  Supersymmetry (SUSY) with bilinearly broken R parity (bRPV) offers an
attractive possibility to explain the origin of neutrino masses and mixings. In
such scenarios, the study of neutralino decays at colliders gives access to
neutrino sector parameters. The ILC offers a very clean environment to study
the neutralino properties as well as its subsequent decays, which typically
involve a $W$ or $Z$ boson and a lepton. This study is based on ILC beam
parameters according to the Technical Design Report for a center of mass energy
of $500\,\mathrm{GeV}$. A full detector simulation of the International Large
Detector (ILD) was performed for all Standard Model backgrounds and for
$\widetilde{\chi}_1^0$-pair production within a simplified model. The bRPV
parameters are fixed according to current neutrino data. In this scenario, the
$\widetilde{\chi}_1^0$ mass can be reconstructed with an uncertainty of $\delta
m = (40(\text{stat.}) + 50(\text{syst.}))\,\mathrm{MeV}$ for an integrated
luminosity of $500\,\mathrm{fb}^{-1}$ from direct $\widetilde{\chi}_1^0$-pair
production, thus, to a large extent independently of the rest of the SUSY
spectrum. The achievable precision on the atmospheric neutrino mixing angle
$\sin^2 \theta_{23}$ from measuring the neutralino branching fractions
$\mathrm{BR}(\widetilde{\chi}_1^0 \rightarrow W \mu)$ and
$\mathrm{BR}(\widetilde{\chi}_1^0 \rightarrow W \tau)$ at the ILC is better
than current uncertainties from neutrino experiments. Thus, the ILC could have
the opportunity to unveil the mechanism of neutrino mass generation.
