Kerma Coefficients Research Articles

Evaluating the Kerma coefficients relevant to various water-equivalent materials at different photon energies

To investigate the water equivalency of some solid phantoms, relevant Kerma coefficients were determined through both Monte Carlo (MC) simulation and analytical approaches over a wide range of photon energies ranging from 1 keV to 20 MeV.MCNPX MC Code was employed to simulate the Kerma coefficients for A-150, PMMA, Polystyrene, Solid Water (RMI 457), Solid Phantom (RW3), Virtual water, Solid Water (WT1), and Water Equivalent (Wte) solid phantoms. Kerma coefficients were also theoretically calculated using the mass energy absorption coefficients at different photon energies ranging from 1 keV to 20 MeV. Obtained Kerma coefficients for considered solid phantoms were also compared with those of water to find which material shows the best water-equivalency.Calculated Kerma coefficients by MC simulation were in a good agreement with those calculated via an analytical method which no statistically significant differences were observed among simulated and analytically calculated Kerma coefficients (p-value>0.05). Solid water (RMI 457) showed the best water-equivalency among studied plastic phantoms for radiology and radiotherapy quality assurance purposes. From the results, the Kerma coefficients for solid phantoms are highly dependent on photon energy.

Analytical and fine Monte Carlo Kerma coefficients evaluation for a wide range photon energy relevant to some chemotherapy agents

Simultaneously combination of chemotherapy drugs and ionizing radiations has become a common treatment method for advanced cancers. Tumor irradiation in presence of chemotherapy drugs can affect deposited energy within tissue. Hence, to evaluate how chemotherapy drugs affect the absorbed dose within tissues during chemoradiotherapy, Kerma coefficient values for 26 anti-cancer agents were estimated for photon energies ranging from 1 keV to 20 MeV through analytical analysis and Monte Carlo (MC) simulation approaches.Estimation of Kerma coefficients through MC simulation relevant to different chemotherapy drugs was performed with MCNPX V.2.6.0 MC code. Besides, Kerma coefficient values were calculated using the reported mass energy absorption coefficients, as the theoretical method. Significant statistical test was also employed to evaluate the accordance of obtained Kerma coefficients by two considered methods.Simulation results were consistent with evaluated Kerma coefficients by analytical method which minimum and maximum mean relative differences are found for Bevacizumab and Methotrexate, respectively. Furthermore, a significant correlation is found with chemical composition of selected chemotherapy drugs at considered photon energy range. Fluorouracil showed the closest Kerma ratio to unity among the studied anti-cancer drugs. Kerma coefficient ratios for most of selected drugs were close to unity at higher energy regions (100 keV–20 MeV) while greater values were found at lower photon energies (below 100 keV).From the results, presence of these anti-cancer agents can impact Kerma coefficient and subsequently alter the absorbed dose within tissue during the cancer treatment with chemoradiotherapy technique.

Accurate gamma-ray dose measurement up to 10 MeV by glass dosimeter with a sensitivity control filter for BNCT

Glass dosimeters are very useful and convenient detection elements in radiation dosimetry. In this study, this glass dosimeter was applied to a BNCT treatment field. Boron Neutron Capture Therapy (BNCT) is a next-generation radiation therapy that can selectively kill only cancer cells. In the BNCT treatment field, both neutrons and secondary gamma-rays are generated. In other words, it is a mixed radiation field of neutrons and gamma-rays. We thus proposed a novel method to measure only gamma-ray dose in the mixed field using two RPLGD (Radiophoto-luminescence Glass Dosimeter) and two sensitivity control filters in order to control the dose response of the filtered RPLGD to be proportional to the air kerma coefficients, even if the gamma-ray energy spectrum is unknown. As the filter material iron was selected, and it was finally confirmed that reproduction of the air kerma coefficients was excellent within an error of 5.3% in the entire energy range up to 10 MeV. In order to validate this method, irradiation experiments were carried out using standard gamma-ray sources. As the result, the measured doses were in acceptably good agreement with the theoretical calculation results by PHITS. In the irradiation experiment with a volume source in a nuclear fuel storage room, the measured dose rates showed larger compared with survey meter values. In conclusion, the results of the standard sources showed the feasibility of this method, however for the volume source the dependence of the gamma-ray incident angle on the dosimeter was found to be not neglected. In the next step, it will be necessary to design a thinner filter in order to suppress the effect of the incident angle.

