# How does nuclear energy work?

1. Mar 31, 2004

### ShawnD

The mass of an atom is less than the sum of its parts. The difference in mass is called the mass defect, and E = mc^2 shows how much energy that difference in mass has.
Since mass and energy interchange in nuclear reactions, mass and energy would go on different sides of the equation.
Here is what nuclear fusion looks like

$$^3_1H + ^2_1H + (mass) \rightarrow ^4_2He + ^1_0n + (energy)$$

The left side is heavier and the right side has more energy. If the components are heavier, how does nuclear fission give off energy? Breaking uranium into components should absorb energy shouldn't it?

Last edited: Mar 31, 2004
2. Mar 31, 2004

### chroot

Staff Emeritus
The most tightly bound nucleus is iron. You can't fission iron without adding energy, and you can't fuse iron without adding energy.

On the left (lower mass) side of iron, the nuclei are less tightly bound, and can be fused to release energy, resulting in a more tightly bound nucleus.

On the right (higher mass) side of iron, the nuclei are less tightly bound, and can be fissioned to release energy, resulting in two atoms with more tighty bound nuclei.

http://hyperphysics.phy-astr.gsu.edu/hbase/nucene/nucbin.html#c2

- Warren

3. Mar 31, 2004

### ShawnD

Awesome, thanks.