1. 1 Improvement of compatibility of liquid metals Li and Pb-17LI Masatoshi KONDO, Minoru TAKAHASHI b), Teruya TANAKA a), Tsisar Valentyn c) and Takeo MUROGA a) Tokai university, Japan, a) National Institute for Fusion Science a) b) Tokyo Institute of Technology, Japan c) Physico-Mechanical Institute of National Academy of Sciences of Ukraine, Ukraine ISLA2011

2. 2 Background -1 Fusion blanket KOREA HCML- TBM (2008)Li/RAFM Dr.KIM et al Japan (2003) molten salt Flibe/RAFM Dr.Sagara et al., FED India TBM (2009) Pb-LI ・ solid breeder/RAFM Dr.Kumar et al FED Liquid breeder Structure Lithium Ｌｉ Lead lithium Pb-17Li Flibe LiF-BeF 2 Vanadium alloy ＳiＣＳiＣ ＯＤＳ Japan Russia Korea USA RAFM Europe India china Toward high temperature Pure metal Molten salt Alloy Coating (MHD, Ttritum.etc) Al2O3 Er2O3 (DiP ・ＭＯＣＶＤ ) Nitride treatment Er2O3 (DiP ・ＭＯＣＶＤ ) Japan (2003) liquid metal Li/vanadium Dr.Muroga et al., FED

3. 3 Background -2 (Structural material) Corrosion of RAFM steel in liquid metals Chemical reaction of steel’s base metal (Fe), alloying elements (Cr, W) and carbides with liquid metals wt%CrWCMnOtherFe ＪＬＦ - 1 ９ 1.940.090.49V: 0.2balance Chemical composition (wt%) Reduced activation ferritic martensitic steel is candidate structural material of blanket. 1 ０ µm Prior austenite grain boundary Packet boundary Lath boundary Some sub grains Block boundary

4. 4 Background -3 (Liquid breeders) M.P. (K) Thermal conductivity (W / (m x K)) Density (kg/m 3 ) Viscosity (mPas) LiAlkali metal453.753.7 (800K)481 (800K)0.344 (800K) Pb-17LiHeavy metal5089568 (800K)- Flinak (LiF-NaF-KF) Molten salt7271.22146 (800K)4.1 (900K) Flibe (LiF-BeF 2 ) Molten salt7321.21993 (800K)7.5 (800K) Flinak Liquid Lithium Li + Free electron High thermal conductivity in liquid metalHigh chemical stability of molten salt Li + F-F- + Already stable state by ion bonding Major characteristics of liquid breeders

5. 5 Purpose Purpose of the present study is follows; - Establish corrosion test technology for liquid Li and Pb-Li - Make clear the corrosion characteristics of RAFM JLF-1 steel in the liquid metals - Make clear the corrosion of coating in the liquid metals - Modeling of the corrosion of RAFM steel in the liquid metals

6. 6 Experimental procedure (1) FeCrWNi Li0.850.120.310.8Nitrogen: 65 Pb-17Li2.20.170.521.3- Pb-17Li provided by santoku coop. Temperature 600ºC Time(hours)Re for mixing-Material Li Static30-250-750 High purity, Li 3 N dope Li 2 O dope, C dope JLF-1 Er 2 O 3 coat Flowing2502859High purityJLF-1 Pb-17Li Static250-3000High purity JLF-1 Er 2 O 3 coat Flowing25018512High purityJLF-1 Initial impurity of liquid metals (wppm) Experimental condition Carbon Li 2 O Li 3 N

7. 7 Experimental procedure (2) Influence of flow 3cc 100cc Fixed specimen Width of impeller 33 ｍ Rotation speed100 rpm Velocity around specimen v=π ｄｎ =0.17cm Re number for mixing 48mm Static test (Simple immersion) Flowing test (Mixing vessel)

8. (c) Impurity analysis of liquid breeders by ICP-MS ( Fe, Cr, W, non metal impurity) (To investigate mass balance between loss in specimen and increase of metal impurity in melt ) (b)SEM/EDX analysis for surface and cross section (To evaluate the metallurgical change of steels) (a) Weight loss measurement (To estimate the corrosion (loss) rate) Analysis of corroded specimen Take out sample Li immersion at 350ºC Acetone Immersion to ethanol Acetone Immersion to ethanol Cleaning procedure for tested specimen Specimen in Li Specimen inPb-Li

9. 9 Experimental results (Mass loss of specimen by corrosion in Li) - The influence of non-metal impurity (i.e. nitrogen and oxygen) in liquid Li was large on the corrosion loss. - The Influence of oxygen in Li on the corrosion was newly found.) Li (+0.8wt%Li 2 O) (Static) 750-hour Li (+0.5wt%Li 3 N) (Static) 250-hour Li (Pure) (Static) 250-hour Li (Pure) (Flow) 250-hour Li (+3.7wt%C) (Static) 250-hour Weight loss of specimens (g/m 2 )

10. Experimental results (Lithium) 20 hour120 hour250 hour Ｌｉ +0.5wt%Li 3 N nitrogen dope (Cr dissplution) 1 ０ µm 20 µm 選択的 250 hour Phase transformation BCT a a c a a a BCC CFe Phase transformation Initial 122 hour 780 hour 287 hour Ｌｉ +0.8wt%Li 2 O oxygen dope (Cr dissolution) Ｌｉ +3.7wt% Ｃ carbon dope 1 ０ µm Phase transformation No phase change

