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

2007 International RERTR Meeting

Abstracts and Available Papers Presented at the Meeting

MNSR Flux Performance and Core Lifetime Analysis with HEU and LEU Fuels

J. R. Liaw and J. E. Matos
RERTR Program
Nuclear Engineering Division
Argonne National Laboratory
Argonne, Illinois 60439-4815 USA


This paper discusses the results of flux performance and the core lifetime analyses for conversion of an MNSR core using LEU-UO2 fuel containing uranium with 12.5% enrichment. Detailed MCNP5 models were used to evaluate the flux performance. Diffusion theory REBUS-3 models were used to estimate fuel depletion rates under various operational schemes and to simulate the long-term fuel depletion history. Core lifetimes were estimated under realistic operational constraints. This study found a reduction of 7- 10% in thermal neutron flux in the irradiation channels for the LEU-UO2 fuel in comparison with the HEU fuel. Therefore, for an LEU fueled core, the reactor power would have to be increased by ~10% from the current level of 30 kW in order to match the nominal flux level. MNSRs have a very small window of excess reactivity for operation and are designed for a very short operational cycle to avoid excessive xenon buildup. Consequently, fuel depletion calculations need to be performed using realistic operational constraints. As fuel depletes, top Be shim plates are added periodically to restore the excess reactivity for continuing operation. The maximum allowed excess reactivity at the beginning of each operating cycle is 4 mk. This study concludes that an MNSR core with LEU UO2-12.5% fuel and a power level of 33 kW can be operated ~25% longer than the current HEU core operated at 30 kW. Both cores will have the same thermal neutron flux in the experiment positions.

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Dr. Jordi Roglans-Ribas
Technical Director, RERTR Department
Nuclear Engineering Division 362
Argonne National Laboratory
9700 South Cass Avenue
Argonne, IL 60439
Fax:  +1 630-252-5161

2016 RERTR Meeting

The 2016 International RERTR Meeting (RERTR-2016) will take place in Belgium. Stay tuned for further details.

2015 RERTR Meeting

The 2015 International RERTR Meeting (RERTR-2015) took place in Seoul, Korea on Oct. 11-14, 2015.
For more information visit RERTR-2015.


ARGONNE NATIONAL LABORATORY, Nuclear Engineering Division, RERTR Department
9700 South Cass Ave., Argonne, IL 60439-4814
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Last modified on July 29, 2008 16:02 +0200