Schroer, C.

Weisenburger, A.

English

KITopen

KIT – University of the State of Baden-Wuerttemberg and National Research Center of the Helmholtz AssociationInstitute for Applied Materials – Material Process Technology (IAM-WPT), Corrosion DepartmentInstitute for Pulsed Power  and Microwave Technology (IHM), Pulsed Power Technology Departmentwww.kit.eduSEARCH/MAXSIMA International Workshop October 7 –10, 2014Karlsruhe Institute of Technology (KIT), GermanyEstimation of corrosion product formation in MYRRHACarsten Schroer,  Alfons WeisenburgerInstitute for Applied Materials – Material Process Technology (IAM-WPT)Institute for Pulsed Power and Microwave Technology (IHM)2 October 2014Corrosion-related issues Materials Thinning of the material cross-section Altered near-surface material properties Impaired properties of functional surfaces Overall change of geometric dimensions, e.g., material plus solid corrosion scale Corrosive medium Depletion in corrosive agents Contamination with corrosion products Contaminant diffusion and convective transport Subsequent chemical reactions Re-precipitation of absorbed elements Deposition of solid matter Plant operation Reduced efficiency of plant components Risk of premature material failure Short- and long-range secondary effects, e.g., plugging of narrow sections Contribution to the emission of pollutantsInstitute for Applied Materials – Material Process Technology (IAM-WPT)Institute for Pulsed Power and Microwave Technology (IHM)3 October 2014MYRRHA reactor: Process medium and materials  Process medium Lead-bismuth eutectic (LBE) Addition of oxygen so as to favour oxidation over solution of material elements Oxygen activity or concentration required is material- and temperature-dependent Goal of deliberate oxygen addition Materials Austenitic steels:316L for the main structural components, 15-15Ti in the core 9Cr ferritic/martensitic steels:T91 for parts of the core support and spallation target assemblyUnder MYRRHA-relevant conditions, the same steel may show different corrosion modes in oxygen-containing LBE!Institute for Applied Materials – Material Process Technology (IAM-WPT)Institute for Pulsed Power and Microwave Technology (IHM)4 October 2014Objectives and approaches Estimation of corrosion product formation in respect of  Solution of steel elements by the LBE Oxygen consumption, i.e., depletion if oxygen is not replaced Uptake/precipitation of solid oxidesMay re-precipitate and contribute to floating solid oxides or pluggingInput for dimensioning appropriate oxygen-transfer devicesContributes to deposition of solid matter; input for dimensioning filters or other to remove floating oxides Work performed Analysis of availability of required corrosion data: mechanisms, rate laws, activation energies, incubation times, surface area affected by local processes Simplified spread sheet calculations for design operating conditions of MYRRHA, separately for the corrosion modes to be considered Specific calculations for reactor start-up and first power cyclesAvailable data is incomplete, requiring a number of assumptions and simplifications!Institute for Applied Materials – Material Process Technology (IAM-WPT)Institute for Pulsed Power and Microwave Technology (IHM)5 October 2014MYRRHA design data usedMaterial Temperature (°C)Surface area (m2)Oxygen conc. (mass%)Average flow velocity (m/s)316L400 120~10–7 To be specified350 419 (360)310 125270 1697 (1596)15-15Ti 410 194 ~10–7 To be specified270 1150T91450 4~10–7 To be specified350 (59)270 1 (102)Duration (days) Temperature (°C)Start-up 180 270°C1st Power cycle 90Components at design operating temperature;temperature transientsDowntime 90 270°C2nd Power cycle 90 As aboveEarly operating stagesDesign operating parametersInstitute for Applied Materials – Material Process Technology (IAM-WPT)Institute for Pulsed Power and Microwave Technology (IHM)6 October 2014Oxidation of 9Cr ferritic/martensitic and austenitic steels in oxygen-containing LBE Protective scaling Thin Cr- (Si-) rich oxide scale (thickness ~1 µm or less) Precursors of this scale are likely to be present already on the original material Local degradation gives way to faster corrosion processes Dominant oxidation process for Type 316 steels and 15-15Ti, especially at T≤ 450°C and cO≤ 10–6 mass% Release of steel elements is likely