(V) Development of a thermooptometric technique for investigating the high temperature regions of radioactive alloys

This talk would highlight the importance of thermal methods of analysis in the characterization of nuclear fission reactor materials. An innovative thermo-analytical method , namely, the illuminated-spot-DTA technique developed in our laboratory would be discussed. This paper would be focusing on the measurement of phase transition temperatures and the thermo-optometric techniques that were developed for carrying out the same with radioactive materials.

The melting point / solidus temperature of a nuclear fuel is a key data that is required for the design of the nuclear fuel. Often information on the solidus temperature of these materials are rather scant owing to both their reactivity and radioactivity. Hence, experimental measurements need to be carried out afresh for validating the fuel design which requires these data as an input. Often experimental determination of the phase transition temperatures of nuclear fuel materials need to be carried out in custom made equipment suitable for handling these chemically reactive and radioactive substances, at temperatures that could could be as high as 2773 K and more. The, "spot technique" developed in the Argonne National Laboratory by Ackermann et al. is one such innovative technique for the measurement of temperatures of the transitions that involve liquids. By using this method in a single experiment the solid solubility, liquid solubility and stoichiometry of the intermetallic could all be established.

Based on this technique an experimental system was developed in our laboratory with which measurements were made on fast reactor fuel materials. The solidus temperatures of U-Pu-Zr ternary alloy, U,Pu mixed carbide fuel, and the high temperature regions of the binary systems, U-Zr, U-Al, Fe-Zr, Fe-Al, Ru-Sn, Zr-Sn, U-Cr and Zr-Cr have been investigated by using the spot technique in combination with Differential Thermal Analysis, Differential Scannning Calorimetry with auxiliary X-ray diffraction data.