Title  Theoretical Modeling of Protective Oxide Layer Growth in Non-isothermal Lead-Alloys Coolant Systems	Researchers Y. Chen, J. Zhang, H. Chen, J. Li Collaborators Ning Li, LBE Team Leader and Jinsuo Zhang, Los Alamos National Laboratory
Background  In advanced nuclear energy systems, lead-alloys (e.g., lead, leadbismuth eutectic) emerge as strong candidates for transmutation and advanced reactor systems as nuclear coolants and high-power spallation neutron targets. However, it is widely recognized that corrosion of materials caused by lead-alloys presents a critical barrier to their industrial use. A few experimental research and development projects have been set up by different groups such as LANL to study the corrosion phenomena in their test facilities and to develop mitigation techniques and materials. One of the central or main techniques in lead-alloys coolant technology under development is to use active control of oxygen thermodynamic activity (OTA) to provide protective oxide layers.  Setting OTA in flowing lead-alloys makes corrosion highly dependent upon the oxygen concentration and the oxidation processes at materials surfaces. The active oxygen control technique exploits the fact that lead and bismuth are chemically less active than the major components of steels, such as Fe, Ni, and Cr. By carefully controlling the oxygen concentration in LBE, it is possible to maintain an iron and chrome based oxide film on the surfaces of structural steels, while keeping lead and bismuth from excessive oxidization that can lead to precipitation contamination. Thermal analysis has given an ideal oxygen level range in a non-isothermal lead-alloy coolant system. However, in a practical coolant loop, the proper oxygen level depends not only on thermal factors but also on hydraulic factors (temperature profile, flow velocity, etc.). In addition, the oxygen distribution in a non-isothermal lead-alloy coolant system is still unclear. The optimal oxygen levels still need to be investigated.  The goal of the proposed research project is to provide basic understanding of the protective oxide layer behaviors and to develop oxide layer growth models of steels in non-isothermal lead-alloys (lead or lead-bismuth eutectic) coolant systems. Precise studies and simulations of all hydrodynamics with thermal conditions encountered in practical coolant loop systems by use of different flowing conditions in the laboratory are difficult and expensive, if not impossible. Therefore it is important and necessary to develop theoretical models to predict the protective oxide layer behaviors at the design stage of a practical lead-alloy coolant system, to properly interpret and apply experimental results from test loops, and to provide guidance for optimization in lead-alloy nuclear coolant systems. The research project, therefore, is aimed at understanding protective oxide layer growth and the optimal oxygen concentration level before lead-alloy nuclear coolants are ready for programmatic implementations and industrial applications.   Snapshots of the simulated layer in the presence of corrosion with scale removal.  They correspond to 2.5 x 104 time step.  The red dot is the oxide site; The blue dot is the walker site; The upper side of the layer is filled with solvent; The lower side of the oxide layer is pure metal.  The corrosion probability of metal is taken as 0.5.  The possibility of scale removal of the oxide site close to solvent is 0.004.	Research Objectives and Methods · To elucidate the mechanism of the protective oxide layer growth of steels in static, non-isothermal flowing lead-alloy coolant systems with oxygen concentration level control. · To elucidate the mechanism of mass transport of oxygen and corrosion products in the multi-phase system. · To develop oxidation growth models of steels in lead-alloy coolant systems. · To clarify the dependence of oxidation processes on thermal hydraulic factors (system operating temperature, temperature profile, flow velocity, etc.) and the oxygen concentration distribution and level. · To clarify the optimal oxygen concentration levels in practical coolant system scales. · To interpret the experimental results from test loops and to apply them to the design of practical nuclear coolant systems.
Students  Taide Tan Chaiyod Soontrapa   Srinivas Kohir   Debajyoti Maitra	Department Mechanical Engineering
Final Report	Annual Report
Proposal 04/30/04	Quarterly Reports  10/01/04-12/31/04   01/01/05-03/31/05  04/01/05-06/30/05  01/01/06-03/31/06