Erosion and fuel retention of different RAFM steel grades

Erosion and fuel retention of different RAFM steel grades Peng Wang 1, Li Qiao 1, Liang Gao 2, Wolfgang Jacob 2, Engang Fu 3 1. Lanzhou Institute of Chemical Physics, Lanzhou, China 2. Max-Planck Institute of Plasma Physics, Garching, Germany 3. Peking University, Beijing, China

Outline Sample preparation & experimental details Erosion of CLF-1 steels exposed to deuterium plasma Comparison of sputtering yield of different RAFM steels Comparison of sputtering yield of RAFM steels with different roughness Fuel retention in various steel grades Work plan

Ion flux (10 20 m -2 s -1 ) Linear experiment plasma system--leps Linear Experimental Plasma System (LEPS) H 2 Parameters of LEPS plasma: Magnet field: 0.12-0.15 T Plasma beam diameter: 50 mm Ion flux: 2-8 10 21 m -2 s -1 Ion composition: mainly D + 3 Electron density: 10 16 --10 18 m -3 Floating potential:-15 V D 2 Working pressure: 0.5-1.0 Pa 40 35 Deuterium 30 25 20 15 N 2 10 5 Beam centre 0 0 10 20 30 40 50 60 70 80 90 100 Location (mm) LEPS deuterium plasma profile measured by LP

RAFM steel materials Table 1. Composition of various RAFM steel grades (in wt.%) (Fe balance) RAFM C Cr W Mn V Ta N P S EUROFER97 0.09-0.12 8.5-9.5 1.0-1.2 0.2-0.6 0.15-0.25 0.10-0.14 0.015-0.045 0.004-0.005 0.003-0.004 CLF-1 0.11 8.5 1.5 0.5 0.25 0.1 0.02 0.003 / RUSFER 0.15 11.17 1.13-1.3 0.74-0.8 0.25-0.4 0.08-0.15 0.04-0.07 0.001 0.006 CLAM 0.11 8.98 1.55 0.4 0.21 0.15 0.02 -- -- CLF-1 steel from ASIPP (Aug, 2015) EUROFER from IPP (2015) CLF-1 CLF-1-L transversal 10 12 1mm longitudinal 15 12 1mm CL AM, 2 Kg from FDS (May, 2017) RUSFER 10 pic (Jan, 2017) 15 12 1mm

Experimental details- Analyses Structure Composition Deuterium retention SEM: (JSM-5601) HRTEM: (FEI Tecnai) Voltage: 200 kv Resolution: 0.24 nm Profilmeter GDOES: (Profiler-2) Ar power:30 W Sputtering rate:2 nm/s RBS: (Peking University) Probing beam: 4 He + Energy: 3 MeV XPS: (Phi-5702) Source: Al kα Pass energy: 29.4 ev TDS: Base pressure:5 10-6 Pa Heating range:rt-1200 K Measuring mass:4(d 2 ) & 3(HD) Heating ramp: 15 K/min NRA: (IPP Garching) Probing beam: 3 He + Energy: 0.7-4.5 MeV Simulation: NRADC

Ra ( m) Morphology changes- Surface roughness Surface roughness of CLF-1 steels after deuterium exposure Surface line profile of CLF-1 exposed to 180 ev/d deuterium plasma 0.35 CLF-1 steels 1.5 10 25 D/m 2 180 ev/d 0.30 0.25 30 ev/d 70 ev/d 150 ev/d 180 ev/d 0.20 1.1 10 25 D/m 2 0.15 0.10 0.05 3.6 10 24 D/m 2 0.00 10 24 10 25 Deuterium fluence (D/m 2 ) 6.0 10 23 D/m 2 Before exposure Surface roughness increases with increasing incident ion energy and fluence, no roughness saturation was observed at a fluence up to 10 25 D/m 2 1 m 100 m

Morphology changes- Fluence dependence Deuterium plasma exposure: energy: CLF-1, 150 ev/d, temperature: 450 K Before exposure 6 10 23 D/m 2 3.6 10 24 D/m 2 7.2 10 24 D/m 2 1.08 10 25 D/m 2 1.5 10 25 D/m 2

