Nuclear Reactions

Powering the Sun since 4.6 Billion B.C.

Nuclear Reactions

Occur when the nucleus of an atom is changed

Nuclear Reactions release the most energy of any type of reactions.

http://education.jlab.org/qa/atom_model_03.gif

Nucleus

Fission

When a large nucleus is split into two or more smaller nuclei

Only certain elements’ nuclei will fission, or split

Uranium & plutonium are the most common fissionable elements

http://holvoet.free.fr/Voyage/energy/img/fission_v.gif

Fission Nuclear Chain Reaction

When one fission reaction sets off several other fission reactions, which each set off new fission reactions.

http://wps.prenhall.com/wps/media/objects/476/488316/Instructor_Resources/Chapter_17/FG17_10.JPG

What happens during a fission reaction?

http://www.oup.co.uk/images/oxed/children/yoes/atoms/fission.jpg

1. A large nucleus is hit with a neutron.

Nucleus: U or Pu

Neutron

What happens during a fission reaction?

http://www.oup.co.uk/images/oxed/children/yoes/atoms/fission.jpg

2. The neutron makes the nucleus of the atom split.

Nucleus: U or Pu

Neutron

What happens during a fission reaction?

http://www.oup.co.uk/images/oxed/children/yoes/atoms/fission.jpg

3. Large amounts of energy are released when it splits

Nucleus: U or Pu

Neutron

What happens during a fission reaction?

http://www.oup.co.uk/images/oxed/children/yoes/atoms/fission.jpg

4. A few neutrons are sent flying from the split nucleus.

•These neutrons start new fission reactions

Nucleus: U or Pu

Neutron

Neutrons

Gamma Ray

Fission

Critical massThe smallest amount of uranium or plutonium

that is needed to start a chain reaction.

The critical mass for Uranium is around 33 pounds.

Fusion

When two small nuclei join together to form a larger nucleus

Fusion releases much more energy than fission

What Happens in a Fusion Reaction?

1.Two hydrogen nuclei smash together at very high speeds

Hydrogen-2

(Dueterium)

Hydrogen-3

(Tritium)

2.The hydrogen nuclei stick together (or fuse) to make a larger nucleus

3.Huge amounts of energy are released

Helium

neutron

http://www.generalfusion.com/images/reaction2.gif

Where does fusion happen?

Occurs in the Sun and other stars

Fusion bombs (H-bombs)