Neutron Attenuation Coefficients Research Articles

Thermal cross section of poly(2-hydroxyethyl methacrylate) hydrogels for neutron dose calculation

Phantom materials are used to design radiation safety and protection strategies by means of numerical dose calculation. In the case of thermal neutrons, the radiation transport in the phantom relies on mass attenuation coefficients and total cross sections which are dependent on the physical and chemical properties of the material. Specifically for medical applications, such as neutron capture therapy, the neutron-induced dose is mainly related to the neutron absorption by hydrogen and nitrogen in the human tissue and body. Here, we investigate the use of poly(2-hydroxyethyl methacrylate) as a phantom material by experimental measurement and modeling of its total neutron scattering cross section and mass attenuation coefficient. We show that by varying the hydration level from 10 to 40 w%, one can obtain a neutron attenuation coefficient similar to polymethyl methacrylate or more representative of the human body, respectively. By benchmarking our phenomenological model on the experimental data, we provide a new example of how to use the average functional group approximation to accurately model total neutron cross sections in the framework of personalized medicine approaches.

Neutron Shielding Properties of Cellulose Acetate CdO-ZnO Polymer Composites

In this work, the neutron shielding ability of Cellulose Acetate-CdO-ZnO Polymer Composites of different concentrations of CdO and ZnO were investigated. Cellulose acetate is a biodegradable good matrix and the used metal oxides are good for absorbing radiation. The neutron attenuation coefficient was calculated by Phy-X computer code for all the samples.

Thermoplastic and thermoset polymer matrix composites reinforced with bismuth oxide as radiation shielding materials

Polymer composites reinforced with heavy metals have wide applications in the nuclear industry as radiation shielding materials against emitted radiation from nuclear equipment. In this study, considering bismuth oxide as reinforcement, various polymers including thermoplastic polymers, such as high-density polyethylene, low-density polyethylene, polypropylene, polyvinyl acetate, polymethyl methacrylate, and thermosetting epoxy resin have been considered as matrices. After preparing various samples of polymer composites loaded with 60 % by weight of bismuth oxide, some physical, mechanical, and radiation shielding properties (neutron and gamma attenuation coefficients) of these polymer composites have been measured and compared with each other. First, the density of the samples was measured, and the response of these samples to varying compressive force was investigated. The stress-strain diagrams of composites with different matrices were compared. Subsequently, the linear and mass attenuation coefficients of the composites were measured over a wide range of energies (32–1480 keV) against direct and collimated beams from various standard gamma-ray sources (134Cs, 60Co, 154Eu, 133Ba, and 22Na) using an HPGe detector. A collimated beam from an Am–Be source was utilized to measure and compare the attenuation properties of the composite samples against neutron flux. Furthermore, the properties of the composites against neutron and gamma radiation were calculated using the MCNP Monte Carlo code over a broad energy range, and the results were compared and validated with the experimental data. The comparison of the calculated and measured results shows reasonable agreement. The results indicate that in situations where high attenuation properties coupled with high strength are desired, polymeric composites with an epoxy matrix can be considered as radiation shielding materials. If the use of flexible and malleable material is required, such as for reactor piping shielding or the fabrication of protective gloves and clothing in a radiation environment, among the polymers studied, polyvinyl acetate is a more suitable matrix.

Uniformity of neutron absorber distribution in Gd-containing neutron absorber materials

For neutron absorber materials (NAMs), it is important to evaluate their neutron-absorption capability and quantitatively evaluate the uniformity of the distribution of neutron-absorbing elements within the materials. In this study, neutron attenuation testing with cold neutrons was conducted on Ti-based model alloys with Gd concentrations ranging from 1 to 10 wt%. The neutron attenuation coefficients (μ) of the Ti-Gd alloys were determined and compared with the total macroscopic cross sections (Σt), which were computed using the latest ENDF/B library. Although the measured μ increases with the Gd-content, the coefficients were not linearly proportional to the absorber amount, and the ratio of μ to Σt gradually decreased. This was caused by beam hardening, which is more significant for higher-absorbing and thicker NAMs. To examine the uniformity of the neutron absorbers (NAs) in plates, we propose a method for characterizing the degree of homogeneity by introducing a radial distribution function (RDF). After the optical microscopic images of the Ti-Gd alloys were converted to grayscale, the RDF of the Gd particles in the alloys was calculated under the assumption that a large particle is composed of many adjacent unit particles. A unit particle was regarded as one pixel in the digital image. For all Ti-Gd alloys, the RDF had a value of > 1 at short interparticle distances, which indicated a dense population of particles in a small area due to cluster formation. The method of using the RDF as a uniformity parameter was validated through a case study involving a fixed NA content with different distributions.