Morphology changes- Energy dependence Deuterium plasma exposure: CLF-1, fluence: 7.2 10 24 D/m 2, temperature: 440-450 K 30 ev/d 70 ev/d 150 ev/d 180 ev/d

Sputtering yield Sputtering yield Sputtering yield Fluence dependence of sputtering yield of CLF-1 steel CLF-1 steels (a) 10-1 70 ev 150 ev 180 ev... Ref 180eV Fe/D 10-2 Energy dependence of sputtering yield of CLF-1 and EUROFER steels (b) CLF-1 7.2 10 24 D/m 2 EUROFER Ref 7.2 10 24 D/m 2 10-2 150eV Fe/D 10-3 70eV Fe/D 10 24 10 25 D Fluence (D/m 2 ) 0 50 100 150 200 D energy (ev per D) Sputter yield was determined by mass loss. Clear decreases of yield of CLF-1 steels with increasing of incident fluence, no clear saturation of yield at fluence up to 10 25 D/m 2. Sputtering yield of CLF-1 and EUROPER steels is lower than pure Fe Preferential sputtering changes the composition, leads to the enrichment of tungsten and reduces the total sputter yield 10-3 Sugiyama K, Schmid K, Jacob W 2016 Nuclear Materials and Energy 8 1-7

Counts Surface tungsten enrichment 500 RBS CLF-1, 180eV/D, 450 K 400 4 He: 3MeV Detector angle: 160 Beam incident angle: 20 Charge: 10 c W Surface 300 200 Before exposure 100 6.0 10 23 D/m 2 3.6 10 24 D/m 2 1.5 10 25 D/m 2 0 420 440 460 480 500 Channel N. Ashikawa, K. Sugiyama, A. Manhard, et al., Fusion Engineering and Design, 112(2016) 236-239 W enrichment was observed by RBS measurements but not not good agreement with data from F82H steel exposed to comparable incident fluence, could be: Measurement difference or various initial W concentration in bulk (1.5 and 2.0 wt% W in CLF-1 and F82H bulk, respectively)

Surface tungsten enrichment Pt-c Pt-c Pt CLF-1 CLF-1 30 nm W Pt-c Pt-c 10 nm Fe CLF-1 CLF-1 Cr

Counts (a.u.) Surface tungsten enrichment Cross-section image Composition depth profile 300 200 Fe Pt-C CLF-1 In the grey region, the Fe and Cr EDX signals increase from background level to their maximum level and this transition region is about 20 nm thick. The Pt EDX line partially overlaps with the W line such that a small fraction of W in a large background of Pt (stemming from the protection layer) cannot be safely distinguished in the EDX line scans. 100 250 200 150 Cr 100 50 0 60 W 40 20 400 300 Pt 200 100 0 0 10 20 30 40 50 60 Position (nm)

Surface tungsten enrichment CLF-1 Deuterium plasma exposure: 150eV, 7.2 10 24 D/m 2 A pure platinum layer were deposited on CLF-1 as a protecting layer Pt-C Pt Pt Pt CLF-1 CLF-1 CLF-1 There is no obvious uneven sputtering region between the crystalline bulk and the Pt protecting layer. Few nm damage zone exists and mixed with pure Pt layer

Counts (a.u.) Surface tungsten enrichment Cross-section image Composition depth profile 300 Pt 200 100 Fe CLF-1 0 200 150 100 50 0 60 40 Cr W 20 The Pt EDX line partially overlaps with the W line such that a small fraction of W in a large background of Pt cannot be safely distinguished in the EDX line scans. 0 300 Pt 200 100 0 0 20 40 60 80 100 Position (nm)

Surface tungsten enrichment CLF-1 sample, Deuterium plasma exposure: 150eV, 7.2 10 24 D/m 2 An amorphous carbon layer was deposited on sample surface before TEM analyses Pt-C C CLF-1 C CLF-1 C CLF-1 About 5 to 10 nm region damaged by plasma exposure was observed by TEM, which partially overlaps with the amorphous carbon at the mixed interface.

