No (253)
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A comparative study of the total mercury determination in highly contaminated soils by AAS and RNAA methods
Sysalová, J.; Kučera, Jan; Zvěřina, O.
2014 - English
Výsledky srovnávací studie stanovení celkové rtuti ve vysoce kontaminovaných půdách do obsahu 25 mg/kg byly získány dvěma nezávislými metodami: metodou AAS s použitím jednoúčelového spektrometru AMA-254 s přímým dávkováním 10-25 mg pevných vzorků a metodou neutronové aktivační analýzy s radiochemickou separací (RNAA) s navážkami 150 mg vzorků. Vzorky půd byly upravovány sítováním a kryogenním mletím. Kontrola kvality výsledků byla provedena analýzami certifikovaných referenčních materiálů NIST SRM 2711 Montana Soil a NIST SRM 2711a Montana Soil II. Pro vyšší obsahy rtuti nad 25 mg/kg, byly vzorky ředěny mořským pískem v poměru 1:10 a homogenizovány před dávkováním do AMA-254. Proces ředění vzorků v pevném stavu byl ověřen analýzou říčního sedimentu ERM-CC580. Výsledky analýz celkových obsahů rtuti v kontaminovaných půdách získané nezávislými metodami AAS a RNAA vykazují velmi dobrou shodu pro oba uvedené postupy. High total mercury (T-Hg) contents in soils, up to 25 mg kg−1, were determined by two independent methods: a one-purpose atomic absorption spectrometer AMA-254 (Advanced Mercury Analyser) with direct solid sampling, and radiochemical neutron activation analysis (RNAA), using sample masses of 10 mg to 25 mg and about 150 mg, respectively. An excellent agreement between results of both methods was obtained. For quality control (QC) purposes, NIST SRM 2711 Montana Soil and NIST SRM 2711a were analysed by both methods using the above sample masses. The results obtained were compared with the NIST certified values within the uncertainty margins, thus proving the accuracy of the procedures employed. It has been found that the cryogenic grinding used provided sufficiently representative and homogeneous samples. A test in which HgS was analysed by RNAA showed that even mercury present in sulfide form would be fully recovered using the procedures employed. For contents of T-Hg above the upper limit of the AMA-254 working range (500 ng), samples were firstly diluted with sea sand in the ratio 1:10 and homogenised well to get RSD below 5%. The dilution procedure was verified using the certified reference material ERM-CC580 Estuarine Sediment.
Keywords:
mercury; RNAA; Advanced Mercury Analyser
Available at various institutes of the ASCR
A comparative study of the total mercury determination in highly contaminated soils by AAS and RNAA methods
Výsledky srovnávací studie stanovení celkové rtuti ve vysoce kontaminovaných půdách do obsahu 25 mg/kg byly získány dvěma nezávislými metodami: metodou AAS s použitím jednoúčelového spektrometru ...
Features of Nuclear Reactions with Light Weakly Bond Nuclei at Energy near the Coulomb Barrier
Skobelev, N. K.; Penionzhkevich, Y. E.; Kroha, Václav; Burjan, Václav; Hons, Zdeněk; Mrázek, Jaromír; Piskoř, Štěpán; Šimečková, Eva; Voskoboynik, E. I.
2012 - English
In the experiments carried out by ion beam He-6 of the cyclotron complex DRIBs (JINR) and He-3 beam cyclotron U-120M of the NPI, Czech Academy of Sciences have been investigated reaction Sc-45+He-3, He-6 and Au-197+He-3, He-6 in the energy range near the Coulomb barrier. It were obtained the experimental values of the cross sections for complete fusion reactions and direct reactions for formation of the isotopes Sc-43, Sc-44 and Sc-46 also Au-196 and Au-198 as a function of the bombarding He-3 and He-6 energy. Despite the low binding energy of He-3 and the positive Q-values leading to the formation of isotopes Sc-44 and Sc-46 also Au-196 and Au-198, the behavior of the excitation functions with the formation of these isotopes is different from the excitation functions for d, He-6.
Keywords:
He-6; cyclotron U-120M; cross section
Available at various institutes of the ASCR
Features of Nuclear Reactions with Light Weakly Bond Nuclei at Energy near the Coulomb Barrier
In the experiments carried out by ion beam He-6 of the cyclotron complex DRIBs (JINR) and He-3 beam cyclotron U-120M of the NPI, Czech Academy of Sciences have been investigated reaction Sc-45+He-3, ...