Computation of Neutron Coefficients for B2O3 reinforced Composite

Radiation is an important phenome and has been used in many different fields since its discovery. Although there are different types of radiation, neutron is one of the most interesting types as it is an uncharged particle. This character made neutron is more dangerous radiation types than others and thus protection from neutron effect requires more care. In this paper neutron attenuation coefficients of B2O3 reinforced composite have been investigated using Phy-X/PSD software.

Visualizing Lithium Ion Transport in Solid‐State Li–S Batteries Using 6Li Contrast Enhanced Neutron Imaging

AbstractThe elucidation of lithium ion transport pathways through a solid electrolyte separator is a vital step toward development of reliable, functional all‐solid‐state batteries. Here, advantage has been taken of the significantly higher neutron attenuation coefficient of one of the most abundant stable isotopes of lithium, 6Li, with respect to that of naturally occurring lithium isotope mixture, to perform neutron imaging on a purpose built all‐solid‐state lithium–sulfur battery. Increasing the 6Li content in the anode while using natural lithium in the solid electrolyte separator and the cathode enhances the contrast such that it is possible to differentiate, during the initial discharge, between the mobile lithium ions diffusing through the cell from the anode and those that are initially located in the solid electrolyte. The sensitivity of neutrons to the different lithium isotopes means that operando neutron radiography allows demonstration of the lithium ion diffusion through the cell while in situ neutron tomography has permitted presentation, in three dimensions, of the distribution of the trapped lithium ions inside the cell in charged and discharged states.

Structural, thermal and nuclear shielding properties of lithium lead phosphate glasses: Influence of lithium oxide additive

In this paper, the structural, thermal and nuclear radiation shielding properties of a new Lead–Lithium-Phosphate glass system with different amount lithium oxide were studied. The glass samples were prepared by the conventional melt-quenching method and they having compositions (75-x) P2O5– 25PbO- xLi2O with x = 0, 5, 10, 15, 20 mol%. The influence of Li2O content on the structural, thermal, radiation shielding properties, and other related properties of the synthesized glasses was studied. The structural properties were investigated using XRD and Raman spectroscopy. The glass transition temperature Tg and crystallization onset temperature Tx are estimated from the DSC profile.The GEANT4 Monte Carlo simulation code was used to estimate thermal neutron attenuation coefficient (μnt) in a wide neutron energy range of 0.0253–100 eV and ParShield code was used to calculate effective fast neutrons removal cross-section (∑R). The gamma-ray attenuation parameters such as mass attenuation coefficients (μm), effective atomic number (Zeff), effective electron density (Neff) and half-value layer (HVL) have been computed by using ParShield code in the energy range of 0.103–1.33 MeV. However, the total mass stopping power (MSP) and projected range (PR) values have been estimated for alpha particles (4He2+) and Triton particle (3H) by using SRIM in the energy range of 0.1–10 MeV.

Monte Carlo simulation study on Barite Concrete for neutron-gamma photon

In the ongoing research, the Monte Carlo simulation of three different Barite Concrete samples coded as C-B0, C-B50 and C-B100 was estimated via MCNPX Monte Carlo Code to investigate the neutron-gamma photon shielding characteristics. Simulations were performed for 252Cf source which is surrounded by the polyethylene cylinder. Using Watt Fission (WF) distribution and Doppler Effect (DE), the neutron-gamma photon flux was obtained and was compared to various types of Barite Concrete samples. The total macroscopic cross section, linear attenuation coefficient (µ), Half Value Thickness (HVT) and Mean Free Path (MFP) were calculated for gamma rays and neutrons. The equivalent absorbed dose rate was estimated for neutrons and showed that an increment of the Barite rate causes a reduction in the equivalent absorbed dose rate from 0.0003572 to 0.0003542 (µSV/h). Moreover, total macroscopic cross section which shows total macroscopic cross section which shows the neutron attenuation coefficient (∑t ) undergoes descending trend of (∑t )C-B0 < (∑t )C-B50 < (∑t )C-B100 which confirms the disability of the Barite Concrete sample against neutrons. The evaluated gamma photon attenuation parameters for energy ranging from 0.05 to 11 MeV are shown graphically. Findings reveal that by increasing the rate of the Barite, the samples’ shielding ability will reduce against neutron whereas it will enhance the gamma photons shielding capability.

