Using synthetic multi-element standards (SMELS) for calibration and quality control of the irradiation facilities in the BR1 reactor

The thermal to epithermal neutron flux ratio (f) and the deviation of the epithermal neutron spectrum from the 1/E shape (α) are essential parameters for the correct application of k ₀-standardized neutron activation analysis. Several methods are applied for the determination of f and α. They are based on Cd-covered multi-monitor or on bare-irradiations methods. The recently developed and characterized synthetic multi-element standards (SMELS) were designed as a validation tool for the proper implementation of the k ₀-NAA method in a laboratory. In particular, SMELS Type III contains Au and Zr, thus allowing the direct determination of f and α. It could, therefore, replace the traditional flux monitors. Furthermore, it could be used as a quality control material to monitor the stability of the irradiation facility and the detector. This paper presents the accuracy of the f and α determination and the feasibility of quality control using SMELS for irradiation channel Y4 of the BR1 reactor.     

Determination and evaluation of fission k0-factors for correctionof the 235U(n,f) interference in k0-NAA

In order to provide a tailored solution for the correction of the ²³⁵U interference in k₀-NAA, fission k₀-factors for the analytically relevant radionuclides/gamma-lines (versus gold as the comparator), are experimentally determined in four channels of the Gent THETIS reactor. A comparison is made with former data from the literature. The new evaluated results are to be implemented in the forthcoming upgrade of the DSMKayzero software package for k₀-NAA.     

The robustness of k 0-NAA in large multi-purpose research reactors

The challenges and opportunities associated with performing k ₀-NAA in high-powered, multi-purpose research reactors are examined and recommendations are made concerning the conditions that need to be met in such facilities in order to allow the potential for this method of elemental analysis to be fully realised.     

k 0-NAA for determination of REE in reference materials of ore sources

Journal of Radioanalytical and Nuclear Chemistry - Multielements, including some rare earth elements, have been determined by k 0-NAA in three types of ore reference materials from Australia...     

The impact of polyethylene vials on reactor channel characterization in k 0 -NAA

Reactor channel characterization is commonly performed by irradiating bare and cadmium-covered “fluence rate monitors”, avoiding as much as possible the use of irradiation vials and spacers to position the monitors inside the channel. However, in routine k ₀ -Neutron Activation Analysis often samples are packed in small polyethylene vials prior to irradiation. This work aims at studying the impact of typical NAA polyethylene vials (~1 mm wall thickness) on the determination of the f and α channel-specific parameters through the “Bare”, “Cadmium-Covered” and “Cadmium-Ratio” methods. The impact of these vials on each method was studied for 3 irradiation channels of the Belgian Reactor 1 at SCK·CEN (Mol, Belgium) with low to high f and α-values. The net impact was 1% on each parameter. Inconsistencies between the different methods were found when the impact of the polyethylene was neglected, implying that all determination methods must be pooled and thin monitors should be used for an accurate channel characterization.     

Comparison of 14 MeV-NAA, k0-NAA and ED-XRF for air pollution bio-monitoring

In this paper the performances and the limitations of three multi-elementary analysis techniques are compared applied to a study of air pollution biomonitoring in Morocco. These techniques are: (1) 14 MeV neutron activation analysis (14 MeV-NAA), (2) thermal neutron activation analysis using the k ₀ quasi-absolute method (k ₀-NAA) and (3) energy dispersive X-ray fluorescence analysis (ED-XRF). The experimental procedures and the control of the analytical results using certified reference materials are described and discussed. The three methods were confronted for the analysis of lichens, mosses and tree-barks. The complementarity of these methods enabled us to determine 43 elements in different samples. The most suitable method for each element was selected according to the sensitivity and selectivity necessitating the minimum corrections of the matrix effects and/or the interfering reactions.     

Validation of the k0_IAEA software using SMELS material at CDTN/CNEN, Brazil

The Laboratory for Neutron Activation Analysis at CDTN/CNEN, Brazil, acquired the k0_IAEA software package during the Workshop on Nuclear Data for Activation Analysis, 2005, held at the Abdus Salam International Centre for Theoretical Physics, Italy. The IAEA distributed the software to several laboratories and has accepted suggestions from the users about the performance of the program. This paper describes the validation procedure carried out aiming at the validation of the software package. The procedure was to analyze the SMELS samples and to compare the results obtained by this software to the commercial KayWin software package, already established at CDTN/CNEN. The results were compared to the values obtained by the Jožef Stefan Institute, Slovenia. The laboratories applied the same software: k0_IAEA and KayWin. The overall results pointed out that the k0_IAEA software set up at CDTN/CNEN, Brazil, is working properly. The u-score test showed that all results, except data in SMELS Type III for Se obtained at the JSI, are within 95% confidence interval once setting up u-score as 1.96 (P = 95% or ±2σ).     

