Which substance does uranium-238 decay into first ?
Plutonium-239 is synthesized via the following reaction using uranium (U) and neutrons (n) via beta decay ( β− ) with neptunium ( Np ) as an intermediate : formula_1 Neutrons from the fission of uranium-235 are captured by uranium-238 nuclei to form uranium-239 ; a beta decay converts a neutron into a proton to form Np-239 ( half - life 2.36 days ) and another beta decay forms plutonium-239 .