Head-end reprocessing studies with irradiated HTGR-type fuels. III. Studies with RTE-7: TRISO UC$sub 2$-TRISO ThC$sub 2$

Head-end reprocessing studies on irradiated Fort St. Vrain type HTGR fuel (TRISO coated UC$sub 2$-TRISO coated ThC$sub 2$) were performed. Fuel sticks were burned quiescently in oxygen at 750$sup 0$C, the ash was screened to separate the fissile SiC-coated particles from the fertile SiC-coated particles, each particle fraction was crushed and burned separately in oxygen, and the secondary burner ash products were leached. These studies concentrated on the release of radionuclides to the burner off-gases after passing through a 20-$mu$ m sintered metal frit held at 500$sup 0$C. Fission product and heavy metal inventories were made on the process gaseous, liquid, and solid streams. Experimental results are compared with pre-irradiation average fuel stick compositions and with calculated fission product inventories. (auth