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Abstract  

The boundary conditions in which Poisson statistics can be applied in nuclear spectrometry are investigated. Improved formulas for the uncertainty of nuclear counting with deadtime and pulse pileup are presented. A comparison is made between the expected statistical uncertainty for loss-free counting, fixed live-time and fixed real-time measurements.

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Journal of Radioanalytical and Nuclear Chemistry
Authors:
P. Robouch
,
G. Arana
,
M. Eguskiza
,
S. Pommé
, and
N. Etxebarria

Abstract  

The concepts of the Guide to the expression of Uncertainties in Measurements for chemical measurements (GUM) and the recommendations of the Eurachem document "Quantifying Uncertainty in Analytical Methods" are applied to set up the uncertainty budget for k 0-NAA. The "universally applicable spreadsheet technique", described by Kragten, is applied to the k 0-NAA basic equations for the computation of uncertainties. The variance components — individual standard uncertainties — highlight the contribution and the importance of the different parameters to be taken into account.

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Abstract  

Three new synthetic multi-element standards (SMELS) were developed for testing the performance of the k 0-standardization neutron activation analysis (k 0-NAA) method when implemented in a laboratory. SMELS consist of a phenol-formaldehyde polymer matrix spiked with different groups of elements according to the half-lives of the formed radionuclides. They are classified as Type I for short-, Type II for medium- and Type III for long-lived radionuclides. This article presents the preparation of SMELS including different aspects such as choice of the matrix and spiking elements, chemical compounds, target concentrations, purity of the matrix and spiking procedure and the homogeneity study for all the spiked elements in order to demonstrate the quality of the produced materials.

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Abstract  

Radiation stability of a set of three synthetic multielement standards (SMELS) designed for validation of k 0-standardization in neutron activation analysis was tested by monitoring mass and element content changes following irradiation at a high neutron fluence rate (up to 9.1013 n.cm-2.s-1) for stepwise increased periods of time. No mass changes were detected and for all the 26 elements investigated only a chlorine content loss was observed. Thus, radiation stability of the SMELS materials for the given purpose and their suitability for use also in high-power reactors was demonstrated.

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Journal of Radioanalytical and Nuclear Chemistry
Authors:
A. Simonits
,
F. De Corte
,
S. Van Lierde
,
S. Pommé
,
P. Robouch
, and
M. Eguskiza

Abstract  

The k 0 and Q 0 values for 94Zr(n,)95Zr(E = 724.2+756.7 keV) and 96Zr(n,)97Zr( ) 97mNb (E = 743.4 keV) were re-investigated. The aim was to further improve the reliability of the neutron spectrum characterization (f and monitoring) in k 0-NAA, based on "bare monitor" methods with the use of these Zr radionuclides. So as to achieve this goal, experimental determinations were performed in three reactor centers: KFKI AEKI, Budapest (WWR-M reactor); INW, Gent (THETIS reactor); SCK·CEN, Mol (BR1 reactor). The results were: Q 0(94Zr) = 5.306; Q 0(96Zr) = 251.6; k 0(95Zr, 724.2+756.7 keV) = 2.000E-4; k 0(97Zr/97mNb, 743.4 keV) = 1.237E-5. This means that the newly evaluated k 0-values are about 4.7% lower than the formerly reported ones. It is also emphasized that the 97Zr half-life is 16.74 hours, contrary to the 1% higher values usually reported.

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