Argonne National Laboratory
Reduced Enrichment for Research and Test Reactors
Nuclear Science and Engineering Division at Argonne
U.S. Department of Energy

Analysis Methods for Thermal Research and Test Reactors


Teresa Kulikowska, Krzysztof Andrzejewski
Institute of Atomic Energy, Swierk, Poland

Manuel M. Bretscher
Argonne National Laboratory, USA


This report discusses methods used to evaluate 6Li and 3He poison concentrations, initiated by the 9Be(n,a ) reaction, in the beryllium blocks of the MARIA reactor. The results are based on ENDF/B-VI neutron cross sections, 3D diffusion neutron fluxes, and solutions to the differential equations which describe the time-dependent poison concentrations as function of reactor operation and shutdown periods. MCNP Monte Carlo calculations were used to verify calculated poison levels for observed critical configurations. Previous evaluations used somewhat less refined methods based on asymptotic solutions for the poison concentrations. It was found that 3He and 6Li in the beryllium blocks limit the available excess reactivities and alter flux and power distributions. Based on analyses of critical cores, it was determined that poison concentrations need be evaluated for only an in-core region and for an ex-core region and not for each beryllium block.

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Teresa Kulikowska
Institute of Atomic Energy,
05-400 Otwock-Swierk,

Email: [email protected]

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Last modified on July 29, 2008 11:32 +0200