Ionising radiation can come from a number of sources. The x-rays produced by dental X-ray sets, CT scanners etc. are a form of ionising radiation. Cosmic rays, from within our solar system and beyond can be ionising. Unstable, naturally-occurring, ‘radioactive’ material here on earth emits ionising radiation. The use of radioactive material within nuclear reactors (to generate electricity) also generates additional ionising radiation during the controlled splitting of atoms, and is associated with the radioactive waste produced.