Neutron Activation Research Articles

Microstructural changes induced in advanced tungsten grades under high temperature neutron irradiation

Recent studies addressing the change of mechanical properties after high temperature irradiation of tungsten have reported substantial increase of the ductile to brittle transition temperature as well as increase of the hardness. In this work, we performed microstructural analysis by means of transmission electron microscopy (TEM) on various tungsten grades earlier exposed to high temperature neutron irradiation at 1200 °C up to 1 dpa. The latter corresponds to the expected irradiation temperature on the surface of a tungsten monoblock during the steady state operation in ITER. TEM was applied to five tungsten (W) materials including ITER specification pure W and precipitate strengthened W alloys. The analysis of TEM data coupled with its discussion led to a number of important conclusions regarding the damage induced at 1200 °C neutron irradiation such as: (i) weak effect of recrystallization on the accumulation of the lattice damage; (ii) promising results on the tolerance of damage accumulation in W-Y2O3 grade and (iii) internal oxidation of TiC particles which may contribute to the huge increase of the irradiation induced hardening.

Effect of hydrogen, helium and dose rate on the evolution of dislocation loop in pure iron during in-situ ion irradiation

Simulating neutron irradiation with ion irradiation requires considering the comprehensive effects of hydrogen, helium and dose rate to fully understand the microstructure evolution of material in an irradiation environment. Here, the characterization and evolution of dislocation loops in pure iron were investigated under heavy ion irradiation with four different injected gas ion types (Fe+, Fe++H2+, Fe++He+and Fe++H2++He+) and under dual-beam (Fe++He+) irradiation with four different dose rates using in-situ transmission electron microscopy at 723 K. Comparing to the single-beam (Fe+) irradiation, the additional injection of H or He, or co-injected H and He, mainly promoted the nucleation of dislocation loops at the early stage of irradiation and enhanced loop growth after that. Among them, the simultaneous irradiation of triple beams (Fe++H2++He+) was most pronounced. Moreover, triple-beam (Fe++H2++He+) irradiation resulted in the highest ratio of the rotation of loop habit-plane. Under dual-beam (Fe++He+) irradiation, the results demonstrated that as the dose rate increased, the loop density increased and the loop size decreased. Moreover, the fraction of 〈100〉 loops at low dose rate was noticeably greater than that at high dose rate. The results of the current work provide important references for a better understanding of the effectiveness of ion irradiation in simulating neutron irradiation.

Development and validation of a Bayesian unfolding program using OpenBUGS open-source software for Bonner spheres neutron spectrometry

This study presents the development of a novel unfolding program based on a Bayesian method for Bonner spheres spectrometry. The program incorporates a priori information on the neutron spectrum, employing a linear superposition of three non-negative parametric functions: thermal-Maxwellian distribution, an intermediate region represented by a straight line in lethargy space (1/E behavior), and the Watt fission distribution for the fast region. The effectiveness of the developed program was validated through its application to two reference cases from the EURADOS 2018 exercise (LINAC and Skyshine), followed by its implementation in characterizing the neutron field around an OB26 neutron irradiator at the Secondary Standards Dosimetry Laboratory (SSDL) of the Nuclear Research Center of Algiers (CRNA), Algeria. While validation results for the LINAC case were promising, achieving comparable neutron spectrum shape and integral quantities to the reference, challenges were encountered with the Skyshine case. However, these challenges were partially addressed through sensitivity analysis, resulting in slightly improved outcomes compared to the previous participation and to the reference. Application of the program to characterize the neutron field around the OB26 irradiator yielded satisfactory results when compared to reference data. A two-step sensitivity analysis further enhanced the outcomes, initially substituting the Watt fission distribution with the evaporation distribution, thereby improving spectrum shape and integral quantities. Subsequently, utilizing the obtained neutron spectra as prior information for unfolding codes MAXED and GRAVEL ensured stability and agreement with reference data and preliminary results.

