1,720,972 research outputs found
Health physics calculation framework for environmental impact assessment of radiological contamination
Full text linkA fundamental step for safety assessment is the study and modeling of the radionuclide transfer through the environment up to reach and expose population to risk. In this vein we are working to provide a reliable and flexible computational framework which can be used for both retrospective and prospective calculations of radiation doses and human health effects, resulting from both routine and uncontrolled releases of radionuclides to the environment and from pre-existing environment contamination. The goal is to provide a multipurpose computational tool to be used for siting facilities, environmental impact statements, and safety analysis reports. The code can handle: external exposure from finite or infinite atmospheric plumes; external exposure from contaminated soil, sediments, and water; external exposure from special geometries; and internal exposures from inhalation, inadvertent intake of soil, consumption of terrestrial foods, aquatic foods, drinking water, and animal products
The latest development and the new extended capabilities of the GENII-LIN soil transfer model
Full text linkSome years ago, we started developing an enhanced soil transport model, where short life nuclide contributions were accurately accounted, Teodori (2017). The aim was to extend the code capabilities to handle incidental release of contaminant to soil, by evaluating exposure since the very beginning of the contamination event, before the radioactive decay chain equilibrium is reached. In this years those new capabilities have been widely extended: the leaching model has been reworked in a more physically based manner, by using a more sophisticated formulation for the transfer rate; the soil compartment number has been increased, by introducing an intermediate layer; bioturbation by animals now also affects downward transfer of materials, by modifying the leaching constant and by void collapse; plant transfer contributes to contaminant redistribution through all soil depth by plant recycle
The new external dose rate factor generator of the GENII-LIN health physics code
No full textIn environmental radiation protection, when external exposure is considered, it is common practice to refer to simplified and idealized exposure geometries: submersion in a semi-infinite cloud, exposure to ground surface contamination and exposure to soil contaminated to an infinite depth. In this vein, the GENII-LIN code offers pre-built dose rate factor libraries for commonly used standard geometries. For all scenarios where these generalized geometries are to be considered not adequate, the GENII-LIN software system provides its own external dose rate factor generator that allows for the creation of special dose rate factors for arbitrarily shaped sources. The GENII-LIN external dose rate factor generator is a modified and enhanced version of the well known shielding code ISOSHLD. In this work, we want to describe its latest development and its improved capabilities
Digital twins in dosimetry and radiotherapy, a survey and some applications
No full textDigital Twins (DTs) are emerging as a powerful tool in several applications, including Dosimetry and Radiotherapy (RT). Indeed, DTs have increased their effectiveness, up to the point that can be considered as virtual replicas of physical objects, processes, or systems. Through predictive modeling, DTs can determine optimal doses in radiation therapy, assist in defining personalized treatment schedules for individual patients, and monitor treatment responses. Moreover, DTs play a pivotal role in designing radioisotope production processes in the field of nuclear medicine. This can help to ensure the most effective treatment possible while minimizing the risk of side effects. As a frontier case example, DTs can be employed in the analysis of a possible new source for flash radiotherapy worth with respect to their effectiveness parameters like Radio-Biological Effectiveness (RBE) or cell Surviving Fraction (SF). Flash techniques involve the delivery of a high dose of radiation in a short time, reducing damage to surrounding healthy tissue while possibly increasing damage to malignant cells. DTs could be used to simulate and collect data about particle interactions with the treated tissues, optimizing the treatment and leading to improved outcomes. The most powerful tools that can be applied in DTs development are the Monte Carlo (MC) codes, particularly those with the highest capability of a detailed material/geometry description through an automatized spatial discretization approach like the one based on Unstructured Mesh (UM), allowing a common mathematical domain for both particle/radiation transport and thermal, fluid-dynamics and mechanical simulations. What comes out from various kind of applications is a common ground in terms of data management, phase space identification, simulation tools, that can be easily recognized even if spanning from cell response to technological devices, making realistic the perspective of the setup of general optimization procedures
The effect of geometry on the fluorescence radiation field
No full textIn X-ray fluorescence spectroscopy, a photon beam is focused on the sample to induce the production of characteristic radiation carrying useful information on the composition of the target. Even if the interpretation of the measurement is simple, the quantification of the total emitted intensity is not straightforward because the primary photons are produced deep in the target and the radiation reaching the detector can be sensibly modified by the interactions which the photons undergo before leaving the specimen. In this work we show that the geometry of the system plays an important role in determining the properties of the radiation field. © 2001 Elsevier Science Ltd. All rights reserved
Kinetic Theory Study of Pressure and Equation of State in a Strongly Degenerate Fermi Gas
No full textStarting from the Fermi-Dirac distribution fuunction, Kinetic Theory prescriptions are applied to express number density and pressure as integrals, which are then solved for nonvanishing temperature. The results are then combined to arrive at an equation of state, given in closed form, yielding pressure as a function of number density
Modelling of radiation transport
No full textIn the application of nuclear radiation, the problem of the transport of photons and neutral or charged particles through the matter is central for understanding the physics of the process, for a correct interpretation of the measurement and for a convenient choice of instrumental operating conditions. This paper, in the first part, is intended as a survey of the genesis of the transport equations, which describe the phenomenon of the diffusion of the particles. With a regressive procedure, it is possible to obtain the commonly used transport equations directly from Liouville equation; the approximations that must always been involved can be related to two dimensionless parameters if suitable dimesionless variables are introduced. In the second part, approximate solutions of Boltzmann and Fokker-Planck equations are given for particular physical situations of interest in X-ray spectroscopy and electron microprobe analysis. © 2003 Elsevier B.V. All rights reserved
3D modelling of unpolarized photon diffusion using the integral form of the transport equation
No full textThe 3D scalar transport equation for unpolarized photons is used to give a detailed description of the fluorescence photon diffusion from a homogeneous slab. As an example, the paper considers, with a complete 3D spatial description in plane geometry, the distribution both in physical and momentum space of the primary photons induced by a narrow radiation beam crossing the slab. Then it is shown how the 3D geometry influences the shape of the continuous spectra due to a second Compton collision which modifies the distribution of the primaries due to photoelectric effect. The possibility of isolating the effect of a particular interaction is one of the strengths of the multiple-scattering scheme in the framework of transport techniques, which allows a better understanding of photon diffusion. In order to evaluate the effects of boundary conditions, the integral transport equation is used instead of the integro-differential equation, which has the advantage of treating the flow of photons from the outer space as an external source. The results are compared with those obtained for a half-infinite medium uniformly irradiated with a plane infinite slant source of monochromatic photons previously solved in 1D. Copyright © 1999 John Wiley & Sons, Ltd
A molecular dynamics simulation of charged particle transfer through metals: The role of multi-body collisions
No full textExploring the transport of high-energy charged particles through solid matter is crucial in various domains, such as radiation shielding and radiation protection. The primary focus lies in accurately quantifying energy deposition and understanding induced reactions. However, addressing this through the solution of the transfer equation poses challenges, largely stemming from the long-range Coulomb interactions that involve multiple particles concurrently. When charged particles traverse dense matter, overlooking multi-body collisions results
in notably inaccurate approximations.
In a prior study Molinari and Teodori (2015), we delved into a numerical simulation of the Fokker–Planck equation, incorporating contributions from multi-body collisions. This model facilitated the precise calculation of point-wise energy and momentum transferred to the target, specifically from high-energy protons. Over the years, the scope of the model has expanded to encompass the description of electron transfer as well. This extension allows for a more comprehensive understanding of the intricate dynamics involved in the interaction of high-energy charged particles with solid materials
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