  The rapid-neutron-capture ("r") process is responsible for synthesizing many
of the heavy elements observed in both the solar system and Galactic metal-poor
halo stars. Simulations of r-process nucleosynthesis can reproduce abundances
derived from observations with varying success, but so far fail to account for
the observed over-enhancement of actinides, present in about 30% of
r-process-enhanced stars. In this work, we investigate actinide production in
the dynamical ejecta of a neutron star merger and explore if varying levels of
neutron richness can reproduce the actinide boost. We also investigate the
sensitivity of actinide production on nuclear physics properties: fission
distribution, beta-decay, and mass model. For most cases, the actinides are
over-produced in our models if the initial conditions are sufficiently
neutron-rich for fission cycling. We find that actinide production can be so
robust in the dynamical ejecta that an additional lanthanide-rich,
actinide-poor component is necessary in order to match observations of
actinide-boost stars. We present a simple actinide-dilution model that folds in
estimated contributions from two nucleosynthetic sites within a merger event.
Our study suggests that while the dynamical ejecta of a neutron star merger is
a likely production site for the formation of actinides, a significant
contribution from another site or sites (e.g., the neutron star merger
accretion disk wind) is required to explain abundances of r-process-enhanced,
metal-poor stars.
