Irradiation behaviors of coated fuel particles, (6)

TRISO coated fuel particles fabricated in the specifications of the VHTR preliminaly design in FY 1973 and 1974, and the TRISO particles imported from England, which had been fabricated in the same specifications, were irradiated by 74F-1A capsule in JMTR reflector region. In this irradiation experiment the maximum fast neutron fluence was 0.96 x 1021 n/cm2 (E > 29fJ) and the maximum fuel burnup, 2.5 %FIMA, but the maximum fuel temperature was 11400C, which was very low, compared with the designed temperature. In the postirradiation examination the irradiaiton performance of the coated fuel particles was examined by the surface inspection, X-ray microradiography, ceramograpy, the acid-leaching and the crushing strength measurement. From the results it was concluded that the coated fuel particles fabricated in FY 1973 exhibited relatively good performance in this irradiation. The coated fuel particles fabricated in 1974, which possessed the propylene derived PyC, behaved in the manner that the outermost PyC layer was mechanically unstable. The imported particles did not good performance. The crushing strength of the coated fuel particles reduced about 67% by irradiation. (author)