Automatic mesh adaptivity for hybrid Monte Carlo/deterministic neutronics modeling of difficult shielding problems
The CADIS and FWCADIS hybrid Monte Carlo/deterministic techniques dramatically increase the efficiency of neutronics modeling, but their use in the accurate design analysis of very large and geometrically complex nuclear systems has been limited by the large number of processors and memory requirements for their preliminary deterministic calculations and final Monte Carlo calculation. Three mesh adaptivity algorithms were developed to reduce the memory requirements of CADIS and FWCADIS without sacrificing their efficiency improvement. First, a macromaterial approach enhances the fidelity of the deterministic models without changing the mesh. Second, a deterministic mesh refinement algorithm generates meshes that capture as much geometric detail as possible without exceeding a specified maximum number of mesh elements. Finally, a weight window coarsening algorithm decouples the weight window mesh and energy bins from the mesh and energy group structure of the deterministic calculations in order to remove the memory constraint of the weight window map from the deterministic mesh resolution. The three algorithms were used to enhance an FWCADIS calculation of the prompt dose rate throughout the ITER experimental facility. Using these algorithms resulted in a 23.3% increase in the number of mesh tally elements in which the dose rates were calculated in a 10daymore »
 Authors:

^{[1]};
^{[2]};
^{[2]};
^{[1]};
^{[1]};
^{[1]};
^{[1]};
^{[1]}
 Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
 Univ. of Wisconsin, Madison, WI (United States)
 Publication Date:
 Grant/Contract Number:
 AC0500OR22725
 Type:
 Accepted Manuscript
 Journal Name:
 Nuclear Science and Engineering
 Additional Journal Information:
 Journal Volume: 181; Journal Issue: 1; Journal ID: ISSN 00295639
 Publisher:
 American Nuclear Society
 Research Org:
 Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
 Sponsoring Org:
 USDOE
 Country of Publication:
 United States
 Language:
 English
 Subject:
 22 GENERAL STUDIES OF NUCLEAR REACTORS; hybrid Monte Carlo/deterministic; CADIS and FWCADIS; ITER neutronics
 OSTI Identifier:
 1213307
Ibrahim, Ahmad M., Wilson, Paul P.H., Sawan, Mohamed E., Mosher, Scott W., Peplow, Douglas E., Wagner, John C., Evans, Thomas M., and Grove, Robert E.. Automatic mesh adaptivity for hybrid Monte Carlo/deterministic neutronics modeling of difficult shielding problems. United States: N. p.,
Web. doi:10.13182/NSE1494.
Ibrahim, Ahmad M., Wilson, Paul P.H., Sawan, Mohamed E., Mosher, Scott W., Peplow, Douglas E., Wagner, John C., Evans, Thomas M., & Grove, Robert E.. Automatic mesh adaptivity for hybrid Monte Carlo/deterministic neutronics modeling of difficult shielding problems. United States. doi:10.13182/NSE1494.
Ibrahim, Ahmad M., Wilson, Paul P.H., Sawan, Mohamed E., Mosher, Scott W., Peplow, Douglas E., Wagner, John C., Evans, Thomas M., and Grove, Robert E.. 2015.
"Automatic mesh adaptivity for hybrid Monte Carlo/deterministic neutronics modeling of difficult shielding problems". United States.
doi:10.13182/NSE1494. https://www.osti.gov/servlets/purl/1213307.
@article{osti_1213307,
title = {Automatic mesh adaptivity for hybrid Monte Carlo/deterministic neutronics modeling of difficult shielding problems},
author = {Ibrahim, Ahmad M. and Wilson, Paul P.H. and Sawan, Mohamed E. and Mosher, Scott W. and Peplow, Douglas E. and Wagner, John C. and Evans, Thomas M. and Grove, Robert E.},
abstractNote = {The CADIS and FWCADIS hybrid Monte Carlo/deterministic techniques dramatically increase the efficiency of neutronics modeling, but their use in the accurate design analysis of very large and geometrically complex nuclear systems has been limited by the large number of processors and memory requirements for their preliminary deterministic calculations and final Monte Carlo calculation. Three mesh adaptivity algorithms were developed to reduce the memory requirements of CADIS and FWCADIS without sacrificing their efficiency improvement. First, a macromaterial approach enhances the fidelity of the deterministic models without changing the mesh. Second, a deterministic mesh refinement algorithm generates meshes that capture as much geometric detail as possible without exceeding a specified maximum number of mesh elements. Finally, a weight window coarsening algorithm decouples the weight window mesh and energy bins from the mesh and energy group structure of the deterministic calculations in order to remove the memory constraint of the weight window map from the deterministic mesh resolution. The three algorithms were used to enhance an FWCADIS calculation of the prompt dose rate throughout the ITER experimental facility. Using these algorithms resulted in a 23.3% increase in the number of mesh tally elements in which the dose rates were calculated in a 10day Monte Carlo calculation and, additionally, increased the efficiency of the Monte Carlo simulation by a factor of at least 3.4. The three algorithms enabled this difficult calculation to be accurately solved using an FWCADIS simulation on a regular computer cluster, eliminating the need for a worldclass super computer.},
doi = {10.13182/NSE1494},
journal = {Nuclear Science and Engineering},
number = 1,
volume = 181,
place = {United States},
year = {2015},
month = {6}
}