Uranium
Uranium-238 is the most stable isotope of uranium, with a half-life of about 4.468 years, roughly the age of the Earth. Uranium-235 has a half-life of about 7.13 years, and uranium-234 has a half-life of about 2.48 years.
For natural uranium, about 49% of its alpha rays are emitted by each of U atom, and also 49% by U (since the latter is formed from the former) and about 2.0% of them by the U. When the Earth was young, probably about one-fifth of its uranium was uranium-235, but the percentage of U was probably much lower than this.
Europium
Eu (half-life 13.516 years) and Eu (half-life 8.593 years) cannot be beta decay products because Sm and Sm are non-radioactive, but Eu is the only long-lived "shielded" nuclide, other than Cs, to have a fission yield of more than 2.5 parts per million fissions. A larger amount of Eu is produced by neutron activation of a significant portion of the non-radioactive Eu; however, much of this is further converted to Eu.