"K-Effective of the World" and Other Concerns for Monte Carlo Eigenvalue Calculations

Conference · Sun Oct 17 00:00:00 EDT 2010 · Progress in Nuclear Science and Technology

DOI:https://doi.org/10.15669/pnst.2.738· OSTI ID:1028196

Brown, Forrest B. ^[1]

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1. Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)

Monte Carlo methods have been used to compute k_eff and the fundamental model eigenfunction of critical systems since the 1950s. Despite the sophistication of today's Monte Carlo codes for representing realistic geometry and physics interactions, correct results can be obtained in criticality problems only if users pay attention to source convergence in the Monte Carlo iterations and to running a sufficient number of neutron histories to adequately sample all significant regions of the problem. Recommended best practices for criticality calculations are reviewed and applied to several practical problems for nuclear reactors and criticality safety, including the "K-effective of the World" problem. Numerical results illustrate the concerns about convergence and bias. The general conclusion is that with today's high-performance computers, improved understanding of the theory, new tools for diagnosing convergence (e.g., Shannon entropy of the fission distribution), and clear practical guidance for performing calculations, practitioners will have a greater degree of confidence than ever of obtaining correct results for Monte Carlo criticality calculations.

• Research Organization: Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
• Sponsoring Organization: USDOE National Nuclear Security Administration (NNSA), Nuclear Criticality Safety Program (NCSP)
• DOE Contract Number: AC52-06NA25396
• OSTI ID: 1028196
• Report Number(s): LA-UR-10-05548; LA-UR-10-5548; TRN: US201122%%745
• Journal Information: Progress in Nuclear Science and Technology, Vol. 2, Issue 0; Conference: SNA+MC - 2010 , Tokyo (Japan), 17 Oct 2010; ISSN 2185-4823
• Publisher: Atomic Energy Society of Japan
• Country of Publication: United States
• Language: English

Related Subjects

61 RADIATION PROTECTION AND DOSIMETRY
97 MATHEMATICAL METHODS AND COMPUTING
73 NUCLEAR PHYSICS AND RADIATION PHYSICS
COMPUTER CALCULATIONS
CONVERGENCE
CRITICALITY
EIGENFUNCTIONS
EIGENVALUES
ENTROPY
INTERACTIONS
MONTE CARLO METHOD
Nuclear Criticality Safety Program (NCSP)
K-Effective
Monte Carlo Methods
Criticality Calculations
Convergence
Undersampling
Bias
Criticality