Calculation Of Buildup Factors Research Articles

Monte Carlo calculation of buildup factors for 50 keV–15 MeV photons in tungsten up to 15 mean free paths

Exposure buildup factor values of tungsten for a point isotropic source in energy range 0.05–15 MeV up to 15 mfp are computed using Monte Carlo N-Particle code. Buildup factors of this study and ANSI/ANS-6.4.3 at some selected energies and penetration depths are compared. Highest discrepancies are observed for high-energy and/or high penetration depths. Highest error occurs at 15 MeV, amounting to 32%. In the energy range 2–6 MeV, our results show smaller values for all penetration depths and vice versa at higher energies.

The buildup factor calculations of concrete with different proportions of CRT based on a BP neural network by MCNP

ABSTRACT Cathode ray tubes (CRTs) are glass materials that contain harmful heavy metal elements such as lead . CRTs have been widely used in electronic products sets for decades. At present, these discarded CRTs endanger the environment. Because the high-density heavy metal elements in CRTs have a good shielding effect for X/γ rays, these raw materials have become a good choice to produce radiation-proof concrete. In the selection and use of shielding materials, the buildup factor must be considered. Monte Carlo code MCNP is used to calculate the exposure buildup factor (EBF) of concrete with different proportions of CRT fragments in the photon energy range of 0.015–15 MeV for shielding thicknesses of up to 20 mean free paths (mfp). Back-propagation (BP) neural network is proposed to predict the EBF, and the prediction effect is evaluated, reliability of this method is verified; the average error is 3.4%, and the maximum error is 9.1%. Using this method, the EBF of concrete with an arbitrary proportion of CRTs, any energy level and any shielding thickness can be quickly obtained in the ranges of the parameters of the neural network training set (0.015–15 MeV and 0–20 mfp in this paper).

EXABCal: A program for calculating photon exposure and energy absorption buildup factors

This research presents a new Windows compatible program (EXABCal) for photon exposure and energy absorption buildup factors for standard energy grid from 0.015- 15 MeV for elements, mixtures and compound. This program was written using Python programming language and the calculation of buildup factors was based on the well-known Geometric Progression (GP) fitting procedure. The equivalent atomic numbers and GP fitting parameters of mixtures and compounds can also be evaluated using this program. The program has been used to evaluate the photon exposure and energy absorption buildup factors for standard energy grid from 0.015- 15 MeV for water, air and concrete, compared with values from the American Nuclear Society (ANS) standard reference data (ANSI-6.4.3) and found to be of high accurate with minimal errors. The program is fast and easy to use and will be of valuable interest to medical Physicist, radiation Physicists, Radiation shielding design engineers, students, teachers and researchers and other experts working in areas where nuclear radiation is applied.

Total Ambient Dose Equivalent Buildup Factors for Portland Concrete.

In this work, total ambient dose equivalent buildup factors for Portland concrete slabs are calculated using Monte Carlo n-particle software MCNP6™. Buildup factor calculations could approach intractable solutions in general as they depend on a large number of variables. These include geometry, source energy, and the composition of the shield (which itself can be heterogeneous). In this work, Cf and americium-beryllium sources are considered, as well as monoenergetic incident neutrons in the energy range from 0.025 eV to 14 MeV at multiple incident angles. The shielding material of interest was taken to be standard Portland concrete. The transmitted neutron and gamma-ray ambient dose rate was calculated first and then used for total buildup factor calculations. Perhaps more telling than the calculated theoretical buildup factor, the credible dispersion in expected resultant buildup factors was also calculated by conducting a very rudimentary sensitivity analysis, varying the water content in the first case and then varying the amount of aggregate. An additional aim of this work is to provide a model based on the machine-learning technique called the support vector regression method in the calculation of concrete buildup factors.

Effective atomic number and buildup factor calculations for metal nano particle doped polymer gel

The present study aimed at verifying the water equivalency of the PAGAT gel and metal nano particle (different concentration of gold and silver) PAGAT (MPAGAT) gel in terms of effective atomic number (Zeff). In addition to Zeff, energy absorption buildup factor (EABF) and exposure buildup factor (EBF) have been calculated for MPAGAT. Auto-Zeff computer program was used to calculate the effective atomic number for MPAGAT in the energy region 10 keV to 1 GeV. EABF and EBF were calculated by using geometric progression (GP) fitting formula in the energy region from 0.015 to 15 MeV up to penetration depths of 40 mean free path. Mass attenuation coefficient of MPAGAT gel was obtained by the XCOM program and the results were compared with Monte Carlo simulation. It has been found that Au and Ag doped PAGAT gels show excellent water equivalency than undoped PAGAT gel at dopant concentrations of 0.1, 0.5 and 1 mM. From the results, it was noted that the EABF and EBF were significantly varied with respect to photon energy and chemical composition of given PAGAT gel with different concentration of metal nano particle. Since mass attenuation coefficients were used to obtain Zeff and EABF, the reliability of the mass attenuation coefficient data were cross checked with Monte Carlo simulation, and a good agreement was obtained between XCOM and Monte Carlo simulation.

