It is produced by inserting a 'target' rod rich in non-radioactive cobalt-59 into a reactor core where free neutrons will be captured, turning cobalt-59 into cobalt-60. After retrieval from the core, processing can extract the cobalt-60 for manufacture into a useful radiation source. The vast majority of the world's cobalt-60 supply - over 80% - has traditionally come from Canada's National Research Universal (NRU) reactor at Chalk River. In general, the supply situation for medical and industrial isotopes is shaky thanks to a reliance on this kind of aging research reactor. Clinton will be the only light water reactor currently producing cobalt-60.