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Modelling Resonance Dependent Angular Distribution via DBRC in Monte Carlo Codes
R. Dagan,B. Becker,Y. Danon,M. Rapp,G. Lohnert 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.23
The development of a new energy dependent double differential resonance scattering kernel by Rothenstein & Dagan, Annals of Nuclear Energy (1998) was shown to have a significant impact on core calculations as far as their criticality, Doppler Effect and the nuclide inventory is concerned. Thereafter, it was of great interest to experimentally validate this scattering kernel in addition to analytically proving its consistency with the integral Doppler broadened cross section, which was achieved by integrating the new kernel over all angles and all scattered energies. This study deals with the unique experiment suggested by Y. Danon at the Gaerttner Linear Accelerator Laboratory at Rensselaer Polytechnic Institute (RPI). The main advantage of this facility is the ability to move the neutron production source off axis relative to the detector beam line. It was, therefore, possible to position the sample, from which the neutron were scattered, on the same axis as the detector. In this way it was possible to directly measure the angular distribution of scattered neutron from heavy nuclides with pronounced resonances. In this study the previous results obtained for ^(238)U were extended to ^(232)Th. Improvements were made to the new resonance scattering kernel by development of a stochastic formalism known as DBRC (Doppler Broadened Rejection Correction) which was implemented by Becker et al. in several Monte Carlo codes. Based on the good agreement between this DBRC model and the measurements presented in this paper, it was shown that the standard asymptotic back angle scattering used previously in Monte Carlo codes differs by almost 80% for highly scattering resonances. Moreover, the scattering angle measurements and the ability to simulate it accurately by means of stochastic methods emphasized the deficiencies of the current methods which use only transmission and capture measurements.
Fission Physics and Cross Section Measurements with a Lead Slowing down Spectrometer
Y. Danon,R. Block,J. Thompson,C. Romanoy 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.23
A Lead Slowing Down Spectrometer (LSDS) provides a high neutron flux environment that enables measurements of small samples (∼μg) or samples with small cross sections (tens of μb). The LSDS at Rensselaer Polytechnic Institute (RPI) was previously used for fission cross section measurements and for studies of methods for assay of used nuclear fuel. The effective energy range for the LSDS is 0.1 eV to 10 keV with energy resolution of about 35%. Two new LSDS applications were recently developed at RPI; the first enables simultaneous measurements of the fission cross section and fission fragment mass and energy distributions as a function of the incident neutron energy. The second enables measurements of the (n,α) and (n,p) cross sections for materials with a positive Q value for these reactions. Fission measurements of ^(252)Cf, ^(235)U and ^(239)Pu were completed and provide information on fission fragment and energy distributions in resonance clusters. Measurements of the (n,α) cross section for ^(147,149)Sm were completed and compared to previously measured data. The new data indicate that the existing evaluations need to be adjusted.
