Prompt Gamma Neutron Activation Analysis Research Articles

Conceptual design of prompt gamma neutron activation analysis facility at Tehran Research Reactor for BNCT application

Abstract Since Tehran Research Reactor (TRR) is the only available neutron source , which can be used for Boron Neutron Capture Therapy (BNCT) in Iran, it is essential to provide an appropriate analysis system at TRR in order to determine 10 B concentration in sample tissue or blood. Based on the advantages, Prompt Gamma Neutron Activation Analysis (PGNAA) facility has been selected. Irradiation channels in TRR have been studied using Monte Carlo MCNPX2.6 code and evaluated to provide the appropriate neutron beam for PGNAA. Based on the results of neutron intensity and spectrum, F-beam tube is considered to be the most favorable for PGNAA, and has therefore been selected for further investigation and MCNP simulation. Bismuth blocks for decreasing gamma radiation , and Fluental™ as a filter for fast neutron have been used in F-beam tube. The convergent collimator with iron and polyethylene has been considered to shape the neutron beam and to reduce the neutron and gamma-ray fluxes at the position of the HPGe gamma-ray detector. The sensitivity of the designed system is determined, from MCNP simulation, to be 7.35 cps/ μ g.

Simulation of a collimator and sapphire filter for PGAA facility of the Moroccan TRIGA MARK II research reactor

The Prompt Gamma Neutron Activation Analysis (PGAA) facility will be commissioned at the NB1 beam tube of the Moroccan TRIGA MARK II research reactor. PGAA is a non-destructive analytical technique used for multi-elemental analysis and especially for light element analysis. For better performances, PGAA requires small and focused beam, and high Фth/Фep and Фth/Фfast ratios, and low background gamma radiation. For this purpose, fast neutron filters are commonly used to reduce fast and epithermal components of neutron flux. In this paper, the impact of sapphire filter, introduced, within the collimator hole, at the beam port on neutron spectra was evaluated. Monte Carlo, MCNP6.2, code has been used with ENDF VII.1 neutron cross section library to perform this study. An approximate TRIGA MARK II reactor MCNP model has been used to generate neutron spectra at the entrance of the collimator. Then an independent model for both collimator and sapphire filter has been brought into calculation to fulfil our purpose. Results showed an increase of about 8 times for both Фth/Фep and Фth/Фfast ratios using a 10 cm length of sapphire.

A PMT gating circuit design for real-time baseline restoration on prompt gamma neutron activation analysis application

Baseline shift seriously affects the accuracy of elemental analyzing when prompt gamma neutron activation analysis (PGNAA) technique is used in industry fields. Baseline is affected by signal pile-ups and environmental factors. We propose a photomultiplier tube (PMT) gating method to eliminate the effects of the environmental factors. The detector system updates the baseline before each single measurement starts. We propose an algorithm to restore the baseline shift caused by signal pile-ups. Test result shows that with the gating method, the hydrogen characteristic peak position fluctuation is reduced by half of the original value. And the resolution does not increased by the using of the gating method.

Study on element detection and its correction in iron ore concentrate based on a prompt gamma-neutron activation analysis system

A prompt gamma-neutron activation analysis (PGNAA) system was developed to detect the iron content of iron ore concentrate. Because of the self-absorption effect of gamma-rays and neutrons, and the interference of chlorine in the neutron field, the linear relationship between the iron analytical coefficient and total iron content was poor, increasing the error in the quantitative analysis. To solve this problem, gamma-ray self-absorption compensation and a neutron field correction algorithm were proposed, and the experimental results have been corrected using this algorithm. The results show that the linear relationship between the iron analytical coefficient and total iron content was considerably improved after the correction. The linear correlation coefficients reached 0.99 or more.

