Nuclear Energy

The Source of Nuclear Energy

The curve of binding energy per nucleon ($E_{bn}$) against mass number $A$ (Figure 13.1 in the textbook) reveals a crucial fact: for nuclei with mass numbers between $A = 30$ and $A = 170$, the binding energy per nucleon is nearly constant at about 8.0 MeV. For lighter nuclei ($A < 30$) and heavier nuclei ($A > 170$), $E_{bn}$ is less than 8.0 MeV.

The binding energy of a nucleus is the energy required to break it apart into its constituent protons and neutrons. A higher binding energy means the nucleus is more tightly bound, and therefore has a lower total mass (since mass and energy are equivalent via $E = mc^2$).

Now consider what happens when a nucleus transforms from a state of lower binding energy to a state of higher binding energy. Because the final system is more tightly bound, its total mass is smaller than the initial system's mass. This mass difference is converted into energy, which is released. This is the fundamental principle behind nuclear energy.

There are two ways this transformation can occur:

1. Nuclear Fission: A heavy nucleus (with low $E_{bn}$) splits into two or more intermediate-mass fragments (which lie in the high-$E_{bn}$ region).
2. Nuclear Fusion: Two very light nuclei (with low $E_{bn}$) combine to form a single, heavier nucleus (with higher $E_{bn}$).

In both processes, the final nuclei have a greater binding energy per nucleon than the initial nuclei, leading to a net release of energy. …