Estimation and Interpretation of k_eff Confidence Intervals in MCNP

Conference · Sun Sep 17 04:00:00 EDT 1995

DOI:https://doi.org/10.2172/212564· OSTI ID:104775

Urbatsch, Todd J. ^[1]; Forster, R. Arthur ^[2]; Prael, Richard E. ^[2]; Beckman, Richard J. ^[2]

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

MCNP has three different, but correlated, estimators for calculating k_eff in nuclear criticality calculations: collision, absorption, and track length estimators. The combination of these three estimators, the three-combined k_eff estimator, is shown to be the best k_eff estimator available in MCNP for estimating k_eff confidence intervals. Theoretically, the Gauss-Markov Theorem provides a solid foundation for MCNP's three-combined estimator. Analytically, a statistical study, where the estimates are drawn using a known covariance matrix, shows that the three-combined estimator is superior to the individual estimator with the smallest variance. The importance of MCNP's batch statistics is demonstrated by an investigation of the effects of individual estimator variance bias on the combination of estimators, both heuristically with the analytical study and empirically with MCNP.

• Research Organization: Univ. of Michigan, Ann Arbor, MI (United States). Department of Nuclear Engineering; 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: W-7405-ENG-36
• OSTI ID: 104775
• Report Number(s): LA-UR--95-1987; CONF-9509100--26; ON: DE95015260
• Country of Publication: United States
• Language: English

Related Subjects

73 NUCLEAR PHYSICS AND RADIATION PHYSICS
97 MATHEMATICS AND COMPUTING
Absorption
CRITICALITY
Collision
Covariance Matrix
DATA COVARIANCES
Gauss-Markov Theorem
M CODES
MONTE CARLO METHOD
Monte Carlo N-Particle Transport (MCNP)
NEUTRON TRANSPORT
Nuclear Criticality Calculations
Nuclear Criticality Safety Program (NCSP)
Track Length Estimators