Experimental Determination of Neutron Room Background at the NPI Cyclotron U-120M
Štefánik, M.; Bém, Pavel; Honusek, Milan; Katovsky, K.; Majerle, Mitja; Novák, Jan; Šimečková, Eva
2012 - English
During the operation of external neutron generators of the Nuclear Physics Institute of The Academy of Sciences of the Czech Republic, the neutron room background is produced in cyclotron hall. To assess this effect, the neutron room background was measured using the activation method of dosimetry foils. To unfold the background spectrum from the set of measured reaction rates, the method of spectrum description by the special analytical function was employed.
Keywords:
activation detector; external neutron generator; gamma-ray spectroscopy; isochronous Cyclotron U-120M; neutron room background; neutron spectrum reconstruction; reaction rate; white neutron spectrum
Available at various institutes of the ASCR
Experimental Determination of Neutron Room Background at the NPI Cyclotron U-120M
During the operation of external neutron generators of the Nuclear Physics Institute of The Academy of Sciences of the Czech Republic, the neutron room background is produced in cyclotron hall. To ...
Nondestructive Neutron Diffraction Residual Stress Measurements in a Large Depth in Steels
Woo, W.; Em, V.; Mikula, Pavol; Šaroun, Jan; Seong, B. S.
2012 - English
Residual stresses can be effectively and nondestructively measured through a large thickness of e.g. welded plates, by means of a new design of a reactor-based neutron diffractometer. Most of the engineering neutron diffractometers have a difficulty in increasing neutron penetration capability over 25 mm total thickness in steels. However, it can be significantly enhanced up to 70 mm with 4-mm spatial resolution along the depth by using the wavelength selection in combination with neutron focusing by cylindrically bent perfect monochromator. Present paper presents details of neutron diffractometer performance and some results.
Keywords:
stress; analysis; neutron diffraction
Available at various institutes of the ASCR
Nondestructive Neutron Diffraction Residual Stress Measurements in a Large Depth in Steels
Residual stresses can be effectively and nondestructively measured through a large thickness of e.g. welded plates, by means of a new design of a reactor-based neutron diffractometer. Most of the ...
A new set-up for total reaction cross section measuring
Sobolev, Yuri, G.; Ivanov, M. P.; Kugler, Andrej; Penionzhkevich, Y. E.
2012 - English
The experimental method and set-up based on 4 P n-gamma-technique for direct and model-independent measuring of the total reaction cross section sigma(R) have been presented. The excitation function sigma(R)(E) for He-6+Au-197 reaction at the Coulomb barrier energy region has been measured. The measured data are compared with the summarized cross section which has been prepared by summing of measured cross sections of main reaction channels: 1n-transfer and Au-197(He-6, xn)Tl203-xn with x = 2 divided by 7 evaporation reaction channels.\n\n
Keywords:
cross section; reaction; measurement
Available at various institutes of the ASCR
A new set-up for total reaction cross section measuring
The experimental method and set-up based on 4 P n-gamma-technique for direct and model-independent measuring of the total reaction cross section sigma(R) have been presented. The excitation function ...
Urban Structure Analysis
Vašata, D.; Exner, Pavel; Šeba, Petr
2011 - English
The built-up land represents an important type of overall landscape. We analyse the structure of built-up land in largest cities in the Czech Republic and selected cities in the USA using the framework of statistical physics. To do this, both the variance of the built-up area and the number variance of built-up landed plots in circles are calculated. In both cases the variance as a function of a circle radius follows a power law. The obtained value of the exponents are comparable to exponents typical for critical systems. The study is based on cadastral data in the Czech Republic and building footprints GIS data in the USA.
Keywords:
Urban structure; critical systems; self-organized criticality
Available at various institutes of the ASCR
Urban Structure Analysis
The built-up land represents an important type of overall landscape. We analyse the structure of built-up land in largest cities in the Czech Republic and selected cities in the USA using the ...
