Neutronic analysis of thorium S&B fuel blocks with different driver fuels in advanced Block-type HTRs.

• The performance of the thorium seed and blanket (S&B) fuel blocks with four type driver fuels in AHTR is investigated. • The discharge burnup is the highest for the fuel block with U-233 as driver fuel. • The fuel block with RGrPu as driver fuel has the highest conversion ratio. • The temperature coefficients of reactivity are more negative for RGrPu and WGrPu driven fuel blocks. Because of the high burnup achieved by thorium fuels, they are attractive for utilization in the so-called advanced high temperature reactor (AHTR), which is a new reactor that merges HTR and molten salt reactor (MSR) designs. Based on a typical fuel block of AHTR, the neutronic characteristics of seed and blanket (S&B) fuel blocks with different driver fuels, including the infinite multiplication factor (k inf), conversion ratio (CR), discharge burnup, energy spectra, equilibrium mass of U-233 and temperature coefficient of reactivity (α T), were investigated based on DRAGON V4. The seed is assumed to contain thorium with either U-233, RGrPu, WGrPu or WGrU while the blanket is always thorium. In terms of maximizing discharge burnup, 6 kg heavy metal (HM) per fuel block was selected for the comparison analysis of the four drivers. The same configuration of S&B 4 + 5 was used for all the investigated fuel blocks. It is shown that the k inf has the highest value for the fuel block with U-233 as driver fuel (Th/U233) and decreases passing to Th/WGrU, Th/WGrPu and Th/RGrPu. Though Th/RGrPu achieves the highest CR, Th/U233 achieves the deepest discharge burnup because of its high k inf. The temperature coefficients of reactivity of fuel (α TF) and moderator (α TM) of Th/RGrPu, Th/WGrPu, and Th/WGrU are all negative. However, α TF of Th/U233 fuel block is negative but its α TM is positive. [ABSTRACT FROM AUTHOR]