Illinois Statutes Chapter 420. Nuclear Safety § 15/1. Spent nuclear fuel defined

§ 1. For the purposes of this Act, “spent nuclear fuel” means the irradiated energy source that is permanently removed from the core of a nuclear fission reactor either because it can no longer effectively sustain a chain reaction due to the depletion of fissionable isotopes and the buildup of by-products that interferes with the chain reaction or because safety or operating concerns dictate such removal.