DefinePK

Abstract

An optimum fuel composition is a very important parameter in the operation of a pebble bed high temperature gas-cooled reactor (HTGR). In the present scoping study, the optimum ranges of heavy metal (HM) loading per pebble and the uranium enrichment are investigated. The HM loading range covers 4 to 10 g per pebble, while the uranium enrichment covers 5 to 20 w/o. Two fuel loading schemes typical to pebble-bed HTGRs are also investigated, i.e. the OTTO and multi-pass schemes. All calculations are carried out using BATAN-MPASS, a general in-core fuel management code dedicated for pebble-bed type HTGRs. The reference reactor design case is adopted from the German 200 MWth HTR-Module but with core height of half of the original design. Other design parameters follow the original HTR-Module design. The results of the scoping study show that, for both once-through-then-out (OTTO) and multi-pass fueling schemes, the optimal HM loading per pebble is around 7 g HM/ball. Increasing the uranium enrichment minimizes the fissile loading however higher enrichment than 15 w/o is not effective anymore. The multi-pass fueling scheme shows lower fissile loading requirement and a significantly lower axial power peaking than the OTTO scheme. It can be concluded that the optimum range of HM loading and uranium enrichment are found to be around 7 g per pebble and 15 w/o. In addition the multi-pass fueling scheme shows superior BURNUP and safety characteristics than the OTTO fueling scheme.