Depleted Uranium has had the highly fissionable isotopes removed leaving only u-238 which I think is almost valueless as a fuel. When used as an anti tank projectile it leaves behind a toxic dust which kills mostly by heavy metal poisoning, although I think some radiation cancers are caused by u-238 dust inhaled into the lungs. U-238 by itself has a four and a half billion year half life.
“U-238 by itself has a four and a half billion year half life.”
U-238 does a great job of fissioning inside a hydrogen bomb. The cases are made of cheaper natural uranium and produce a tremendous amount of the energy released through fission.
Not sure how to make a reactor out of it, though.