Delayed Neutron Activation Analysis Research Articles

Application of Neutron Flux from PUSPATI TRIGA Mark II Research Reactor in Enhancing Superconducting Properties of BSCCO Superconductor

The PUSPATI TRIGA Mark II Research Reactor is currently been used in various applications such as Neutron Activation Analysis (NAA), Delayed Neutron Activation Analysis (DNAA), radioisotope production for medical, industrial and agricultural purposes, Neutron Radiography and Small Angle Neutron Scattering (SANS). However, there are not much research activities on utilizing neutron flux from the reactor to study properties of superconducting materials. For superconductors to be fabricated into components of electrical and magnetic devices, the sustainability of the transition temperature, TC and the transport critical current density, JC of the materials is vital to ensure the durability and effectiveness of the devices. A strong superconducting flux pinning capability of superconductors is necessary to maintain high TC and larger JC. Meanwhile, exposure of superconductors to neutron flux is able to create the self-organization of defects that are responsible in producing higher TC and JC in superconductors where the defects act as the flux pinning centres. In this paper, we report the utilization of neutron flux from the PUSPATI TRIGA Mark II research reactor in enhancing the TC and JC of bismuth-strontium-calcium-copper oxide (BSCCO) superconductor. Appropriate sample holder and shielding was fabricated as protection from radiation effect. In this work, 2212-phase BSCCO superconductor (Bi-2212 phase) samples were synthesized using the conventional solid-state reaction method. The samples underwent fast neutron irradiation with neutron flux of 2.0 × 1011 neutrons/(cm2.s) for 6 hours. Results showed that the TC of the samples improved slightly, and the JC was found to increase by more than 3 folds.

Feasibility of chromium measurement in skin using a portable hand-held XRF system

Abstract Chromium (III) is a trace mineral that plays an important role in glucose and lipid metabolism in the body, in addition to being used in clinical formulations for the treatment of hypoglycemia. Chromium (Cr) deficiency in humans is known to cause insulin resistance and diabetes, however, effects of over exposure are not well studied or understood. This study aims to determine the feasibility of measuring Cr in skin using a portable InnovX XRF system at 40 kVp and 100 μA with a mean beam energy of 20 keV. Calibration lines were developed for K α and K β X-ray peaks using fiberglass resin phantoms with 1000 mg/L Cr(III) atomic standard solution, assuming a homogeneous distribution of Cr in skin. This assumption was validated through previously acquired XRF data from tissue cross-sections. Analysis of these data not only showed the presence of Cr in tissue samples, but also that Cr was distributed evenly across the tissue cross-section. Phantom concentrations were validated using delayed neutron activation analysis of fragments of each phantom via the neutron capture reaction 50Cr(n,γ)51Cr. Minimum detection limit (MDL) of the XRF system was determined using these calibration lines to be 5 ± 1 μg/g. This system was used to acquire data from the skin surface of five different parts of the body on four cadavers through a 300 s acquisition at each location. Cr was measurable at the 95% confidence level in 90% of the cadaver skin sites. The effective dose was determined to be 0.013 μSv which is small compared to a dental X-ray. However, the beam was very narrow so the skin dose delivered at the central axis of the beam was 201 mSv. Although the Cr levels did not vary significantly between the cadavers, the different parts of the body showed statistically significant differences in Cr levels. The XRF system used for this study shows promise as an effective monitoring tool for quantifying Cr levels in skin, although adjustments to produce a less collimated beam, and interrogate a larger area of skin, will be preferable so that the central dose is not as intense.

Health Effects Due to Radionuclides Content of Solid Minerals within Port of Richards Bay, South Africa.

This study assessed the radiological health hazards to various body organs of workers working within Transnet Precinct in Richards Bay in Kwazulu-Natal, South Africa due to radionuclide content of mineral ores often stored within the facility. Thirty samples were collected from five mineral ores (rock phosphate, rutile, zircon, coal and hematite) and analyzed for 238U, 234U, 226Ra, 210Pb, 235U, 232Th, 228Ra, 228Th and 40K using delayed neutron activation analysis and low energy gamma spectroscopy. Rutile was found to be the most radioactive mineral ore within the facility with 210Pb concentration of 759.00 ± 106.00 Bq·kg−1. Effective annual dose rate in (mSv·y−1) delivered to different organs of the body: testes, bone marrow, whole body, lungs and ovaries from mineral ores were such that dose from mineral ores decreased in the order coal > rutile > rock phosphate > hematite > zircon. The organs with the highest received dose rate were the testes and this received dose was from coal. However, all of the calculated absorbed dose rates to organs of the body were below the maximum permissible safety limits.