to be negligible Oxygen consumption mainly confined to the initial formation of this scaleInstitute for Applied Materials – Material Process Technology (IAM-WPT)Institute for Pulsed Power and Microwave Technology (IHM)7 October 2014 Accelerated oxidation Typical for and, finally, the general corrosion process of 9Cr steels, after failure of the thin Cr-rich scale Less frequent occurrence on austenitic steels, especially at T≤ 450°C and cO≤ 10–6 mass% Comparatively thick scales generally consisting of Fe3O4, Fe(FexCr1–x)2O4 and an internal oxidation zone Release of Fe to the LBE at the oxide scale surface Oxygen consumption due tocontinuous growth of oxidesOxidation of 9Cr ferritic/martensitic and austenitic steels in oxygen-containing LBEInstitute for Applied Materials – Material Process Technology (IAM-WPT)Institute for Pulsed Power and Microwave Technology (IHM)8 October 2014 Type 316 steels, 15-15Ti Selective leaching of Ni and Cr Formation of a ferritic depletion zone that is penetrated by the liquid metal Occasionally oxide (precipitated) on the surface, but transfer of removed elements to the LBE dominates Starts locally from failure of the thin Cr-scaleSolution-based corrosion in oxygen-containing LBE 9Cr ferritic/martensitic steel Probably starts from penetration of LBE into the oxide scale formed during accelerated oxidation Steel elements may be selectively (Cr) or generally removed, depending on local conditions Predominance of steel element release over accumulation in oxides not always clearInstitute for Applied Materials – Material Process Technology (IAM-WPT)Institute for Pulsed Power and Microwave Technology (IHM)9 October 2014Quantitative results from experiments in the CORRIDA loop:T91 in LBE at 450–550°C, 2 m/s and 10–6% dissolved oxygen Accelerated oxidation Thickness of magnetite approximates the overall increase in specimen radius  Dissolved Fe from balancing the mass consumed and present in oxides Extrapolation of data naturally depends strongly on the type of rate law assumed  Solution-based corrosion Significantly increased material loss Comparatively smalldatabase for kineticanalysis Underlying corrosion mechanisms may differ for the particular data pointsInstitute for Applied Materials – Material Process Technology (IAM-WPT)Institute for Pulsed Power and Microwave Technology (IHM)10 October 2014Quantitative results from experiments in the CORRIDA loop:Type 316 in LBE at 450–550°C, 2 m/s and 10–6% dissolved oxygen Accelerated oxidation Observed locally at 550°C In parts continuous scale after long exposure time Not observed at 450°C Solution-based corrosion Only few sites on investigated specimens may be affected Mostly selective leaching of Ni and Cr But also general dissolution of all steel elements at 450°C Incubation time decreases from around 5000 h at 450°C to 1000 h at 550°CInstitute for Applied Materials – Material Process Technology (IAM-WPT)Institute for Pulsed Power and Microwave Technology (IHM)11 October 2014Estimation of steel element transfer Solution-based corrosion Not considered for T91 due to the lack of appropriate mechanism and kinetic data (not justified at low oxygen concentration?) Selective leaching of 316L, 15-15Ti: Linear kinetics in terms of maximum depth of attack as observed for 316L at 500°C, <10–8 mass% O, static LBE; k1= 0.017 µm/h (Yamaki et al., 2011) Activation energy 75 kJ/mol(Yamaki et al., 2011) Complete solution of Ni, 50 and 10% of available Cr and Fe, resp. Protective scaling Neglected Accelerated oxidation Neglected for 316L  and 15-15Ti T91: Only release of Fe into the LBE considered Mass of Fe in consumed steel (ST) balanced with mass of Fe accumulated in Fe(FexCr1–x)2O4 (SP) and Fe3O4 (M) Parabolic rate laws of steel recession and scale thicknesses as observed in flowing LBE at 450°C, 10–6 mass% O and 2 m/s: k2,ST= 0.023; k2,SP= 0.013; k2,M= 0.025 µm²/h Activation energy 160 kJ/mol considered for start-up, downtime or transient temperature during power cycle Procedure:  Calculate material- and area-specific transfer of metals at relevant temperatures after given time Multiply by associated surface area in the reactorInstitute for Applied Materials – Material Process Technology (IAM-WPT)Institute for Pulsed Power and Microwave Technology (IHM)12 October 2014Results on transferred mass of steel elements