Background: The advanced high-temperature reactor (AHTR) is conceptional designed by Oka Ridge National Laboratory (ORNL) for a central generating station type of 3400 MWt fluoride-salt-cooled high-temperature reactor (FHR). The design employs an innovative plate-type coated particle fuel assembly with uranium enrichment of 9%?20%. The initial core excess reactivity is too large to be handled by the control blades alone. Purpose: This study aims to eliminate the problem of high excess reactivity by analyzing the use of spherical burnable particles. Methods: First of all

according to the physical properties and burn-up chain of burnable poison (BP) materials

six potential candidates were analyzed

and four of them

i.e. B4C

Gd2O3

CdO and Er2O3 were chosen for further study. Then

the MCNP and Origen2 coupling program were employed to optimize the BP loading using single fuel assembly calculations. Finally

the keff

which changes with burn-up time

was used as optimization parameter to attain the optimal radius and mass. Results: Simulation results showed that the reactivity swing reduced from 39% to about 4.4%

6.8%

7.3% and 13.1% respectively

when loading 176 g Er2O3 with a radius of 740 μm

3 g B4C with a radius of 100 μm

120 g Gd2O3 with a radius of 1 500 μm and 160 g CdO with a radius of 2 000 μm separately. Conclusion: Er2O3 is recommended as the best BP material to eliminate the problem of high excess reactivity in plate-fuel type AHTR. Abstract