Correction methods for uranium analysis by DNAA

Uranium determination by delayed neutron activation analysis is carried out by comparing the delayed neutron counts of a test sample to those of a uranium standard irradiated under identical conditions. Inaccurate results are obtained at high uranium concentrations (greater than approximately 0.05 mg 235U), due to the deterioration of the linear relationship between delayed neutron counts and uranium content, and also when the sample matrix contains other elements that are neutron enhancers or absorbers, for example rare earth elements. In this paper, a correction method has been developed for the accurate analysis of samples with high uranium content (e.g. uranium peroxide). A second correction method, based on the thermal neutron self-shielding calculation developed by Chilian et al., has been applied to DNAA for the first time to correct for neutron absorption interferences in uranium analysis of rare earth-containing samples.

Analytical applications of delayed and instrumental neutron activation analysis

Delayed neutron activation analysis (DNAA) is a rapid and sensitive analytical method for the determination of fissile elements in a variety of samples. The present work describes two different analytical applications of delayed neutron activation for the analysis of biological and environmental samples, respectively. In the first application, DNAA was utilized to determine the natural uranium content in NIST standard reference materials (SRM) 1547 peach leaves and 1573a tomato leaves. Measured uranium mass fractions are comparable to the non-certified values listed on the certificates for these materials. In the second application, delayed neutron activation is coupled with instrumental neutron activation analysis (INAA) for the measurement of rare earth elements (REE) (cerium, lanthanum, neodymium, and ytterbium) in NIST SRM 2586, Trace Elements in Soil Containing Lead from Paint. DNAA was utilized to determine the uranium mass fraction in SRM 2586 for the subsequent application of a correction factor to account for cerium, lanthanum, and neodymium produced as part of the INAA irradiation. Measured and corrected mass fractions for the REEs described here are all within the uncertainty limits provided on the NIST certificate for SRM 2586. These results and the demonstrated sensitivity of the DNAA system establish and validate the use of this method for the determination of REEs and for potential nuclear forensics applications.

The simultaneous determination of 235U and 239Pu using delayed neutron activation analysis

Delayed neutron activation analysis (DNAA) remains one of the most sensitive methods of nondestructively determining fissile materials in a variety of sample matrices, provided that the samples contain only a single fissile component. This has historically been the limiting factor in many applications of DNAA, and often chemically destructive methods of analysis have needed to be utilized for many real-world samples. This work seeks to develop a method that will allow for DNAA to be utilized on samples containing multiple fissile components. Initial efforts, presented here, show that using a multivariate linear regression model to describe the delayed neutron emission profile of an irradiated sample allows for the concurrent determination of fissile nuclides in samples containing both 235U and 239Pu, without chemical separations and using only a single counting step.

Determination of aluminium, silicon and magnesium in geological matrices by delayed neutron activation analysis based on k0 instrumental neutron activation analysis

In this work, concentrations of silicon, aluminium and magnesium in geological matrices were determined by Neutron Activation Analysis based on k0-IAEA software. The optimum activation and delay times were found to be 5min and 15–20min respectively for the determination of Si via 29Si (n,p) 29Al reaction. The adopted irradiation scheme did not work for the determination of magnesium. Each sample was irradiated under a thermal neutron flux density of 5.0×1011ncm−2s−1. Cadmium covered activation indicated that a permanent epithermal irradiation site for research reactors would be very useful for routine determination of silicon in environmental samples.

Delayed-neutron activation analysis at NIST

An automated delayed-neutron activation analysis system has been installed at the NIST research reactor. This work involved characterization of the transfer time of the system, evaluation of blanks, and tests of the system’s analytical capabilities through quantitative analysis for uranium in several natural matrix standard reference materials (SRMs). The calibration curve was shown to be linear up to at least 20 μg of uranium, and the well-thermalized reactor irradiation position makes the system insensitive to thorium and oxygen. For SRMs 1646a Estuarine Sediment and 2710a Montana Soil the values determined for this work agree with the reference and certified values, respectively. The mass fraction of uranium in SRM 695 Multi-Nutrient Fertilizer is the first reported for this material. For this system and the irradiation, transfer, and counting times used, the limit of detection for natural uranium is 20 ng, which corresponds to approximately 200 pg of 235U.

