For example, radiotherapy treatment for cancer works by using radiation to destroy the cancer cells. Radiation occurs naturally. We are surrounded by radiation. Radioactivity was discovered by Henri Becquerel in 1896, the year after Wilhelm Rontgen discovered X-rays. There are now nine known naturally occurring radioactive elements.
Nuclear fission is the splitting of the nucleus of a radioactive element into two smaller fragments.
The nucleus is caused to fission by striking it with a neutron. If the radioisotope used is uranium-235, then the fission reaction, as well as releasing energy, also releases three more neutrons. In other words, a chain reaction can be generated, which releases a lot of energy. Nuclear fission power is based on the safe harnessing of this energy. Nuclear fusion Nuclear fusion is the opposite of fission.