Monte Carlo Modeling of the Initial Radiation Emitted by a Nuclear Device in the National Capital Region

Abstract : This document presents the results from an analysis of the impact of urban terrain on the transport of initial radiation from a low yield nuclear device in the National Capital Region. The objective of the work was to use high-fidelity models of radiation propagation to quantify the attenuation and scattering caused by an urban landscape. The results are based on simulated data from the propagation of initial photons and neutrons emitted from a 10 kiloton fission device, detonated at ground level, through both an open-field and urban environment. Scattered radiation from atmosphere, ground, and urban structures is also simulated in the models. Data was derived from calculations using the three-dimensional Monte Carlo radiation transport code MCNP (Monte Carlo N-Particle). The emphasis of this report is on the radiation dose that would be received by individuals, and how that dose is perturbed by an urban environment. Consequently, radiation dose to tissue is reported and neutron doses are not modified to account for their relative biological effectiveness. The results shown in this report indicate the urban terrain provides significant attenuation of the initial neutron and photon emissions. These results show that the dose is reduced to between 20-30% of the open field dose depending on the building characteristics.