Calculation of The Effects of Fly Ash in Concrete Samples Used as Construction Materials on Radiation Shielding Efficiency Using EGS4 Code

The aim of this study is to determine the effects of reducing cement and replacing it with fly ash in concrete samples used as construction materials on the radiation shielding efficiency. The radiation shielding effect of concrete samples was determined using the EGS4 code. By contrasting the outcomes with XCOM data, theoretical discussion was conducted. At gamma ray energies between 59.5 and 1332 keV, the mass attenuation coefficients (μ/ρ) of concrete samples mixed with fly ash were theoretically investigated using WinXCOM and EGS4. Then, several shielding parameters, including mean free path (MFP), half value layer (HVL), radiation protection efficiency (RPE), effective atomic number (Zeff), and gamma-ray kerma coefficients (kγ), were found using the mass attenuation coefficients. It has been noted that the parameters governing radiation shielding performance of concrete samples used as building materials are altered when cement is reduced and fly ash is substituted.

Calculation of radiation shielding parameters of YBa2Cu3O7 and Y3Ba5Cu8O18 superconductors for the energies from 122 to 1332 keV using EGS4 code

This Study aims to evaluate the radiation shielding efficiency of YBa2Cu3O7 and Y3Ba5Cu8O18 superconducting ceramics. In the current study, the radiation shielding efficiency of YBa2Cu3O7 and Y3Ba5Cu8O18 superconducting ceramics were calculated using the EGS4 code and discussed experimentally and theoretically by comparing with XCOM data. The mass attenuation coefficients (μ/ρ) for YBa2Cu3O7 and Y3Ba5Cu8O18 superconductors and their contents was investigated theoretically (EGS4 and WinXcom) and experimentally at gamma-ray energies from 122 to 1332 keV. The theoretical values have been computed in the energy range from 1 keV to 100 MeV using WinXcom program. Then, using the mass attenuation coefficients, it was determined some shielding parameters such as mean free path (MFP), half value layer (HVL), effective atomic number (Zeff), radiation protection efficiency (RPE) and gamma–ray kerma coefficients ((kγ). It has been seen that the theoretical and the empirical results were in agreement. The data and findings from this study can guide further research and development of shielding materials for gamma-ray and neutron shielding applications.

Radiation shielding properties of aluminium alloys

X-ray/gamma, neutron, electromagnetic and Bremsstrahlung shielding parameters were studied for the different aluminium alloys such as Al–Li, Duralumin, Hiduminium, Hydronalium, Italma, Magnalium, Ni–Ti–Al and Y-alloy. X-ray/gamma shielding properties such as mass attenuation coefficient, Half Value layer (HVL), Tenth Value layer (TVL), effective atomic number (), electron density (), build-up factors (BF), KERMA coefficient (KE), and radiation protection efficiency (RPE) of Al alloys of various compositions were studied. Shielding effectiveness for electromagnetic radiation at different frequency ranges from radio waves to infrared radiations is studied in the above-mentioned aluminium alloys. Further, we investigated neutron scattering lengths and cross sections for the above alloys. Bremsstrahlung shielding parameters such as Bremsstrahlung dose rate, probability of bremsstrahlung and bremstrahlung production efficiency were also studied. Bremsstrahlung's dose rate for the distinct β emitters corresponding to maximum energy are investigated for the different aluminium alloys. Thorough investigations reveal that Ni–Ti–Al aluminium alloy is found to be a good absorber of X-ray/γ radiation, neutron, electromagnetic and Bremsstrahlung radiations. As a consequence, we recommend Ni–Ti–Al as a good radiation shielding material among the aluminium alloys.