In Situ Imaging Comparison of Lithium Electrodeposits By Neutron and X-Ray (Synchrotron and Laboratory) Tomography

Most of the post-Lithium-ion (Li-ion) devices, such as Li–sulfur, Li–O2, or all-solid-state Li batteries, have in common an negative electrode made of metallic Li.1 The main failure mode of Li based batteries is the inhomogeneity of the Li electrodeposits onto the Li metal negative electrode during charge steps, leading to dendrite growth and low Coulombic efficiency.2 Tomography and radiography imaging techniques are now vastly employed for battery materials analysis thanks to the possibility to perform noninvasive in situ and operando experiments.3 X-ray tomography is a powerful tool for studying dendrites as it provides useful information about their locations, dynamics, and microstructures. However, the use of neutron tomography is scarcely reported for Li electrodeposit analysis due to the difficulty to reach sufficient image resolution to capture the deposit microstructure, that is, typically below 10 to 20 µm. Furthermore, the different interactions of X-rays and neutrons with Li, which has significantly different opacity in the two cases, make the two techniques highly complementary.4 Notably, the capacity of neutrons to discern different Li isotopes is pivotal to get insight into the composition of Li deposits, by distinguishing between Li originating from an electrode (6Li in this study) and Li originating from the Li salt electrolyte (mainly in 7Li here). Indeed, the theoretical linear neutron attenuation coefficient of 6Li is about 15 and 2,000 times larger than that of natural Li and 7Li, respectively.In this study, we report as a proof of concept, an in situ neutron tomography imaging of Li electrodeposits in a cycled Li symmetric cell (see Figure 1).5 The electrochemical cell comprises a natural Li electrode, a 6Li electrode, and a deuterated liquid electrolyte. The neutron tomography is compared with X-ray tomography images of the same electrochemical cell acquired both at an X-ray synchrotron beamline and at a laboratory X-ray tomograph. Neutron tomography is shown to be compatible with in situ analysis and capable of capturing the overall morphology of the Li deposits in good accordance with X-ray tomography analyses. References M. S. Whittingham, Lithium batteries and cathode materials. Chem. Rev. 104 (2004) 4271.Z. Li et al., A review of Li deposition in Li-ion and Li metal secondary batteries. J. Power Sources 254 (2014) 168.K. Harry et al., Detection of subsurface structures underneath dendrites formed on cycled Li metal electrodes, Nat. Mater. 13 (2014) 69.M. Strobl et al., Advances in neutron radiography and tomography. J. Phys. D: Appl. Phys. 42 (2009) 243001.L. Magnier et al., Tomography imaging of Li electrodeposits using Neutron, synchrotron X-ray, and laboratory X-ray sources: A comparison. Front. Energy Res., 9 (2021) 657712. Figure 1

Prompt-gamma activation analysis and neutron imaging of layered metal structures

We present here Monte Carlo computer simulations to broaden the scope of the prompt-gamma activation analysis (PGAA) from the elemental composition measurement of ideal, point-like, homogeneous samples towards non-homogeneous or heterogeneous but still regularly-shaped samples. The successful correction for the negative matrix effect related to the neutron self-shielding and gamma self-absorption is a key step in the quantitative analysis of layered metal structures. This geometry is relevant to practical cases where corrosion layer, patina, paint, coating, gilding, or segregation are present on the surface of a core metal. Linear neutron attenuation coefficients are measured in a polychromatic neutron beam by radiography, while the gamma attenuation calculations by MCNP6 simulations were validated by gamma transmission measurements. Finally, the method was successfully applied to correct for the PGAA matrix effect in double- and triple-layer metal stacks and a real structured numismatic sample.