Regular operation starting at t= 0 Remarkable influence of Fe release due to accelerated oxidation of T91 components confined to the first 10 h Average transfer rates in the order of 1–2 g/h for each Fe, Cr and Ni Start-up operation and first two power cycles Transfer of 0.2–0.4 g/h of each Fe, Cr, and Ni during start-up at 270°C Fe release due to accelerated oxidation of T91 components negligible for power cycles and intermittent downtime at 270°C Power cycle: 1–2 g/h of each Fe, Cr and Ni released into the LBE from austenitic steelsInstitute for Applied Materials – Material Process Technology (IAM-WPT)Institute for Pulsed Power and Microwave Technology (IHM)13 October 2014Estimation of oxygen consumption Protective scaling All steels/component surfaces initially form a thin chromia (Cr2O3) scale An equivalent mass of 0.5 µm scale thickness has to form, irrespective of the actual operating temperature Instantaneously – in 1 h – 10 h – 100 h …  From solved steel elements Steel elements released into the LBE may oxidise somewhere in the reactor Accelerated oxidation of T91 Formation of adherent Fe(FexCr1–x)2O4 and Fe3O4 (M) under design operating conditions Same assumptions in regard of the oxidation process as for steel element transfer Procedure:  Calculate material- and area-specific oxygen consumption at relevant temperatures after given time Multiply by associated surface area in the reactorInitial demand for oxygen replacementAfter typical corrosion processes have establishedInstitute for Applied Materials – Material Process Technology (IAM-WPT)Institute for Pulsed Power and Microwave Technology (IHM)14 October 2014Results on oxygen consumption for design operating conditions Protective scaling 3.2 kg of oxygen being consumed when formation of 0.5 µm thick scale is assumed Corresponds to 43.5 kg or 2.2 Ncm³ of PbO and gaseous O2, respectively 3.2–32 g/h average rate of oxygen consumption if the scales form in 10–100 h Initial oxygen concentration in LBE may be higher than required, i.e., only partial replacement of consumed oxygen needed Subsequent corrosion processes Solid oxides on T91 surfaces initially contribute by 50% to the over all oxygen consumption  Oxidation of previously solved steel elements dominates oxygen consumption in the long run Oxygen consumption rate averages 2–3 g/hInstitute for Applied Materials – Material Process Technology (IAM-WPT)Institute for Pulsed Power and Microwave Technology (IHM)15 October 2014Amount of formed oxides Design operating conditions Estimation without protective scaling Qualitative same results as for oxygen consumption in regard of accelerated oxidation (T91) and transformation of solved elements Average formation rate in the order of 1–2 cm³/h Oxides formed on steel surfaces are immobile as long as they do not detach  Start-up operation and first power cycles Average 1.25 cm³/h oxide formation estimated for the first power cycle Associated oxygen consumption of 1.8 g/hInstitute for Applied Materials – Material Process Technology (IAM-WPT)Institute for Pulsed Power and Microwave Technology (IHM)16 October 2014Summary and conclusions In regard of the method of estimating corrosion products Simplified procedure Gives estimates of the order of magnitude Overall conservative, because most detrimental corrosion was assumed especially for austenitic steels (selective leaching) More sophisticated estimating procedures useful only after existing gaps in the available quantitative corrosion data were closed Implications for “chemistry control” 2–3 g/h oxygen needs to be replaced using an oxygen-transfer device, possibly except for the very initial stage (for protective scaling of steels) Initially higher than required oxygen concentration in the LBE may partially compensate for increased consumption (up to 30 g/h?) 1–2 cm³/h of produced solid oxides are to be removed by filters or other Oxide particle size and distribution not yet investigated in detailInstitute for Applied Materials – Material Process Technology (IAM-WPT)Institute for Pulsed Power and Microwave Technology (IHM)17 October 2014Thank youfor your attention!

Estimation of corrosion product formation in MYRRHA

https://publikationen.bibliothek.kit.edu/240097092/3816614

Estimation of corrosion product formation in MYRRHA

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