Impact of molybdenum cross sections on FHR analysis

Kyle M. Ramey, Marat Margulis, Nathaniel Read, Eugene Shwageraus, Bojan Petrovic

Research output: Contribution to journalArticlepeer-review


A recent benchmarking effort, under the auspices of the Organization for Economic Cooperation and Development (OECD) Nuclear Energy Agency (NEA), has been made to evaluate the current state of modeling and simulation tools available to model fluoride salt-cooled high temperature reactors (FHRs). The FHR benchmarking effort considered in this work consists of several cases evaluating the neutronic parameters of a 2D prismatic FHR fuel assembly model using the participants’ choice of simulation tools. Benchmark participants blindly submitted results for comparison with overall good agreement, except for some which significantly differed on cases utilizing a molybdenum-bearing control rod. Participants utilizing more recently updated explicit isotopic cross sections had consistent results, whereas those using elemental molybdenum cross sections observed reactivity differences on the order of thousands of pcm relative to their peers. Through a series of supporting tests, the authors attribute the differences as being nuclear data driven from using older legacy elemental molybdenum cross sections. Quantitative analysis is conducted on the control rod to identify spectral, reaction rate, and cross section phenomena responsible for the observed differences. Results confirm the observed differences are attributable to the use of elemental cross sections which overestimate the reaction rates in strong resonance channels.

Original languageEnglish
Pages (from-to)817-825
Number of pages9
JournalNuclear Engineering and Technology
Issue number3
StatePublished - 1 Mar 2022
Externally publishedYes


  • Fluoride salt cooled high temperature reactor (FHR)
  • Molten salt reactor (MSR)
  • Molybdenum cross section
  • Serpent
  • WIMS

ASJC Scopus subject areas

  • Nuclear Energy and Engineering


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