Microstructure and Leaching Characteristics of a Technetium Containing Metal Waste Form

Abstract

Argonne National Laboratory is developing an electrometallurgical treatment for spent fuel from the experimental breeder reactor II. A product of this treatment process is a metal waste form that incorporates the stainless steel cladding hulls, zirconium from the fuel and the fission products that are noble to the process, i.e., Tc, Ru, Pd, Rh, Ag. The nominal composition of this waste form is stainless steel/15 wt% zirconium/ 1–4 wt% noble metal fission products. The behavior of technetium is of particular importance from a disposal point of view for this waste form due to its long half life, 2.14E5 years, and its mobility in groundwater. To address these concerns a limited number of spiked metal waste forms were produced containing Tc. These surrogate waste forms were then studied using scanning electron microscopy (SEM) and selected leaching tests.

Design and Application of Materials for Sequestration and Immobilization of 99Tc

“…In Section , the focus shifts to material waste forms used to impede the release of 99 Tc into the geosphere after disposal by the immobilization of 99 Tc liquid waste within a stable, solid matrix. Over a period of time, many waste forms have been proposed to accommodate and immobilize 99 Tc. − However, herein, we discuss three specific classes of inorganic waste forms used for the efficient immobilization and disposal of liquid 99 Tc nuclear wastes: glass, cement, and iron minerals.…”

Characterization of Irradiated Metal Waste from the Pyrometallurgical Treatment of Used EBR-II Fuel

“…Development of the metal waste form has progressed from the initial surrogate test program [8,9] to production-scale irradiated operations and includes compositional and microstructural evaluations for phase stability, [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] corrosion testing, [26][27][28][29][30][31][32][33] mechanical as well as thermophysical property testing, and process qualification. [34,35] As a result of the extensive developmental test program, the following conclusions can be stated: (1) the intermetallic ZrFe 2 phase incorporates the noble metals and actinides exclusively, with the exception of technetium which may also be present in the iron solid solution, (2) the metal waste alloy is as corrosion resistant as borosilicate glass based on a variety of durability tests including immersion, electrochemical, galvanic, hydration, and toxicity, and (3) the alloy is a viable high-level waste form for geological disposal despite the recent delay in repository licensing.…”

The Corrosion Behavior of Technetium Metal Exposed to Aqueous Sulfate and Chloride Solutions

“…14 Johnson et al examined the release rate of Tc from a complex alloy containing small amounts of Tc and found that the Tc release rate was low. 15 Spitsyn found that exposure of technetium metal to seawater resulted in minimal Tc corrosion and no biofouling. 16 There is somewhat more work in the literature regarding the electrochemistry of Tc in solution, including the effect of TcO 4 − ions on corrosion of iron.…”