Tomography Imaging of Lithium Electrodeposits Using Neutron, Synchrotron X-Ray, and Laboratory X-Ray Sources: A Comparison

X-ray and neutron imaging are widely employed for battery materials, thanks to the possibility to perform noninvasive in situ and in operando analyses. X-ray tomography can be performed either in synchrotron or in laboratory facilities and is particularly well-suited to analyze bulk materials and electrode/electrolyte interfaces. Several post-lithium-ion (Li-ion) devices, such as Li–sulfur, Li–O2, or all-solid-state Li batteries, have an anode made of metallic Li in common. The main failure mode of Li batteries is the inhomogeneity of the Li electrodeposits onto the Li anode during charge steps, leading to dendrite growth and low Coulombic efficiency. X-ray tomography is a powerful tool for studying dendrites as it provides useful information about their locations, dynamics, and microstructures. So far, the use of neutron tomography is scarcely reported for Li deposit analysis due to the difficulty in reaching sufficient image resolution to capture the deposit microstructure, that is, typically below 10–20 µm. The very different interactions of X-rays and neutrons with Li, which has significantly different opacity in the two cases, make the two techniques highly complementary. Notably, the capacity of neutrons to discern different Li isotopes is pivotal to getting an insight into the composition of Li deposits by distinguishing between Li originating from an electrode (6Li in this study) and Li originating from the Li salt electrolyte (mainly in 7Li here). Indeed, the theoretical linear neutron attenuation coefficient of 6Li is about 15 and 2,000 times larger than that of natural Li and 7Li, respectively. Therefore, a high imaging contrast difference is obtained between 6Li (high attenuation) and natural Li and 7Li (lower attenuations), which could allow a better understanding of the origin of the Li comprising the electrodeposits. In this work, we report, as a proof of concept, an in situ neutron tomography imaging of Li electrodeposits in a cycled Li symmetric cell. The electrochemical cell comprises a natural Li electrode, a 6Li electrode, and a deuterated liquid electrolyte. The neutron tomographies are compared with X-ray tomography images of the same electrochemical cell acquired both at an X-ray synchrotron beamline and at a laboratory X-ray tomograph. Neutron tomography is shown to be compatible with in situ analysis and capable of capturing the overall morphology of the Li deposits in good accordance with X-ray tomography analyses.

Spatial distribution of graphite in cement materials used for radioactive waste conditioning: An approach to analysis of neutron tomography data

The spatial arrangement of the graphite inside the cement-based materials has been studied using neutron tomography. The large differences in the neutron attenuation coefficients for the graphite and cement phases and the application of mathematical algorithms for an analysis of the three-dimensional reconstructed data allowed us to obtain the distributions of the average sizes, orientation and shape-related parameters of the graphite particles in studied cement samples. The results of calculations of the elastic properties of the graphite contented cement materials based on the obtained structural features of the morphology of graphite phase are presented.

Optimizing the shielding properties of strength-enhanced concrete containing marble

The purpose of this study is to develop a low cost, locally produced concrete mixture with optimum marble content. The resulting mixture would have enhanced strength properties compared to the non-marble reference concrete, and improved radiation shielding properties. To accomplish these goals five concrete mixtures were prepared, containing 0, 5, 10, 15, and 20% marble waste powder as a cement replacement on the basis of weight.These samples were subjected to a compressive strength test. The shielding parameters such as mass attenuation coefficients μm, mean free path MFP, effective atomic number $Z_{eff}$ and exposure build-up factors EBF were measured, and results were compared with those obtained using the WinXcom program and MCNPX code in the photon energy range of 0.015 - 3 MeV. Moreover, the macroscopic fast neutron removal cross-section (neutron attenuation coefficient) was calculated and the results presented. The results show that the sample which contains 10% marble has the highest compressive strength and potentially good gamma ray and neutron radiation shielding properties.

