Promethium is found, with other metals, as a fission product from nuclear reactors. Promethium can be separated from americium in aqueous solution: Separation Of Americium From Promethium (1959).
Promethium 147 is a beta-emitter and can also be used as a source of x-rays in analytical instruments: X-Ray Analysis With A Source Of Beta Rays (1964). Its high energy density means that Pm 147 can be used as a source of thermal (Radioisotope Heat Source (1970)), and electrical energy (Nuclear Battery (1972)).
References:
All patent information has been obtained from Espacenet (European Patent Office).