Author :
Publisher :
ISBN 13 :
Total Pages : 9 pages
Book Rating : 4.:/5 (684 download)
Book Synopsis Modeling the Long - Term Degradation of a Metallic Waste Form by :
Download or read book Modeling the Long - Term Degradation of a Metallic Waste Form written by and published by . This book was released on 2002 with total page 9 pages. Available in PDF, EPUB and Kindle. Book excerpt: The principal aim of this effort is to develop models of long-term metal waste form (MWF) degradation that are credible, mechanistically based, and empirically calibrated. Utilizing new experimental data and analyses, this paper outlines an updated approach and summarizes the progress made. The current modeling approach emphasizes the analysis of constituent release data from immersion tests. A significant amount of recently obtained immersion test data is described. Test solutions included both mild (well-water), and aggressive (high-chloride and strongly acidic) environments. In addition to predominant constituents Fe, Zr, Cr, and Ni, MWF test samples included: U, Pu, Tc, and Np. Guided by analysis of new immersion test data, a mechanistic model has been developed that describes the time dependence of MWF corrosion leading to passivation. A common functional form relates MWF degradation from different passivating solution environments via scale factors for magnitude and passivation time. Passivation is identified as the most important factor governing long-term durability, along with the long-term stability of oxide barrier layers that cause passivation. Experimental data demonstrated passivation behavior in nominal well water, concentrated well water, an aggressive high-chloride solution, but not in a strong acid. Credible bounding estimates of long-term corrosion for nominal well water solution environments are based on fits to time dependence scaled by the measured release of uranium (empirically identified as the most efficiently released MWF constituent). These estimates involve no significant extrapolation beyond the data and time span of the present experiments. However, using the mechanistic model, these estimates of corrosion and release could be lowered and/or extended to more aggressive solution environments (via scale factors) provided barrier layer stability can be assumed (or demonstrated) to persist for longer times.
