In nuclear technology the conversion of a substance in a fissile substance, e.g. uranium-238 plutonium-239 or thorium-232 uranium-233. fertile material
Winfried Koelzer, Nuclear Terms, Karlsruher Institut for Technologie KIT (Ed.), ISBN German print version 2001: 3-923704-32-1, Translation by Informationskreis KernEnergie (Berlin), Karlsruhe, Germany 2013. https://www.euronuclear.org/info/encyclopedia/pdf/ Nuclear_Glossary-%202013-02-13.pdf, (Nucl Sfty - Amer) {1011}