Prevailing dimensional tolerance for sintered UO₂ reactor fuel components to be enclosed in metal jackets are expensively small. For instance, the PWR fuel pellet, as of November, 1955, consisted of a centerless ground UO₂ cylinder 0.3560" (+0.0005", -0.000") in diameter and 0.3527" (±0.0008") long. This pellet was designed to fit in a Zircaloy tube 0.3585" (+0.0005", -0.0000") inside diameter. The use of UO₂ shapes as pressed, or extruded, and sintered with diameter variations controlled to a tolerance of ±0.003" to ±0.005" would represent a fabrication cost saving worth considering. It is reasonable to assume that the annulus between a sintered UO₂ shape and its container will vary as a function of time of irradiation. Shrinkage from the can walls occurs with relatively low density (i.e., 85% of theoretical) sintered irradiation (cf. MTR Test GEH-4-3C). Contrary to this effect, the thermal expansion coefficient of UO₂ is about twice that of Zircaloy. Of possibly greater significance is the inevitable fractuce of dense UO₂ due to thermal stress. Such cracking effectively relocates the annular heat transfer gap to the interior of the oxide where the higher temperatures enhance the heat transfer coefficient. Thus, possibly the worst condition, with respect to heat transfer, is …

This report analyzes Parian and Teflon that were exposed to solutions of 1AX, 1AS, and 1AF, ANL June 1, 1948 Flowsheet, under conditions described in the following report.