Influence of heavyweight aggregates on the physico-mechanical and radiation attenuation properties of serpentine-based concrete

To highlight the impact of barite and hematite addition on selected physical, mechanical, and radiation attenuation properties of serpentine concrete (A), different replacement ratios of barite and hematite aggregates (25, and 50% by volume) were used separately. The physico-mechanical properties of the prepared serpentine-barite (AB25, 50) and serpentine-hematite (AH25, 50) concrete mixes compared to those of the control (A) were evaluated. The radiation shielding properties of these concrete mixes against both γ-ray and thermal neutrons were experimentally measured. The linear attenuation coefficient of γ-ray, µ, and thermal neutron attenuation coefficient, Ʃth, were determined experimentally by the transmission method in a fine beam geometry setup using 60Co γ-ray source and a moderated PuBe source, respectively. The experimental results of γ-rays were verified by the correlation with the theoretical data obtained by the WinXCom program. Besides, many γ-ray attenuation parameters, such as a half-value layer, HVL, single-valued, and energy-dependent effective atomic number, Zeff, as well as effective electron density, Neff, were determined. It was found that the addition of barite and hematite aggregates to serpentine concrete increased its bulk density, and decreased its mechanical strength. Moreover, unlike barite, the hematite increased the water absorption and porosity of concrete. In conclusion, this study revealed that the prepared hematite- and barite-serpentine concrete mixes, except for AB50, have acceptable mechanical properties with enhancing radiation shielding performance.

Use of borosilicate glass powder in cementitious materials: Pozzolanic reactivity and neutron shielding properties

This work evaluates both the pozzolanic reactivity and neutron shielding properties of cementitious paste and mortar mixtures containing varying amount of borosilicate glass powder. The experimental results indicate that the use of borosilicate glass powder results in a greater heat of hydration than that expected for cement paste alone at early ages (despite the fact that the cumulative heat release was reduced as the replacement of borosilicate glass powder increased). The maximum pozzolanic reactivity of borosilicate glass powder was estimated to be 55%, which was greater than a typical class F fly ash (≈30%). Borosilicate glass powder resulted in a 8% increase in the 28 d compressive strength of mortar for the replacement levels of up to 25% by mass. The neutron attenuation coefficient of mortar increased (10–40%) as the amount of borosilicate glass powder increased; however, it appears to plateau when the cement replacement ratio was higher than 25%. This plateau appears to be the result of competing effects (i.e., the addition of borosilicate glass powder continuously increases the attenuation coefficient while the reduction in hydration products reduces the attenuation coefficient). Based on initial testing, considering compressive strength and neutron shielding properties, the use of borosilicate glass powder in cementitious materials shows the best results when the replacement level is between 20 and 25% by mass of cementitious materials and when the cementitious system is properly cured. A simplified model was introduced to determine the required thickness of mortar with different mixture proportions for neutron shielding.

In-situ observation and analysis of solid-state diffusion and liquid migration in a crystal growth system: A segregation-driven diffusion couple

Energy-resolved neutron imaging is employed for in-situ measurements of dopant transport in a simple experiment performed before the crystal growth of the scintillator BaBrCl:5%Eu via a vertical gradient freeze technique. During a stabilization period preceding growth, we observed the diffusion of Eu from the solid phase into the melt over a period of approximately 4 h. Comparing the measured centerline concentration profile with a mathematical model for the system, we estimate the solid-state diffusivity of Eu in BaBrCl as D1=1.9×10−10 m2/s and an upper limit for the liquid-phase diffusivity of Eu in the melt as D2*=2.5×10−10 m2/s, at temperatures near the melting point. We compare this experiment, where diffusion is driven by a concentration discontinuity arising from segregation, to the classical diffusion couple technique. Suggestions are offered on how this segregation-driven couple might be improved as a tool for measuring diffusion coefficients, and we draw attention to the great promise of neutron imaging for in-situ measurements of the distribution of elements, with sufficiently high neutron attenuation coefficients, in difficult environments.

Studies of the Processes of Hardening of Cement Materials for the Storage of Aluminum Radioactive Waste by Neutron Radiography

The processes occurring during hardening of special cement pastes for the construction of storage facilities or disposal of radioactive waste containing aluminum metal were studied by means of a neutron radiography method. High reactivity of aluminum causes rapid release of hydrogen-containing components from the entire volume of cement paste. The cement pastes with organic additives to suppress the process of hydrogen-contained gases formation during the hardening of the cement materials were studied. Time dependences of the neutron attenuation coefficients for these special cement materials were obtained. Based on the neutron radiography data, the kinetics of hardening of those special cement pastes is discussed.