Calculation of the Effects of Silver (Ag) Dopant on Radiation Shielding Efficiency of BiPbSrCaCuO Superconductor Ceramics Using EGS4 Code

In the current study, the effects of silver (Ag) additive on the radiation shielding efficiency of BiPbSrCaCuO superconducting ceramics was calculated using the EGS4 code and discussed theoretically by comparison with XCOM data. The mass attenuation coefficients (µ/ρ) for BiPbSrCaCuO superconductor ceramics and their contents were investigated theoretically (WinXcom and EGS4) at gamma-ray energies ranging from 59.5 to 1332 keV. The theoretical values were computed in the energy range from 1 keV to 100 MeV using the WinXcom program. Then, using the mass attenuation coefficients, some shielding parameters were determined, such as the mean free path (MFP), the half value layer (HVL), the effective atomic number (Zeff), the radiation protection efficiency (RPE), the macroscopic fast neutron removal cross-sections (ΣR, cm−1) and the gamma-ray kerma coefficients (kγ). Theoretically, the results obtained with XCOM and EGS-4 were found to be in good agreement. The radiation shielding efficiency (RPE), neutron removal cross-section (ΣR, cm−1), maximum and semi-valent layer (HVL), and mean free path (MFP) values were found to be smaller for BiPbSrCaCuO superconducting ceramics as the silver (Ag) contribution was increased. Data from this study can guide further research and development of shielding materials for gamma-ray and neutron shielding.

Synthesis and Characterization of Zinc-Lead-Phosphate Glasses Doped with Europium for Radiation Shielding

Appropriate glass systems can provide efficient transparent radiation shielding. The current study involved the preparation of the glass system with a composition of xEu2O3-(15-x)ZnO-10CaO-35PbO-40P2O5 (where x = 0, 1, 2, 3, and 4 wt.% Eu2O3). The formation of the glass phase was confirmed using X-ray diffraction (XRD). The study analyzed physical and structural parameters, such as optical conductivity (σopt), refractive index (n), and optical band gap (Eg), with the amount of Eu2O3. The findings indicate that the optical band gap increased as the Eu2O3 content increased. Additionally, a decrease in Urbach energy (EU) was observed, suggesting an improvement in the orderliness of the glass. The study also determined various parameters for gamma-ray shielding, including mass attenuation coefficient (μm), effective atomic number (Zeff), and kerma coefficient (k). For neutron shielding characteristics, the macroscopic effective removal cross-section (ΣR) of fast neutrons was calculated.

Stray neutron radiation exposures from proton therapy: physics-based analytical models of neutron spectral fluence, kerma and absorbed dose

Objective. Patients who receive proton beam therapy are exposed to unwanted stray neutrons. Stray radiations increase the risk of late effects in normal tissues, such as second cancers and cataracts, and may cause implanted devices such as pacemakers to malfunction. Compared to therapeutic beams, little attention has been paid to modeling stray neutron exposures. In the past decade, substantial progress was made to develop semiempirical models of stray neutron dose equivalent, but models to routinely calculate neutron absorbed dose and kerma are still lacking. The objective of this work was to develop a new physics based analytical model to calculate neutron spectral fluence, kerma, and absorbed dose in a water phantom. Approach. We developed the model using dosimetric data from Monte Carlo simulations and neutron kerma coefficients from the literature. The model explicitly considers the production, divergence, scattering, and attenuation of neutrons. Neutron production was modeled for 120–250 MeV proton beams impinging on a variety of materials. Fluence, kerma and dose calculations were performed in a 30 × 180 × 44 cm3 phantom at points up to 43 cm in depth and 80 cm laterally. Main Results. Predictions of the analytical model agreed reasonably with corresponding values from Monte Carlo simulations, with a mean difference in average energy deposited of 20%, average kerma coefficient of 21%, and absorbed dose to water of 49%. Significance. The analytical model is simple to implement and use, requires less configuration data that previously reported models, and is computationally fast. This model appears potentially suitable for integration in treatment planning system, which would enable risk calculations in prospective and retrospective cases, providing a powerful tool for epidemiological studies and clinical trials.