Petrographic and geochemical analyses of pottery from Wadi Tanuf, Oman: Approaching pottery production in south‐eastern Arabia during the second and first millennia BCE

AbstractThis study describes the petrographic and geochemical characteristics of pottery collected from Mugharat al‐Kahf and WTN02 in Wadi Tanuf, north‐central Oman, to clarify interregional similarities and differences in pottery production techniques and examine the existence of interregional trade in pottery with respect to changes in mobile communities. Potsherds from these sites were characterised using thin‐section petrography and instrumental neutron activation analysis. Results revealed that several clay fabrics and tempers were used during the Wadi Suq period (2000–1600 BCE). A region‐wide similarity exists in pottery‐making techniques in terms of the tempering of specific minerals (Oman ophiolite) used in the Early Iron Age (1300–300 BCE). Geochemical results indicate differences in clay sources between the Wadi Suq period and the Early Iron Age in Wadi Tanuf and the unlikelihood of the interregional trade of domestic pottery.

Determination of moisture content in coal using pulsed fast thermal neutron activation technique

The quality of coal is greatly influenced by the residual moisture content, which in turn affects the Gross Calorific Value (GCV) by limiting the maximum energy that can be extracted from a given mass of coal. Various methods have been developed to measure this residual moisture, including gravimetric techniques, near-infrared spectroscopy, microwave, and infrared moisture meters. Amongst these, neutron-based techniques offer distinct advantages for bulk and rapid characterization, making them suitable for online monitoring. This article presents the use of a Pulsed Fast Thermal Neutron Activation technique to determine moisture content in various coal samples acquired from Indian coal mines. A 14.1 MeV D-T neutron source coupled with a Bismuth Germanate (BGO) detector and associated electronics have been used. The hydrogen content in the sample has been used as an indicator for the moisture and the technique has been calibrated with samples of known moisture content. The results obtained for the coal samples demonstrate a remarkable agreement with the findings of proximate analysis. A minimum quantity of 2% moisture by weight has been detected with a relative error of 0.4%.

Correlation between nutrients, rare earth elements and heavy metals in O. Sativa rice plant organs by instrumentation neutron activation analysis and proton induced x-ray emission techniques

The accumulation of halogens and metals from roots to stems, leaves and grains of Oryza sativa rice plant collected in Northern Senegal (St Louis region) at the same stages of growth but at different salinity soil levels was investigated by measuring their elemental concentration by invasive instrumental techniques of neutron activation analysis and proton induced x-ray emission. The normalized elemental concentration of Na, Cl, K, (Cs, Rb, Sr, Sb, Ba Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Cu, Zn, As, Se, Br, Rb, Sb was correlated with one of rare earth elements, La, Ce, Sm, Yb, Nd, Eu, Tb, Tm, and Lu) and the one of the heavy metals Hf, Ta and Th and to assess their subsequent distribution within the Oryza sativa rice plant in a particular salinity environment. The exploration of the experimental data was performed by applying machine learning techniques with Python to find their elemental correlations. This study shows that the accumulation of iron is highly correlated with the amount of rare earth elements and heavy metals investigated. We observe an inverse correlation between Fe and Cl concentrations in the roots and stems of the Oryza sativa rice plant, in which higher levels of Fe in the roots relative to stems correspond to lower levels of Cl. We also remark that there is no accumulation of rare earth elements in the root tissues of the different Oryza sativa rice plants studied. Whereas, in the stem, leaf, and grain organs there is a strong correlation between metal contents and rare earth elements.

Measurements of neutron capture cross-sections for nuclides of interest in decommissioning: 45Sc, 63Cu, 64Zn, 109Ag, and 113In

ABSTRACT As nuclear facilities are dismantled in decommissioning, various and large amounts of waste are generated. Even more inconveniently, they are radioactive waste due to neutron activation. Thus, the neutron capture cross-sections of nuclides targeted for decommissioning are required to evaluate the radioactivity produced. The present study selected 45Sc, 63Cu, 64Zn, 109Ag and 113In among targeted nuclides, and performed the measurements of thermal-neutron capture cross-sections by an activation method at the Kyoto University Research Reactor. The thermal-neutron capture cross-sections were derived on the basis of Westcott’s convention. The present results were obtained as follows: 27.18 ± 0.28 barn for 45Sc(n,γ)46Sc, 4.34 ± 0.06 barn for 63Cu(n,γ)64Cu, 0.719 ± 0.011 barn for 64Zn(n,γ)65Zn, 4.05 ± 0.05 barn for 109Ag(n,γ)110mAg and 8.53 ± 0.27 barn for 113In(n,γ)114Inm1+m2 reactions. The results for 45Sc and 64Zn support evaluated cross-section data within the limits of uncertainties, while those for the other nuclides were slightly different from evaluated ones. The obtained results are useful not only for the evaluation of isotope production, but also for the consideration of those nuclides as flux monitors, as an alternative to Au and Co.

