Taking advantages of nuclear analytical techniques (NATs) with non-destruction, multielement capability, small and estimable
uncertainties over a wide range of sample sizes, the sampling behavior of multielements for a home-made natural matrix material
was studied with sample sizes ranging from several hundred mg down to tenths ng, namely nine orders of magnitude, by a combination
of three NATs, neutron activation analysis (NAA), proton induced X-ray emission (PIXE) and synchrotron radiation X-ray flurescence
(SR-XRF), in an effort to explore a procedure for the development of certified reference materials (CRMs) suitable for quality
control of microanalysis. For accurately weighable sample sizes (>1 mg), sampling uncertainties for 13 elements were found
to be less than 1% by INAA. For sample sizes unable to be accurately weighed (<1 mg), PIXE and SR-XRF were used, respectively.
Sampling uncertainties were found to be less than 1% at sample sizes of tenth mg level for seven elements, and less than 10%
on ng levels for three elements. Considering these three elements have satisfied homogeneity (sampling uncertainty less than
10%) at ng sample size level, any one of them can be served as a “relative balance” in sampling behavior characterization
of multielements on sample size levels larger than ng (e.g., μg level). On this basis, sampling uncertainties for nine elements
were found to be less than 10% on μg sample size level by INAA. The results indicate that the matrix is eligible as a candidate
of CRMs suitable for quality control of solid sampling microanalysis.
A sensitive and accurate method for determination of radium isotopes in soil samples by α-spectrometry has been developed 225Ra, which is in equilibrium with its mother 229Th, was used as a yield tracer. Radium in soil samples was fused together with Na2CO3 and Na2O2 at 600 °C, leached with HNO3, HCl and HF, preconcentrated by coprecipitation with BaSO4, separated from uranium, thorium and iron using a Microthene-TOPO chromatographic column, isolated from barium in a cation-exchange
resin column using 0.05M 1,2-cyclohexylene-dinitrilo-tetraacetic acid monohydrate as an eluant, electrodeposited on a stainless
steel disc, and counted by α-spectrometry. The detection limit of the method is 0.43 Bq·kg−1 for 226Ra, 228Ra and 224Ra if 0.50 g of soil sample are analyzed. The method was checked with two certified reference materials supplied by the IAEA,
and reliable results were obtained Fourteen soil samples collected from the refractory industry in Italy were also analyzed.
The mean radiochemical yields for radium were 85.7±4.3%, and the obtained radium concentrations in the soil samples were in
the range of 8.08–3878 Bq·kg−1 for 226Ra, of 1.60–678 Bq·kg−1 for 228Ra and 1.25–550 Bq·kg−1 for 224Ra, with 228Ra/226Ra and 224Ra/226Ra ratios ranged from 0.159–0.821 and from 0.142 to 0.525, respectively.
Authors:S. Jonah, M. Oladipo, I. Umar, N. Rabiu, Y. Idris, and I. Zakari
An irradiation procedure with fast and thermal neutrons from a 5 Ci Am-Be isotopic neutron source irradiation facility in
combination with a 3''3' NaI(Tl) detector system has been used to determine Al/Si weight ratios in alumino-silicates. Samples
were irradiated with and without Cd cover for 10 minutes and counted for 10 minutes after a waiting time of 1 minute. The
peak area analysis of the 1779 keV gamma-ray line of 28Al product radionuclide produced via 27Al(n,γ)28Al and 28Si(n,p)28Al reactions in combination with the neutron flux parameter at the irradiation site and nuclear data were used to determine
Al/Si ratios. Due to discrepancy in literature data, Am-Be neutron source spectrum averaged cross sections of (n,p) reactions
on 27Al, 28Si and 56Fe were determined by the activation technique using 115In(n,n')115mIn as the fast neutron flux monitor reaction. The method was tested using mixtures of high-purity Al2O3 and SiO2 with known weight ratios of Al/Si and validated by a certified reference material BCS-CRM 348 (Ball Clay). Results are presented
for bentonite, kaolin, bauxite, feldspar and ball clay samples from Nigeria. The method is non-destructive, rapid and suitable
for use in-situ for large-scale exploration works and industrial process control.
