Technetium Waste Form Development - Progress Report

Abstract

This project has focused on the immobilization of Tc waste streams and undissolved solids (UDS) which consists mainly of the 5-metal particles (Mo-Ru-Tc-Rh-Pd). Composition of UDS will have strong impact on composition of the final waste form alloy. Idaho National Laboratory (INL) has added Re and Mo (as surrogates for Tc and UDS metals) to the SS-15Zr alloy that was previously developed for EBR-II metal wastes.Microanalysis using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) has been used to analyze a ~5 g. ingot with composition 71.3 wt% 316SS-5.3 wt% Zr-13.2 wt% Mo-4.0 wt% Rh-6.2 wt% Re prepared at the Idaho National Laboratory. Four phase fields have been identified, two of which are lamellar eutectics, with a fifth possibly present. A Zr rich phase was found distributed as fine precipitate, ~10 µm in diameter, often coating large cavities. A Mo-Fe-Re-Cr lamellar eutectic phase field appears as blocky regions ~30 µm in diameter, surrounded by a Fe-Mo-Cr lamellar eutectic phase field, and that in turn is surrounded by a Zr-Fe-Rh-Mo-Ni phase field. The eutectic phase separation reactions are different. The Mo-Fe-Re-Cr lamellar eutectic appears a result of austenitic steel forming at lower volume fraction within an Mo-Fe-Re intermetallic phase, whereas the Fe-Mo-Cr lamellar eutectic may be a result of the same intermetallic phase forming within a ferritic steel phase. Cavitation may have arisen either as a result of bubbles, or from loss of equiaxed particles during specimen preparation.v

Technetium Waste Form Development Progress Report

“…Unlike the metals examined in the last campaign reported in Gelles et al (2009), these materials did not contain zirconium. Initial XRD and SEM analyses at INL indicated both materials were multi-phase alloys.…”

Electron Microscopy Characterization of Tc-Bearing Metallic Waste Forms- Final Report FY10

“…The minimum additive waste stabilization approach is being utilized to produce a metal waste form that both addresses the performance goals and minimizes the amount of additional materials that needs to be added to make a durable material. Previous work had revealed a complex microstructure with multiple phases in the FeMo-Zr system for metallic waste form alloys [6]. In this study, a 48wt% Fe, 38 wt% Mo, with 14 wt% Re alloy (termed FeMo-Re alloy in this paper) and a 52 wt% Fe, 41 wt% Mo with 7 wt% Tc (termed FeMo-Tc alloy) were prepared at INL [7].…”