Capture enhanced neutron irradiation for the treatment of the Alzheimer Disease: Micro-nanodosimetric characterization of beta amyloid peptide samples

Alzheimer Disease (AD) is the most common cause of dementia. 46.8 million people live with AD worldwide, with numbers projected to almost double every 20 years. The etiological mechanisms underlying the neuropathological changes in AD remain unclear. The beta amyloid peptide Aβ is considered to be the main culprit of the pathological processes. NECTAR (NEutron Capture-enhanced Treatment of neurotoxic Amyloid aggRegates) project proposes an alternative and revolutionary strategy to address AD, investigating the safety, feasibility and effectiveness of a Capture-Enhanced Neutron Irradiation to structurally damage Aβ aggregates, by exploiting capture agent vectors containing B-10 and Gd-157.Among many others, one of the goals of the project is to perform calculations and measurements of microdosimetric and nanodosimetric quantities to characterize the effect of reaction products at local level and to link it to the fibrils depolymerization process. In this framework, a new low-pressure tissue-equivalent proportional counter (TEPC) was designed and developed. The system is a wall-free TEPC able to measure micro-nanometric dose deposition for different biological samples. It is characterized by two main features: i) a wall-less structure allows the charged particles produced by the sample to access the sensitive volume, where their effects are studied; ii) a trigger system enables the assessment of the number of ionizations induced in the sensitive volume related to a single primary particle for obtaining nandosimetric information.The prototype system was tested in the PGNAA (Prompt Gamma Neutron Activation Analysis) facility of the LENA reactor (Pavia) to directly study secondary particles from Aβ fibrils, loaded with Boron. Results of the micro-nanodosimetric characterization of high LET secondaries from Aβ-fibrils were compared to a reference Boron sample. For a 500 nm simulated site size, the presence of Boron in the Aβ sample greatly populates microdosimetric spectra at high lineal energy values. Instead, lower LET particles (photons, protons) from reactions on the other Aβ aggregate solution molecules populate the low lineal energy portion of the distribution.The nanodosimetric distributions highlights the presence of different field components on the nanodosimetric spectra: low LET particles (protons/electrons) produce small ionization clusters, while alpha and Lithium ions induce larger clusters, thus have a higher biological effect. The nanodosimetric measurements have been compared with Monte Carlo simulations performed with a track-structure code, showing a good agreement.This multi-level approach provides a deeper physical understanding of the mixed secondaries field coming from B-enriched target, as well as a reference for the biological effect on Aβ fibrils at nanometer level. These preliminary measurements represent the first microdosimetric and nanodosimetric characterization of the secondary mixed field directly emitted by a biological sample irradiated with neutrons.

A novel aloe vera mediated Bismuth–Magnesium–Copper nanocomposite for radiation shielding applications

In the current study, Bismuth-Magnesium-Copper nanocomposites (BMC NCs) are synthesized using versatile solution combustion synthesis using Alovera extract as a reducing agent. As obtained BMC NCs are characterized using standard techniques. Bragg’s reflections confirmed the formation of multi-phase BMC NCs with crystal sizes 18.11 nm and 21.12 nm. The surface morphology of BMC NCs confirmed the agglomeration of spherical-shaped nanoparticles. EDAX spectrum analyzed the presence of Bi, Mg, and Cu. The direct energy gap is found to be 3.08 eV. X-ray/gamma radiation shielding properties are then evaluated using a NaI(Tl) detector coupled with MCA. Shielding parameters are slightly higher than lead. Neutron shielding parameters are compared with conventional shielding materials. Scattering length is found to be 8.8 fm, and neutron absorption cross-section and neutron attenuation parameters of BMC NCs are found to be efficient when compared with lead, concrete, and steel. Bremsstrahlung radiation shielding parameters are computed at 1.511 MeV. Bremsstrahlung efficiency is comparable to lead, bremsstrahlung dose rate and specific bremsstrahlung constant are found to be more in comparison with lead. Thus, BMC NCs are highly efficient in shielding X/gamma ray and neutron radiations.