Farklı metotlar ile sürekli enerji aralığında toplam foton etkileşimi için farklı tipteki malzemelerin etkin atom numarası ve elektron yoğunluklarının hesaplanması

Effective atomic number ( Z eff ) and electron density ( N eff ) are convenient parameters used to characterise the radiation response of a multi-element material in the technical and industrial applications, radiation shielding design, absorbed dose and build-up factor calculations. Thus, it is very significant to choose accurate method to determine these parameters unambiguously. In the present study, effective atomic numbers and electron densities of different types of materials have been calculated by using a direct method and an interpolation method for total photon interaction in the energy region of 1 keV to 100 GeV. In addition, agreements and disagreements of the used methods have been discussed, and from the results, significant variations have been observed between the methods used to compute for the materials in the different energy regions.

Comparison of the methods available for calculation of effective atomic numbers and effective electron densities in different types of materials for total photon interaction in the energy region 1 keV - 100 GeV

Effective atomic number, Z eff , and electron density, N eff , are convenient parameters used to characterise the radiation response of a multi-element material in the technical and industrial applications, radiation shielding design, absorbed dose and build-up factor calculations. Thus, it is very significant to choose accurate method to determine these parameters unquestioningly. In the present study, effective atomic numbers and electron densities of different types of materials have been calculated by using a direct method and an interpolation method for total photon interaction in the energy region of 1 keV to 100 GeV. In addition, agreements and disagreements of the used methods have been discussed, and from the results, significant variations have been observed between the methods used to compute for the materials in the different energy regions.

Finite and infinite system gamma ray buildup factor calculations with detailed physics

Examination of physical interactions of photons in materials is a significant subject for buildup factor studies. In most of the buildup calculations, by default, coherent (Rayleigh) scattering is ignored and the Compton scattering is modeled by free-electron Klein–Nishina formula with “simple physics” treatment. In this work, photon buildup factors are calculated for many different cases including “detailed physics” by taking into account coherent and bound-electron Compton scatterings with the Monte Carlo code, MCNP5, and the results are compared with the literature values. They are computed for point isotropic photon sources up to depths of 20 mean free paths and at the three photon energies most widely used (0.06, 0.6 and 6MeV). Calculations are made for both finite and infinite homogeneous ordinary water media. It is concluded that Coherent scattering is very dominant at low energies and for deep penetrations and assumed physical approximation (simple/detailed, finite/infinite) is the critical point for determining shielding material dimensions. After all, it can be stated that all parametric assumptions should be clearly given and indicated in the tabulation of photon buildup factors.

Gamma-ray energy buildup factor calculations and shielding effects of some Jordanian building structures

Abstract The shielding properties of three different construction styles, and building materials, commonly used in Jordan, were evaluated using parameters such as attenuation coefficients, equivalent atomic number, penetration depth and energy buildup factor. Geometric progression (GP) method was used to calculate gamma-ray energy buildup factors of limestone, concrete, bricks, cement plaster and air for the energy range 0.05–3 MeV, and penetration depths up to 40 mfp. It has been observed that among the examined building materials, limestone offers highest value for equivalent atomic number and linear attenuation coefficient and the lowest values for penetration depth and energy buildup factor. The obtained buildup factors were used as basic data to establish the total equivalent energy buildup factors for three different multilayer construction styles using an iterative method. The three styles were then compared in terms of fractional transmission of photons at different incident photon energies. It is concluded that, in case of any nuclear accident, large multistory buildings with five layers exterior walls, style A, could effectively attenuate radiation more than small dwellings of any construction style.

Generation and Application of Bremsstrahlung Production Data Calculated by EGS4 Code

Bremsstrahlung radiation (hereinafter referred to as bremsstrahlung) production data are needed in the calculation of buildup factors, including the contribution of secondary photons by the photon transport codes, which do not handle electron transport. The emission of bremsstrahlung is treated as exactly as possible by the introduction of EGS4 results. The bremsstrahlung production data by pair-created electrons per pair creation reaction and Compton scattered electrons per Compton scattering are evaluated for 26 elements from hydrogen to uranium and four compounds and mixtures of water, concrete, air, and lead glass. The error estimation of bremsstrahlung contribution to buildup factors by the invariant embedding (IE) method coupled with these bremsstrahlung data is coincident with fully transported results by the EGS4 code within ˜5%. By the introduction of bremsstrahlung production data into IE methods, we can calculate buildup factors included by the contribution of those with good accuracy up to deep penetration. By the interpolation and mixture of bremsstrahlung production data for each element, we can evaluate the data of the element or mixture whose data are not evaluated by the EGS4 code.

Calculation of Photon Exposure and Ambient Dose Slant-Path Buildup Factors for Radiological Assessment

Slant-path photon buildup factors for nine radiation shielding materials (air, aluminum, concrete, iron, lead, leaded glass, polyethylene, stainless steel, and water) are calculated with the most recent cross-section data available using Monte Carlo and discrete ordinates methods. Discrete ordinates calculations use a 244-group energy structure based on previous research at Los Alamos National Laboratory (LANL) and focus on the effects of group widths in multigroup calculations for low-energy photons. Buildup-factor calculations in discrete ordinates benefit from coupled photon/electron cross sections to account for secondary photon effects. Also, ambient dose equivalent buildup factors were analyzed at lower energies where corresponding response functions do not exist in the literature. The results of these studies are directly applicable to radiation safety at LANL, where the dose-modeling code PANDEMONIUM is used to estimate worker dose in plutonium-handling facilities. Buildup factors determined in this work will be used to enhance the code’s modeling capabilities but also should be of general interest to the radiation shielding community.