Improvement of Shielding Properties of Cement Paste by Slag Addition from Local Steel Industry

Abstract The effect of iron slag powder (ISP) obtained from the local steel industry as an effective addition to improve the radiation shielding ability of cement paste was evaluated. Ten cement pastes with different ISP-to-cement ratios, up to 90 % by mass of cement, were prepared. In addition, the compressive strength of the cement paste as a function of slag content was investigated. The γ-ray attenuation measurements were performed by a NaI (Tl) detector at 59.54, 511, 662, 1,173.2 and 1,332.5 keV. The computation of γ-ray attenuation parameters was obtained by the WinXCom program. Both measured and calculated shielding results are in good agreement. The results demonstrate that the addition of slag significantly alters the cement paste density, γ-ray attenuation coefficient, effective atomic number (Zeff), effective electron density (Neff), and kerma coefficients (k). Moreover, the neutron shielding of cement paste has been evaluated in terms of the macroscopic removal cross section of the fast neutron (ΣR). In conclusion, it is argued that the incorporation of slag results in a significant improvement in γ-ray shielding ability. In addition, the results showed that the best ISP addition proportion that leads to the best shielding properties is about 60 % (by mass of cement).

Gamma / neutron radiation shielding, structural and physical characteristics of iron slag nanopowder

The current study explores the effectiveness of an iron slag nanopowder (ISNP), which prepared from local iron steel industry, against gamma/neutron shielding. The structural and physical characteristics were experimentally determined. The crystal structure, morphology and elemental composition of the ISNP were studied using X-ray diffraction, scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX). On the other hand, a comprehensive experimental and theoretical study on the γ-ray shielding effectiveness of the ISNP was performed. In which, the experimental results have been validated by comparison with theoretical data which obtained by using the WinXcom program. This paper uses the well-known mathematical relationships to derive many shielding and dosimetry parameters such as effective atomic number and, effective electron density, for photon interaction and photon energy absorption as well as the γ-ray kerma coefficient from the mass attenuation coefficient. The exposure and energy absorption buildup factors have been also calculated. Furthermore, the shielding effectiveness against thermal and fast neutrons has been tested in terms of total macroscopic cross-sections. The results have revealed that the produced ISNP, with crystallite size of 24.5nm, exhibits good shielding characteristics. Finally, based on this preliminary study, we can have concluded that the iron slag nanoparticles can be suitably used as an effective and safe (lead - free) component for radiation shielding.

The effect of titanium (Ti) additive on radiation shielding efficiency of Al25Zn alloy

In this study, gamma ray and neutron shielding properties of Al25Zn alloy samples prepared by induction melting technique with the composition of (75−x)Al–25Zn–xTi (x = 0, 0.01, 0.1 and 1 wt %) were investigated theoretically and experimentally. The mass attenuation coefficients (μ/ρ) of the alloys were measured experimentally with a coaxial high purity germanium (HPGe) detector at 59.54, 662, 1173 and 1332 keV photon energies. The theoretical values have been calculated in the energy ranging from 1 keV to 1 GeV using WinXcom database. Afterwards, the obtained mass attenuation coefficient values have been utilized for determination of some shielding parameters such as half value layer (HVL), mean free path (MFP), effective atomic number (Zeff) and gamma–ray kerma coefficients (kγ). The calculated values are in good agreement with the observed values. Furthermore, the macroscopic fast neutron removal cross-sections (ΣR, cm−1) have also been calculated. Ti1 coded alloy sample containing 1% Ti was found to have maximum radiation protection efficiency (RPE) and neutron removal cross section (ΣR, cm−1) as well as the smallest half value layer (HVL) and mean free path (MFP) values. Hence, the results of this study showed that Ti1 alloy specimen has superior gamma and neutron radiation shielding performance among the other compared alloys.

Assessment of Kerma coefficients for OSL dosimeters by analytical and Monte Carlo approaches

In optically stimulated luminescent dosimeters (OSLD), the intensity of luminescent is a function of the dose of radiation absorbed and then it may be utilized as the basis of a radiation dosimetry method. For photons in the energy range from 1 keV to 20 MeV, the Kerma coefficients for fifteen OSLD, air, and ICRU standard tissue were calculated respectively from the analytical method and Monte Carlo simulation (MCNPX code). The results of MCNPX are consistent within estimated uncertainties with values evaluated by analytical method. The Kerma ratios of the OSLD relative to tissue were also obtained. The BeO has the closer Kerma to the tissue and alkaline OSL materials have relatively more values so that in 50 keV these ratios reach about 100.

