Review of aluminum solubility behavior in the Hanford 200 South West Area tanks targeted for retrieval

Abstract The behavior of aluminum‐bearing phases in tank wastes from the southwest quadrant of the Hanford Site's 200 West Area primarily determines solids accumulation, retrieval performance, and downstream processability. This review synthesizes historical tank characterization data, laboratory dissolution studies, and process‐relevant observations to evaluate the thermodynamic and kinetic controls governing aluminum solubility under alkaline tank waste conditions. Across waste classes—REDOX sludge, saltcake, and cladding waste—aluminum is predominantly present as boehmite, gibbsite, and aluminate salt. The dominant phase depends heavily on the originating process history. Aluminum‐rich sludges are largely insoluble under typical retrieval processes, while saltcake phases exhibit more composition‐dependent solubility. Integration of available data reveals that nonideal dissolution behavior and phase transformation reactions are key contributors to residual solids during water addition and retrieval. A bounding analysis of solids accumulation in the SY‐103 staging tank indicates that aluminum‐rich wastes, particularly REDOX‐derived sludges, dominate projected solids inventories and may exceed operational limits early in retrieval under conservative assumptions. Uncertainty is driven primarily by variability in solids loading, phase distribution, and scale‐dependent settling behavior. This review provides a mechanistic framework linking mineral phase behavior to process‐scale outcomes and identifies dominant uncertainty sources. Temperature and hydroxide concentration emerge as key process mechanisms for aluminum dissolution, supporting prioritization of specific waste types for characterization. These findings provide a scientific basis for reducing uncertainty in West Area Tank Treatment flowsheet development and improving predictability of solids management during retrieval.