Authors:M. Toribio, J. García, A. Izquierdo-Ridorsa, G. Rauret, A. Coll, I. Vallés, and X. Ortega
The activity of -emitting radionuclides is usually measured by semiconductor detectors (surface barrier or ion implanted). Overlapping and composite bands are quite common problems depending on energy differences of the radionuclides and counting source preparation. The classical approach to activity quantification is based on peak integration and, when it is used, overlapping may be overcome by a detailed study of each case, whereas composite bands can not be completely resolved. Here, spectra of the -emitting plutonium isotopes, obtained by ion implanted semiconductor detectors, have been used to compare the classical approach with a multivariate calibration method (MVC-PLS). The study is performed at environmental activity levels (0–52 dpm). The relative errors obtained for239+240Pu activity determination, using either the classical or the MVC-PLS approach with replicates, are good enough to quantify isotopes at low level activities. The distribution of relative errors is asymmetric, with a positive component for 0–10.5 dpm subset, in the classical approach whereas it is more symmetric in the MVC-PLS method. The results show that the classical approach depends on peak overlap, whereas the MVC does not. As a whole, MVC is a more robust method than the classical approach. Composite bands were studied using the239Pu–240Pu mixture; the MVC approach did not allow individual quantification due to the lack of signal reproducibility. This instability does not affect the regular integration procedures but it is important in the deconvolution processes. The lack of reproducibility is related to the source preparation process.
An empirical procedure is described which is readily capable of producing reliable and accurate efficiency calibration sources of low activity for high-resolution -ray spectrometers. Known activities of a multiisotopic solution are adsorbed onto a mixture of cation and anion-exchange resins and chromatographic-grade cellulose. The dried powder that results can be mixed with any desired solid natural matrix material to produce a homogeneous, extended geometry, efficiency calibration source. Results are presented which enable the method to be critically evaluated.
Authors:R. Romvári, A. Dobrowolski, I. Repa, P. Allen, E. Olsen, A. Szabó, and P. Horn
Sixty left sides of pig carcasses were scanned by spiral computed tomography (CT) to measure lean meat weight and percentage. The carcasses were fully dissected and scanned to develop a calibration protocol. Different image analyses were performed on the basis of anatomically defined scans, direct volumetric estimation, body- and grey-scale ranges and using Partial Least Squares (PLS) regression of data provided by CT. The R2values of the calibrations for lean meat weight were 0.874, 0.976, 0.983 and 0.992, respectively, depending on the method applied. The PLS proved to be the best approach with a calibration RSD of 232 g. When changing from lean meat weight to percentage, the statistical goodness drops to a very small extent (R2= 0.988, RSD = 0.56). According to the results, the CT method can be recommended as a reference for determining the lean meat content of pig carcasses.
Authors:R. Dewberry, D. Williams, R. Lee, D. Roberts, L. Arrigo, and S. Salaymeh
In this paper, the setup, calibration, and testing of the F-Area Analytical Labs active well neutron coincidence counter (HV-221000-NDA-X-1-DK-AWCC-1)
in SRNL are described for use in the Savannah River Site (SRS) transuranium metal production facility to enable assay of mixed
uranium/plutonium metal product. The instrument was required within a three-month window for availability upon receipt of
LANL uranium oxide samples into the SRS facility. Calibration of the instrument in the SRNL nuclear nondestructive assay facility
in the range 10–400 g HEU is described. We also report qualification and installation of the instrument for assay of the initial
suite of product samples.
Thermoanalytical instruments are extensively used in R&D as well as in industrial quality control. A quantitative analysis
of the data of a thermoanalytical measurement requires a careful calibration of the instrument. In differential scanning calorimetry
(DSC) the quantities that have to be calibrated are the temperature and the heat flow. These two quantities are usually calibrated
by evaluating melting or solid-solid transitions of some reference materials with well known transition enthalpies and temperatures.
In this contribution we investigate temperature and heat flow calibration in the temperature range between −100 and 160C.
We included 9 different samples for the analysis and established some general rules for the calibration process. As a result
we found that with a well calibrated instrument the heat flow can be measured with 90% confidence to about 3% accuracy in
this temperature range. With respect to temperature calibration we find that accuracies of 0.8C (90% confidence) may be
expected. These values represent general accuracy limitations of DSC’s due to varying heat transfer conditions within the
Authors:H. Dung, M. Freitas, S. Sarmento, M. Blaauw, and D. Beasley
A new Compton suppression system (CSS) for the gamma-ray spectrometer portion of the neutron activation analysis (NAA) was
set up at the RPI/ITN. The pneumatic transfer system, SIPRA, for short-lived nuclides and cyclic irradiations was improved.
A full calibration procedure of the CSS and SIPRA systems was performed. Two certified reference materials, NIST-SRM-1572
(Citrus Leaves) and NIST-SRM-1633a (Coal Fly Ash) were analyzed using the calibration factors. The CSS was instrumental in
lowering the detection limits of Cr, Fe, Hg, Rb, Sr, Th and Zn by reducing background and/or spectral interference considerably.
The analytical results were evaluated by comparison to the NIST certified values with deviations ranging from 2% to 8% for
the above mentioned elements, except Zn ranging from 10% to 15% for biological and environmental samples, respectively.
Authors:D. Arginelli, J. Heikkonen, A. Miranti, C. Peroni, S. Ridone, and L. Vigna
SPECT studies are sensitive but inaccurate means through which to analyze small volumes such as, for instance, remnant tissues
after thyroidectomy. We studied the relation between known volumes (0.1–10 cm3) and volumes measured with SPECT studies and using solutions of four different isotopes: 99mTc, 117mSn, 111In, 131I. The curves we determined were tested on SPECT images of two patients treated with 131I. Our work suggests the possibility to evaluate the small remnant mass using calibration curves specific to the system of
image acquisition. However, it is necessary to extend the study to a larger number of patients.
Authors:S. Bhade, P. Reddy, A. Narayanan, K. Narayan, D. Babu, and D. Sharma
Simultaneous measurement of gross alpha and gross beta activities by liquid scintillation counting technique using LKB Wallac
Quantulus 1220 liquid scintillation counter (LSC) equipped with Pulse Shape Analyzer (PSA) is described. Three sets of pure
alpha and pure beta standards simulating the activity concentration values of real samples in terms of α/β activity ratios
were used to calibrate the LSC. Calibration methodology for the Quantulus 1220 with respect to the above measurements using
241Am and 90Sr/90Y standards of respective activity concentrations of ~25 dpm and ~104 dpm is described in detail. Also highlighted the need to calibrate the LSC using another set of 241Am and 90Sr/90Y standards of low and high activity concentrations respectively. The practicability and working performance of these calibration
plots was checked by the validation trials with test samples spiked with 241Am and 90Sr/90Y covering range of α/β activity ratios from 1:1 to 1:50.