Stationarity and Source Convergence in Monte Carlo Criticality Calculation

Conference · Sat Apr 06 00:00:00 EST 2002

OSTI ID:976363

Ueki, Taro ^[1]; Brown, Forrest B. ^[1]

---

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

In Monte Carlo (MC) criticality calculations, source error propagation through the stationary cycles and source convergence in the settling (inactive) cycles are both dominated by the dominance ratio (DR) of fission kernels, Le., the ratio of the second largest to largest eigenvalues. For symmetric two fissile component systems with DR close to unity, the extinction of fission source sites can occur in one of the components even when the initial source is symmetric and the number of histories per cycle is larger than one thousand. When such a system is made slightly asymmetric, the neutron effective multiplication factor (kern) at the inactive cycles does not reflect the convergence to stationary source distribution. To overcome this problem, relative entropy (Kullback Leibler distance) is applied to a slightly asymmetric two fissile component problem with a dominance ratio of 0.9925. Numerical results show that relative entropy is effective as a posterior diagnostic tool.

• 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)
• OSTI ID: 976363
• Report Number(s): LA-UR-02-6228; TRN: US1006887
• Resource Relation: Conference: American Nuclear Society Topical Meeting in Mathematics and Computations , Gatlinburg, TN (United States), 6-11 Apr 2003
• Country of Publication: United States
• Language: English

Related Subjects

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
97 MATHEMATICS AND COMPUTING
CONVERGENCE
CRITICALITY
DISTRIBUTION
EIGENVALUES
ENTROPY
FISSION
KERNELS
MULTIPLICATION FACTORS
NEUTRONS
MONTE CARLO METHOD
MATHEMATICS
COMPUTERS
Nuclear Criticality Safety Program (NCSP)
Monte Carlo (MC) Criticality Calculations
Neutron Effective Multiplication Factor (kern)
Stationarity
Source Convergence