Pages: 1-9

Authors: Zuhair, Wahid Luthfi, R. Andika Putra Dwijayanto, Anis Rohanda, and Suwoto

Abstract

Thorium, in this case, ²³²Th has a higher thermal neutron capture cross-section than ²³⁸U, which means that more fertile isotopes can be transmuted and could lead to higher fissile isotope ²³³U. In addition, ²³³U has a good performance in the thermal spectrum. Theoretically, a nuclear reactor using thorium fuel can also last longer than one using uranium fuel. The use of TRISO duplex fuel is predicted to produce better neutronic behavior in a pebble bed reactor. This work aims to study the kinetic parameters of a pebble bed reactor with TRISO duplex fuel. The configuration of the TRISO duplex fuel pebble consists of an inner region filled with UO₂ TRISO particles and an outer region filled with ThO₂ TRISO particles surrounded by a graphite matrix of fuel pebble. Three configurations with volume fraction of UO₂-ThO₂ were considered in this study: 80-20 %, 75-25 %, and 70-30 %. The HTR-10 reactor was chosen as a reactor model because its geometry and material specifications are known. A series of calculations were conducted using the Monte Carlo transport code MCNP6 and ENDF/B-VII.1 nuclear data library. The calculation results were then analyzed to investigate the effect of UO₂ and ThO₂ compositions in TRISO duplex fuel on the kinetic parameters of the pebble bed reactor with various TRISO packing fractions of 1-50 %. It can be concluded that the utilization of TRISO duplex fuel in a pebble bed reactor could significantly affect the core multiplication factor and kinetic parameters caused by an increase in Th content. On the other hand, the  TRISO packing fraction is taking part in neutron moderation since a lower packing fraction means higher moderation for fueled pebble.

Key words:kinetic parameter, pebble bed reactor, TRISO duplex fuel, MCNP6, ENDF/B-VII.1

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