Determination of elemental concentrations in biological and geological samples using PGNAA facility at the Dalat research reactor

This article presents the results of the determination of element concentrations in biological and geological samples by using the Prompt Gamma Neutron Activation Analysis (PGNAA) facility that was installed at horizontal channel No. 4 of the Dalat research reactor. The biological standard sample Bovine Liver NBS 1577a and environmental standard sample Coal Fly Ash NBS 1633a were analyzed to verify the analytical ability of the facility. After that, the concentrations of N, K, Cl, Fe, Ca, Mn and B in biological samples and concentrations of K, Al, Si, Fe, Ca, Mn, Gd, Sm, Ti, and B in geological samples were determined in the framework of quality assurance and quality control programme at the Dalat Nuclear Research Institute. The analytical results indicated that this PGNAA facility can be used as a suitable instrumental tool to study in the fields of environment, biology and geology.

Using neutron methods SANS and PGAA to study evolution of structure and composition of alkali-doped polybenzimidazole membranes

Potassium hydroxide (KOH) doped polybenzimidazole (PBI) membranes are investigated as compelling candidates for water electrolysis applications, drastically reducing the ohmic losses in contrast to thick ZrO2 based diaphragms. Using small angle neutron scattering (SANS) we have found that the structure of the (KOH doped) PBI changes with doping time on a minute time scale, and that the development of the structure is highly dependent on the KOH concentration. This data is correlated with macroscopic measurements of membrane swelling resulting from the doping process which also occurs on a minute time scale. Then, using prompt gamma activation analysis (PGAA) to follow the changes in time of the chemical composition, we have found that the K concentration of these samples only increases slightly with doping times after a very rapid initial uptake, reaching a saturation value that is relatively independent of KOH concentration for long doping times of up to 24 h. However measurements of similarly doped samples show increases in ion-conductivity of nearly 3 fold, and resistivity reductions of over 2 fold on the same time scales. These measurements prove that PGAA is a sensitive method to follow changes in the chemical compositions during doping, while SANS can give information on the sub-micro structural changes of polymer electrolyte membranes. Since these methods can be correlated with ex-situ measurements of composition, resistance, ion-conductivity and macro-structure, the combined use of PGAA and SANS provides a promising means for in-operando study in order to elucidate changes in membrane performance due to electrochemical cycling, as well as to help characterize and optimize doping parameters though in-situ doping measurements, by enabling real-time study of such membrane systems.

Application of the collective model to determine some rotational bands of 239U nucleus

238U material is component in fuels of nuclear reactor core. Understanding properties and structure of 238U nucleus is necessary before simulating and designing nuclear reactor. Besides that, the study of nuclear reaction is necessary to identify the specific characteristics of nucleus, it is the most effective experimental method up to now. However, in order to explain the properties of nuclear structure, in addition to study of the nuclear reaction, nuclear structure models and its theory must be used. There are many nuclear structure models to solve those properties of nucleus. This paper presents application of the Collective Model to determine some rotational bands of 239U nucleus, using Prompt gamma neutron activation analysis method (PGNAA). Experiment is performed at channel No.2 of Dalat Research Reactor (DRR), using Filtered Thermal Neutron Beam and Compton Suppression Spectroscopy with High – Purity Germanium detector (HPGe). The results have found 11 rotational bands of 239U nucleus. This work is very necessary for the research of nuclear structure which controls material technology by itself.

A spectrometer with baseline correction and fast pulse pile-up rejection for prompt gamma neutron activation analysis technology.

The prompt gamma neutron activation analysis (PGNAA) technology is an online nondestructive material analysis technology widely used in industries. In order to achieve real-time measurements, the gamma ray count rate should reach 400 kcps. Due to the limitation of the detector's decay time, the signal output from the detector is heavily piled up. Meanwhile, the industrial site has a temperature fluctuation of 0-50 °C, causing the peak drift in the energy spectrum. This paper presents a readout electronic system specified for PGNAA and proposes series of algorithms that are dedicated for the gamma-ray spectrometric system. The system can achieve a count rate of 400 kcps, and it overcomes poor resolution, spectral distortion, and peak position shift, which are caused by pulse pileups and temperature fluctuations.

