Answer
The nuclide which remains after the decay is: $~~^{239}Np$
Work Step by Step
$^{238}U$ has 238 nucleons
$^{238}U$ has 92 protons and 146 neutrons
If $^{238}U$ swallows a neutron, then there are 239 nucleons
There are 92 protons and 147 neutrons
When an atom decays by beta-decay, a neutron decays into a proton.
Then there are 93 protons and 146 neutrons, for a total of 239 nucleons.
Note that Neptunium has 93 protons.
The nuclide which remains after the decay is: $~~^{239}Np$
