The design that resulted involved a facility with two identical reactors, each capable of supplying 100% of the world's medical isotope demand. The second reactor would function primarily as a back-up, to ensure that the supply of isotopes would not be interrupted by maintenance or unplanned shutdowns. This is made necessary by the nature of medical isotopes; many have short half-lives, and must be used within a few days of production. With treatments being constantly carried out around the globe, an uninterruptible supply was essential.