Californium (252Cf) and its use as neutron source in science, medicine and technology

Due to it partial radioactive decay of 3.2% by spontaneous fission the radioisotope 252Cf of element californium (proton number = 98, ekadysprosium according to its position in the Periodic Table) is a widely used neutron emitter. Application in science, medicine and technology is based on the emission rate of 2.34 . 109 neutrons per milligram 252Cf and second, therefore being a true alternative to the more common (α, n)-neutron sources. The energy distribution shows a maximum at about 1 MeV with an average neutron energy of about 1.5 MeV, similar to the (induced) fission neutron energy spectra of e.g., 235U or 239Pu. A production rate of about 0.5g 252Cf per year in USA - the main producer in western countries - by long-time irradiation of plutonium in special high-flux-reactor is presently sufficient for its application in several fields of technology, e.g., on-line activation analysis and nuclear medicine, e.g. cancer therapy. (orig.)