Detectability of changes in cosmic-ray counting rate measured with the Liulin detector
Malušek, Alexandr; Kubančák, Ján; Ambrožová, Iva
2011 - English
Keywords:
cosmic-ray; Liulin detector; solar energetic particles
Available at various institutes of the ASCR
Detectability of changes in cosmic-ray counting rate measured with the Liulin detector
Spectator invariance test in the study of the Li-6,Li-7 fusion reactions via the Trojan Horse Method
Pizzone, R. G.; Lamia, L.; Bertulani, C. A.; Mukhamedzhanov, A.; Spitaleri, C.; Blokhinstev, L.; Burjan, Václav; Cherubini, S.; Hons, Zdeněk; Kiss, G. G.; Kroha, Václav; La Cognata, M.; Li, C.; Mrázek, Jaromír; Piskoř, Štěpán; Puglia, S. M. R.; Rapisarda, G. G.; Romano, S.; Sergi, M. L.; Tumino, A.
2011 - English
Fusion reactions play a crucial role for several astrophysical scenarios. At the low energies typical of such environments direct measurements of reaction cross sections are very difficult, and even sometimes impossible. In such cases the use of indirect methods can give a substantial help. The Trojan Horse Method (THM) is based on the quasi-free break-up of a nucleus, which can be described in terms of a cluster structure. In such applications the independence of THM results with different break-up schemes, was tested using the quasi free(3)He(Li-6,alpha alpha)H and He-3(Li-7,alpha alpha)H-2 reactions. Results were then compared with the direct behaviours obtained from available data as well as with the cross sections extracted from previous indirect investigations of the same binary reactions using a different nuclide as a Trojan Horse nucleus.
Keywords:
fusion reactions; indirect methods; cross section
Available at various institutes of the ASCR
Spectator invariance test in the study of the Li-6,Li-7 fusion reactions via the Trojan Horse Method
Fusion reactions play a crucial role for several astrophysical scenarios. At the low energies typical of such environments direct measurements of reaction cross sections are very difficult, and even ...
High accuracy O-18(p, alpha)N-15 reaction rate in the 8 . 10(6)-5 . 10(9) K temperature range
La Cognata, M.; Spitaleri, C.; Mukhamedzhanov, A.; Banu, A.; Cherubini, S.; Coc, A.; Crucilla, V.; Goldberg, V.; Gulino, M.; Irgaziev, B.; Kiss, G. G.; Lamia, L.; Mrázek, Jaromír; Pizzone, R. G.; Puglia, S. M. R.; Rapisarda, G. G.; Romano, S.; Sergi, M. L.; Tabacaru, G.; Trache, L.; Tribble, R. E.; Trzaska, W.; Tumino, A.
2011 - English
The O-18(p, alpha)N-15 reaction is of great importance in several astrophysical scenarios, as it influences the production of key isotopes such as F-19, O-18 and N-15. In this work, a high accuracy O-18(p, alpha) N-15 reaction rate is proposed, based on the simultaneous fit of direct measurements and of the results of a new Trojan Horse experiment. In particular, we have focused on the study of the broad 660 keV 1/2(+) resonance. Since Gamma similar to 100 - 300 keV, it strongly influences the nearly-zero-energy region of the cross section by means of the low-energy tail of the resonant contribution and dominates the cross section at higher energies. Here we provide a factor of 2 larger reaction rate above T similar to 0.510(9) K based over our new improved determination of its resonance parameters.
Keywords:
nuclear reactions; nycleosynthesis; abundances
Available at various institutes of the ASCR
High accuracy O-18(p, alpha)N-15 reaction rate in the 8 . 10(6)-5 . 10(9) K temperature range
The O-18(p, alpha)N-15 reaction is of great importance in several astrophysical scenarios, as it influences the production of key isotopes such as F-19, O-18 and N-15. In this work, a high accuracy ...
Vertex Couplings in quantum Graphs: Approximations by Scaled Schrödinger Operators
Exner, Pavel
2011 - English
We review recent progress in understanding the physical meaning of quantum graph models through analysis of their vertex coupling approximations.
Keywords:
quantum graphs; vertex coupling; tube networks
Available at various institutes of the ASCR
Vertex Couplings in quantum Graphs: Approximations by Scaled Schrödinger Operators
We review recent progress in understanding the physical meaning of quantum graph models through analysis of their vertex coupling approximations.
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