Proton beam dumps used as a source of neutrinos could also be a source of dark sector particles. Therefore experiments sensitive to the decay of nuclei excited states by inelastic scattering of neutrinos are likewise sensitive to dark matter inelastic scattering. Using this channel we demonstrate world-leading sensitivity to a dark photon portal DM model compared to the existing constraints. With present and future experiments constraints on this parameter space will rule out large regions of the thermal benchmark.