Determination of major and trace elements in iron reference materials using k0-NAA

Major and trace element contents in iron ore reference materials were investigated using k ₀-instrumental neutron activation analysis (k ₀-INAA). To avoid iron interferences, radiochemical separation was developed (k ₀-RNAA). The determination of the investigated elements in the inorganic phase from hydrochloric acid solution was performed after radiochemical separation of iron by diisopropyl ether. It was found that after the Fe elimination, the limit of detection for some elements was much lower that enables their direct determination. The distribution of 39 elements (with intermediate/medium and long half-life radionuclides) after Fe removal was investigated.     

Determination of α and f for k0-NAA in irradiation sites with high thermalized neutrons

We have measured the ⁵⁷Fe Mössbauer spectra of the Hofmann pyridine complex Fe(pyridine)₂Ni(CN)₄ sample before and after exposure to high pressure of gaseous xenon. The temperature dependence of the high spin molar fraction has been determined from the ⁵⁷Fe Mössbauer spectra. The spin transition of the sample without the high pressure treatment occurs between 175 and 220 K with a hysteresis width of 15 K. Although the ⁵⁷Fe Mössbauer spectra suggest that the spin crossover behavior of the sample before and after the high pressure treatment are almost the same, the hysteresis of the latter sample is somewhat larger.     

Monte Carlo generated spectra for QA/QC of automated NAA routine

A quality check for an automated system of analyzing large sets of neutron activated samples has been developed. Activated samples are counted with an HPGe detector, in conjunction with an automated sample changer and spectral analysis tools, controlled by the Canberra GENIE 2K and REXX software. After each sample is acquired and analyzed, a Microsoft Visual Basic program imports the results into a template Microsoft Excel file where the final concentrations, uncertainties, and detection limits are determined. Standard reference materials are included in each set of 40 samples as a standard quality assurance/quality control (QA/QC) test. A select group of sample spectra are also visually reviewed to check the peak fitting routines. A reference spectrum was generated in MCNP 4c2 using an F8, pulse-height, tally with a detector model of the actual detector used in counting. The detector model matches the detector resolution, energy calibration, and counting geometry. The generated spectrum also contained a radioisotope matrix that was similar to what was expected in the samples. This spectrum can then be put through the automated system and analyzed along with the other samples. The automated results are then compared to expected results for QA/QC assurance.     

The role of k0-NAA in the assessment of the annual radiation dose for use in TL/OSL dating of sediments

An account is given of the role and the strength of k ₀-INAA to assess the annual radiation dose (contribution of U, Th, K and Rb) for use in TL/OSL dating of sediments. Mention is made of: (1) its simplicity of sample preparation, (2) its accuracy and even its reference character for other elemental determination methods, (3) the possibility of obtaining the Rb content with no extra effort and (4) its capability to easily and reliably quantify U and Th in a small amount of etched quartz grains, followed by evaluating the importance of their presence in the quartz inclusion technique.     

A database for QA/QC in neutron activation analysis and gamma-ray spectrometry

A database has been designed for storing, retrieving and analyzing information about samples, experimental conditions and results obtained by neutron activation analysis and gamma-ray spectrometry. It has been created using Microsoft ACCESS 2002 under a Windows operating system. The database has been designed not only for saving information but also for quality assurance and quality control purposes. The structure of the relational design has been discussed and demonstrated with a new graphical feature of ACCESS 2002 called PIVOTCHART.     

Determination of 135Cs in nuclear power plant wastes by ICP-MS and k 0-NAA

A radiochemical method for the determination of ¹³⁵Cs in radioactive wastes has been adopted/developed. For the separation of cesium from other elements ammonium-molybdophosphate precipitation and cation exchange chromatography were used. The chemical yield of the method was about 60–100 %. ¹³⁵Cs was measured by two methods. In neutron activation analysis (NAA), Cs was irradiated with reactor neutrons. ¹³⁶Cs was detected by gamma spectrometry, wherefrom the activity/mass of ¹³⁵Cs was calculated according to the k ₀-standardization technique. The Cs containing fractions were measured by inductive coupled plasma mass spectrometry, as well. NAA and ICP-MS techniques were comparatively evaluated and a good agreement between the results was found. The activity concentration of ¹³⁵Cs in a couple of waste samples originating from VVER-440 type nuclear reactors was in the range of 1–5 Bq L^?1 (20–120 ng L^?1) while ¹³⁷Cs activity concentrations varied between 0.1 and 1 MBq L^?1.     

k0-NAA quality assessment by analysis of different certified reference materials using the KAYZERO/SOLCOI software

A suite of natural matrix reference materials (RMs) were used to assess the quality of analytical results obtained by k ₀-instrumental neutron activation analysis (k ₀-INAA) at the Joef Stefan Institute (IJS). Five certified reference materials (CRMs) from the Institute for Reference Materials and Measurements (IRMM), two standard reference materials (SRMs) from the National Institute of Standards and Technology (NIST), three RMs from the International Atomic Energy Agency (IAEA) and one RM from IJS were analyzed. Altogether, results for twenty-four elements in inorganic matrices and twenty-nine elements in organic matrices, obtained by k ₀-INAA, were compared to certified values. Results obtained show good agreement with certified or assigned values except for Fe, La, Nd, Sm and U in inorganic matrices, and Ag, Al and Cr in organic matrices.     