An experimental investigation on the effects of barite/hematite on the radiation shielding properties of serpentine concretes

To modify some properties of serpentine-based concretes, serpentine aggregate (S) was partially replaced with either hematite aggregate (H) or barite aggregate (B) at levels of 25% and 50%, by volume. To evaluate the impact of these aggregates, selected physical properties of the prepared serpentine-barite (AB25, 50) and serpentine-hematite (AH25, 50) concretes were measured and compared to those of the control serpentine concrete (A). In addition, the fast neutrons and gamma-rays shielding properties of these concretes in comparison with those of the control (A) were experimentally measured using a239Pu-Be source and stilbene detector. These shielding properties were determined by measuring the neutron and gamma-ray attenuation coefficients (ΣR(En) and μ(Eγ), respectively), as well as parameters of relaxation length (λ) and half value length (HVL) at different energies. It was found that incorporation of B and H had a negative impact on the physical properties of the serpentine-based concretes except for density. On the other hand, this incorporation improved the attenuation properties of serpentine-based concretes. This improvement was more effective in the case of using B rather than H in the equivalent ratios. Finally, 50% B was the best ratio in enhancing the shielding of fast neutrons and gamma-rays.

Gamma and neutron attenuation properties of alkali-activated cement mortars

Radiation-shielding properties of alkali-activated cement (AAC) mortar mixtures prepared using different precursors such as ground granulated blast furnace slag (GGBFS), fly ash (FA), metakaolin (MK) and waste clay material containing boron (WCB) were investigated comparatively with Ordinary Portland Cement (OPC) mixture. The gamma linear attenuation coefficients of the mixtures were determined both experimentally and theoretically. The experimental coefficients of the mixtures were measured with NaI(Tl) detection system for gamma energies of 137Cs (662 keV) and 60Co (1173 and 1332 keV) and the gamma transmission parameters (half-value layer, HVL; tenth-value layer, TVL and mean free path, MFP) were determined using these coefficient values. The theoretical coefficients of the mixtures were calculated using XCOM software for the energy range of 10–3000 keV. In addition, neutron attenuation coefficients of the mortar mixtures were theoretically calculated with the NCNR computation software for thermal (0.025–1 eV), slow (1–10 eV), resonance (10–300 eV), intermediate (300 eV-1 MeV) and the fast neutrons (1 MeV–20 MeV). Test results indicated that GGBFS and FA based alkali-activated cement mortars had similar gamma attenuation properties to the OPC mortar while the WCB and MK-incorporating AAC mixtures had slightly worse properties in this respect. In terms of thermal and slow neutron shielding properties only AAC mixtures containing WCB showed significantly better behaviour compared to OPC. For neutrons having higher energy levels than slow neutrons, all AAC and OPC mortar mixtures showed comparable properties.

Probing the 3D molecular and mineralogical heterogeneity in oil reservoir rocks at the pore scale

Innovative solutions have been designed to meet the global demand for energy and environmental sustainability, such as enhanced hydrocarbon recovery and geo-sequestration of CO2. These processes involve the movement of immiscible fluids through permeable rocks, which is affected by the interfacial properties of rocks at the pore scale. Overcoming major challenges in these processes relies on a deeper understanding about the fundamental factors that control the rock wettability. In particular, the efficiency of oil recovery strategies depends largely on the 3D wetting pattern of reservoir rocks, which is in turn affected by the adsorption and deposition of ‘contaminant’ molecules on the pores’ surface. Here, we combined high-resolution neutron tomography (NT) and synchrotron X-ray tomography (XRT) to probe the previously unobserved 3D distribution of molecular and mineralogical heterogeneity of oil reservoir rocks at the pore scale. Retrieving the distribution of neutron attenuation coefficients by Monte Carlo simulations, 3D molecular chemical mappings with micrometer dimensions could be provided. This approach allows us to identify co-localization of mineral phases with chemically distinct hydrogen-containing molecules, providing a solid foundation for the understanding of the interfacial phenomena involved in multiphase fluid flow in permeable media.