Monte Carlo simulation of an upgraded PGNAA shielding at TRR–1/M1

This paper describes the upgraded collimator and shielding design principle for the prompt gamma neutron activation analysis (PGNAA) facility at the Thai Research Reactor. The neutronic calculations with different geometry and material conditions are simulated using the Monte Carlo code. Then, the optimal parameters to maximize the thermal neutrons and minimize background radiations are obtained. The simulation result provides significant contribution in upgrading the PGNAA facility to be available in various applications.

Logging method for formation water salinity determination by PGNAA technology

A prompt gamma neutron activation analysis logging method for formation water salinity determination is proposed. The response of formation water salinity for capture gamma ray spectrum and thermal neutron counts ratio are studied by Monte Carlo simulation method. Formation porosity and borehole fluid salinity influence on formation water salinity is corrected. A synthetical logging case is simulated to indicate the effectiveness of this logging method. The new logging method is also applied in oil field, and the formation water salinity of different depth is calculated.

Set-up of prompt gamma neutron activation analysis system at Kartini reactor

Setup and testing of prompt gamma neutron activation analysis (PGNAA) system by using neutron source from the radial beam-port of Kartini reactor have been done. The method used is an experimental characterization of neutron flux in the radial beam-port then setting up of PGNAA system and determination of elements in a bulk solution sample of salt (NaCl). The PGNAA system configuration consists of the collimator with L/D of 28.9 made from lead placed inside the beam-port, bulk sample with 20cm x 20cm x 43cm in dimension located at 30 cm from outer surface of the beam-port, and NaITl detector. The distance of sample to NaITl detector is 20 cm. The experimental test results show that the elements contained in the sample solution of salt can be detected well. The neutron flux in the outer surface of beam-port was measured using activation foil detector, the result was in the order of 106 n cm-2 s-1 with a cadmium ratio of 14.

A method for improving the evaluation of elemental concentrations measured by geochemical well logging

The increasing complexity of oil and gas reservoirs demands an accurate understanding of formation composition and mineralogy. Geochemical well logging based on prompt gamma neutron activation analysis technique (PGNAA) plays a crucial role in determining elemental concentrations, identifying lithology and improving the evaluation of matrix properties. The accuracy of elemental concentrations dictates the accuracy of other derived parameters. Elemental standard gamma ray spectra, which are predetermined for each instrument in the research and development phase, can be obtained by experimental measurements. These standards are the foundation of the processing of the neutron induced gamma ray spectroscopy and are considered to be fixed for each instrument. By using Monte Carlo numerical modelling, the standard gamma ray spectra of individual elements under different conditions are calculated. The results show that variation of borehole size, drilling mud types and other logging conditions have impacts on the shapes of the standard libraries. Therefore, if only one set of fixed standard spectra is utilized in processing measured spectra, the accuracy of elemental concentrations is affected. To address this problem, a model for compensating for the effect of logging conditions on the shapes of standard spectra is proposed. A field example is illustrated to validate the proposed method and result shows that the agreement between computed elemental weight fractions and XRF core analysis results is improved by using the introduced method.

Noise reduction of PGNAA spectrum using empirical mode decomposition technique

Prompt gamma neutron activation analysis (PGNAA) is frequently used in on–line analysis of raw materials in cement and coal industries which normally incorporates bismuth germanate (BGO) or sodium iodide (NaI(Tl)) scintillators. The quantitative results are basically undertaken through full–spectrum analysis method which requires an efficient noise reduction procedure to optimize PGNAA data. Here in this study, the empirical mode decomposition (EMD) technique has been used to reduce the noise level of PGNAA spectra of a neutron–irradiated NaCl·H2O solution and then the results have been compared with those of wavelet technique. The mean square errors (MSEs) comparisons confirm that both EMD and wavelet techniques can be efficiently used for noise reduction purposes, however, this study recommends the EMD technique for its independency of basic functions, simplicity and spectrum data-based operation.