Compositional characterization of paint sample by neutron and charge particle activation analysis: validation by energy dispersive X-ray fluorescence spectrometry

The elemental composition of the paint was determined by non-destructive nuclear analytical techniques, namely neutron activation analysis (NAA), charge particle activation analysis (CPAA), and energy dispersive X-ray fluorescence (EDXRF). NAA was chosen as the primary method of analysis as there is no matrix effect, requirement of a small quantity of a sample, detection capability down to ppb level, and self-validation. Ba, Ca, and Cr are detected as the major constituents, whereas Co, Hf, Mn, Y, Sr, Sb, W, Zn and Zr were detected at trace levels in the paint sample by NAA. CPAA was also utilized for the analysis, and elements like Ca, Cr, Fe, Sr, Ti and Zr were detected in the sample. The validation of the analytical results obtained in NAA and CPAA was carried out by the EDXRF technique, in which, including Si, most of the transition and high Z elements like Ca, Cr, Fe, Sr, Zr and Ba were detected. Analysis of variance was carried out to establish the statistical indistinguishability and acceptability of the analytical results obtained by these three methods. This study showcases the capability of NAA and CPAA for routine compositional analysis of paint sample without the requirement of a matrix matched standard.

Structure, mechanical, and neutron radiation shielding characteristics of mechanically milled nanostructured (100-x)Al-xGd2O3 metal composites

Metallic substances are favored for storing and transporting spent nuclear fuels (SNFs) due to their thermal stability, mechanical strength, and corrosion resistance. Adding gadolinium (Gd) significantly enhances neutron shielding, improving efficiency with reduced thickness and dimensions. In this study, Al–Gd2O3 metal nanocomposites were synthesized using powder-processed mechanical milling. The crystal structure features of (100-x)Al-x%Gd2O3 samples with varying percentages of Gd2O3 (5 %, 10 %, and 15 % by weight) were analyzed by X-ray diffraction. Microstructural properties were studied using scanning and transmission electron microscopy (SEM and TEM). The synthesized composites' neutron and γ-radiation shielding characteristics were investigated theoretically using the MCNP6.2 transport code. Analysis of the XRD data revealed prominent peak shifts with increased milling time, indicating reduced particle sizes. Differential scanning calorimetry (DSC) indicated Gd2O3-induced changes in temperature behavior, and the Vickers microhardness tests demonstrated enhanced mechanical strength with increasing gadolinium concentration. Improved neutron radiation shielding was observed with higher Gd2O3 content. Our study highlights the potential of Gd2O3-enriched metal matrix composites for advanced industrial applications.

Correlation between charge and current gain in LGADs treated with IR lasers

This study investigates the correlation between the gain, defined as the increase of measured charge generated from the absorption of incident radiation, and the gain measured as the increase of sensor leakage current in Low Gain Avalanche Detectors (LGAD) before and after neutron irradiations. LGADs exhibit high signal-to-noise ratios for minimum ionizing particles and will be used in high-energy physics experiments, mainly related to timing applications. Transient Current Technique (TCT) measurements were conducted with LGADs and PIN diodes. The electric field screening effect, caused by free and trapped carriers, is identified as the main reason for the differences measured in gain determined from the increase in leakage current and collected charge. These effects are more significant in irradiated LGAD sensors. The experimental results confirm expectations, demonstrating a growing spread between the two measured gains with fluence. The study enables the prediction of charge gain from the leakage current measurements, which are easier to conduct.

