Tho rium, in this case, 232Th has a higher ther mal neu tron cap ture cross-sec tion than 238U, which means that more fer tile iso topes can be trans muted and could lead to higher fis sile isotope 233U. In ad di tion, 233U has a good per for mance in the ther mal spec trum. The o ret i cally, a nu clear re ac tor us ing tho rium fuel can also last lon ger than one us ing ura nium fuel. The use of TRISO du plex fuel is pre dicted to pro duce better neutronic be hav ior in a peb ble bed re ac tor. This work aims to study the ki netic pa ram e ters of a peb ble bed re ac tor with TRISO du plex fuel. The con fig u ra tion of the TRISO du plex fuel peb ble con sists of an in ner re gion filled with UO2 TRISO par ti cles and an outer re gion filled with ThO2 TRISO par ti cles surrounded by a graph ite ma trix of fuel peb ble. Three con fig u ra tions with vol ume frac tion of UO2-ThO2 were con sid ered in this study: 80-20 , 75-25 , and 70-30 . The HTR-10 re actor was chosen as a reactor model because its geometry and material specifications are known. A se ries of cal cu la tions were con ducted us ing the Monte Carlo trans port code MCNP6 and ENDF/B-VII.1 nu clear data li brary. The cal cu la tion re sults were then an a lyzed to in ves ti gate the ef fect of UO2 and ThO2 com po si tions in TRISO du plex fuel on the ki netic pa ram e ters of the peb ble bed re ac tor with var i ous TRISO pack ing frac tions of 1-50 . It can be con cluded that the uti li za tion of TRISO du plex fuel in a peb ble bed re ac tor could sig nif icantly af fect the core mul ti pli ca tion fac tor and ki netic pa ram e ters caused by an in crease in Th con tent. On the other hand, the TRISO pack ing frac tion is tak ing part in neu tron mod er ation since a lower pack ing frac tion means higher mod er a tion for fu eled peb ble.
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