Inconsistencies in widely used Monte Carlo methods for precise calculation of radial resonance captures in uranium fuel rods

Journal Article · Sat Jun 01 04:00:00 EDT 1996 · Nuclear Science and Engineering

OSTI ID:264341

Bogart, D ^[1]

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1. National Aeronautics and Space Administration, Cleveland, OH (United States). Lewis Research Center

Although resonance neutron captures for {sup 238}U in water-moderated lattices are known to occur near moderator-fuel interfaces, the sharply attenuated spatial captures here have not been calculated by multigroup transport or Monte Carlo methods. Advances in computer speed and capacity have restored interest in applying Monte Carlo methods to evaluate spatial resonance captures in fueled lattices. Recently published studies have placed complete reliance on the ostensible precision of the Monte Carlo approach without auxiliary confirmation that resonance processes were followed adequately or that the Monte Carlo method was applied appropriately. Other methods of analysis that have evolved from early resonance integral theory have provided a basis for an alternative approach to determine radial resonance captures in fuel rods. A generalized method has been formulated and confirmed by comparison with published experiments of high spatial resolution for radial resonance captures in metallic uranium rods. The same analytical method has been applied to uranium-oxide fuels. The generalized method defined a spatial effective resonance cross section that is a continuous function of distance from the moderator-fuel interface and enables direct calculation of precise radial resonance capture distributions in fuel rods. This generalized method is used as a reference for comparison with two recent independent studies that have employed different Monte Carlo codes and cross-section libraries. Inconsistencies in the Monte Carlo application or in how pointwise cross-section libraries are sampled may exist. It is shown that refined Monte Carlo solutions with improved spatial resolution would not asymptotically approach the reference spatial capture distributions.

• OSTI ID: 264341
• Journal Information: Nuclear Science and Engineering, Journal Name: Nuclear Science and Engineering Journal Issue: 2 Vol. 123; ISSN NSENAO; ISSN 0029-5639
• Country of Publication: United States
• Language: English

Related Subjects

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS
CAPTURE
FUEL RODS
MONTE CARLO METHOD
NEUTRON REACTIONS
NEUTRON TRANSPORT
REACTOR KINETICS
RESONANCE INTEGRALS
RESONANCE NEUTRONS
URANIUM 238
WATER COOLED REACTORS