MPACT Subgroup SelfShielding Efficiency Improvements
Recent developments to improve the efficiency of the MOC solvers in MPACT have yielded effective kernels that loop over several energy groups at once, rather that looping over one group at a time. These kernels have produced roughly a 2x speedup on the MOC sweeping time during eigenvalue calculation. However, the selfshielding subgroup calculation had not been reevaluated to take advantage of these new kernels, which typically requires substantial solve time. The improvements covered in this report start by integrating the multigroup kernel concepts into the subgroup calculation, which are then used as the basis for further extensions. The next improvement that is covered is what is currently being termed as βLumped Parameter MOCβ. Because the subgroup calculation is a purely fixed source problem and multiple sweeps are performed only to update the boundary angular fluxes, the sweep procedure can be condensed to allow for the instantaneous propagation of the flux across a spatial domain, without the need to sweep along all segments in a ray. Once the boundary angular fluxes are considered to be converged, an additional sweep that will tally the scalar flux is completed. The last improvement that is investigated is the possible reduction of the numbermore »
 Authors:

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 Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
 Univ. of Michigan, Ann Arbor, MI (United States)
 Publication Date:
 OSTI Identifier:
 1328310
 Report Number(s):
 ORNL/TM2016/407; CASLU20161063001
NT0304000; NEAF343; CASLU20161063001; TRN: US1700303
 DOE Contract Number:
 AC0500OR22725
 Resource Type:
 Technical Report
 Research Org:
 Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Consortium for Advanced Simulation of LWRs (CASL)
 Sponsoring Org:
 USDOE Office of Nuclear Energy (NE)
 Contributing Orgs:
 Univ. of Michigan, Ann Arbor, MI (United States)
 Country of Publication:
 United States
 Language:
 English
 Subject:
 97 MATHEMATICS AND COMPUTING; 22 GENERAL STUDIES OF NUCLEAR REACTORS; M CODES; EIGENVALUES; COMPUTER CALCULATIONS; SELFSHIELDING; KERNELS; EFFICIENCY; MULTIGROUP THEORY; NEUTRON FLUX; SCALARS
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