Monte-Carlo Modeling of the Prompt Radiation Emitted by a Nuclear Device in the National Capital Region, Revision 1

Abstract : This document presents the results from an analysis of the impact of urban geometry on the transport of prompt radiation from a simulated 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 prompt 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 the atmosphere, ground, and urban structures is also simulated in the models. Dose output 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 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 prompt neutron and photon emissions, transmitting between 14-42 percent of the open-field dose depending on the building characteristics.