First-principles study of helium solution and diffusion in tungsten borides

The behavior of helium (He) in plasma facing materials (PFMs) is crucial for the performance of PFMs under neutron irradiation in a fusion environment. First-principles density functional theory calculations have been performed to model the solution and diffusion of He in six stoichiometric ground-state tungsten borides (WxBy), including W2B, WB, WB2, W2B5, WB3 and WB4. The solution energy of He interstitial in W borides linearly decreases with increasing B content, except for the deviation in WB and WB3. The mechanical and electronic contributions to He solubility in WxBy have been discussed. The calculated diffusion energetics indicates that He transport in W2B5, WB3 and WB4 is much more difficult than in W2B, WB and WB2. Subsequently, we investigate the influence of vacancies on the He behavior. Except for WB3, He is more strongly bound in W vacancies rather than B vacancies and the He binding energy to a W vacancy generally decreases with increasing B content in WxBy. These findings can be used to predict the potential influence of He on the properties of different W borides in the fusion environment.

Effect of 14.1 MeV Fusion Neutron Irradiation on YBCO Thin Films and Commercial REBCO Tapes

Effect of 14.1 MeV Fusion Neutron Irradiation on YBCO Thin Films and Commercial <i>RE</i>BCO Tapes

Study of the thermal neutron activation of a gamma-ray detector for BNCT dose monitoring

We present a study on the neutron activation of a gamma-ray detector for a BNCT-SPECT dose imaging system. The detector is based on a LaBr3(Ce+Sr) scintillator crystal, coupled with a matrix of Silicon Photomultipliers (SiPMs), read by a dedicated electronics system. This detector has successfully demonstrated to be capable to identify the 10B compounds when irradiating borated vials with thermal neutrons. However, a background signal around 478 keV was detected, suggesting the activation of the detector itself. This study aims to determine the origin of this background signal by simulating the two main parts of the detector, which are the crystal and electronic boards, in order to assess their contribution to the background signal. The results of the FLUKA simulations show that the neutron capture reactions on both the crystal and electronic boards cause a relevant background nearby the BNCT signal, thereby limiting the detector's sensitivity. To address this issue, a customized cadmium shielding has been developed. This solution was tested at the TRIGA Mark II research nuclear reactor of Pavia University, where experimental measurements and corresponding FLUKA simulations proved its effectiveness.

Evaluation of elemental pollution in soil samples from Klang industrial area

Rapid development in industries will contribute to the pollution of the soil. Studies of elemental pollution in the soil in the Klang industrial area were conducted to determine the concentration level in that area. Analysis of the content of elemental pollution in soil samples has used neutron activation analysis (NAA) techniques. The average concentration of major elements (Fe, Mg, Ti), heavy metals (As, Sb, Cr, Zn), uranium (U) and thorium (Th) in the soil of the Klang industrial area exceeded the average concentration in granitic igneous rocks. In comparison, the average concentration of rare earth elements (REEs) in soil samples in the study area is lower than the reference value of granitic igneous rocks. The elements of As, Zn and Cr showed a high concentration in the SL 11 area, where business activities, vehicle workshops and residential were located. The REEs show a high concentration in the SL 14 area compared to other sites. The geo-accumulation (Igeo) index was applied to identify the pollution status. The Igeo index for the elements of Mg and U can be categorised as unpolluted to moderately polluted. As and Sb can be categorised as unpolluted to moderately polluted, and as extremely polluted in the areas of SL 11 and SL 14. The element of Th can be categorised as unpolluted to moderately and strongly polluted. The Igeo index of REEs can be categorised as unpolluted in the soil of the Klang Industrial area.

The potential of NAA and ICP-MS for determining soil dispersibility in relation to landslide incidents

Dispersive soils pose significant challenges due to their inherent tendency to rapidly respond to the presence of water, resulting in erosion and heightened susceptibility to landslides. The inclusion of sodium (Na) onto the surface of soil clay particles results in the attenuation of the electrochemical interactions between the dispersed soil, leading to the repulsion and subsequent migration of the clay particles away from one another. This study employed Neutron Activation Analysis (NAA) and Inductively Coupled Plasma Mass Spectrometry (ICP-MS) to assess the Sodium Adsorption Ratio (SAR) and Exchangeable Sodium Percentage (ESP) as indicators of soil dispersibility. The results indicate that soils containing montmorillonite clay mineral exhibit greater values of SAR > 11 and ESP > 20 in comparison to soils containing other clay minerals i.e. kaolinite, illite, and vermiculite. The calculated SAR and ESP values obtained from both analyses demonstrate a notable agreement, indicating a positive correlation. In conclusion, it is apparent that both NAA and ICP-MS method has the capability to be applied for the purpose of predicting soil dispersibility in landslide-prone regions of Malaysia.

