Optimization of Thermochemical, Kinetic, and Electrochemical Factors Governing Partitioning of Radionuclides During Melt Decontamination of Radioactively Contaminated Stainless Steel [report]

1999 unpublished
The goal of this project is to characterize and optimize the use of molten slags to melt decontaminate radioactive stainless steel scrap metal. The major focus is on optimizing the electroslag remelting (ESR) process, a widely used industrial process for stainless steels and other alloys, which can produce high quality ingots directly suitable for forging, rolling, and parts fabrication. It is our goal to have a melting process ready for a DOE D&D demonstration at the end of the third year of
more » ... SP sponsorship, and this technology could be applied to effective stainless steel scrap recycle for internal DOE applications. It also has potential international applications. The technical approach has several elements: 1) characterize the thermodynamics and kinetics of slag/metal/contaminate reactions by models and experiments, 2) determine the capacity of slags for radioactive containment, 3) characterize the minimum levels of residual slags and contaminates in processed metal, and 4) create an experimental and model-based database on achievable levels of decontamination to support recycle applications. Much of the experimental work on this project is necessarily focussed on reactions of slags with surrogate compounds which behave similar to radioactive transuranic and actinide species. This work is being conducted at three locations. At Boston University, Prof. Uday Pal's group conducts fundamental studies on electrochemical and thermochemical reactions among slags, metal, and surrogate contaminate compounds. The purpose of this work is to develop a detailed understanding of reactions in slags through small laboratory scale experiments and modeling. At Sandia, this fundamental information is applied to the design of electroslag melting experiments with surrogates to produce and characterize metal ingots. In addition, ESR furnace conditions are characterized, and both thermodynamic and ESR process models are utilized to optimize the process. To complete the process development, ESR melting experiments, which include actual radioactive contaminates as well as surrogates, are being conducted at the Mining & Chemical Combine in Zheleznogorsk, Russia. These experiments measure decontamination efficiencies in ingots for uranium and plutonium in stainless steel, as well as correlate removal of radioactive and surrogate compounds in the same melts. This will "close the loop" and allow us to use measured surrogate behaviors to model removal of radioactive species. Research Progress and Implications At Boston University, experiments were conducted to measure the dissolution of cerium oxide, as a surrogate for uranium and plutonium compounds, into the baseline ESR slag (60wt%CaF 2 -20wt%CaO-
doi:10.2172/14910 fatcat:rdk2f3dbhvhy3e27hic3agdnxa