Uranium Contamination in Coating and in Matrix Material of Unirradiated Coated Particle Fuel

抄録

A study was made of uranium contamination in (a) the coating layers of TRISO particles (a-1) before compacting and (a-2) separated from once-compacted fuel heat-treated at 1, 400 or 1, 800°C, and (b) in the matrix material of the same compacts. The contamination in the pyrocarbon layers of the coating was determined, after mechanically separating the coating layers, by a procedure of neutron activation, burn-off and ¹³³Xe trapping. For the silicon carbide coating layer, the fragments of coating left from the above procedure were fused into alkaline melt, and the ¹³³Xe released at each heating step was trapped. For the matrix material, the fuel compacts were deconsolidated electrolytically or mechanically, followed by activation analysis. The results of the foregoing measurements proved the uranium con- tamination in pyrocarbon and silicon carbide coating to be at most of the order of 10^-4 in reference to uranium content in kernel, while the corresponding value for particles sampled from fuel compacts heat-treated at 1, 800°C were appreciably higher. The corresponding values found for the matrix material were of the order of 10^-5.