An Etymological Dictionary of Astronomy and Astrophysics

An → isotope not itself → fissile but that is converted into a fissile isotope, either directly or after a short → decay process following absorption of a → neutron. Example: U-238 can capture a neutron to give U-239. U-239 then decays to Np-239 which in turn decays to fissile Pu-239.

The most important fertile isotope is U-238. This is by far the most abundant isotope of natural uranium, making up 99.28%. The important transformation chain is: ₉₂U²³⁸ + ₀n¹→ ₉₃Np²³⁹ + β^- (23.5 minutes) → ₉₄Pu²³⁹ + β^- (2.36 days).

See also: → fertile; → isotope .