11. 11 Er concentration in Li unit: wppm (ICP-MS) 0 10 20 30 exposure (hour) 600ºC Er 2 O 3 /JLF-1 Surface color was black after the corrosion test though the color was metallic luster before the test. ２０ µm normal Corroded (Er-Cr rich) Peeling off ＳＥＭ Crack Thermal linear expansion % Temperature (ºC) Li JLF-1 Er 2 O 3 Corrosion of Er 2 O 3 coating in Li The oxide itself might be chemically stable in the liquid breeders. The damage was possibly made by a large difference of the thermal expansion ratio between adhered Li and the coating during a heat up and a cool down procedure of the corrosion test when the Li was solidified.

12. 12 Summery for corrosion in Li -Nitrogen dissolved in Li has big influence on the compatibility. It was newly found that oxygen in Li can increase the corrosion of steel. The nitrogen and oxygen dissolved as non-metal impurity in Li must be removed before the use. Carbon in Li can suppress the the depletion of carbon in the steel. -The issue for the coating of liquid blanket is the peeling of the coatings in the liquid metals.

13. 13 Experimental results (Weight loss of specimen in Pb-Li at static condition) Corrosion was suppressed when the metal element, i.e. Fe and Cr, in Pb-17Li was saturated..

14. Experimental results (Pb-17Li) 600 o C 750 hours High mag. (x3000) 20µm 5µm5µm Low mag. (x1000) 600 o C 3000 hours 20µm 5µm5µm High mag. (x3000) Low mag. (x1000) The corrosion in JLF-1 was selective attack to some boundaries of microstructure.

15. 15 Experimental results (Corrosion of Er 2 O 3 coating in Pb-Li) The oxide itself might be chemically stable in the Pb-Li. The damage of the coating was possibly made by a large difference of the thermal expansion ratio between adhered Pb-Li and the coating during a heat up and a cool down procedure of the corrosion test when the Pb-Li was solidified.

16. 16 Flowing Li Internal diffusion of liquid metals (FAC) (Erosion corrosion) 10µm Erosion- corrosion was caused by peeling of subgrains after corrosion on surface. Flowing Pb-17Li 10µm Experimental results (Corrosion in flowing Li and Pb-Li)

17. 17 Corrosion modeling Li (65wppm nitrogen)Pb-17LiPb Solubility (Cs) wppm Molppm Fe- *47 (600ºC) ~ 34 (600ºC) Cr 52.4 (800 ºC) ~ 94.3 (600ºC) 10 (500ºC) 1 (600ºC) Transient of metal impurity in liquid breeders Corrosion ratio Mass loss of specimen by corrosion Concentration of metal in liquid breeders Mass balance between increase of metal impurity in liquid breeders and corrosion ratio of specimen

18. 18 Mass transfer model in corrosion (Li) Different corrosion device 600 o C (Li) Different geometrical factor of corrosion system Volume / corrosion surface area V/S Large Small

19. 19 600 o C (Pb-Li) Mass transfer model in corrosion (Pb- Li)

20. 20 Summery Major conclusions are follows; - Corrosion test technology for liquid Li and Pb-Li was established. - The corrosion characteristics of JLF-1 in static Li and Pb-Li were investigated. Then, we started to study about the corrosion in flowing condition. -Modeling of corrosion of JLF-1 in Li and Pb-Li was started. - Fundamental corrosion characteristics of anti corrosion coating in liquid Li and Pb-Li was studied. The issue is the peeling off of the coatings in liquid metals.

21. 21

22. 22 Corrosion of Fe-Al coating in liquid Pb-Li 10 µm Fe-Al coating 剥離 316L Pb-Li Pb O Fe Al ＳＥＭ After 500- hour immersion in Pb-17Li at 600 degree C Coating it self was chemically stable in liquid Pb-Li. However, the peeling off is issues for the coating. Now, study on metal plating technology is under going.

23. 23 Background -4 Corrosion phenomena Solubility of metal elements and chemical potential of non- metal impurity in liquid metals are important parameters which determine the corrosion. 23 Compatibility Liquid metal corrosion Formation of corrosion products (Carbides, oxides, nitrides, hydrides and so on) -Dissolution of steel element into liquid metals -Diffusion of metal elements of liquid metal into steel matrix Determined by alloying process Determined by chemical potential of non-metal impurity All liquid metals especially heavy liquid metal Pb, Pb-Bi Li, Na, K, Pb-Li(?) GB attack Erosion- corrosion Peering of corrosion products FAC At flowing condition At flowing static condition

24. 24 Effect of nitrogen on corrosion in Li

25. 25 Experimental results (Transient of metal impurity in Pb-17Li) [1] M. G. Barker, P. Hubberstey, A. T. Dadd, S. A. Frankham, J. Nucl Mater., 114, 143-149 (1983). [2]V. Tsisar, M. Kondo, et al., J. Nucl. Mater, under review. H. U. Borgstedt, H. Feuerstein, J. Nucl. Mater., 191-194, 988-991. [3]N. Simon et al., Int. J. Heat Mass Transfer., vol.38, No.16, 3085-3090 (1995). After the immersion of JLF-1 in Pb-Li.