) NUCLEAR REACTION is when a nuclear reaction is caused by bombarding a nucleus with alpha, beta, or gamma rays.

※ Example of an induced nuclear reaction equation

• CANDU Reactors are Canadian nuclear reactors.• CANDU Reactor stands for: CANadian Deuterium

Uranium reactor. Deterium is an isotope of Hydrogen-1 that is twice as

heavy. It has a proton and a neutron.

CANDU Reactors

• NUCLEAR FUSION is the process in which two low mass nuclei join together to make a massive nucleus.

• Fusion occurs at the core of sun and other stars, where there is sufficient pressure and high enough temperature to force isotopes of Hydrogen to collide with great force.

In the sun, fusion reaction occurs between hydrogen-2 and hydrogen-3. When these two combine, they produce a huge amount of energy.

Nuclear Fusion

※Fusion nuclear equation

Video : Fission Vs. Fusion

http://www.youtube.com/watch?v=3rn339v_Q-w

1. Where is one location at which nuclear fusion occurs?a. Core of Sunb. Core of Moonc. Core of Earth

2. What does CANDU stand for?a. Canadian Diterium Ununtriumb. Canadian Dioxide Uraniumc. Canadian Deuterium Uranium

3. What is produced when hydrogen-2 and hydrogen-3 are combined?

a. Smokeb. Energyc. Gamma Rays

Quiz

1. A) Core of Sun2. C) Canadian Deuterium Uranium3. B) Energy

Answers :