DEVELOPMENT OF A NEW SECONDARY STANDARD FOR H*(10).

A secondary standard for ambient dose equivalent, H*(10), is necessary for the dissemination of the unit Sievert (Sv), but there is no such standard commercially available currently. Furthermore, the measurement of H*(10) instead of calculating H*(10) from air kerma and conversion coefficients is needed for unknown radiation fields. We developed a prototype of a new secondary standard for H*(10) based on a spherical 1l ionization chamber for air kerma. This chamber was modified with copper wires at the inner surface to adjust the response of the chamber according to H*(10). Additionally, a Makrolon shell and an aluminium coating were added to optimize the response at energies below 50keV. The prototype fulfils the requirements given in ISO 4037-2 in the energy range from 12keV to 7MeV. In combination with an electrometer, it can be used as area dosemeter, suitable for pulsed fields and for low energy radiation.

Assessment of neutron kerma coefficients and its calculation methodologies using recent basic ENDF-6 libraries

The generation of heat due to interaction of neutrons with matter is an important aspect in the designing of nuclear reactors. The estimation of neutron heating depends profoundly on the evaluated nuclear reaction parameters. Hence, within the purview of radiation damage of materials, it is necessary to investigate the effects of improvements in nuclear databases on the neutron heating rates under various neutron spectra. There are two well established methods to quantify the neutron kerma coefficients in matter: energy balance method and direct method. The well established code like NJOY21 gives the energy balance neutron kerma. In this study, the importance and performance of the direct method has been investigated, as the recent general purpose basic evaluated nuclear data files provide more complete database. Though both the methods predict closely the reported measured values of neutron kerma coefficients for structural elements, significant differences are observed between these two methods at higher energies where contributions from charged particle emitting reactions become important. The direct method is found to be more meaningful as it always ensures positive kerma coefficients and helps to separately identify the contributions from light charged particles and recoil nucleus. The neutron spectrum dependence of neutron kerma from both the methods are also investigated. Further, the nuclear data uncertainties in neutron heating are quantified by the Total Monte Carlo (TMC) methodology using the random ENDF-6 files in TENDL-2015 and the results show that the nuclear data uncertainties are in the range of 9–29%.

Evaluation of gamma attenuation parameters and kerma coefficients of YBaCuO and BiPbSrCaCuO superconductors using EGS4 code

The levels of the coefficients of the mass attenuation (μ/ρ) for YBaCuO and BiPbSrCaCuO superconductors and their contents were determined theoretically, using EGS4 simulation code and the XCOM database, and experimentally at gamma-ray energies of 511, 661 and 1274 keV. Additionally, radiation attenuation parameters such as half value layer (HVL), mean free path (MFP) and effective atomic number (Zeff) for investigated superconductors samples were calculated using the obtained μ/ρ values. It was observed that the theoretical and the experimental values were in agreement. Furthermore, the gamma-ray kerma coefficient k of these elements and superconductor samples was evaluated theoretically and experimentally, based on results of the mass attenuation coefficients determined at the same energies, and good agreement was observed. The theoretical levels of these coefficients were also computed over an expanded energy interval from 1 keV to 100 MeV using the WinXCom program. The results show that the calculated gamma kerma coefficient values of BiPbSrCaCuO had the highest atomic number, which was higher than for the YBaCuO superconductor.

