Abstracts and Available Papers Presented at the
2004 International RERTR Meeting

Feasibility Study for LEU Conversion of the WWR-K Reactor at the Institute of Nuclear Physics in Kazakhstan Using a 5-Tube Fuel Assembly

N.A. Hanan, J.R. Liaw and J.E. Matos
RERTR Program, Argonne National Laboratory Argonne, IL 60439

ABSTRACT
 

A feasibility study by the RERTR program for possible LEU conversion of the 6 MW WWR-K reactor concludes that conversion is feasible using an LEU 5-tube Russian fuel assembly design. This 5-tube design is one of several LEU fuel assembly designs being studied (Ref. 1) for possible use in this reactor. The 5-tube assembly contains 200 g 235U with an enrichment of 19.7% in four cylindrical inner tubes and an outer hexagonal tube with the same external dimensions as the current HEU (36%) 5-tube fuel assembly, which contains 112.5 g 235U. The fuel meat material, LEU UO2-Al dispersion fuel with ~2.5 g U/cm3, has been extensively irradiation tested in a number of reactors with uranium enrichments of 36% and 19.7%.

Since the 235U loading of the LEU assemblies is much larger than the HEU assemblies, a smaller LEU core with five rows of fuel assemblies is possible (instead of six rows of fuel assemblies in the HEU core). This smaller LEU core would consume about 60% as many fuel assemblies per year as the current HEU core and provide thermal neutron fluxes in the inner irradiation channels that are ~17% larger than with the present HEU core. The current 21 day cycle length would be maintained and the average discharge burnup would be ~42%. Neutron fluxes in the five outer irradiation channels would be smaller in the LEU core unless these channels can be moved closer to the LEU fuel assemblies.

Results show that the smaller LEU core would meet the reactor’s shutdown margin requirements and would have an adequate thermal-hydraulic safety margin to onset of nucleate boiling.

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