The Evolution of Microstructure Due to Heat Treatment on Highly Porous Copper/Silver Systems

The sintering phenomenon is examined in highly porous materials by first cold pressing powdered copper and silver and separately heat treating them in an un-pressurized furnace. The initial microstructure prior to heat treatment as compared to that after heat treatment showed similar characteristics regardless of the material or powder geometry. However, after heat treatment, there are significantly different microstructures among samples. The microstructures depend on the maximum furnace temperature, the particle geometry, material composition, and the particle surface area. While the microstructures change significantly, there is no change in porosity between pre- and post-heat treated samples.

Leaching/Migration of UO2-Fuel in Compacted Bentonite

ABSTRACTThe release and migration of the fission products cesium, europium and technetium, the actinides plutonium, americium and curium, and the activation product cobalt from spent nuclear fuel pellets in highly compacted bentonite clay has been measured after contact times of 101 and 386 days. Experiments at longer contact times are in progress. In some cases small amounts (0.5–1%) of powdered copper or iron metal, or vivianite (Fe3(PO4)2) have been mixed with the bentonite clay.The results indicate as expected a high mobility of cesium. The actinides have a very low mobility. After 386 days, plutonium has diffused less than 0.5 mm away from the fuel, while americium and curium appear to be somewhat more mobile. The behaviour of europium is similar to that of trivalent actinides. Very little technetium has been leached from all samples. Cobalt shows a strong retention in pure bentonite as well as in the presence of vivianite, while the mobility is much larger when iron or copper is added.