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Abstract  

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 k0-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 k0-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.

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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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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  

After critical evaluation of a number of existing standardization methods a new approach introducing generalized k0-factors was suggested in 1975 for use in (n, γ) reactor neutron activation analysis (RNAA). In order that the new method could soon be applied competitively in actual analytical work a cooperation between the Activation Analytical Laboratories of the Central Research Institute for Physics (KFKI), Budapest and the Institute for Nuclear Sciences (INW), Gent was established to determine the k0 and other related nuclear data (Q0, T1/2, Ēr, etc.) with a high accuracy, to develop procedures for monitoring essential irradiation and measuring parameters (Φse, α, ∈p,
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, etc.) as well as to share experiences when applying the method. This paper summarizes the main results of this cooperative work obtained in the last five years. The current status and recent developments in the k0-method are reviewed and a “Status and Request List” compiled from more than a thousand surveyed nuclear data on about 150 analitically important (n, γ) reactions in being prepared to suggest new or refined measurements and to prevent the use of unreliable data.
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Abstract  

A best choice from literature was made of the isotopic abundance values for64zn,112Sn and174Yb, and of the absolute gamma-intensities for65Zn,113mIn and175Yb. From these data and from activation method experiments, the following 2200 m·s–1 cross sections were determined:65Zn(n, )65Zn; 0=(0.726±0.0007) barn [cf. literature 0.76–0.78 barn];112Sn(n,)113(m)Sn; 0(0.91 m+g)=(0.539±0.011) barn [cf. literature 1 barn];174Yb(n,)175(m)Yb; 0(m+g)=(130+4) barn [cf. literature 65 barn].

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Abstract  

In this second part the list of resonance integrals is completed with 63 values for (n, γ) reactions mainly from the second part of the periodic system. The resonance integral for (n, fission) of235U is included as well as thermal and epithermal self-shielding curves for the elements Sm, Eu, Gd, Dy and Cd.

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Abstract  

The isotopes97Ru,103Ru and105Ru, produced by reactor irradiation of elemental ruthenium, were applied as triple comparators in the activation analysis of rock FU-41, a basanitoid from Fuerteventura, Canary Island. The concentrations of the following elements were determined: Sm, Sc, Fe, Co, Na, La, Hf, Eu, Th and Cr. The aim of this work was the experimental control of the error theory of the multiple comparator method as well as the experimental check of the accuracy.

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Abstract  

For 13 isotopes, the resonance integral to thermal crosssection ratio was studied. The results of two different methods, applied in two different laboratories, are compared. One method consists in a direct determination of I00-values from Cd-ratio measurements, the other is based on the evaluation of literature data, using accurately determined k0-factors from two irradiation channels with largely different thermal-to-epithermal flux ratios.

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Abstract  

The infinite dilution resonance integrals of fifteen (n,γ)reactions leading to the production of short-lived radioisotopes were determined. The irradiation parameters were checked by comparing the results of different methods and the measuring equipment was carefully controlled.

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Abstract  

By comparison of experimental k0-factors, determined in reactor positions with greatly different thermal-to-epithermal neutron flux ratios, and by comparison of experimentally determined and theoretically calculated k0-factors, it is possible in some cases to select best values from literature data for (n, γ) activation cross-sections and for absolute gamma intensities. This is demonstrated for97Zr,95Zr,56Mn and65Zn.

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