text: The only stable yttrium isotope, Y, will be found with yield somewhat less than 1% in a fission product mixture which has been allowed to age for months or years, as the next-longest lived yttrium isotopes have half-lives of only 107 days (Y) or 59 days (Y). However, a small amount of yttrium-90 will be found in secular equilibrium with its parent strontium-90 unless the two elements are separated from each other.
  Sr decays into Y which is a beta emitter with a half-life of 2.67 days.
  Y is sometimes used for medical purposes and can be obtained either by the neutron activation of stable Y or by using a device similar to a technetium cow.
  As the half lives of the unstable Yttrium isotopes are low ( being the longest at 106 days), yttrium extracted from strontium-free moderately aged spent fuel has negligible radioactivity. However, the strong gamma emitter  will be present as long as its parent nuclide  is. Should a nonradioactive sample of Yttrium be desired, care must be taken to remove all traces of strontium and sufficient time to let the short lived Y-90 (64 hours half life) decay must be allowed  before the product can be used.