Application of multidimensional spectrum analysis for neutron activation analysis

Feasibility of the method of multidimensional -ray spectrometer for neutron activation analysis was examined. Reference igneous rock (JP-1, JB-1a and JB-1) samples issued by the Geological Survey of Japan (GSJ) and the Allende meteorite reference sample were irradiated in a research reactor, and multiple -rays from the produced radioisotopes via neutron capture reactions were measured using an array of twelve germanium detectors with BGO Compton suppressors called GEMINI. Simultaneously thirty elements were observed with no chemical separation. The observed smallest component was Eu contained in JP-1 with abundance of 4 ppb.     

Application of neutron activation analysis to metallobiochemistry

Some typical applications of long-term/low-level exposure (LLE) is presented including in vivo LLE study on rats and in vitro experiments on some metal binding components as well as on cadimium binding protein.     

Application of neutron activation analysis to bone samples

Summary Neutron activation analysis technique, using Au as flux monitor, was applied to determine element concentrations of Ca, K, Na, Mg, Mn and Sr in certified reference material (NIST 1400 Bone Ash). The results were compared with those using comparative INAA and they were compatible. The same results were obtained using the recommended k₀ factors, in order to obtain the activation cross section as input in concentration for the same reference material. Some applications in the health area aiming clinical evaluation in bone samples of medium and small-sized animals were performed and the viability of using this methodology was discussed.     

Application of the radioreagent method for yield determination in neutron activation analysis

A very convenient method for yield determination in NAA is the use of isotopic radiotracers. But for the majority of elements determinable by NAA no suitable isotopic radiotracers exist. For some of these elements the radioreagent methodoffers afvourable opportunity to use also non-isotopic radiotracers. An activation analytical copper determination method is described using a radioactively labelled reagent for correction of separation losses. Results of copper determinations in 8 international standard reference materials are given.     

Application of the 30 MeV microtron for gamma and neutron activation analysis

Based on studies of variable multiplicity electron acceleration, the power-current microtron, a cyclic electron accelerator up to energies of 30–35 MeV has been developed at the Institute on Physical Problems of the Academy of Sciences of the USSR. The 1–1.5 kW electron beam of the microtron is comparable to the power output of modern linear accelerators operating at similar energies. At the same time, the microtron has a number of significant advantages, due to the simplicity of design of both accelerator and ultrahigh-frequency tract, the high efficiency of ultrahigh-frequency power utilization, good operating characteristics, strictly monochromatic electron beams (variations not exceeding ±50 keV at 30 MeV) and the possibility of continuously changing particle energy as required by the given experimental task.     

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.     

Multivariate calibration for neutron activation analysis

The application of target factor analysis to the analysis of gamma-ray spectra collected for activation analysis is proposed. Satisfactory analysis of a trial set of samples was carried out using measured spectra as targets. Single-isotope spectra were obtained from mixture spectra by free-floating and performed satisfactorily as target spectra. The factor analysis method requires less resolution than peak-based methods.     

Optimization of Linac-based neutron source for thermal neutron activation analysis

Journal of Radioanalytical and Nuclear Chemistry - A 20 MeV electron Linac based neutron beam has been shaped for neutron activation analysis (NAA) technique. A beam shaping assembly (BSA)...     

Application of anti-Compton counting in instrumental neutron activation analysis

The inherent advantage of anti-coincidence counting of low-level radioactivity is defined in terms of changes in the limits of decision, detection and determination. It appears that the advantage factor can be expressed in the experimentally observed reductions of peak area, compton continuum and natural background. For an array equipped with a sample changer the advantage factor for interference by the compton continuum is4, while that for interference by the natural background amounts to 3. By sacrificing the sample changer and closing its gap with a Nal-plug, additional factors of 1.5 and 2 can be obtained for compton and natural background respectively.     

