Ceramic and glass radioactive waste forms

This report contains 14 individual presentations and 6 group reports on the subject of glass and polycrystalline ceramic radioactive waste forms. It was the general consensus that the information available on glass as a waste form provided a good basis for planning on the use of glass as an initial waste form, that crystalline ceramic forms could also be good waste forms if much more development work were completed, and that prediction of the chemical and physical stability of the waste form far into the future would be much improved if the basic synergistic effects of low temperature, radiation and long times were better understood. Continuing development of the polycrystalline ceramic forms was recommended. It was concluded that the leach rate of radioactive species from the waste form is an important criterion for evaluating its suitability, particularly for the time period before solidified waste is permanently placed in the geologic isolation of a Federal repository. Separate abstracts were prepared for 12 of the individual papers; the remaining two were previously abstracted

Modification of Sensitization Resistance of AISI 304L Stainless Steel through Changes in Grain Size and Grain Boundary Character Distributions

Sensitization behavior of thermomechanically processed AISI 304L stainless steel has been investigated. The mechanical processing was carried out at deformations of 30 to 90 pct (reduction in thickness), and annealed subsequently at temperatures ranging from 800 °C to 950 °C for 15 to 60 minutes. Stainless steel was then sensitized at 675 °C both for short (2 hours) and long (53 hours) durations. Thus treated specimens were characterized for grain boundary character distribution, grain size, and degree of sensitization (DOS). The increase in annealing temperature and time following mechanical processing showed an increase in grain size (up to 37 μm) and in the DOS. The fraction of coincident site lattice (CSL) boundaries (Σ3 to Σ29) was also noticed to increase with the annealing temperature, which implied that an increasing fraction of low energy boundaries did not cause a decrease in the DOS. The grain size through its effect on grain boundary surface area and the effective grain boundary energy correlated well with the extent of sensitization. Grain growth reduces the grain boundary surface area and the effective grain boundary energy as well, which, in turn, enhanced the DOS. A critical grain size (∼0.05), above which, sensitization reduced to insignificant levels was observed