Design of a phantom equivalent to measure bone-fluorine in a human's hand via delayed neutron activation analysis

Fluorine is an element that can be either beneficial or harmful, depending on the total amount accumulated in the teeth or bones. In our laboratory, we have developed a non-invasive technique for the in vivo measurement of fluoride in bone using neutron activation analysis and performed the first pilot human study. Fluoride in humans is quantified by comparing the γ-ray signal from a person to the γ-ray signal obtained from appropriate anthropomorphic calibration phantoms. An identified problem with existing fluoride phantoms is contamination with aluminum. Aluminum creates an interfering γ-ray signal which, although it can be subtracted out, increases the uncertainty in the measurement and worsens the detection limit. This paper outlines a series of studies undertaken to develop a better calibration phantom for fluorine measurement, which does not have aluminum contamination.

In vivo quantification of bone-fluorine by delayed neutron activation analysis: a pilot study of hand-bone-fluorine levels in a Canadian population

Humans can be exposed to fluorine (F) through their diet, occupation, environment and oral dental care products. Fluorine, at proper dosages, is believed to have positive effects by reducing the incidence of dental caries, but fluorine toxicity can occur when people are exposed to excessive quantities of fluorine. In this paper we present the results of a small pilot in vivo study on 33 participants living in Southwestern Ontario, Canada. The mean age of participants was 45 ± 18 years with a range of 20–87 years. The observed calcium normalized hand-bone-fluorine concentrations in this small pilot study ranged from 1.1 to 8.8 mg F/g Ca. Every person measured in this study had levels of fluorine in bone above the detection limit of the system. The average fluorine concentration in bone was found to be 3.5 ± 0.4 mg F/g Ca. No difference was observed in average concentration for men and women. In addition, a significant correlation (r2 = 0.55, p < 0.001) was observed between hand-bone-fluorine content and age. The amount of fluorine was found to increase at a rate of 0.084 ± 0.014 mg F/g Ca per year. There was no significant difference observed in this small group of subjects between the accumulation rates in men and women. To the best of our knowledge, this is the first time data from in vivo measurement of fluorine content in humans by neutron activation analysis have been presented. The data determined by this technique were found to be consistent with results from ex vivo studies from other countries. We suggest that the data demonstrate that this low risk non-invasive diagnostic technique will permit the routine assessment of bone-fluorine content with potential application in the study of clinical bone-related diseases. This small study demonstrated that people in Southern Ontario are exposed to fluoride in measureable quantities, and that fluoride can be seen to accumulate in bone with age. However, all volunteers were found to have levels below those expected with clinical fluorosis, and only one older subject was found to have levels comparable with preclinical exposure.

The feasibility of in vivo quantification of bone-fluorine in humans by delayed neutron activation analysis: a pilot study

Fluorine (F) plays an important role in dental health and bone formation. Many studies have shown that excess fluoride (F−) can result in dental or skeletal fluorosis, while other studies have indicated that a proper dosage of fluoride may have a protective effect on bone fracture incidence. Fluorine is stored almost completely in the skeleton making bone an ideal site for measurement to assess long-term exposure. This paper outlines a feasibility study of a technique to measure bone-fluorine non-invasively in the human hand using in vivo neutron activation analysis (IVNAA) via the 19F(n,γ)20F reaction. Irradiations were performed using the Tandetron accelerator at McMaster University. Eight NaI(Tl) detectors arranged in a 4π geometry were employed for delayed counting of the emitted 1.63 MeV gamma ray. The short 11 s half-life of 20F presents a difficult and unique practical challenge in terms of patient irradiation and subsequent detection. We have employed two simultaneous timing methods to determine the fluorine sensitivity by eliminating the interference of the 1.64 MeV gamma ray from the 37Cl(n,γ)38Cl reaction. The timing method consisted of three counting periods: an initial 30 s (sum of three 10 s periods) count period for F, followed by a 120 s decay period, and a subsequent 300 s count period to obtain information pertaining to Ca and Cl. The phantom minimum detectable limit (MDL) determined by this method was 0.96 mg F/g Ca. The MDL was improved by dividing the initial timing period into three equal segments (10 s each) and combining the results using inverse variance weighting. This resulted in a phantom MDL of 0.66 mg F/g Ca. These detection limits are comparable to ex vivo results for various bones in the adult skeleton reported in the literature. Dosimetry was performed for these irradiation conditions. The equivalent dose for each phantom measurement was determined to be 30 mSv. The effective dose was however low, 35 µSv, which is comparable to other clinical diagnostic tools. The MDL, relatively low radiation dose and non-invasiveness indicate the suitability of this method for routine in vivo analysis of bone-fluorine content. This prompted us to perform a trial study in human subjects. A preliminary human study on 34 participants was completed, with 33 of the 34 measurements proving to be successful. The in vivo MDL based on the improved timing method was determined to be 0.69 mg F/g Ca for the 33 successful human measurements. In our opinion, this technique has been demonstrated to be a suitable method for in vivo assessment of fluorine bone-burden.

