Design study of small modular gas-cooled fast reactor employing modified CANDLE burnup with radial direction shuffling scheme

Design Study of Small Modular Gas-cooled Fast Reactors Employing Modified CANDLE Burnup with Radial Direction Shuffling Scheme has been performed with the power level 325-525 MWt. In this study Modified CANDLE burn-up scheme with radial direction shuffling has been employed with special attention to minimize reactivity swing during burn-up. The reactor cores are divided into 10 regions with equal volume in radial direction. The shuffling scheme of Modified CANDLE in radial direction can be described as follows. The natural uranium input is initially loaded in region 1. After 10 years of burnup the fuel in region 1 is shifter to region 2, the fuel in region 2 is shifted to region 3, etc. till the fuel of region 9 is shifter to region 10. The fuel from region 10 is taken out. Region 1-5 basically breeding zones in which plutonium is accumulated in fuels, while regions 5-10 have enough accumulated plutonium so that they contribute significantly to the power production. We call region 5-10 as burning zone. Nitride fuel is adopted as fuel in this study. Some parametric studies have been performed including variation of core height and power level. The neutronic calculations have been performed using the SRAC 2006 code with JENDL 4.0 nuclear data library. The optimized result shows the reactor could be operated 10 years continuously with maximum excess reactivity less than 1 % ?k/k for 500 MWt output power, 160 cm core active height and 110 cm core active radius.