Lead Alloy Corrosion R&D for Gen-IV S. Sharafat UCLA ITER TBM Meeting Agenda UCLA, Eng. IV – Conference Room September, 2004

Typical Steel Compositions Typical Compositions of RA and Conventional Steels (wt%)* “Annual Report of the Association EURATOM/CEA 1998,” Compiled by : P. MAGAUD and F. LE VAGUERES ASSOCIATION CEA/EURATOM DSM/DRFC CEA/CADARACHE Saint-Paul-Lez-Durance (France)

Lead-Alloy Compatibility Research for Gen-IV Reactors REVIEW Article: “Status of Research and Development of the Lead-Alloy-Cooled Fast Reactor,” E.P. Loewen (INEEL) and A.T. Tokuhiro (U. Missouri-Rolla) J. Nuclear Science and Technology, Vol. 40, No. 18 (2003) Institutions Researching Pb-Alloy Corrosion: –INEEL –MIT –LANL –IPPE (Russia) –FZK –CMHDS (Israel)

Lead-Alloy Compatibility Research Molten-Pb corrosion research since 1950 –Main form of corrosion is mass transfer of structural materials along a thermal gradient, via dissolution in the hot regions and precipitation in the cold regions. –Liquid-Pb-alloy corrosion of structural steels depends heavily on the solubility rate of the structural material in the liquid metal. –Diffusion barriers, metal oxides, nitrides, other surface compounds, and impurities in both the molten Pb-alloy and the structural materials affect the solubility rates.

Pb-Alloy Steel Corrosion: Ferritic steels: –Increased Cr increases corrosion resistance below 650 o C –Decreased Cr increases corrosion resistance above 750 o C Low-carbon steels: –Suffer moderate penetration in static tests, usefulness limited to below 450 o C. Nickel alloys: –Austenitic steels, are unsatisfactory for liquid Pb-alloys above 500 o C (preferential dissolution of Ni).

Reducing Corrosion Rates: Pb-Alloy Corrosion of steels are reduced through addition of oxidation inhibitors Zr, W, Cr to coolant. Deposition of Al, Mo, Zr or Carbide on the surface can also reduce corrosion, but erratic adherence and non-uniformity.

Reducing Corrosion: Recent Findings USE of OXYGEN: –Ferritic and austenitic steels under the presence of a dilute solution of oxygen has shown no dissolution attack (below 550 o C). –Strict oxygen-chemistry control as a means to prevent corrosion and to minimize solubility of structural metals in Pb. –To successfully control corrosion in molten-Pb systems, the O2 potential must be controlled. –Oxygen potential of the metal is kept at a level at which the oxide layer on the steel is stable, USE of CERAMICS: –The Russians developed an O2-control for Pb-alloy systems along with a structural-steel alloy that was more resistant to attack by molten Pb. –The probes used to monitor oxygen in molten Pb are constructed of yttrium-oxide-stabilized (Y2O3) zirconia (ZrO2) ceramic (YSZ). Findings confirmed by Karlsruhe Lead Laboratory (KALLA) in Germany

Pb-Li Corrosion Thermodynamics Ceramic Stability in Pb-Li (773K): –Decreasing Solutes*  Decreases Stability *O, C, N, or H by cold trapping [P. P.Hubberstey and T. Sample, JNM 248(1997) ]

Recommendations Leverage off the ongoing Pb-Alloy research for Gen-IV Pb-Bi cooled fission reactors. Addition of Oxygen can stabilize protective coatings. Yittrium-Stabilized Zirconia has shown good stability in Pb-alloy corrosion tests.

The most significant corrosion work on ferritic steel and PbLi eutectic has been done in the EU between MANET and LiPb. The work was done in the PICOLO loop, with flowing LiPb at temperatures of 450 to 550 C. The velocity was 0.3 m/s. It is stated that "LiPb is compatible with MANET up to 470C." (1) The corrosion rate can be calculated by the following equation:(2) log(d) = /T in which d is the loss of wall thickness in micor-m/h and T is the wall temperature in K. BCSS recomended that the maximun corrosion rate be kept below 20 um/y. Therefore, the temperature limit set by the EC team at 470 C maximum appears to be reasonable. References 1. "Developement of Self-cooled Liquid Metal Breeder Blankets," FZKA 5581, Nov P "Dual Coolant Blanket Concept," KfK 5424, Nov. 1994