Case Studies on Corrosion Protection and Material Integrity in Nuclear Engineering

Abstract The waste stored at the Hanford Site was generated during the Manhattan Project of World War II and throughout the Cold War. It encompasses a wide range of chemical compositions and physical phases, including liquids, acids and bases, insoluble sludge containing mud-like particulates, and hardened salt cake formed by evaporation and solubility changes. These wastes are held in multiple sets of tanks, many of which have exceeded their original design life. While careful monitoring and maintenance have extended their service lives, some single walled tanks have begun leaking into the surrounding soil. Converting this waste into a stable solid form is essential to move from a short-term solution, which is a maintenance-intensive solution, towards a longer-term strategy that resists corrosion, withstands unforeseen events, and requires significantly less upkeep. The mission of the Waste Treatment and Immobilization Plant is to vitrify the liquid and aqueous wastes by incorporating them into glass “logs” for long-term storage in a Integrated Disposal Facility at Hanford. To support this process, the Glass-Forming Reagent (GFR) Facility is being designed to receive, store, measure, mix, and transfer glass-forming chemicals (GFCs) to the melter operations. These chemicals will be conveyed pneumatically from storage silos to the mixing equipment, and subsequently from the mixing system into the melters (Ref. 1). Corrosion prevention strategies can be grouped into four primary mechanisms: cathodic protection, coatings and linings, material verification, and material selection. Cathodic protection equalizes the electrochemical potential of a metallic surface, so the entire structure behaves more nobly than a corroding anode. Coatings and linings act as physical barriers to corrosive environments, limiting the exposed surface area and thereby reducing the cathodic protection current required. Material selection and verification are critical in extremely aggressive environments where other methods are insufficient. Positive Material Identification (PMI) ensures that installed materials meet required specifications. Corrosion allowance provides additional wall thickness to accommodate predictable metal loss over time, especially in high-velocity streams that may carry abrasive particles. This paper presents four case studies where the underlying science and engineering principles were well established, yet significant challenges still emerged in practice.