Indoor concentrations of radioactive aerosols from nuclear accidents.

In previous studies, some of the important factors that affect the spread of radioactive aerosols into indoors were considered. The studies were based on a new CFD approach and provided good descriptions for the deposition of aerosol particles inside small spaces and the penetration of aerosols into buildings through wall cracks. In this article, an application of those studies is implemented, where all the graphical relations that are required to estimate the indoor concentrations of radioactive aerosols from nuclear accidents are provided. This includes the deposition velocities, deposition rate, and the penetration factor. Particular interest is in the Fukushima-Daiichi nuclear power plant accident that took place in Japan in 2011. The aerosols carrying the radioiodine iodine-131 and the radiocesium cesium-134 and cesium-137 are studied. Based on the model's assumptions, and assuming steady-state air concentrations, the radioactive aerosols' concentrations in indoor air are about 97% of the concentrations in outdoor air. The applications demonstrate the model to be convenient and practical.

MODELLING THE INDOOR RADIATION DOSES: A REVIEW AND PERSPECTIVE.

Theoretical models to calculate the indoor gamma and radon doses are reviewed, refined and applied. The model for gamma doses is built based on the relative effects of the different room elements that control the amount of radiation. The relative doses are calculated by the MCNP5 simulation software. The gamma sources are due to the natural radiation from the 238U series, 232Th series and the radionuclide 40K. An application of the model that involves all the considered elements is demonstrated. The elements are the thickness of the walls, the density of the building material, the dimensions of the room, the existence of other rooms surrounding the room under study, the split of some walls into two portions, the existence of internal thin partial walls inside the room, the existence of windows and doors, and the incompleteness of the secular equilibrium in the 238U decay series due to radon release from the building materials. The model for radon doses is built based on Fick's laws. The radon surface exhalation rate from a wall and that from a building material sample are calculated from a one-dimension and three-dimension diffusion description by Fick's second law, respectively. The two rates are compared, and the radon indoor concentration and inhalation doses are formulated.

Utilizing Monte Carlo Computations to Estimate Radiation Doses From Some Cosmetics.

Monte Carlo simulations are exploited to assess the annual radiation doses from some cosmetics due to the radioactive decay series of U and Th and to the radionuclide K. The measured radioactivity concentrations are entered into simulation codes modeled and implemented by Monte Carlo n-particle software. The concentrations are found to be relatively high for a large number of the samples. The Monte Carlo-simulated gamma-radiation annual doses are compared with the results of another theoretical approach. Both methods are in good agreement with each other and predict low doses from use of cosmetics.

Radon Release and Its Simulated Effect on Radiation Doses.

One of the main factors that affect the uncertainty in calculating the gamma-radiation absorbed dose rate inside a room is the variation in the degree of secular equilibrium of the considered radioactive series. A component of this factor, considered in this paper, is the release of radon (Rn) from building materials to the living space of the room. This release takes place through different steps. These steps are represented and mathematically formulated. The diffusion of radon inside the material is described by Fick's second law. Some of the factors affecting the radon release rate (e.g. covering walls, moisture, structure of the building materials, etc.) are discussed. This scheme is used to study the impact of radon release on the gamma-radiation absorbed dose rate inside a room. The investigation is carried out by exploiting the MCNP simulation software. Different building materials are considered with different radon release rates. Special care is given to Rn due to its relatively higher half-life and higher indoor concentration than the other radon isotopes. The results of the presented model show that the radon release is of a significant impact in some building materials.