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RISS 인기검색어
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- 저자 : Belgya (검색결과 4 건)
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Neutron Capture on <SUP>209</SUP>Bi: Determination of the Production Ratio of ^(210m)Bi/^(210g)Bi
F. Gunsing,E. Berthoumieux,A. Borella,T. Belgya,L. Szentmiklosi,P. Schillebeeckx,J. C. Drohe,R. Wynants,N. Colonna,S. Marrone,G. Tagliente,R. Terlizzi,C. Domingo-pardo,J. Tain,T. Martinez,C. Massimi,P 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.23
Neutron capture on ^(209)Bi produces either an isomeric state ^(210m)Bi with a half life of 3×10^6 years, or the ground state ^(210g)Bi which decays with a half life of 5 days to the alpha emitter ^(210)Po. Therefore the neutron capture cross section ratio ^(209)Bi(n,γ) ^(210m)^(Bi)/^(210g)Bi plays an important role in predicting the short- and long-term radio-toxicity produced by ^(209)Bi under neutron irradiation. This ratio is dependent on the neutron energy. We have measured this ratio for cold neutrons at the cold neutron beam facility of the Budapest Neutron Centre by observing the population of the ground- and the metastable state using high resolution gamma-ray spectroscopy. The same technique hasbeen used at the pulsed white neutron source GELINA of the IRMM, Geel in combination with the neutron time-of-flight technique. Results for the neutron-energy dependent branching ratio will be presented. In addition we performed simulations using a statistical decay code.
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Neutron-capture Studies on ^(235)U and ^(238)U via AMS
A. Wallner,K. Buczak,F. Quinto,P. Steier,T. Belgya,L. Szentmiklosi,M. Bichler,I. Dillmann,F. Kappeler,A. Mengoni 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.23
Major nuclear data libraries exhibit some discrepancies for the neutron capture reactions ^(235)U(n,γ) and ^(238)</SUP>U(n,γ) at keV energies. These differences reflect also the scatter of experimental data that are primarily based on time-of-flight measurements (TOF) with detection of prompt γ-rays. We report here on an independent approach for studying such reactions: Neutron activations with subsequent accelerator mass spectrometry (AMS) measurement represent an independent technique, where interference from fission is completely excluded. Activations of natural uranium samples were performed with cold neutrons (Budapest), thermal (Vienna) and with neutrons of 25 and 500 keV (Karlsruhe) for the measurement of ^(235)U(n,γ) and ^(238)U(n,γ). The produced long-lived ^(236)U and the decay product of ^(239)U, ^(239)Pu, respectively, were subsequently counted by AMS at the Vienna Environmental Research Accelerator. This method for measuring the neutron capture cross section has the advantage that the involved systematic uncertainties are in no way correlated with those inherent to the TOF technique. Preliminary data for these neutron energies indicate good agreement with evaluations and seem to support in the keV energy range the reported lower cross-section values for both capture reactions.
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Capture Gamma-ray Libraries for Nuclear Applications
B. W. Sleaford,N. Summers,J. Escher,R. B. Firestone,S. Basunia,A. Hurst,M. Krticka,G. Molnar,T. Belgya,Zs Revay,H. D. CHOI 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.23
The neutron capture reaction is useful in identifying and analyzing the gamma-ray spectrum from an unknown assembly as it gives unambiguous information on its composition. This can be done passively or actively where an external neutron source is used to probe an unknown assembly. There are known capture gamma-ray data gaps in the ENDF libraries used by transport codes for various nuclear applications. The Evaluated Gamma-ray Activation file (EGAF) is a new thermal neutron capture database of discrete line spectra and cross sections for over 260 isotopes that was developed as part of an IAEA Coordinated Research Project. EGAF has been used to improve the capture gamma production in ENDF libraries. For medium to heavy nuclei the quasi continuum contribution to the gamma cascades is not experimentally resolved. The continuum contains up to 90% of all the decay energy and is modeled here with the statistical nuclear structure code DICEBOX. This code also provides a consistency check of the level scheme nuclear structure evaluation. The calculated continuum is of sufficient accuracy to include in the ENDF libraries. This analysis also determines new total thermal capture cross sections and provides an improved RIPL database. For higher energy neutron capture there is less experimental data available making benchmarking of the modeling codes more difficult. We use CASINO, a version of DICEBOX that is modied for this purpose. This can be used to simulate the neutron capture at incident neutron energies up to 20 MeV to improve the gamma-ray spectrum in neutron data libraries used for transport modeling of unknown assemblies.
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Gamma Spectrum from Neutron Capture on Tungsten Isotopes
A. M. Hurst,N. C. Summers,B. W. Sleaford,R. B. Firestone,T. Belgya,Z. S. Revay 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.23
An evaluation of thermal neutron capture on the stable tungsten isotopes is presented, with preliminary results for the compound systems ^(183,184,185,187)W. The evaluation procedure compares the γ-ray cross-section data collected at the Budapest reactor, with Monte Carlo simulations of γ-ray emission following the thermal neutron-capture process. The statistical-decay code DICEBOX was used for the Monte Carlo simulations. The evaluation yields new γ-rays in ^(185)W and the confirmation of spins in ^(187)W, raising the number of levels below which the level schemes are considered complete, thus increasing the number of levels that can be used in neutron data libraries.
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