Evaluation of bulk and particle sensor-based sorting systems for the New Afton block caving operation

Block and panel caving mines are increasingly being proposed for the excavation of massive ore-bodies located at depth. The lack of selectivity associated with the mining methods results in both ore and waste being caved and transported through material handling systems to the surface for processing and waste rock disposal. Sensor-based sorting systems provide an opportunity to automate the discrimination between ore grades and rock types, providing an enhanced level of selectivity for ore control and thereby improving mine productivity.To evaluate the potential to add value to a caving operation, a sensor-based ore sorting study, incorporating bulk and particle sorting systems, was carried out for the New Afton block cave mine. Results showed that rock from the copper-gold porphyry deposit is amenable to prompt gamma neutron activation analysis, and to X-ray fluorescence sensors. A conceptual flowsheet, where both technologies are used as separate unit operations, was evaluated. Test samples of varying copper head grades allowed an ore value calculation method to be developed based on the integration of continuous bulk sorting and particle sorting. The calculation method can be applied to block models of a future cave at New Afton and used to evaluate the change in the economic footprint. It was found that the concept demonstrated an improvement in the net smelter return of excavated material.

Research on Interaction Between Elements for PGNAA Cement Sample

The interactions between elements such as Ca, Fe, Si, Na, Mg, Al, and S in a cement sample were analyzed using prompt gamma neutron activation analysis (PGNAA). The actual Ca, Si, and Fe contents in the cement sample and the measured values from the PGNAA were compared in terms of the interactions between the elements using a linear fitting technique, followed by applying a regression analysis correction. The results show that the linearly fitted graphs have more decentralized data points, with relatively larger errors in the measured Ca, Fe, and Si contents (maximum errors are 18.07, 1.68, and 18.47, respectively). However, the interactions between Ca, Fe, Si, Na, Mg, Al, S, and other elements were eliminated after applying the correction. Accordingly, the errors in the measured Ca, Fe, and Si contents were lower (maximum values are 0.97, 0.13, and 0.01, respectively). The correction method helps in improving the measurement accuracy.

Defect mechanisms in BaTiO3‐BiMO3 ceramics

AbstractOften, addition of BiMO3 to BaTiO3 (BT) leads to improvement in resistivity with a simultaneous shift to n‐type conduction from p‐type for BT. In considering one specific BiMO3 composition, that is, Bi(Zn1/2Ti1/2)O3 (BZT), several prospective candidates for the origin of this n‐type behavior in BT‐BZT were studied—loss of volatile cations, oxygen vacancies, bismuth present in multiple valence states and precipitation of secondary phases. Combined x‐ray and neutron diffraction, prompt gamma neutron activation analysis and electron energy loss spectroscopy suggested much higher oxygen vacancy concentration in BT‐BZT ceramics (>4%) as compared to BT alone. X‐ray photoelectron spectroscopy and x‐ray absorption spectroscopy did not suggest the presence of bismuth in multiple valence states. At the same time, using transmission electron microscopy, some minor secondary phases were observed, whose compositions were such that they could result in effective donor doping in BT‐BZT ceramics. Using experimentally determined thermodynamic parameters for BT and slopes of Kröger‐Vink plots, it has been suggested that an ionic compensation mechanism is prevalent in these ceramics instead of electronic compensation. These ionic defects have an effect of shifting the conductivity minimum in the Kröger‐Vink plots to higher oxygen partial pressure values in BT‐BZT ceramics as compared to BT, resulting in a significantly higher resistivity values in air atmosphere and n‐type behavior. This provides an important tool to tailor transport properties and defects in BT‐BiMO3 ceramics, to make them better suited for dielectric or other applications.

