Fuel burnup of modified fuel assembly configurations for a small medical reactor

A 300 kW small medical reactor was designed to be used for boron neutron capture therapy (BNCT) at the Korea Advanced Institute of Science and Technology (KAIST) in 1996. The analysis of the core life cycle of the original design of the fuel assembly for the BNCT facility was performed and several modifications of the fuel assembly configuration were carried out. The analysis for the core life cycle of the original assembly design of the BNCT facility with low enrichment uranium (≯20 wt.% 235U) fuels was performed. It was found that the neutron fluxes are almost stable during burned days and it is good characteristics of the design for irradiation result. The core life cycle was evaluated about 10 years for 20 w/o enrichment while for 17 w/o enrichment is about 200 days. The results also show that the original design with reduced enrichment of fuel or decreased number of fuel rods in the fuel assembly can give enough life cycle of the core.