  We study the alpha-decay half-lives of 84 <= Z <= 92 even-even nuclei in the
semiclassical WKB approximation framework using the density-dependent cluster
model and the density distribution described by various Korea-IBS-Daegu-SKKU
(KIDS) models. Main goal of this work is to find a correlation between the
alpha-decay half-lives and the stiffness of the symmtery energy. Parameters of
KIDS model are determined to reproduce the nuclear data (energy and charge
radii of 40Ca, 48Ca and 208Pb) and the neutron star observations including
constraints by NICER, tidal deformability from GW170817, and the maximum mass
limit of neutron star observations. We use the KIDS models (A-D) which have
distinctive values for the parameters controlling the stiffness of the nuclear
matter equation of state. We find that the alpha-decay half-lives increase
systematically from KIDS-A model to KIDS-D model. This implies a correlation
between the alpha-decay half-lives and the symmetry energy. We find that the
correlation can be understood from the dependence of the particle distribution
in the core and the surface region on the symmetry energy.