Support vector regression model for the estimation of γ-ray buildup factors for multi-layer shields

The accuracy of the point-kernel method, which is a widely used practical tool for γ-ray shielding calculations, strongly depends on the quality and accuracy of buildup factors used in the calculations. Although, buildup factors for single-layer shields comprised of a single material are well known, calculation of buildup factors for stratified shields, each layer comprised of different material or a combination of materials, represent a complex physical problem. Recently, a new compact mathematical model for multi-layer shield buildup factor representation has been suggested for embedding into point-kernel codes thus replacing traditionally generated complex mathematical expressions. The new regression model is based on support vector machines learning technique, which is an extension of Statistical Learning Theory. The paper gives complete description of the novel methodology with results pertaining to realistic engineering multi-layer shielding geometries. The results based on support vector regression machine learning confirm that this approach provides a framework for general, accurate and computationally acceptable multi-layer buildup factor model.

Gamma-Ray Buildup Factors for a Point Isotropic Source in the Single Layer Shield by Using BERMUDA Code

In order to modify the standard data of gamma-ray buildup factors for a point isotropic source in the single layer, the applicability of the direct integration method code BERMUDA to buildup factor calculations was surveyed. In this code, group-angle transfer matrix of photons is calculated by numerically integrating the Klein-Nishina formula for Compton scattering taking the energy-angle correlation into account. In the low energy region, the four K-shell fluorescence are considered whose isotropic emission intensity can be calculated from the primary photon intensity, the K-shell absorption cross section data and fluorescence yield. In the higher energy region for high-Z materials, the Bremsstrahlung is considered whose energy-angle production correlation matrixes were obtained by EGS4 code. The exposure buildup factors of lead for low energy photons calculated by using BERMUDA code without and with fluorescence were good agreement with those by EGS4 and PALLAS codes. Those of lead for high energy photons without Bremsstrahlung were also good agreement with those by EGS4 and PALLAS codes, but those with Bremsstrahlung were smaller than those by EGS4 code.

An historical review and current status of buildup factor calculations and applications

The γ-ray buildup factor is a multiplicative factor which corrects the response to uncollided photons so as to include the contribution of the scattered photons. Buildup factors are important data implemented in point kernel codes for use in shield design, together with attenuation coefficients. The Goldstein-Wilkins buildup factors calculated with the moments in 1954 were used as standard data until recently, but new and improved data filling present needs are available based on the latest cross sections and include the secondary radiation contributions. A new fitting formula, called Geometric Progression, was developed to reproduce the data in codes used for shield design . This formula can reproduce the data over the full range of distance, energy and atomic number within a few percent.

Gamma ray buildup factor calculations for iron by the discrete ordinates code XSDRNPM-S

Air kerma buildup factors for iron are calculated by the discrete ordinates code XSDRNPM-S for an isotropic point source in a homogeneous medium. By comparing the results with buildup factors from literature, conditions for gamma ray deep penetration calculations are retrieved. It turned out that many energy groups and an extremely fine space and angular mesh are needed to achieve reasonable accurate results. Because of these requirements, it is very difficult to calculate buildup factors up to 40 mfp shield thickness for energies above 5 MeV. Below this energy, calculated buildup factors agree with literature values within 10%, approximately, which seems quite reasonable.

Empirical formulae for build-up factor calculations in wide conical γ-ray beams

The work deals with build up factors for the number of photons and for the exposure in wide conical γ-ray beams penetrating through iron slabs. The formulae for calculation of build up factor values and comparison of computed results with the experimental ones are presented.

The use of the Monte Carlo method for the calculation of build-up factors in wide conical gamma-radiation beams

The values of the build-up factors for the number of photons are presented in this paper. The results were obtained for the number of photons in wide conical gamma-ray beams penetrating through various material slabs. The dependence of the build-up factor on the thickness of the material slabs were computed by the Monte Carlo method.

Moments Method Calculation of Buildup Factors for Point Isotropic Monoenergetic Gamma-Ray Sources at Depths Greater than 20 Mean-Free-Paths

A method of extending moments method calculations for monoenergetic, point isotropic gamma ray sources to depths of approximately 50 mean-free-paths is described. Sample calculations are given for water and aluminum. A method of error analysis recently developed by Spencer suggests that for the range from 10 to ∼50 mean-free-paths, the errors associated with the reconstruction of the flux from moments are generally <1%. Comparisons are made between the asymptotic, deep penetration trend of the calculated results and the trend predicted by a theory developed by Fano.

Calculation of buildup factors at deep penetrations

Calculation of buildup factors at deep penetrations

Calculation of buildup factors for?-radiation from nonstationary sources

Calculation of buildup factors for?-radiation from nonstationary sources