Instrumental neutron activation analysis for the elemental analysis of cement

Cement is widely used as a construction material in Libya. Production plants introduce certain contaminants to the environment. The dust from such plants is carried away to neighbouring areas. This dust contains a substantial amount of contaminants depending on the origin of clays used in the production. In this study, a survey of elemental concentration of clay and cement was carried out to assess the environmental impact of such plants, especially those that are situated near residential and agricultural areas. Cement and clay samples, imported and locally produced, were analyzed. Instrumental neutron activation analysis was utilized to determine the elemental concentration of As, Ca, Ce, Co, Cr, Eu, Fe, Hf, La, Na, Rb, Sb, Sc, Sm, Ta, Th, U, Yb and Zn. Elevated concentrations of U and Th were found in a number of cement samples. The two nuclides are part of an elaborate decay scheme producing a range of radioactive elements, which emit alpha-, beta- and gamma-radiation. With ⁴⁰K, they could give elevated levels of background radiation in buildings resulting in higher exposure doses. This could pose a health hazard and a detrimental effect on the well being of residents, especially in poor ventillated buildings. Also, cement is the main component for constructing underground reservoirs for collecting rainwater for drinking in private residences, so some harmful elements could leach into water. This is the first comprehensive survey of commercial cement brands and clays used in Libya. These results are intended to build a database for trace element concentrations using INAA.     

Application of neutron activation analysis in acid precipitation studies

Instrumental neutron activation analysis has been successfully employed in three distrinct acid precipitation studies. These include the determination of ten (Al, Br, Ca, Cl, Cu, I, Mg, Mn, Na and V) elements in urban rainfall, elevated aluminum concentrations in acidified lakes and major ions (Ca, Cl, K, Mg and Na) in small-mouth bass kept in controlled pH environments. Quality control was assured by analyzing two certified standard reference materials prepared by the National Bureau of Standards (NBS 1643a) and National Research Council of Canada (hepatopancreas TORT-1 marine biological tissue).     

Multiparameter neutron activation analysis

An advanced neutron activation technique has been developed for the accurate analysis of elemental and isotopic fissile material required in nuclear safeguards, nuclear material standardization and other applications. It is based on reactor neutron flux spectrum differentiation by cadmium screening and multistandard calibration, including the solution of a second order equation system or of computerized calibration curve fitting, taking into account the thermal neutron flux depression. Some discrepancies at high enrichments have still to be eliminated in order to achieve the required measurement accuracy.     

Epithermal instrumental neutron activation analysis in conjunction with anti-coincidence gamma-ray spectrometry for investigating iodine levels in Canadian foods

In order to reduce interferences from high activities of ²⁴Na, ⁵⁶Mn, ⁸²Br, and ³⁸Cl as well as to improve detection limits, precision, and accuracy of measuring iodine levels in biological materials, foods and diets in particular, an epithermal instrumental neutron activation analysis (EINAA) method in conjunction with anti-coincidence (EINAA-AC) gamma-ray spectrometry was employed. The Compton scattering background in the region of the 442.9-keV photopeak of ¹²⁸I was significantly suppressed by anti-coincidence counting. In order to validate the EINAA-AC method as well as to evaluate its broad applicability to diverse types of biological material, 17 NIST and IAEA reference materials containing very low to high levels of iodine as well as interfering elements were analyzed by the EINAA-AC method. The samples were irradiated in the cadmium-lined pneumatic site at a neutron flux of 2 × 10¹¹ cm^?2 s^?1 of the Dalhousie University SLOWPOKE-2 Reactor (DUSR) facility for 10 or 20 min followed by 1-min decay and 30-min counting. The detection limit for iodine by EINAA-AC was improved by a factor of 2–5 compared to EINAA depending on the sample matrix and other factors, and a limit of 3–5 μg kg^?1 was achieved for low-salt foods. We found the RSD to be about ±5 % above 200, increasing to ±10 % at 20, and then to greater than ±30 % at about 5 μg kg^?1 iodine levels.     

Application of neutron activation analysis for trace element determinations in biological materials

Over the past three decades, more and more interest has been focused on trace eleemnts in biological materials. This increasing interest has gone hand in hand with the continuous improvement of analytical techniques. Neutron activation analysis has proven to be a most suitable method for the quantitative determination of a wide variety of trace (0.01–100 μg g^?1) and ultratrace (<0.01 μg g^?1) elements in biological materials. This technique has even played a preponderant role in this field.     

