During nuclear fission, an atom splits into two or more smaller nuclei along with
by-product particles (neutrons, photons, gamma rays, and alpha and beta
particles). The reaction gives off heat (exothermic). If controlled, the heat that is
produced is used to produce steam that turns generators that then produce
electricity. If the reaction is not controlled, a “meltdown” can result. A nuclear
“meltdown” is an informal term for a severe nuclear reactor accident that results
in core damage from overheating (e.g., Fukushima Daiichi).
Figure 8.7 Nuclear fissionThe amount of potential energy contained in nuclear fuel is 10 million times
more than that of more traditional fuel sources such as coal or petroleum. The
downside is that nuclear wastes remain highly radioactive for thousands of years
and are difficult to dispose of. The most common nuclear fuels are U-235, U-
238, and Pu-239.
NUCLEAR FUEL
U-235
U-235 differs from U-238 in its ability to produce a fission chain (self-
sustaining) reaction. The minimum amount of U-235 required for a chain
reaction is called the critical mass. Low concentrations of U-235 can be used if