The Graduate University for Advanced Studies, Oroshi-cho, Toki , Japan 2

Transcription

1 Bi-directional hydrogen isotopes permeation through a reduced activation ferritic steel alloy F82H (Effects of tungsten coatings on hydrogen isotopes permeation) Yue Xu 1 and Yoshi Hirooka 1,2 1 The Graduate University for Advanced Studies, Oroshi-cho, Toki , Japan 2 National Institute for Fusion Science,322-6 Oroshi-cho, Toki , Japan 12 th QUEST research meeting, Kyushu U., Sept. 21 th,

2 Outline 1. Background and motivation 2. Experimental facility and setup 3. Bi-directional D-PDP and H-GDP through F82H 4. Effects of W coatings (SP-W) on hydrogen isotopes permeation 5. Summary and future work GDP: gas-driven permeation PDP: plasma-driven permeation SP-W: sputtering deposited tungsten 2

3 First wall of a fusion power reactor Definition of the first wall: All the fusion experimental devices up to ITER: the first wall is a vacuum chamber wall to separate the plasma from environment. Power reactors: the first wall is the plasma-facing surfaces of breeding blanket units. First wall JET LHD The first walls of existing fusion devices. FFHR reactor A. Sagara et al., research report, NIFS-MEMO-64 (2013). 3

4 Bi-directional hydrogen isotopes permeation For the self-cooled breeder blankets, hydrogen isotopes will penetrate through the first wall by plasma-driven permeation (PDP) in one direction and gas-driven permeation (GDP) in the opposite direction, referred to as bi-directional permeation. T + T + Edge plasma ~10 16 DT/cm 2 /s D + D + D + T + T + T + D + D + D + T + D + T + Implantation T + re-emission T + First wall ~500, ~5 mm T-GDP Diffusion D,T-PDP Diffusion Breeding blanket ~10 3 Pa (H. Zhou) n + Li T + He Dissociation & Solution Important parameters GDP: Solubility Diffusivity External pressure PDP: Surface recombination coefficient Diffusivity Implantation flux Reflection coefficient PDP GDP: Bi-directional permeation H. Zhou et al., J. Plasma Fusion Res. 11 (2015). 4

5 Potential issues associated with bi-directional D/T permeation: PDP D lowers the recovery efficiency of T from the breeder. Gas-T permeation increases recycling on the first wall side. Earlier studies of hydrogen permeation through F82H [1-5] : Hydrogen transport parameters have been evaluated for F82H. Bi-directional H-PDP and H-GDP through F82H (experimental and DIFFUSE-code modeling). Effects of surface oxidation on the behavior of H-PDP. This work focuses on: Motivation Bi-directional D-PDP and H-GDP through F82H. Effects of W coatings on the behavior of hydrogen isotopes permeation. [1] Y. Hirooka et al., Fusion Sci. Tech. 64 (2013) [2] Y. Hirooka et al., Fusion Sci. Technol. 66 (2014) [3] H. Zhou et al., J. Nucl. Mater. 455 (2014) [4] H. Zhou, et al., Fusion Sci. Technol. 63 (2013) [5] H. Zhou et al., J. Nucl. Mater. 463 (2015)

6 Experimental facility and setup VEHICLE-1 [1] Sample F82H PDP plasma parameters: n e : ~10 10 cm -3 T e : 5~10 ev Ion flux : ~10 16 cm -2 s -1 GDP gas pressure: Pa Ion energy: 100 ev (controlled by a negative bias) Plasma exposure is controlled by a pneumatic shutter. Sample: F82H (Fe-8Cr-2W), polished SP-W coated F82H Membrane thickness: mm Temperature: ~ Argon plasma pre-treatment at -50 V for 10 min. [1] Y. Hirooka et al., J. Nucl. Mater (2005) SP-W: sputtering-deposited W 6

