Pre- and Postirradiation Evaluation of TRISO ThO sub 2 Particles Irradiated in Capsule HT-34

摘要

Capsule HT-34 was irradiated jointly by General Atomic Company (GA) and Oak Ridge National Laboratory (ORNL). This report presents the pre- and postirradiation evaluation conducted by GA. The purpose of the test was to characterize the mechanical and chemical performance and fission product release of TRISO ThO sub 2 particles. Sixteen TRISO ThO sub 2 samples, which had been fabricated in the production-line (240-mm-ID) coater, were irradiated at approximately 1200 and 1450 exp 0 C to neutron fluences of 5.1 to 10.2 x 10 exp 25 n/m exp 2 (E > 29 fJ)/sub HTGR/, and burnups of 5.1 to 12.7% FIMA. Following are the results of the postirradiation examination: the OPyC coating failure of the 800- mu m-diameter particles irradiated at 1200 exp 0 C was less than or equal to 1.8%; the pressure-vessel model overpredicted failure up to seven times the observed failure for the samples irradiated at 1200 exp 0 C; palladium attack and internal corrosion of the SiC coating was observed in the samples irradiated at 1200 exp 0 C; internal corrosion of the SiC coating caused SiC failure up to 100% in the samples irradiated at 1450 exp 0 C; and an average of 16 and 90% of the Cs was released from failed particles irradiated at 1200 and 1450 exp 0 C, respectively, after 2686 h of irradiation. (ERA citation 06:009136)