Counts (a.u.) Surface tungsten enrichment Cross-section image Pt C CLF-1 Amorphous carbon layer was deposited on CLF- 1 surface to avoid the influence of Pt on composition depth profile measurement, however, W enrichment was found in whole carbon layer region and much thicker than as expected 400 300 200 100 0 250 200 150 100 50 1000 80 60 40 20 3000 200 100 0 400 300 200 100 0 Composition depth profile Fe 0 100 200 300 400 Position (nm) Cr W Pt C

Outline Introduction Sample preparation & experimental details Erosion of CLF-1 steels exposed to deuterium plasma Comparison of sputtering yield of different RAFM steels Comparison of sputtering yield of RAFM steels with different roughness Fuel retention in various steel grades Work plan

Sputtering yields of various RAFM steels Table 1. Composition of various RAFM steel grades (in wt.%) (Fe balance) RAFM steel EUROFE R97 C Cr W Mn V Ta N P S 0.09-0.12 8.5-9.5 1.0-1.2 0.2-0.6 0.15-0.25 0.10-0.14 0.015-0.045 0.004-0.005 0.003-0.004 CLF-1 0.11 8.5 1.5 0.5 0.25 0.1 0.02 0.003 / RUSFER (EK-181) 0.15 11.17 1.13-1.3 0.74-0.8 0.25-0.4 0.08-0.15 0.04-0.07 0.001 0.006 CLAM 0.11 8.98 1.55 0.4 0.21 0.15 0.02 -- --

Sputtering Yield Counts Sputtering yields of various RAFM steels 0.020 Sputtering yield of RAFM steels 1200 RBS 180eV/D, 7.2 10 24 D/m 2 0.015 RAFM steels 70eV/D 1.08 10 25 D/m 2 180eV/D 7.2 10 24 D/m 2 1000 800 CLF-1 CLF-1-L EUROFER 0.010 600 0.005 0.000 CLF-1 CLF-1-L EUROFER Samples 400 4 He: 3MeV 200 Detector angle: 160 Beam incident angle: 20 Charge: 20 c 0 380 400 420 440 460 480 Channel Initial W concentration of various RAFM steels: W CLF-1 =W CLF-1-L >W EUROFER Sputtering yield of various RAFM steels: Y CLF-1 >Y CLF-1-L >Y EUROFER Other factor influence of sputtering yield? (Grain orientation, roughness)

Morphology changes Deuterium plasma exposure (180 ev/d, 450K, 7.2 10 24 D/m 2 ) CLF-1 CLF-1-L CLAM EUROFER RUSFER

Sputtering Yield Sputtering Yield Sputtering yields of various RAFM steels 0.020 Sputtering yield of RAFM steels RAFM steels 70eV/D 1.08 10 25 D/m 2 180eV/D 7.2 10 24 D/m 2 0.020 Sputtering yield of RAFM steels 180 ev/d 7.2 10 24 D/m 2 ------- 180 ev/d from Ref. [1] 0.015 0.015 0.010 0.010 0.005 0.005 0.000 CLF-1 CLF-1-L EUROFER Samples 0.000 CLF-1 CLF-1-L EUROFER CLAM RUSFER Samples Initial W concentration of various RAFM steels: W CLF-1 =W CLF-1-L >W EUROFER Sputtering yield of various RAFM steels: Y CLF-1 >Y CLF-1-L >Y EUROFER Other factor influence of sputtering yield? (Grain orientation, roughness)

Sputtering yields of various RAFM steels Deuterium plasma exposure at: 180eV, 7E24 D/m2 Ra=20 nm Ra=50 nm Ra=100 nm Ra=400 nm

Sputtering yields of various RAFM steels Deuterium plasma exposure at: 70eV, 7E24 D/m2 Ra=20 nm Ra=50 nm Ra=100 nm Ra=400 nm

Sputtering yields of various RAFM steels Deuterium plasma exposure at: 180eV, 7E24 D/m2 Ra=20 nm Ra=50 nm Ra=100 nm Ra=400 nm