Analysis of SMELS by k 0-based IM-NAA method using PFTS position of KAMINI reactor for quality control exercise

As a part of QA/QC of k ₀-based internal monostandard neutron activation analysis (IM-NAA), three types of synthetic multielement standards (SMELS) were analyzed using pneumatic fast transfer system irradiation position of KAMINI reactor, IGCAR. Radioactive assay of activation products was carried out by high resolution gamma ray spectrometry. IM-NAA was used to determine relative concentration ratios of 22 elements with respect to gold internal monostandard. Absolute concentrations were calculated using assigned concentration of Au in all the types of SMELS. Z-score values within ±1 at 95.5 % confidence level and percentage deviations within ±5 % indicated good quality of the results by IM-NAA in most of the cases. Using this methodology, an ilmenite mineral sample was analyzed and concentrations of 14 elements were determined using Sc as monostandard.     

The preparation of monitors and comparators for k0-INAA using standard solutions

Journal of Radioanalytical and Nuclear Chemistry - The methodology adopted at the Laboratory of Analytical Techniques of Instituto Peruano de Energía Nuclear for preparation of monitors and...     

Micro-PIXE characterization of reference samples intended for QA/QC of k<Subscript>0</Subscript> NAA

Cellulose cylinders and circular filter papers spiked with known amounts of standard element solutions were prepared for studying some aspects of assessing measurement uncertainty of NAA and the elemental distribution measured by micro-PIXE analysis. Results for the cylinders showed strongly non-homogeneous distribution of the elements, both in radial and vertical directions, dominantly caused by osmosis driven transport of added liquid solution from the centre to the edges. Results for the thin cellulose filter paper disks exhibited weaker peaking of the standard element concentrations at the edges in comparison with the thick cylinders.     

Determination of polybrominated diphenylethers (PBDEs) in biological tissues with special emphasis on QC/QA measures

This paper gives an overview on the determination of PBDEs in biological tissues, such as human blood and milk, cow’s milk and fish with special emphasis on quality control and assurance measures which are mandatory and a prerequisite for a reliable determination of environmental pollutants at trace levels. First experiences in the determination of PBDEs have been gained nearly 20 years ago. Due to great progress in the development of analytical instrumentation, the applied GC/MS methods resulted in very low detection limits. Furthermore, because of unexpected findings in biological tissues, the determination of PBDEs became of growing importance in the past few years. The analysis of hundreds of samples demonstrated the need for extensive quality control/quality assurance (QC/QA) measures which will be reported in detail in the following.     

Establishment of the k 0, \bar{E}_{\rm r}, Q 0, and cascade coincidence correction factors for the determination of 129I by k 0-NAA

A k ₀-NAA procedure used in the determination of ¹²⁹I is established. For this purpose, the k ₀-values for the reaction ¹²⁹I (n, ??) ¹³⁰I are determined, the Q ₀- and $\bar{E}_{\rm r}$ -values are calculated, and the correction procedure for the cascade coincidence effects is established by calculation of the correction factor COI for five ¹³⁰I ??-rays (418.0, 536.1, 668.5, 739.5, and 1157.5 keV).     

Results of the second inventory on quality assurance/quality control (QA/QC) and good laboratory practice (GLP) for European Union National Reference Laboratories for residue analyses.

In February 1996 the "Second inventory on QA/QC and GLP for EU-NRLs" was submitted to all European Union National Reference Laboratories (EU-NRLs) for residue analyses. This second inventory was a follow up on the "Inventory on QA/QC" (1993) which was used for the organisation of the first workshop on "GLP for EC-NRLs". In February 1997 a response on the second inventory of 100% was achieved. From the completed inventories it became evident that almost all EU-NRLs for residue analyses now have a described quality program based on an international standard. However only 33% of the EU-NRLs are officially accredited, certified or in compliance with good laboratory practice (GLP) principles. Most of the accredited EU-NRLs have a quality program based on the European Standard EN45001. Seven of the EU-NRLs still do not have a described quality program or have not appointed a quality officer and for 12 of the EU-NRLs the independence of the QA officer is not formally arranged. Only about 50% of the EU-NRLs have a standard operating protocol (SOP) to handle complaints. Almost all of the EU-NRLs have SOPs available and a system to control them. In comparison with the results of the first inventory it is evident that most of the EU-NRLs have made considerable progress in the implementation of quality systems. However it is also evident that a substantial number of EU-NRLs still lack some critical QA facilities. The new deadline for the full implementation of all relevant QA facilities is January 2002.