Leaching Characteristics of the Metal Waste Form From the Electrometallurgical Treatment Process: Product Consistency Testing

Host phases for actinides in simulated metallic waste forms

“…These observations suggest that deformation microstructures may have been introduced into the intermetallic materials during TEM sample preparation. More extensive introduction of deformation microstructures may have occurred while finishing the surfaces of U-bearing samples for immersion tests with an abrasive wheel on a Dremel tool [11]. Other possible reasons why U-bearing samples tend to have more stacking faults than those with Pu or Np include orientation of the specific crystals examined relative to the applied stress responsible for the deformation and differences in stacking-fault energies and dislocation mobility between U-bearing intermetallic materials and those with other actinides.…”

“…Thus, differences in dissolution behavior between U and Pu must be caused by something other than different crystal structures of the high-actinide phases. A defect-related increase in the dissolution rate of the U-bearing materials may be part of the answer, but requires either a dissolution mechanism favoring the release of U or preferential retention of other elements in corrosion products to explain the dissolution-experiment results of Johnson et al [10,11]. Other possible structural and microstructural factors influencing dissolution behavior may include a composition-dependent dissolution rate for C15 Fe 2 Zr or differences in volume fractions and dissolution rates for the C15 and C36 Fe 2 Zr structures in the different samples.…”

“…These Np and Pu concentrations are too low for convenient detection by electron microscopy, and simulated metallic waste forms consisting of SS15Zr with realistic concentrations of U and elevated concentrations of Np and Pu are commonly used in materials-characterization and corrosion studies (e.g., [8][9][10][11]). SEM images of simulated metallic waste forms [8,12] show eutectic microstructures similar to those in SS15Zr.…”

“…Experimental measurements of elemental releases during immersion tests of actinide-bearing simulated metallic waste forms show that the normalized release rate of U is higher than that of any other element [10,11]. Previous attempts to understand this behavior have included characterization of actinide-bearing phases using SEM and neutron-diffraction data [8,9].…”

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.…”