Sputtering yield Sputtering yields of various RAFM steels 0.03 0.02 D plasma: 180 ev 6 10 24 D/m 2 CLF-1-L 873 K CLF-1-L 1173 K EUROFER 873 K RAFM steel samples with different initial rough show comparable sputtering yield 0.01 More accurate measurement based on spectroscopy is needed 0.00 R20 R50 R100 R400 Sample

D retention (D/m 2 ) Fuel retention of CLF-1 steel after deuterium exposure 10 22 RAFM steel 30 ev/d 320 K 70 ev/d 460 K 30 ev/d 330 K 150 ev/d 450 K 30 ev/d 325 K 180 ev/d 470 K EUROFER 30 ev/d 320 K 10 21 Fluence dependence of D retention in CLF-1 1E21 1E20 (b) D fluence: 7.2 10 24 D/m 2 CLF-1-L EUROFER 10 20 Retention D/m 2 1E19 10 19 10 18 10 24 10 25 D fluence (D/m 2 ) 1E18 30 60 90 120 150 180 D Energy (ev) Deuterium retention in CLF-1 decreases with increasing fluence except the samples exposed to 30 ev/d deuterium plasma, in which D retention keeps as a constant (about 3 10 20 D/m 2 )

Concentration (at.fr) Deuterium retention (D 2 /m 2 /s) Fuel retention of various RAFM steels Deuterium depth profiles of CLF-1 and EUROFER97 measured by TDS Deuterium release from CLF-1, CLAM, EUROFER97 and RUSFER measured by TDS 10-3 10-4 LEPS deuterium plasma: 30 ev/d, 1 10 25 D/m 2 CLF-1 EUROFER 1.5x10 16 CLF-1 CLF-1-L CLAM EUROFER RUSFER 1.0x10 16 10-5 5.0x10 15 10-6 0 20000 40000 60000 80000 Depth (10 15 atoms/cm 2 ) Deuterium retention at 30 ev/d is one order of magnitude higher than EUROFER, NRA show a high D retention region at near surface region (surface to 2μm) 0.0 300 400 500 600 700 800 Temperature (K) Deuterium plasma exposure: 180 ev/d 440-450 K)

Deuterium retention (D 2 /m 2 /s) Concentration (at.fr) Fuel retention of various RAFM steels Deuterium release of CLF-1 and EUROFER97 measured by TDS Deuterium depth profiles of CLF-1 and EUROFER97 measured by TDS 1.5x10 16 CLF-1 CLF-1-L CLAM EUROFER RUSFER 1.0x10 16 10-3 10-4 LEPS deuterium plasma: 30 ev/d, 1 10 25 D/m 2 CLF-1 EUROFER 5.0x10 15 10-5 10-6 0.0 300 400 500 600 700 800 Temperature (K) 0 20000 40000 60000 80000 Depth (10 15 atoms/cm 2 ) CLF-1, CLF-1-L and EUROFER samples were exposed in one batch (30 ev/d 320 K) CLF-1 & CLF-1-L: deuterium release at 450 K EUROFER: deuterium release at 420 K Deuterium retention at 30 ev/d is one order of magnitude higher than EUROFER, NRA show a high D retention region at near surface region (surface to 2μm)

Fuel retention of various RAFM steels Comparison of fluence dependence of D retention between W and RAFM steels (CLF-1, EUROFER and F82H) LEPS CLF-1 30 ev/d 320 K CLF-1 70 ev/d 460 K CLF-1 180 ev/d 470 K EUROFER 30 ev/d 320 K RUSFER 30 ev/d 320 K D in W Deuterium retention after LEPS plasma exposure measured by TDS D retention in RAFM steels is lower than in W D retention in RAFM steel decreases with increasing incident fluence D retention in CLF-1 steel at 30 ev/d is higher than other RAFM steels W. Jacob, IAEA steel CRP meeting

Work plan Erosion of RAFM steel samples extends to higher temperature, to study the surface W enrichment with RBS and TEM Compare sputtering yield more precisely using other methods Study the fuel retention in steel samples after 3.5 MeV iron ions damaging Extend the fuel retention and composition depth profile up to several tens nm region using GDOES

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