Neutronics calculation of the conceptual TRISO duplex fuel rod design

Abstract

The duplex fuel pellet includes UO2 components as seed and ThO2 blanket, originally designed to increase the breeding rate of fissile materials in light water breeder reactors. However, the seed portion alone concentrates most of the energy released from the fission reaction, which can make the seed temperature too high. The duplex fuel potential for the high-temperature reactor (HTR) using TRISO fuel has never been researched. MCNPX simulation was conducted to compare the neutronics performance of normal TRISO fuel with that of TRISO duplex fuel. Two types of HTR fuel rod, the cylinder and the annular rod, were simulated and compared to see whether the duplex neutron characteristics would be better in the cylinder or annular fuel compact design. The TRISO duplex rods produced higher burnup than normal rods up to 5% higher for cylinder and 6% for annular rods. The TRISO duplex rod is also capable of maintaining longer criticality, producing smaller kinf changes and reducing the potential for plutonium build-up. The proposed TRISO duplex conceptual fuel design has an interesting neutronic properties, which offers possibilities for future studies.

Keywords

• Thorium reactor
• High temperature reactor
• Micro modular reactor
• TRISO-duplex