SECOND-ORDER CROSS TERMS IN MONTE CARLO DIFFERENTIAL OPERATOR PERTURBATION ESTIMATES

Conference · Thu Mar 01 04:00:00 EST 2001

OSTI ID:776530

FAVORITE, J A; PARSONS, D K

Given some initial, unperturbed problem and a desired perturbation, a second-order accurate Taylor series perturbation estimate for a Monte Carlo tally that is a function of two or more perturbed variables can be obtained using an implementation of the differential operator method that ignores cross terms, such as in MCNP4C{trademark}. This requires running a base case defined to be halfway between the perturbed and unperturbed states of all of the perturbed variables and doubling the first-order estimate of the effect of perturbing from the ''midpoint'' base case to the desired perturbed case. The difference between such a midpoint perturbation estimate and the standard perturbation estimate (using the endpoints) is a second-order estimate of the sum of the second-order cross terms of the Taylor series expansion. This technique is demonstrated on an analytic fixed-source problem, a Godiva k{sub eff} eigenvalue problem, and a concrete shielding problem. The effect of ignoring the cross terms in all three problems is significant.

• Research Organization: Los Alamos National Lab., NM (US)
• Sponsoring Organization: US Department of Energy (US)
• DOE Contract Number: W-7405-ENG-36
• OSTI ID: 776530
• Report Number(s): LA-UR-01-1640
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
CONCRETES
EIGENVALUES
IMPLEMENTATION
SERIES EXPANSION
SHIELDING