Epithermal neutron activation analysis

Different modes of epithermal neutron activation analysis are described. The principles and examples are given for each.     

Correction for neutron self-shielding in large-sample prompt-gamma neutron activation analysis

When a sample is analysed with neutron activation analysis (NAA) neutron self-shielding and gamma self-absorption affect the accuracy. Both effects become even more important when the mass of a sample analysed is changed from small (say, 1 g) to large (say 30 kg). Therefore, corrections have to be carried out. In this article only the correction method for neutron self-shielding is considered for a thermal neutron beam irradiating large homogeneous samples for prompt-gamma NAA (PGNAA). The correction method depends on the macroscopic scattering and absorption cross sections of the sample. To avoid doing experiments with samples with different macroscopic scattering and absorption cross sections, the Monte Carlo model MCNP is applied in the development of the correction method. The computational development of the method to determine these cross sections through flux monitoring outside the sample is described.     

Gamma-ray tables for neutron fast neutron and photon activation analysis

In the past several years, a number of gamma-ray tables have been published. All of the tables limit themselves to those nuclides formed in (n, γ) reactions or at most to a few of the more prominent (n, 2n) products. A number of investigators are developing activation analysis methods using fast neutrons or photons. These investigations have been hampered by the lack of tables of gamma-rays of those nuclides that can be formed by (n, 2n), (n, p), (n, α), (n, n′) and (n, d) reactions. Since (γ, n) yields the same product as (n, 2n) the table would also be useful to photon activation studies. The authors have compiled such a table. Section II: list of the gamma-rays for all isotopes in order of increasing energy will be published in the J. Radioanal. Chem., 25 (1975) No. 2.     

Determination of the chemical composition of the South Pole aerosol by instrumental neutron activation analysis

Atmospheric particulate samples were collected at the geographic South pole, using cellulose and polycarbonate filters and cascade impactors. The samples were analysed for 40 elements by instrumental neutron activation analysis. From the filter samples atmospheric concentrations for 33 elements could be obtained. The highest atmospheric concentrations were found for S: 49 ng/standard cubic meter (SCM) of air, Na: 3.3 ng/SCM and Cl: 2.6 ng/SCM. In the cascade impactor samples, only a few elements were observed above blank. For these elements it could be concluded that they are associated for over 80–90% with submicron size paricles.     

Capillary neutron optics for prompt-gamma activation analysis

A neutron lens has been constructed to focus cold neutrons from the exit of a⁵⁸Ni neutron guide, which delivers a beam to the Prompt-Gamma Activation Analysis (PGAA) station at the NIST Cold Neutron Research Facility. The lens compresses a neutron beam of cross section 50 mm× 45 mm onto a focal spot of diameter 0.53 mm (fwhm) wich an average gain of 80 in neutron current density. PGAA measurements have been performed to demonstrate the enhanced sensitivity and detection limits for various elements and the spatial resolution in one transverse dimension. For the two test particles (a gadolinium glass bead and cadmium metal of sizes less than 0.5 mm), the gain in the -count rate with the lens is a factor of 60, and the detection limit is improved by a factor of 20. The system can be used for two-dimensional mapping of samples on a sub-millimeter scale to complement other analytical techniques such as neutron depth profiling (NDP).     

An automated facility for neutron activation analysis

A fully automated neutron activation analysis (NAA) facility has been constructed at the Whiteshell Nuclear Research Establishment. This high-capacity facility has been designed for use with a wide variety of neutron sources, including Canada's SLOWPOKE II and MAPLE research reactors. Its pneumatic transfer system is driven by a Square-D Model 500 programmable controller, linked in turn to a Nuclear Data ND6700 computer/spectrometer. Custom software for data entry and system control has been combined with Nuclear Data software for gamma-spectrum acquisition and processing to create a flexible, easy-to-use facility for NAA. Its design and performance are discussed.