Optimization design for moderator, reflector, and shielding of Deuterium-Deuterium neutron source

Deuterium-Deuterium (D-D) neutron source, which could be used in both laboratory and outdoors due to its light weight, small volume and low cost, has been widely applied in thermal neutron imaging (TNI) and prompt gamma-ray neutron activation analysis (PGNAA). And the its optimization design is to obtain highly intense thermal neutrons and low dose rate around the facility with light weight and compact volume. In this paper, the genetic algorithm (GA) combined with MCNP6 was applied to globally optimize moderator, reflector, and shielding structures. As a result, the optimized thermal neutron intensity increased by 1.68 times, while the dose rate, weight and volume respectively decreased by 37%, 52%, and 27%, compared with the data based on the current design. This method could be an effective tool for the compact neutron source design.

Neutron detection in mixed short-pulsed fields with intense photon flashes for LINAC-based active interrogation applications

High-energy photon interrogation has established itself as a valuable tool for detecting special nuclear materials and characterizing nuclear waste. Previous research predominantly uses around 9-MV linear electron accelerators (LINACs) as photon sources and limited exploration has been conducted on the use of organic scintillators to determine the energy deposited in the detector and to separate photon and neutron radiation, crucial when the photon interrogation is based on the measurement of the neutron emission. The challenge arises from the intense photon flux typically produced by electron accelerators, resulting in issues such as pulse pile-up, detector saturation, and a suboptimal signal-to-background ratio. This study aims to extend the applicability of the conventional Active Photon Interrogation (API) techniques by introducing a novel method enabling the detection, in addition to nuclear materials, of light elements—specifically nitrogen, oxygen, and carbon—known to be present in conventional explosives, narcotics, and chemical weapons. The approach relies on active photon interrogation at high energies above 12 MeV, coupled with photoneutron spectrometry. Using a 22-MV electron LINAC, pulse shape discrimination with an organic liquid scintillator demonstrated promising performance. Our results highlight that the conventional pulse shape discrimination capabilities and rapid time-scale operation of organic scintillators enable the detection of fast neutrons from (γ,Xn) reactions, even in a mixed short-pulsed field of photon and neutron radiation with intense photon flashes. This exploration of the initial experimental aspects of photoneutron detection induced by high-energy photons establishes a foundation for a promising new method for the detection of illicit materials.

Irradiation Effects on Tensile Properties of Reduced Activation Ferritic/Martensitic Steel: A Micromechanical-Damage-Model-Based Numerical Investigation

The tensile properties of reduced activation ferritic/martensitic (RAFM) steels are significantly influenced by neutron irradiation. Here, a mechanism-based model taking account of the typical ductile damage process of void nucleation, growth, and coalescence was used to study the temperature and irradiation effects. The elastic–plastic response of RAFM steels irradiated up to 20 dpa was investigated by applying the GTN model coupled with different work hardening models. Through a numerical study of tensile curves, the GTN parameters were identified reasonably and satisfying simulation results were obtained. A combination of Swift law and Voce law was used to define the flow behavior of irradiated RAFM steels. The deformation localization could be adjusted effectively via setting the nucleation parameter εn close to the strain where necking occurs. Because εn changed with uniform elongation, εn decreased with the testing temperature and rose with an irradiation temperature above 300 °C. The nucleation parameter fn increased with the testing temperature for RAFM steels before irradiation. For irradiated RAFM steels, fn barely changed when the irradiation temperature was below 300 °C and then it rose at a higher irradiation temperature. Meanwhile, the ultimate strength of the simulated and experimental curves showed good agreement, indicating that this method can be applied to engineering design.