William A Wieselquist

William A Wieselquist

SCALE Director


Dr. William Wieselquist is Research and Development Staff in the Reactor Physics Group of the Reactor and Nuclear Systems Division at Oak Ridge National Laboratory (ORNL). He earned a Ph.D. in Nuclear Engineering from North Carolina State University in 2009. From 2009 to 2012 was staff at the Paul Scherrer Institut, where he established an uncertainty quantification platform around the Studsvik Scandpower core analysis codes in addition to core follow and safety analysis duties for the Swiss nuclear power plant, Beznau Units 1 and 2. At ORNL, he has assumed development roles in the SCALE code suite, currently lead developer and manager of the ORIGEN depletion/decay and the Sampler sampling-based uncertainty quantification codes. He has also played a role in developing the new Polaris lattice physics code in SCALE, particularly with regard to the input design. His main interests include sensitivity analysis, uncertainty quantification, data assimilation, verfication and validation, lattice physics, depletion methodologies, multi-physics couplings, as well as user and application interface design. 


  • 2015 Significant Achievement Award: DOE Level 1 Milestone: CASL Simulations 12 Fuel Cycles of Watts Bar Nuclear Plant


SCALE/ORIGEN Application Programming Interface (API)

  • funded by DOE and ORNL
  • part of an extensive ORIGEN modernization effort
  • develop C++/Fortran API to run high-performance, in-memory depletion/decay
  • currently being used by
    • DOE-sponsored platforms
      • CASL core simulator, VERA-CS, jointly developed by ORNL and University of Michigan (early results paper)
      • NEAMS neutronics code, PROTEUS, developed at ANL (contact nera-software@anl.gov)
      • NEAMS fuel performance code, BISON, developed at INL
      • CYCLUS fuel cycle analysis code funded by NEUP
    • SCALE coupled transport/depletion codes (Polaris, TRITON, etc.)
    • SHIFT massively parallel Monte Carlo depletion

SCALE/Polaris lattice physics development 

  • funded by U.S. NRC
  • easy-to-use, fast lattice physics for LWRs

SCALE/Sampler development

  • funded by U.S. NRC
  • uncertainty quantification for any SCALE simulation


Please see listing on ORCID.