7 Deuterium gas-driven permeation (GDP) through F82H has been found to be diffusion-limited GDP flux (D/cm 2 /s) Breakthrough curves o C 0.5 mm F82H 420 o C ~3.5 x 10 3 Pa 325 o C 230 o C 180 o C 145 o C 120 o C GDP flux (D/cm 2 /s) D-GDP through 0.5 mm F82H mm F82H 490 o C 420 o C o C 230 o C 150 o C Time (s) Thickness dependence of D-GDP GDP flux (x D/cm 2 /s) Thickness (mm) ~490 o C ~10 4 Pa Pressure (Pa 0.5 ) GDP in diffusion-limited model [1] : J = DS P up L D: diffusivity S: solubility P up : upstream gas pressure L: membrane thickness [1] J. Crank, The Mathematics of Diffusion, 2nd Edition,

8 Evaluated deuterium transport parameters for F82H are comparable to some of the published values Permeability (mol cm -1 s -1 Pa -0.5 ) Solubility (mol cm -3 Pa -0.5 ) ( o C) This work D 2 Serra D 2 (0.42 ev) [1] Pisarev D 2 (0.50 ev) [2] Kulsartov D 2 (0.46 ev) [3] Kulsartov H 2 (0.42 ev) [3] Zhou H 2 (0.39 ev) [4] This work D 2 Serra D 2 (0.28 ev) [11] Pisarev D 2 (0.34 ev) [12] Kulsartov D 2 (0.38 ev) [13] Kulsartov H 2 (0.34 ev) [13] Zhou H 2 (0.25 ev) [7] Permeability 0.46 ev Solubility 0.32 ev ( o C) Diffusivity (cm 2 s -1 ) ( o C) 0.14 ev This work D 2 Serra D 2 [11] Shestakov D 2 (0.11 ev) [16] Kulsartov D 2 (0.08 ev) [13] Kulsartov H 2 (0.08 ev) [13] Zhou H 2 (0.14 ev) [7] 0.14 ev P = exp D = exp S = exp Diffusivity 0.50 ev ev kt ev kt ev kt [1] E. Serra et al., J. Nucl. Mater. 245 (1997) [2] A. Pisarev et al., Phys. Scr. T94 (2001) [3] T. V. Kulsartov et al., Fusion Eng. Des. 81 (2006) [4] H. Zhou et al., J. Nucl. Mater. 455 (2014) [5] V. Shestakov et al., J. Nucl. Mater (2002) [6] R. A. Oriani, Acta Metall. 18 (1970) Trapping effect [6] : D eff = [mol cm -1 s -1 Pa -0.5 ] [cm 2 s -1 ] [mol cm -3 Pa -0.5 ] D L 1 + N t N l ex p( E t RT D eff :effective diffusivity D L : lattice diffusivity E t : trapping energy N t, N l : density of trapping and lattice sites (T > 250 ) 8

9 Surface recombination coefficient K r has been measured by plasma-driven permeation (PDP) experiments PDP flux (D/cm 2 /s) Thickness dependence of D-PDP PDP flux (x D/cm 2 /s) ~1 x D/cm 2 /s, 100 ev 445 o C 510 o C Thickness (mm) Temperature dependence of D-PDP ( o C) ~1x10 16 D/cm 2 /s, 100 ev 1 mm F82H 0.5 mm F82H Recombination coefficient (cm 4 /s) Recombination coefficient Nagasaki [2] (D-Fe) This work (D-F82H) Zhou [3] Doyle [1] (H-Fe) (H-F82H) [cm 4 s -1 ] K r = exp ( o C) ev kt J + = D L [1] B. L. Doyle et al., J. Nucl. Mater. 122 & 123 (1984) [2] T. Nagasaki et al., J. Nucl. Mater. 202 (1993) [3] H. Zhou et al., J. Nucl. Mater. 455 (2014) PDP in RD-regime [1]: J 0 K r J + : permeation flux; J 0 : net implantation flux; K r : recombination coefficient; L: membrane thickness. 9