The Portuguese Research Reactor (RPI) is a 1 MW swimming pool type reactor, operating since the early 1960s. The fuel is MTR type, with flat plates of U-Al alloy enriched to 93% in 235U. As the core configuration changed in April 2000, it became essential to characterise the neutron field in the most useful irradiation positions of RPI, in order to guarantee the accuracy in the application of k0-neutron activation analysis (k0-NAA). Experimental values of the thermal to epithermal neutron flux ratio (f) and of the deviation of the epithermal neutron spectrum from the 1/E shape (a) were determined using the Cd-ratio for multi-monitor method. The neutron temperature (Tn) was obtained from co-irradiation of Lu with 1/v
monitors. The results for several irradiation positions are presented and discussed in this work. Some element concentrations are determined based on the parameters obtained in this work, and compared with the certified reference material concentrations.
Authors:Ho Dung, Menno Blaauw, Daniel Beasley, and Maria Freitas
The k0-based cyclic neutron activation analysis (k0-CNAA) technique has been studied to explore the applicability at the Portuguese research reactor (RPI). In particular, for
the determination of elements which form short-lived radionuclides, particularly fluorine (20F, 11.16 s half-life) and selenium (77mSe, 17.36 s half-life) in polymer, biological and environmental samples. The detection limits obtained for F and Se were about
50 and 0.01 mg kg−1, respectively, in the investigated materials. The timing parameters for the procedure were 10 to 20 s for irradiation, 5 s
decay, 10 to 20 s counting, 5 s waiting and performed with eight cycles. The k0-IAEA program was modified to use millisecond time resolution for irradiation, decay and counting times as needed for interpreting
k0-CNAA data in terms of concentration, accuracy and detection limit. The quality control of the procedure was performed by
preparing a standard solution containing fluorine with different contents as well as using the certified reference materials
containing selenium from which the bias between the results and the certified values were within 15% for most elements at
the investigated content ranges. The analytical results for several other elements producing short-lived or detectable radionuclides,
e.g., Al, Ca, Cl, Cu, Dy, I, Mg, Mn, Ti, and V were also obtained by the k0-CNAA procedure with accuracy within 12%.
A simple, fast, low cost, and precise direct β-correction spectrophotometric method was developed for thorium determination in water. The method is based on the reaction
of Th(IV) with 4-(2-pyridylazo)-resorcinol (PAR) in aqueous solution of pH 5–6 and measuring the absorbance of the resulting
red-colored complex at λmax 497 nm. The effective molar absorptivity of the Th(IV)-PAR complex was 2.52 × 104 L mol−1 cm−1. Beer’s law and Ringbom plots were obeyed in the concentration range 0.04–2.0 and 0.07–1.2 μg mL−1 of thorium ions using β-correction spectrophotometry, respectively. The limits of detection and quantification of Th(IV)
were 0.02 and 0.066 μg mL−1, respectively. The developed method was applied for the analysis of thorium in certified reference material (IAEA-soil-7), tap-, underground- and Red-sea water samples. The validation of the method was also tested by comparison with data obtained
by ICP-MS. The method is convenient, less sensitive to common interfering species and less laborious than most of published
methods. The statistical treatment of data in terms of Student t-tests and variance ratio f-tests has revealed no significance differences. The structure of the Th(IV)-PAR complex was determined with the aid of spectroscopic
measurements (UV–Visible and Fourier Transform Infrared Spectroscopy).
Neutron Activation Analysis (NAA) was applied to determine trace and major elements in Mission–Progresso (Texas) soils. The
Rio Grande river runs along the USA—Mexico border. The soil samples were collected at Mission and Progresso areas of the Rio
Grande riverbank in the USA side. Soils were analyzed for the presence of toxic effluents due to human activities that might
affect agricultural products and health because one of the possible paths of intoxication is the agricultural product consumption.