GGR Biennial Review: Atomic Absorption, Inductively Coupled Plasma‐Atomic Emission Spectrometry, Neutron Activation Analysis and X‐Ray Fluorescence Spectrometry Review for 2008–2009

This review describes developments major and in trace element determination using atomic absorption spectroscopy (AAS), inductively coupled plasma‐atomic emission spectrometry (ICP‐AES), instrumental neutron activation analysis (INAA), and X‐ray fluorescence (XRF) spectrometry that were reported in 2008 and 2009. Publication levels were comparable to those of previous years, except for XRF which showed an increase in the number of articles published in the past 2 years. In terms of number of publications and impact, the most active field was AAS, while INAA was the least active. As expected for well‐established and mature methods, novel developments for all four analytical techniques were relatively sparse. For AAS, the most notable publications concerned developments in sample introduction, particularly focussing on solid samples, increasing analyte sensitivity, and higher sample throughput. For ICP‐AES, publication of developments in sample introduction, remediation of matrix effects and calibration continues. Compared with past years, there was a clear focus on sample preconcentration methods, but very few publications reporting new hyphenated speciation methods. For INAA, there were several publications exploring the accuracy and robustness of the method, as well as the requirements for INAA to meet criteria for a primary method of measurement. Two other related techniques, delayed neutron activation analysis, and prompt gamma activation analysis, were also described. Hyphenated XRF techniques showed interesting developments in enabling XRF and XRD analysis on the same spot, and further work characterising and calibrating three‐dimensional micro‐XRF shows promising results for investigating sample heterogeneity.

INAA and DNAA for uranium determination in geological samples from Egypt

Uranium isotopes found in soil, rock, water, plants, air, etc., contribute to the natural radiation exposure of the population. U concentrations in some Egyptian environmental samples like Toshki soil, Aswan iron-ore, and phosphate samples from El-Sibayia in the Nile Valley and El-Quseir in the Red Sea coast were determined using instrumental neutron activation analysis (INAA) and delayed neutron activation analysis (DNAA) in the Mainz TRIGA research reactor. The results showed that the phosphate rocks are rich natural sources of uranium among the other minerals forming the earth crust.

CHARACTERISTICS OF A NEW PNEUMATIC TRANSFER SYSTEM FOR A NEUTRON ACTIVATION ANALYSIS AT THE HANARO RESEARCH REACTOR

A rapid pneumatic transfer system (PTS) for an instrumental neutron activation analysis (INAA) is developed as an automatic irradiation facility involving the measurement of a short half-life nuclide and a delayed neutron counting system. Three new PTS designs with improved functions were constructed at the HANARO research reactor in 2006. The new system is composed of a manual system and an automatic system for both an INAA and a delayed neutron activation analysis (DNAA). The design and basic conception of a modified PTS are described, and the functions of system operation and control, radiation protection and emissions of radioactive gas are improved. In addition, a form of capsule transportation of these systems is tested. The experimental results pertaining to the irradiation characteristics with variation of the neutron flux and the temperature of the irradiation position with the irradiation time are presented, as is an analysis of the reference material for analytical quality control and uncertainty assessments.

U determination in environmental samples by delayed neutron activation analysis in Korea

A delayed neutron counting system has been implemented at the HANARO research reactor in 2007. Thermal neutron flux measured at the NAA #2 irradiation hole coupled to the delayed counting system, was higher than 3 × 1013 n cm−2 s−1. The delayed neutron counting system is composed of 18 3He detectors which are divided into three groups with six detectors and the collected signals of each group are processed to a digital signal. The count numbers were measured with the uranium mass by using NIST SRMs under fixed analytical condition and their correlation could be determined. Finally, delayed neutron activation analysis has been carried out for the determination of uranium mass fraction in the collected environmental samples.

