Onthefly generation of differential resonance scattering probability distribution functions for Monte Carlo codes
Abstract
Current Monte Carlo codes use one of three models to model neutron scattering in the epithermal energy range: (1) the asymptotic scattering model, (2) the free gas scattering model, or (3) the S({alpha},{beta}) model, depending on the neutron energy and the specific Monte Carlo code. The free gas scattering model assumes the scattering cross section is constant over the neutron energy range, which is usually a good approximation for light nuclei, but not for heavy nuclei where the scattering cross section may have several resonances in the epithermal region. Several researchers in the field have shown that using the free gas scattering model in the vicinity of the resonances in the lower epithermal range can underpredict resonance absorption due to the upscattering phenomenon. Existing methods all involve performing the collision analysis in the centerofmass frame, followed by a conversion back to the laboratory frame. In this paper, we will present a new sampling methodology that (1) accounts for the energydependent scattering cross sections in the collision analysis and (2) acts in the laboratory frame, avoiding the conversion to the centerofmass frame. The energy dependence of the scattering cross section was modeled with evenordered polynomials to approximate the scattering cross sectionmore »
 Authors:

 University of Michigan, 2355 Bonisteel Boulevard, Ann Arbor MI 48109 (United States)
 Publication Date:
 Research Org.:
 American Nuclear Society, 555 North Kensington Avenue, La Grange Park, IL 60526 (United States)
 OSTI Identifier:
 22212811
 Resource Type:
 Conference
 Resource Relation:
 Conference: M and C 2013: 2013 International Conference on Mathematics and Computational Methods Applied to Nuclear Science and Engineering, Sun Valley, ID (United States), 59 May 2013; Other Information: Country of input: France; 11 refs.; Related Information: In: Proceedings of the 2013 International Conference on Mathematics and Computational Methods Applied to Nuclear Science and Engineering  M and C 2013 3016 p.
 Country of Publication:
 United States
 Language:
 English
 Subject:
 97 MATHEMATICAL METHODS AND COMPUTING; APPROXIMATIONS; ASYMPTOTIC SOLUTIONS; COMPARATIVE EVALUATIONS; CRITICALITY; CROSS SECTIONS; DISTRIBUTION FUNCTIONS; ELASTIC SCATTERING; ENERGY DEPENDENCE; FUEL ASSEMBLIES; FUEL PINS; GRAPH THEORY; HEAVY NUCLEI; LIGHT NUCLEI; MONTE CARLO METHOD; NEUTRON DIFFRACTION; PROBABILITY; RESONANCE; RESONANCE ABSORPTION; SAMPLING
Citation Formats
Sunny, E. E., and Martin, W. R. Onthefly generation of differential resonance scattering probability distribution functions for Monte Carlo codes. United States: N. p., 2013.
Web.
Sunny, E. E., & Martin, W. R. Onthefly generation of differential resonance scattering probability distribution functions for Monte Carlo codes. United States.
Sunny, E. E., and Martin, W. R. Mon .
"Onthefly generation of differential resonance scattering probability distribution functions for Monte Carlo codes". United States.
@article{osti_22212811,
title = {Onthefly generation of differential resonance scattering probability distribution functions for Monte Carlo codes},
author = {Sunny, E. E. and Martin, W. R.},
abstractNote = {Current Monte Carlo codes use one of three models to model neutron scattering in the epithermal energy range: (1) the asymptotic scattering model, (2) the free gas scattering model, or (3) the S({alpha},{beta}) model, depending on the neutron energy and the specific Monte Carlo code. The free gas scattering model assumes the scattering cross section is constant over the neutron energy range, which is usually a good approximation for light nuclei, but not for heavy nuclei where the scattering cross section may have several resonances in the epithermal region. Several researchers in the field have shown that using the free gas scattering model in the vicinity of the resonances in the lower epithermal range can underpredict resonance absorption due to the upscattering phenomenon. Existing methods all involve performing the collision analysis in the centerofmass frame, followed by a conversion back to the laboratory frame. In this paper, we will present a new sampling methodology that (1) accounts for the energydependent scattering cross sections in the collision analysis and (2) acts in the laboratory frame, avoiding the conversion to the centerofmass frame. The energy dependence of the scattering cross section was modeled with evenordered polynomials to approximate the scattering cross section in Blackshaw's equations for the moments of the differential scattering PDFs. These moments were used to sample the outgoing neutron speed and angle in the laboratory frame onthefly during the random walk of the neutron. Results for criticality studies on fuel pin and fuel assembly calculations using these methods showed very close comparison to results using the reference Dopplerbroadened rejection correction (DBRC) scheme. (authors)},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {2013},
month = {7}
}