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The displacement mean-square parameters X²(t), Y²(t) and Z²(t) need to be increasing functions of time. In a stable and homogeneous field of turbulence, the variances of Lagrangian velocity fluctuations must be equal to the corresponding Eulerian velocity variances and independent of time. The mean-square particle displacement rises proportionately to the square of the diffusion time t for small diffusion times. The mean-square diffusion finally becomes proportional to the diffusion time (t) and the Lagrangian integral time scale (TiL) for long diffusion times. The three-dimensional advectiondiffusion equation and Gaussian model are computed using these dispersion values. The results of these concentrations are contrasted with Iodine-131 experimental data that was gathered at the Egyptian Atomic Energy Authority under steady conditions. [ABSTRACT FROM AUTHOR]

The proposed concentrations model was compared to observed data from air diffusion studies for hexafluoride (SF6) conducted in the northern area of Copenhagen, Denmark, and earlier work for the Gaussian puff model. The predicted concentrations and earlier studies were found to be within a factor of two of each other, indicating that the predicted data is compatible with the observed concentrations data. Under unstable conditions, the statistical statistics show a reasonable agreement between the expected and observed concentrations at the Copenhagen Experimental. In contrast to the previous work's results, which had an NMSE of 0.3 and an FB of 0.21, we discovered that the data obtained using the statistical method had an NMSE of 0.2 and an FB of 0.25. The projected COR is 0.95, compared to 0.97 in a previous computation. The observed concentration data was 88% of the expected value, compared to 78% in previous research. The expected data are consistent with the observed concentration measurements. When compared to previous work, the Copenhagen experiment was conducted under unstable conditions, and statistical data show good agreement between predicted and observed concentrations. [ABSTRACT FROM AUTHOR]

The advection-Diffusion Equation in three dimensions was solved using the Separation variable, Substitution and Laplace transform methods, taking into account that eddy diffusivity along the horizontal, lateral coordinates and wind velocity are constant respectively, while the vertical eddy diffusivity is a function of the vertical height z, Monin-Obukhov length L friction velocity at different emission rate and operation of iodine (I-131) in an unstable condition. We took the measured data from Inshas, Cairo, Egypt and compared the concentration of the calculated results with the results obtained from the solution equation at heights of 0.7, 27, and 43 meters. We found that all models are within a factor of two with the observed data from statistical evaluations in unstable conditions, we found that all models fell into a factor of two with the observed data. Whereas with NMSE and FB, the current models correlate better with the observed data. [ABSTRACT FROM AUTHOR]

This work aims to determine the maximum concentration and downwind distance at the earth's surface in two methods Briggs and standard for two conditions are slightly unstable and neutral by using the Gaussian equation at different effective heights and wind seeped at (8.9, 8.5 and 8 m/s) under lateral and vertical dispersion coefficient measurement. [ABSTRACT FROM AUTHOR]

The investigated work aims to calculate the concentration of different isotopes through short downwind distances. A theoretical model was designed to calculate the isotope concentration in the wind. The mathematical calculation depends on wind speed, decay distance and the dilution factor to get the concentration of isotopes (131I, 133I, 135I and 137Cs) detected in wind at different distances from a nuclear power station. There is a good agreement between the calculated and observed concentrations of 131I, 133I, 135I and 137Cs. [ABSTRACT FROM AUTHOR]

A short range model calculating ground-level concentration from elevated sources is estimated, which realized a Fickian-type formula, taking the source and mixing height as functions of the wind velocity and eddy diffusivity profiles. The model estimated with an exact solution of the advection diffusion equation as compared with experimental ground level concentrations using meteorological data collected near the ground. [ABSTRACT FROM AUTHOR]

A total of 37 different soil samples and 22 air samples were collected from natural industrial sources. The air samples were collected at a height of 1 m above the ground on 10.4 cm diameter filter paper (with a desired collection efficiency) using a high-volume air sampler. The activity concentration levels of naturally occurring radionuclides such as the U-238 series and Th-232 series were measured using high-resolution γ-ray spectrometry. Specific activities ranged from 3.9 to 8574 Bq/kg for different types of rocks for the U-238 series and from 2.9 to 6431 Bq/kg for the Th-232 series. The activity concentration for the air samples ranged from 0.29 to 0.56 Bq/m³ for the U-238 series and from 0.1 to 0.17 Bq/m³ for the Th-232 series at a 1 m circle. The γ-absorbed dose rates (nGy/h) due to contaminated ground and air submersion were calculated. The equivalent dose (mSv/y) for each organ was calculated. Then, the total annual effective dose (mSv/y) to workers due to the U-238 series and Th-232 series was estimated to be 0.6014 mSv/y. [ABSTRACT FROM AUTHOR]