Current nuclear arms control agreements include mechanisms to verify numerical limits of deployed strategic nuclear weapons. Future disarmament agreements will likely rely on approaches to authenticate nuclear weapons and to demonstrate their dismantlement. Both types of agreements could benefit from reliable ways of detecting nuclear weapons at a distance - or showing that they are absent from a facility or larger site.Revisiting a public notional weapon model created by Fetter et al. in 1990, we use the Open Source Monte Carlo code OpenMC to simulate the detection of passive neutron emissions from plutonium-based weapons. The distance from which these types of weapons can be detected depends on two aspects: Firstly the neutron absorption and the scattering in materials between the weapon and detector (e.g., container or shielding), and secondly the ability of a measurement system to discriminate between the signal and the cosmic ray neutron background. We analyze potential neutron detection systems and estimate detection ranges for plausible nuclear weapon deployment and storage scenarios based on simulations.