SIMULTANEOUS OPTIMIZATION OF TALLIES; IN DIFFICULT SHIELDING PROBLEMS

Conference · Thu Jan 01 04:00:00 EST 2009

OSTI ID:948054

Peplow, Douglas E. ^[1]; Evans, Thomas M ^[1]; Wagner, John C ^[1]

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1. ORNL

Monte Carlo is quite useful for calculating specific quantities in complex transport problems. Many variance reduction strategies have been developed that accelerate Monte Carlo calculations for specific tallies. However, when trying to calculate multiple tallies or a mesh tally, users have had to accept different levels of relative uncertainty among the tallies or run separate calculations optimized for each individual tally. To address this limitation, an extension of the CADIS (Consistent Adjoint Driven Importance Sampling) method, which is used for difficult source/detector problems, has been developed to optimize several tallies or the cells of a mesh tally simultaneously. The basis for this method is the development of an importance function that represents the importance of particles to the objective of uniform Monte Carlo particle density in the desired tally regions. This method utilizes the results of a forward discrete ordinates solution, which may be based on a quick, coarse-mesh calculation, to develop a forward-weighted source for the adjoint calculation. The importance map and the biased source computed from the adjoint flux are then used in the forward Monte Carlo calculation to obtain approximately uniform relative uncertainties for the desired tallies. This extension is called forward-weighted CADIS, or FW-CADIS.

• Research Organization: Oak Ridge National Laboratory (ORNL)
• Sponsoring Organization: EM USDOE - Environmental Restoration and Waste Management (EM)
• DOE Contract Number: AC05-00OR22725
• OSTI ID: 948054
• Country of Publication: United States
• Language: English

Related Subjects

73 NUCLEAR PHYSICS AND RADIATION PHYSICS
97 MATHEMATICS AND COMPUTING
ADJOINT FLUX
DATA COVARIANCES
DISCRETE ORDINATE METHOD
MONTE CARLO METHOD
RADIATION TRANSPORT
SHIELDING