Dried, sieved, and blended soil samples (~1.5 g) were irradiated at the UT Austin TRIGA reactor at a thermal neutron flux
of 1 × 1012 n cm−2s−1 and epithermal neutron flux of 1 × 1011 n cm−2s−1. Different irradiations, decay, and counting times were combined to determine concentration and detection limits of 21 elements
which represent four areas in Mission–Progresso (Texas) with the aim to achieve a consistent characterization. NIST certified
reference materials were used in relative analysis and also to determine the accuracy and reproducibility values. The neutron
flux was monitored using sulfur flux monitor wires. Normal and Compton suppression gamma ray spectrometers were used to detect
different gamma ray energy peaks and this Compton system greatly reduces the background. Concentrations are evaluated in per
cent and parts per million and errors are within acceptable levels and these values are compared with values reported in literatures
from other countries. The results do not show significant contaminations neither from the Rio Grande river nor from nearby
The laboratory for instrumental neutron activation analysis at the Reactor Institute Delft, Delft University of Technology
uses a network of 3 gamma-ray spectrometers with well-type detectors and 2 gamma-ray spectrometers with coaxial detectors,
all equipped with modern sample changers, as well as 2 spectrometers with coaxial detectors at the two fast rabbit systems.
A wide variety of samples is processed through the system, all at specific optimized (and thus different) analytical protocols,
and using different combination of the spectrometer systems. The gamma-ray spectra are analyzed by several qualified operators.
The laboratory therefore needs to anticipate on the occurrence of random and systematic inconsistencies in the results (such
as bias, non-linearity or wrong assignments due to spectral interferences) resulting from differences in operator performance,
selection of analytical protocol and experimental conditions. This has been accomplished by taking advantage of the systematic
processing of internal quality control samples such as certified reference materials and blanks in each test run. The data
from these internal quality control analyses have been stored in a databank since 1991, and are now used to assess the various
method performance indicators as indicators for the method’s robustness.
Authors:T. Miura, S. Oikawa, T. Kishimoto, S. Banba, and T. Morimoto
A rapid analytical method of Pu in environmental samples by alpha-ray spectrometry and high-resolution inductively coupled plasma mass spectrometer (HR-ICP-MS) using a 3M Empore anion exchange resin disk for solid phase extraction has been developed. A trace amount of Pu was quantitatively adsorbed with an Empore anion exchange resin disk (47 mm diam.) at a flow rate of 150–200 ml/min from 8M HNO3 sample solution. The disk was washed with 10 ml of 8M HNO3 and 12 ml of 9M HCl and then the Pu was quantitatively eluted with 15 ml of 1M HNO3/0.03M ascorbic acid solution. The time needed to separate Pu from the sample solution with the present method was about 20 minutes. The separated Pu was determined with alpha-ray spectrometry and HR-ICP-MS. The present method was applied to the determination of Pu in the certified reference material (IAEA-135) and the environmental soil sample. The analytical results were almost in good agreement with the literature values.
Performance characteristics (especially accuracy) of a routine INAA with k0 standardization were verified and compared with those of INAA with a classical single comparator. For this purpose, samples of three certified reference materials of environmental origin (Fly Ash, Orchard Leaves and Buffalo River Sediment—all supplied by NIST) were irradiated with both kinds of comparators (Au–Zr for k0 and Zn for classical k method) in one irradiation rabbit. Also the following steps of INAA procedure were practically the same for both standardization methods used (counting, spectral processing, etc.). The results have shown that the k0 method gives sufficiently accurate results comparable with those of the well established and routinely used single comparator (Zn) method, provided proper neutron flux monitoring, efficiency calibration and also coincidence summing corrections are applied. This work shows that modern k0 standardization method in INAA can be sucessfully used in routine practice and applied with an advantage in INAA laboratories subject to changes of neutron spectra or counting conditions.