Thermal scattering law of C2H4 n: Integrating experimental data with DFT calculations

Kemal Ramić, Carl Wendorff, Yongqiang Cheng, Alexander I. Kolesnikov, Doug L. Abernathy, Luke Daemen, Goran Arbanas, Luiz Leal, Yaron Danon, Li (Emily) Liu

Research output: Contribution to journalArticlepeer-review

9 Scopus citations

Abstract

Improvements in determination of the thermal scattering law of moderator materials (measuring, calculating and validating) are important for accurate prediction of neutron thermalization in nuclear systems. In this work a methodology for producing thermal scattering libraries from the experimental data for polyethylene C2H4 n is discussed. Double differential scattering cross section (DDSCS) experiments were performed at the Spallation Neutron Source of Oak Ridge National Laboratory (SNS ORNL). New scattering kernel evaluations, based on phonon spectrum for C2H4 n, are created using the NJOY2016 code. Two different methods were used: direct and indirect geometry neutron scattering at ARCS and SEQUOIA, and VISION instruments, respectively, where the phonon spectrum was derived from the dynamical structure factor S(Q,ω) obtained from the measured DDSCS. In order to compare and validate the newly created library, the experimental setup was simulated using MCNP6.1. Compared with the current ENDF/B-VII.1, the resulting RPI C2H4 n libraries improved both double differential scattering and total scattering cross sections. A set of criticality benchmarks containing C2H4 n from HEU-MET-THERM resulted in an overall improved calculation of Keff, although the libraries should be tested against benchmarks more sensitive to C2H4 n. The DFT + oClimax method is used and is shown to be most comprehensive method for analysis of moderator materials. The importance of DFT + oClimax method lies in the fact that it can be validated against all data measured at VISION, ARCS and SEQUOIA, and experimental total scattering cross section measurements.

Original languageEnglish
Pages (from-to)778-787
Number of pages10
JournalAnnals of Nuclear Energy
Volume120
DOIs
StatePublished - Oct 2018

Funding

This research used resources of the National Energy Research Scientific Computing Center, a DOE Office of Science User Facility supported by the Office of Science of the U.S. Department of Energy. The research at Oak Ridge National Laboratory’s Spallation Neutron Source was sponsored by the U.S. Department of Energy and by the Scientific User Facilities Division, Office of Basic Energy Sciences, the U.S. Department of Energy. This research was supported by the Nuclear Criticality Safety Program in the U.S. Department of Energy .

Keywords

  • Criticality safety
  • Density function theory
  • Double differential scattering cross section
  • ENDF
  • GDOS
  • Neutron scattering
  • Phonon spectrum
  • Polyethylene

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