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  • Author or Editor: Bangfa Ni x
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Abstract  

A post-Ko study of parametric reactor NAA is described including the determination and applications of working KoS for non-1/V reactions151Eu(n,)152Eu and176Lu(n,)177Lu; parametric corrections for235U fission, threshold reaction and -spectral interferences; and parametric normalizations for different counting geometries. The analytical significance, the principles, the experimental confirmations, and the application examples of these methods are briefly introduced.

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Abstract  

Forty elements in IAEA-331 (Spinach), an intercomparison material, have been determined using NAA. Among them, 30 elements, Ag, Al, Ba, Br, Ca, Ce, Cl, Co, Cr, Cs, Eu, Fe, Hf, K, La, Mg, Mn, Na, Ni, Rb, Re, Sc, Se, Sr, Ta, Tb, Th, V, Zn and Zr were determined by INAA. A series of simple and quantitative radiochemical separation procedures were established for the determination of ten additional elements. Cd, Lu, Mo, Sb, Sm, Yb, U were determined by removing the major interfering nuclide82Br. Cu was determined by 0.048M NaDDTC/CHCl3 extraction from 1M HCl medium. As and P were determined using an inorganic exchange column of acid aluminium oxide (AAO). Integral counts from 80 keV to 130 keV contributed by Bremsstrahlung from32P -were used to evaluate the content of phosphorus.

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Abstract  

45 elements have been determined by NAA in an IAEA Lake Sediment RM SL-3 Multitechniques were used to fully tap the potential of NAA in terms of the number of the determinable elements and the accuracy of each data.

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Abstract  

Characterizations of three major parameters of Certified Reference Materials (CRMs) concentration values of multielements, homogeneities of multielements, and stabilities of the materials, were further studied by NAA. In the determinations of multielements in RMs, both relative and K0 (and its extension) standardizations were used in an effort to detect hidden systematic errors and expand the number of determinable elements. In the evaluations of multielemental homogeneities, double sampling constants as well as Ingamells' Ks and F-test were used to establish semi-quantitative expressions of sampling uncertainty vs. size and number of subsamples for given elements in given materials. For the investigation of the stabilities of certified values, K0 NAA is to be used in follow-up analyses to test variations of certified values and provide updated and/or newly determined data. The final goal is to make NAA a definitive method for multi-trace element certification, a reliable method for homogeneity characterization, and a reproducible method for stability test. Examples are given to show preliminary results on the above aspects.

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Abstract  

A procedure of pre-irradiation concentration of zinc in fecal samples using anion exchanger was developed for the study of the bioavailability of zinc by neutron activation analysis. The mass ratios between70Zn and68Zn, or64Zn and their contents between natural zinc and enriched zinc are used to calculate the bioavailability of zinc when the abundance of the isotope70Zn is not high ehough.

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Abstract  

Certifications of trace elements in existing CRMs, especially biological CRMs, are far from satisfactory. Neutron activation analysis (NAA) for its inherent advantages combined with newly established parametric standardization, may contribute to improve this situation. The continuing progress of the hybrid extended k 0-relative NAA technique developed in our laboratory is discussed. Examples are given to show the reliability of the method in certification of multielements. RNAA is still one of the best methods, or even the method of choice, in analysis at sub-g/g concentration levels. The suitability of the technique for this purpose has been studied through the determination of rare earth elements at ng/g concentration level in two Chinese biological CRMs using both RNAA and ICPMS. Sampling behaviors of multielements in CRMs have been studied by INAA in an effort to develop CRMs suitable for analysis with small sample sizes.

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Abstract  

Mn-nodule is one of the most important deep sea mineral resources to be explored and exploited in the next century. Analytical quality control based on this kind of Certified Reference Materials (CRMs) is therefore necessay. In the present work, nearly 30 elements in two Chinese Mn nodule Reference Materials (RMs), GSPN-2 and GSPN-3, were determined using extendedK 0-relative comparison NAA technique, developed in our laboratory. The unique features of this work include; (1) high accuracy obtained by the interal validation function of our technique; (2) extensive determinable elements obtained by the hybrid nature of our software and (3) neutron flux self-shielding corrections.

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Abstract  

The Effective Interaction Depth (EID) law has been systematically studied and applied to parametric normalization for peak count rates obtained at different source-detector distances (S-D). The errors caused by EID normalization are less than 4% over the full range of S-D (from to several mm) for true coincidence-free -rays. Parametric corrections for the true coincidence (summing) effect are also established, based on simplified decay schemes and P/T ratio determinations. The total response of Ge detector for single-energy -rays (T) is clearly defined with scattering contributions from surroundings included. Errors from summing effect corrections are also less than 4%. The combined EID normalization and summing effect corrections give an error no greater than 5.7% for the worst situations (several mm S-D and cascade-crossover decay scheme), acceptable for most practical K0 NAA.

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Abstract  

Thirty two elements were determined in five pieces of presumed cosmic dust samples with the weights of 5 to 25 g by neutron activation analysis (NAA). All the interferences from fission, threshold reactions and -spectra were corrected for and different counting geometries normalized. Enrichment factors with reference to C1-chondrite are about 200 and 100 for lithophile refractory elements (e.g., V, Th, Hf and W) and rare earth elements (REE), respectively. Deficiencies were observed for Co, Cr, Mg and Na, etc. The C1-chondrite normalized REE patterns are close to those of extraterrestrial materials, with no anomaly of Eu, indicating an extraterrestrial origin of the grain samples analyzed.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: Bangfa Ni, Pingsheng Wang, Huiling Nie, Shuyuan Li, Xuefeng Liu, and Weizhi Tian

Abstract  

A PC controlled automatic INAA system is briefly introduced. The unique features of the system in software, hardware, and quality control procedures are described. Major performances are given to show the analytical quality and productivity of the system.

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