The characterization of radioactive waste: a critical review of techniques implemented or under development at CEA, France

This review paper describes the destructive and non-destructive measurements implemented or under development at CEA, in view to perform the most complete radioactive waste characterization. First, high-energy photon imaging (radiography, tomography) brings essential information on the waste packages, such as density, position and shape of the waste inside the container and in the possible binder, quality of coating and blocking matrices, presence of internal shields or structures, presence of cracks, voids, or other defects in the container or in the matrix, liquids or other forbidden materials, etc. Radiological assessment is then performed using a series of non-destructive techniques such as gamma-ray spectroscopy, which allows characterizing a wide range of radioactive and nuclear materials, passive neutron coincidence counting and active neutron interrogation with the differential die-away technique, or active photon interrogation with high-energy photons (photofission), to measure nuclear materials. Prompt gamma neutron activation analysis (PGNAA) can also be employed to detect toxic chemicals or elements which can greatly influence the above measurements, such as neutron moderators or absorbers. Digital auto-radiography can also be used to detect alpha and beta contaminated waste. These non-destructive assessments can be completed by gas measurements, to quantify the radioactive and radiolysis gas releases, and by destructive examinations such as coring homogeneous waste packages or cutting the heterogeneous ones, in view to perform visual examination and a series of physical, chemical, and radiochemical analyses on samples. These last allow for instance to check the mechanical and containment properties of the package envelop, or of the waste binder, to measure toxic chemicals, to assess the activity of long-lived radionuclides or pure beta emitters, to determine the isotopic composition of nuclear materials, etc.

Monte Carlo simulation of Cu, Ni and Fe grade determination in borehole by PGNAA technique

A prompt gamma neutron activation analysis borehole logging method for copper, nickel and iron grade estimation is proposed. The performance of the method was simulated by MCNP5 code. Based on the theory of neutron–gamma distribution on the borehole condition, the BGO scintillator and 3He neutron tube are adopted to record gamma ray spectrum and thermal neutron simultaneously, and least square method is used for the characteristic gamma ray counts calculation in the high energy range. The results of detection limit of metal grade in borehole condition indicate that the effectiveness of this logging method.

Study on the PGNAA measurement of heavy metals in aqueous solution by the Monte Carlo–Library Least-Squares (MCLLS) approach

In the present work, a prompt gamma neutron activation analysis (PGNAA) setup, which consists of a 300mCi 241Americium–Beryllium (Am–Be) neutron source and a 4 × 4-in. Bismuth germanium oxide (BGO) detector, was developed for heavy metal detection in aqueous solutions. A series of standard samples with analytical purity were prepared by dissolving heavy metals in deionized water. Quantitative spectrum analysis was performed by the Monte Carlo–Least-Squares (MCLLS) approach to measure the standard samples. The detector response functions of 4 × 4-in. BGO detector were generated by using the CEARDRF code. The element libraries were simulated in silico by the CEARCPG code, which was developed by Dr. Gardner. The simulation results presented were in very good agreement with the experimental results. The correlation coefficients were very close to 1 when the fitted spectrum was compared with the experimental spectrum. By applying the MCLLS approach, the relative deviation of the measurement accuracy was less than 2.27% for Ni, Mn, and Cu and up to 69.33% for Pb.

Preparation of the Nanostructured Radioisotope Metallic Oxide by Neutron Irradiation for Use as Radiotracers

Metallic oxides manganese dioxide (MnO2), samarium oxide (Sm2O3), and dysprosium oxide (Dy2O3) with nanorod-like structures were synthesized by the hydrothermal synthesis method, respectively. Subsequently, the nanostructured radioisotopes MnO2 with Mn-56, Sm2O3 with Sm-153, and Dy2O3 with Dy-165 were prepared by neutron irradiation from the HANARO research reactor, respectively. The three different elements, Mn, Sm, and Dy, were selected as radiotracers because these elements can be easily gamma-activated from neutrons (activation limits: 1 picogram (Dy), 1–10 picogram (Mn), 10–100 picogram (Sm)). Furthermore, the synthesized radioisotopes can be used as radiotracers in Prompt Gamma Neutron Activation Analysis as the rare earth metals Dy and Sm were not present in the Korean environment. The successful synthesis of the radioisotope metallic oxides was confirmed by Transmission Electron Microscopy (TEM), Energy Dispersive X-ray Spectrometry (EDS), X-ray Diffraction (XRD) analysis, and gamma spectroscopy analysis. The synthesized nanostructured radioisotope metallic oxides may be used as radiotracers in scientific, environmental, engineering, and industrial fields.