Neutron capture measurements and resonance parameters of dysprosium
Shin, S. G.,Kye, Y. U.,Namkung, W.,Cho, M. H.,Kang, Y. -R.,Lee, M. W.,Kim, G. N.,Ro, T. -I.,Danon, Y.,Williams, D.,Leinweber, G.,Block, R. C.,Barry, D. P.,Rapp, M. J. Springer-Verlag 2017 The european physical journal. A, Hadrons and nucl Vol.53 No.10
<P>Neutron capture yields of dysprosium isotopes (Dy-161, Dy-162, Dy-163, and Dy-164) were measured using the time-of-flight method with a 16 segment sodium iodide multiplicity detector. The measurements were made at the 25m flight station at the Gaerttner LINAC Center at Rensselaer Polytechnic Institute. Resonance parameters were obtained using the multilevel R-matrix Bayesian code SAMMY. The neutron capture data for four enriched dysprosium isotopes and one natural dysprosium sample were sequentially fitted. New resonances not listed in ENDF/B-VII. 1 were observed. There were 29 and 17 new resonances from Dy-161 and Dy-163 isotopes, respectively. Six resonances from Dy-161 isotope, two resonances from Dy-163, and four resonances from Dy-164 were not observed. The capture resonance integrals of each isotope were calculated with the resulting resonance parameters and those of ENDF/B-VII. 1 in the energy region from 0.5 eV to 20MeV and were compared to the capture resonance integrals with the resonance parameters from ENDF/B-VII. 1. A resonance integral value of the natural dysprosium calculated with present resonance parameters was 1405 +/- 3.5 barn. The value is similar to 0.3% higher than that obtained with the ENDF/B-VII. 1 parameters. The distributions of the present and ENDF/B-VII. 1 neutron widths were compared to a Porter-Thomas distribution. Neutron strength functions for Dy-161 and Dy-163 were calculated with the present resonance parameters and both values were in between the values of 'Atlas of Neutron Resonances' and ENDF/B-VII. 1. The present radiation width distributions of Dy-161 and Dy-163 were fitted with the chi(2) distribution by varying the degrees of freedom.</P>
M. J. Rapp,Y. Danon,F. J. Saglime,R. Bahran,R. C. Block,G. Leinweber,D. P. Barry,J. G. Hoole 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.23
Neutron transmission measurements were made on natural molybdenum and zirconium samples using the time of flight method at the Rensselaer Polytechnic Institute Gaerttner Linac Laboratory. These measurements utilize a 100 meter flight path, fast detector response and electronics and a narrow neutron pulse width to provide high accuracy data. Neutron total cross sections have been determined in the energy range of 0.5 to 20 MeV and are compared to commonly used nuclear data evaluations. Molybdenum shows good agreement with the evaluations, while zirconium shows improvement is required with the most recent evaluations in the range of 0.5 to 15 MeV.
Neutron Capture and Total Cross-Section Measurements and Resonance Parameters of Gadolinium
Leinweber, G.,Barry, D. P.,Trbovich, M. J.,Burke, J. A.,Drindak, N. J.,Knox, H. D.,Ballad, R. V.,Block, R. C.,Danon, Y.,Severnyak, L. I. AMERICAN NUCLEAR SOCIETY 2006 Nuclear science and engineering Vol.154 No.3
Neutron transmission and capture measurements and analysis of Dy from 0.01 to 550 eV
Block, R.C.,Bishop, M.C.,Barry, D.P.,Leinweber, G.,Ballad, R.V.,Burke, J.A.,Rapp, M.J.,Danon, Y.,Youmans, A.,Drindak, N.J.,Kim, G.N.,Kang, Y.-R.,Lee, M.W.,Landsberger, S. Elsevier 2017 Progress in nuclear energy Vol.94 No.-
<P><B>Abstract</B></P> <P>Neutron capture and transmission measurements were carried out from 0.01 to over 600 eV on both natural Dy and samples highly enriched in <SUP>164</SUP>Dy. These data were analyzed for resonance parameters utilizing the SAMMY Bayesian analysis code to simultaneously fit both the capture and transmission data. Parameters were obtained for 17 resonances in Dy isotopes up to 18 eV and for the <SUP>164</SUP>Dy resonances near 147, 450 and 540 eV. The thermal capture cross section (at 0.0253 eV) and capture resonance integral were determined for <SUP>164</SUP>Dy.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Transmission and capture measurements from thermal to 550 eV on Dy and <SUP>164</SUP>Dy samples. </LI> <LI> Bayesian analysis provided resonance parameters from the combined measurements. </LI> <LI> Liquid samples were used to obtain uniformly thin <SUP>164</SUP>Dy samples. </LI> <LI> The <SUP>164</SUP>Dy thermal cross section and resonance integral were obtained from these measurements. </LI> <LI> Improvements were made for the 5.45 eV <SUP>162</SUP>Dy resonance parameters. </LI> </UL> </P>