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Intermediate Resonance Absorption in Heterogeneous Media

Bal Raj Sehgal, Rubin Goldstein

Nuclear Science and Engineering

Volume 25 / Number 2 / June 1966 / Pages 174-182


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Resonance absorption in heterogeneous media with intermediate-mass moderators is investigated under the assumption that the flux is spatially flat in each region. Intermediate resonance parameters are introduced for scattering by all species present in the system and an intermediate resonance approximation is developed for calculating them. An improved rational representation for the lump escape probability is used and the calculation of the Dancoff factor is modified to account for the intermediate nature of the scattering-removal process by the outside moderator. The resonance integrals from the intermediate resonance approximation are compared with those from Monte Carlo and ZUT computer code calculations for the 6.7-eV resonance of 238U. The intermediate-resonance approximation results are found to be in good agreement with the Monte Carlo results. The ZUT results have large errors for heavy moderators, especially in undermoderated systems. Equivalence among heterogeneous systems and between heterogeneous and homogeneous systems is discussed. In the former case, an equivalence through the intermediate parameters is established.

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