Automatic variance reduction for 3-D Monte Carlo simulations by the local importance function transform

Journal Article · Tue Dec 31 04:00:00 EST 1996 · Transactions of the American Nuclear Society

OSTI ID:426385

Turner, S A ^[1]; Larsen, E W ^[2]

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1. Los Alamos National Lab., NM (United States)
2. Univ. of Michigan, Ann Arbor, MI (United States)

This paper describes a new automated variance reduction method for the Monte Carlo simulation of multigroup neutron transport source-detector problems. The method is based on a modified transport problem that can be solved by analog Monte Carlo with zero variance. However, the implementation of this modified problem is impractical, in part because it requires the exact solution of an adjoint transport problem. The new local importance function transform (LIFT) method developed in this paper overcomes this difficulty by approximating the exact adjoint solution with a piecewise-continuous function containing parameters that are obtained from a deterministic adjoint calculation. The transport and collision processes of the transformed Monte Carlo problem bias source distribution, distance-to-collision, and selection of postcollision energy groups and directions. The LIFT method described here is a three-dimensional generalization of an earlier two-dimensional Monte Carlo variance reduction method.

• OSTI ID: 426385
• Report Number(s): CONF-961103--
• Journal Information: Transactions of the American Nuclear Society, Journal Name: Transactions of the American Nuclear Society Vol. 75; ISSN TANSAO; ISSN 0003-018X
• Country of Publication: United States
• Language: English

Related Subjects

66 PHYSICS
DATA COVARIANCES
MONTE CARLO METHOD
NEUTRON TRANSPORT THEORY
THREE-DIMENSIONAL CALCULATIONS