[3O10-14] new type reactor development

[3O10] Optimization of initial fuel composition for Small Pebble Bed Reactor with accumulative fuel loading scheme

(2)Use of burnable poison

＊Irwan Simanullang¹, Toru Obara¹ (1.Tokyo Institute of Technology)

Keywords:Pebble bed reactor, Accumulative fuel loading scheme, Burnable poison, Burnup analysis

The analysis for Small PBR110 MWt with the accumulative fuel loading scheme was performed. The optimum fuel composition was found using 4g uranium per ball with 20% of ²³⁵U enrichment. Nevertheless, large excess reactivity occurred in the initial condition. In the previous study, the excess reactivity reduced by using low enriched uranium. As the results, the burnup value decreased and operation period became shorter. Based on that condition, it is necessary to perform another method to reduce the initial excess reactivity. In the current study, the use of burnable poison was introduced only at the initial condition to reduce the initial excess reactivity.