Preparation and characterization of zinc, lanthanum white sand glass for use in nuclear applications

Glass derived from natural sand such as the white Sinai sand (WSS) is considered to be natural glass. It is known for its remarkable properties that exhibits excellent mechanical properties. Six natural glass networks had been prepared using the melt quenching method. The structural properties of the prepared samples were investigated by the X-ray diffraction (XRD) technique. Optical properties the glasses were evaluated by the UV–visible absorption measurements. Glass systems were evaluated for density, molar volume (VM), oxygen molar volume (VO), oxygen packing density (POD), and radiation properties according to the substitution of ZnO by La2O3. The mass attenuation coefficients (μm), effective atomic numbers (Zeff) and gamma-ray kerma coefficients (k) of the glasses at different photon energies were determined experimentally and calculated theoretically. The obtained results have shown that the current glasses have superior shielding properties compared to basalt magnetite concrete (BMC) and steel scrap concrete (SSC) as standard radiation shielding materials. The substitution of ZnO by La2O3 improves all gamma-ray attenuation parameters by about 20–29%. Moreover, the attenuation of neutrons was discussed in terms of the macroscopic removal cross-section (ΣR) and the glasses were found to have better neutron radiation shielding properties than SSC and BMC. These findings have demonstrated that the present glass systems can be suitably used as a shielding material at sites of the nuclear and X-ray facilities.

Radiation shielding properties of mortars with minerals and ores additives

Incorporation of mineral and ores as fine aggregate additives was investigated for its effect on the neutron and gamma-ray shielding properties of cement mortar. Five mortar mixtures have been prepared with different proportions of additives ranging from 0% to 30% of the cement mass by weight. Evaluation of gamma-ray attenuation was both measured experimentally and computed by means of a software. The measurements have been carried out for ores and mortar samples using 59.54, 662 and 1332 keV gamma photons. The theoretical values have been calculated in the energy range from 10 keV to 1 GeV. Many shielding parameters such as mass attenuation coefficient (μ/ρ), effective atomic number (Zeff) and corresponding electron density (Neff) and gamma–ray kerma coefficients (kγ) have been determined. The calculated values are in good agreement with the observed values. Furthermore, the macroscopic fast neutron removal cross-sections (ΣR, cm−1) have also been calculated by means of a software. The results of this study showed that the gamma-ray and neutron attenuation parameters of the studied mortar samples do not display any significant variation due to the addition of ores and minerals at the investigated mixing proportion (30% of the cement mass by weight).

Semi-empirical determination of gamma-ray kerma coefficients for materials of shielding and dosimetry from mass attenuation coefficients

In the present study, a semi-empirical formula for determination of gamma-ray kerma coefficient, k, has been developed. It based on the experimental total mass attenuation coefficient and the theoretical partial photon interaction probabilities. This semi-empirical technique has been applied to determining semi-empirical values of k for three elements, and 20 compounds and materials at different photon energy values; also, the theoretical values of this coefficient were calculated in the extended energy range from 1 keV to 100 MeV. The results showed that all kerma coefficient curves followed the same trend, regardless the material type. Shifting in kerma coefficient minima has been observed towards the high energy by increasing the average atomic number of sample. The results of the study have also shown that the proposed formula is simple and has potential application for determining the semi-empirical kerma coefficient of various elements, compound, and materials over a wide range of photon energy from 1 keV to 100 GeV.

Calculation of photon shielding properties for some neutron shielding materials

The objective of the present study is to calculate photon shielding parameters for seven polyethylene-based neutron shielding materials. The parameters include the effective atomic number (Zeff), the effective electron density (Neff) for photon interaction and photon energy absorption, and gamma-ray kerma coefficient (kγ). The calculations of Zeff are presented as a single-valued and are energy dependent. While Zeff values were calculated via simplistic power-law method, the energy-dependent Zeff for photon interaction (ZPI-eff) and photon energy absorption (ZPEA-eff ) are obtained via the direct method for energy ranges of 1 keV–100 GeV and 1 keV–20 MeV, respectively. The kγ coefficients are calculated by summing the contributions of the major partial photon interactions for energy range of 1 keV–100 MeV. In most cases, data are presented relative to pure polyethylene to allow direct comparison over a range of energy. The results show that combination of polyethylene with other elements such as lithium and aluminum leads to neutron shielding material with more ability to absorb neutron and γ-rays. Also, the kerma coefficient first increases with Z of the additive element at low photon energies and then converges with pure polyethylene at energies greater than 100 keV.