The human health and environmental effects following a postulated accidental release of radioactive material to the environment have been a public and regulatory concern since the early development of nuclear technology. These postulated releases have been researched extensively to better understand the potential risks for accident mitigation and emergency planning purposes. The objective of this investigation is to provide an updated technical basis for contemporary building shielding factors for the US housing stock. Building shielding factors quantify the protection from ionising radiation provided by a certain building type. Much of the current data used to determine the quality of shielding around nuclear facilities and urban environments is based on simplistic point-kernel calculations for 1950s era suburbia and is no longer applicable to the densely populated urban environments realised today. To analyse a building's radiation shielding properties, the ideal approach would be to subject a variety of building types to various radioactive sources and measure the radiation levels in and around the building. While this is not entirely practicable, this research analyses the shielding effectiveness of ten structurally significant US housing-stock models (walls and roofs) important for shielding against ionising radiation. The experimental data are used to benchmark computational models to calculate the shielding effectiveness of various building configurations under investigation from two types of realistic environmental source terms. Various combinations of these ten shielding models can be used to develop full-scale computational housing-unit models for building shielding factor calculations representing 69.6 million housing units (61.3%) in the United States. Results produced in this investigation provide a comparison between theory and experiment behind building shielding factor methodology.

This paper presents validated building shielding factors designed for contemporary US housing-stock under an idealized, yet realistic, exposure scenario within a semi-infinite cloud of radioactive material. The building shielding factors are intended for use in emergency planning and level three probabilistic risk assessments for a variety of postulated radiological events in which a realistic assessment is necessary to better understand the potential risks for accident mitigation and emergency response planning. Factors are calculated from detailed computational housing-units models using the general-purpose Monte Carlo N-Particle computational code, MCNP5, and are benchmarked from a series of narrow- and broad-beam measurements analyzing the shielding effectiveness of ten common general-purpose construction materials and ten shielding models representing the primary weather barriers (walls and roofs) of likely US housing-stock. Each model was designed to scale based on common residential construction practices and include, to the extent practical, all structurally significant components important for shielding against ionizing radiation. Calculations were performed for floor-specific locations as well as for computing a weighted-average representative building shielding factor for single- and multi-story detached homes, both with and without basement, as well for single-wide manufactured housing-units.

This paper presents validated building shielding factors designed for contemporary US housing-stock under an idealized, yet realistic, exposure scenario from contaminant deposition on the roof and surrounding surfaces. The building shielding factors are intended for use in emergency planning and level three probabilistic risk assessments for a variety of postulated radiological events in which a realistic assessment is necessary to better understand the potential risks for accident mitigation and emergency response planning. Factors are calculated from detailed computational housing-units models using the general-purpose Monte Carlo N-Particle computational code, MCNP5, and are benchmarked from a series of narrow- and broad-beam measurements analyzing the shielding effectiveness of ten common general-purpose construction materials and ten shielding models representing the primary weather barriers (walls and roofs) of likely US housing-stock. Each model was designed to scale based on common residential construction practices and include, to the extent practical, all structurally significant components important for shielding against ionizing radiation. Calculations were performed for floor-specific locations from contaminant deposition on the roof and surrounding ground as well as for computing a weighted-average representative building shielding factor for single- and multi-story detached homes, both with and without basement as well for single-wide manufactured housing-unit.

We describe a simplified method for calculating both building protection- and shielding-factors for generic one- and two-story housing-unit models that are source-term dependent. Typically, radionuclide-independent factors are applied generically to external dose coefficients to account for the radiation shielding effects of indoor residences. In reality, the shielding effectiveness of each housing-unit would change over time as the radionuclide mixture and gamma-ray energy spectrum change due to physical effects such as deposition, radioactive decay, weathering effects, and decontamination efforts. Thus, it is necessary to develop factors designed for multiple photon energy spectrums to generate a more realistic estimate of the shielding effectiveness of a particular building. It is impractical to develop factors specific to a spectrum of photons emitted by each radionuclide of interest. Therefore, Monte Carlo simulations have been performed for sixteen monoenergetic photon energies from 0.10 to 3.0 MeV to characterize the 3D radiation fluence through each housing-unit produced by two idealized, yet realistic, environmental exposure scenarios. Results of these simulations were then used to develop fitted logarithmic functions (extrapolated to 0.0 MeV) to correlate an estimated factor to any monoenergetic photon energy up to 3.0 MeV. To verify these functions, another series of Monte Carlo simulations were performed for a select set of radionuclides to develop radionuclide-specific building protection- and shielding-factors. Good agreement is achieved between factors estimated using the presented functions and those calculated directly using Monte Carlo methods. Factors predicted by these functions are found to be in general agreement with other study results reported on similar structures which applied various computational methods and source-terms. This study only focuses on generic one- and two-story homes to provide a practical application that can contribute to improve the preparedness for and the response to a nuclear or radiological emergency.

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