Commissioning of NAA at the new OPAL reactor in Australia

In April 2007 the new nuclear research reactor, OPAL, was opened at Lucas Heights in Sydney. OPAL is a 20 MW open pool light water reactor with a heavy water reflector vessel and contains a cold neutron source. It is a multi-purpose facility for radioisotope production, irradiation services and neutron beam research. The OPAL design includes purpose-built facilities for instrumental neutron activation analysis (INAA) and delayed neutron activation analysis (DNAA). For INAA there is a short residence time facility in a neutron flux of around 2·1013 cm−2·s−1 and a number of long residence time facilities providing fluxes from 3·1012 to 1·1014 cm−2·s–1. The flux at the short residence time DNAA facility is around 6·1012 cm−2·s−1. The main focus for INAA at OPAL is the research community, meeting the needs of a wide range of disciplines, including mineral processing, geology, the environment, health and archaeology. Both the relative (comparator) method and the k 0-method of standardization for INAA are being established in OPAL. A description of progress, plans and capabilities are presented.

Delayed neutron activation analysis for safeguards

Delayed neutron activation analysis (DNAA) presents a fast, accurate, and reliable method for quantification of fissile material. The method has relatively few sources of error and may be accomplished nondestructively. The need for a fast, accurate screening of materials stems from the necessity to protect cleanroom facilities from widely varying fissile quantities in samples and from desired gains in efficiency of mass spectrometric analysis by assisting in spike level selection and by removing from the sample set those materials that are not of interest. During the last several years, many different materials have been screened or analyzed in support of international safeguards, internal process control for actinide separations, and in uranium contamination assessments. Swipes from a variety of sources have been analyzed, either before or after dissolution, and comparison of the DNAA results to mass spectrometry results is generally favorable. A facility characterization of the High Flux Isotope Reactor was performed using filter paper swipes to demonstrate the utility of the DNAA technique.

High-energy and thermal-neutron imaging and modeling with an amorphous silicon flat-panel detector

The Los Alamos Neutron Science Center (LANSCE) operates two spallation neutron sources dedicated to research in materials science, condensed-matter physics, and fundamental and applied nuclear physics. Prior to 1995, all thermal neutron radiography at Los Alamos was done on a beam port attached to the Omega West reactor, a small 8 MW research reactor used primarily for radioisotope production and prompt and delayed neutron activation analysis. After the closure of this facility, two largely independent radiography development efforts were begun at LANSCE using moderated cold and thermal neutrons from the Target-1 source and high-energy neutrons from the Target-4 source. Investigations with cold and thermal neutrons employed a neutron converter and film, a scintillation screen and CCD camera system, and a new high-resolution amorphous silicon (a-Si) flat-panel detector system. Recent work with high-energy neutrons ( E n>1 MeV) has involved storage-phosphor image plates. Some comparison high-energy images were obtained with both image plates and the a-Si panel and showed equivalent image quality for approximately equal exposure times.

Experimental Determination of Detection Limits for Performing Neutron Activation Analysis for Gold in the Field

Measurements are presented of gold concentration in rock/soil samples by delayed neutron activation analysis using a device and method that are potentially field portable. The device consists of a polyethylene moderator and 252Cf as the source of neutrons for activating the samples and a high-purity germanium detector to measure the 412-keV gamma-ray emissions from activated gold. This information is used to extract the gold concentration in the sample. Two types of samples were investigated: (a) pure SiO2 doped with a known amount of gold chloride and (b) U.S. Geological Survey standards. The former types were used to evaluate optimum device performance and to calibrate the device and method. The latter types were used to show typical system performance for the intended application (field exploration for gold deposits). It was found that the device was capable of determining gold concentrations to ~10 ppb with a turnaround time (the sum of irradiation, decay, and counting times) of ~10 days. For samples where the gold concentration was much higher (i.e., gold ore), turnaround times are ~2 days and could be shortened further by sacrificing accuracy (e.g., lessening irradiation, decay, and counting times) or by augmenting source strength.

Heavy metals and rare earth elements source-sink in some Egyptian cigarettes as determined by neutron activation analysis

Heavy metals and rare earth elements in two types of cigarettes were studied. The contents of trace elements were determined by using delayed neutron activation analysis. In the present study 11 elements have been detected in popular and fine brand cigarettes marketed in Egypt. Evaluation of these elements with their potential hazards for smokers is briefly discussed. The material balance (source and sink) for each element was determined. Also the ratio of element recovery to the total amount was assessed.