Development of a thermal hydraulic analysis code for gas-cooled reactors with annular fuels

Gas-cooled reactors have been highlighted as a promising option for next generation reactor technology. A thermal hydraulic analysis code for gas-cooled reactors has been developed with a heat transfer model of a block element, which is solved implicitly with the helium energy equation. Validation was carried out through comparison with both experimental and analytical results. A computation module for annular fuel rods has been coupled to the code for comparative analyses of an annular fuel-based block element. At normal operation, the annular fuel shows 80 oC lower peak temperature than the solid fuel for the same power in Japan's high temperature engineering test reactor (HTTR), even though the pressure drop is higher in the annular fuel