Why does splitting a uranium atom release energy?
The answer has to do with Einstein’s most famous equation — E=mc² — which essentially says that energy is directly related to mass. Under the right conditions, a uranium atom will split into two smaller atoms and throw off two or sometimes three neutrons in the process. (Neutrons are the glue that hold atoms together.) The combined mass of these resulting particles tends to be roughly 99.9 percent of the mass of the original uranium atom. The other 0.1 percent of the original mass got converted to energy, as Einstein described. The energy is released in the form of gamma rays. These rays are similar to X-rays and can cause burns, cancer and genetic mutations in living things. They can be slowed or stopped with thick walls of concrete, lead or packed dirt. Where do the extra neutrons go when the atom splits? The neutrons hit other atoms in the reactor core, starting a chain reaction. Initially, about 3 or 4 percent of the uranium atoms are uranium-235 — the same as the first set of a
