A New Equivalence Theory Method for Treating Doubly Heterogeneous Fuel - I. Theory

Journal Article · Wed Mar 04 00:00:00 EST 2015 · Nuclear Science and Engineering

DOI:https://doi.org/10.13182/NSE14-68· OSTI ID:1223634

Williams, Mark L. ^[1]; Lee, Deokjung ^[2]; Choi, Sooyoung ^[2]

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1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
2. Ulsan National Institute of Science and Technology (UNIST), Ulju-gun (South Korea)

A new methodology has been developed to treat resonance self-shielding in doubly heterogeneous very high temperature gas-cooled reactor systems in which the fuel compact region of a reactor lattice consists of small fuel grains dispersed in a graphite matrix. This new method first homogenizes the fuel grain and matrix materials using an analytically derived disadvantage factor from a two-region problem with equivalence theory and intermediate resonance method. This disadvantage factor accounts for spatial self-shielding effects inside each grain within the framework of an infinite array of grains. Then the homogenized fuel compact is self-shielded using a Bondarenko method to account for interactions between the fuel compact regions in the fuel lattice. In the final form of the equations for actual implementations, the double-heterogeneity effects are accounted for by simply using a modified definition of a background cross section, which includes geometry parameters and cross sections for both the grain and fuel compact regions. With the new method, the doubly heterogeneous resonance self-shielding effect can be treated easily even with legacy codes programmed only for a singly heterogeneous system by simple modifications in the background cross section for resonance integral interpolations. This paper presents a detailed derivation of the new method and a sensitivity study of double-heterogeneity parameters introduced during the derivation. The implementation of the method and verification results for various test cases are presented in the companion paper.

• Research Organization: Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
• Sponsoring Organization: USDOE
• Grant/Contract Number: AC05-00OR22725
• OSTI ID: 1223634
• Journal Information: Nuclear Science and Engineering, Vol. 180, Issue 1; ISSN 0029-5639
• Publisher: American Nuclear Society - Taylor & Francis
• Country of Publication: United States
• Language: English

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