10 Bi-directional D-PDP and H-GDP has been demonstrated for the first time under controlled experimental conditions H 2 partial pressure (x10-5 Pa) Effects of D plasma bombardment on H-GDP (Plasma exposure is controlled by a pneumatic shutter) H 2 pressure Temperature D Time (min) 4 D Intensity (a. u.) Temperature ( o C) 0.5 mm F82H H 2 : 1 x 10 4 Pa D + : 1E16 D/cm 2 /s, 100 ev The H 2 partial pressure and D α signal nicely keep track of each other in the duration period of shutter-on and off. Upstream plasma exposure will hinder the H- GDP flux in the opposite direction. Measured D 2 and HD partial pressures after D-PDP accumulation Temperature ( o C) Pressure (x10-5 Pa) Pressure (x10-6 Pa) Temperature HD D 2 accumulation accumulation Time (hour) 0.5 mm F82H H 2 : 1.4 x 10 3 Pa D + : 1E16 D/cm 2 /s, 100 ev Both D 2 and HD partial pressures increased after D-PDP accumulation. 10

11 PDP flux (H/cm 2 /s) Permeation rate (D/m 2 /s) Sputtering-deposited W (SP-W) coatings tend to enhance hydrogen isotopes PDP fluxes Literature data: Deuterium PDP at ~ 500 Hydrogen PDP: at ~500 Temperatures SP-W coated F82H 300 VPS-W coated F82H 200 ~2x10 16 H/cm 2 /s SP-W 0.5 m, 0.5mm F82H 100 VPS-W 90 m, 0.5mm F82H ~5.5 ev 0.5mm F82H 100 ev Time (hour) SP-W coated SS SS After R. Anderl [1] VPS-W coated SS Time (min) F82H SP-W: sputtering deposited W VPS-W: vacuum plasma-sprayed W Temperature ( o C) Temp. dependence of D-PDP flux PDP flux (D/cm 2 /s) ( o C) SP-W coated F82H SP-W:1.2 µm, F82H: 1 mm F82H K r is a key parameter relating to the permeation flux for PDP. K r H W = exp K r D W = exp This work D-SP-W Takagi [3] D-bulk W This work D-F82H [1] R. Anderl et al., J. Nucl. Mater (1994) [2] T. Nagasaki et al., J. Nucl. Mater. 202 (1993) [3] I. Takagi et al., J. Nucl. Mater. 417 (2011) Recombination coefficient (cm 4 /s) ev kt ev kt Recombination coefficient ( o C) cm 4 s 1 cm 4 s 1 Nagasaki [2] D-Fe J + = D L J 0 K r

12 Increased D retention in SP-W coated F82H has been observed ( ): traps for hydrogen isotopes [1]? PDP (implantation) TDS (desorption) Deuterium retention (D/cm 2 ) D retention by TDS x D/cm 2, 100 ev SP-W coated F82H (1.2 m/1 mm) F82H (1 mm) ( o C) [1] B. Zajec, et al., J. Nucl. Mater. 412 (2011) D retention in SP-W coated F82H is about a factor of 3 higher than that of bare F82H in the temperature range of And the differences become smaller with increasing temperature. SP-W: sputtering-deposited W 12

13 Characteristic microstructure of sputtering-deposited tungsten (SP-W) coatings SP-W (sputtering-deposited W) as-deposited PM-W (powder metallurgical W) rolled FIB cross-section 100 nm 200 µm Density: 19.2 g/cm 3, ~99.5% of bulk W The grain size of SP-W is ~100 nm, while bulk polycrystalline W is ~100 µm. This suggests that most trapping sites might be located at grain boundaries although dislocations and vacancy clusters are also possible candidates.

14 Summary Summary and future work 1. Deuterium GDP through F82H have been found to be diffusion-limited. 2. Deuterium transport parameters have been evaluated for F82H. 3. Bi-directional D-PDP and H-GDP has been demonstrated for the first time under controlled experimental conditions. 4. SP-W coatings tend to enhance hydrogen isotopes PDP fluxes due to its surface recombination characteristics. 5. Increased deuterium retention in SP-W coated F82H has been observed, which is probably due to the presence of traps for hydrogen isotopes. Such information is important for the assessment of tritium inventory in the re-deposited tungsten layers of ITER and future fusion reactors. Future work Thank you for your attention! GDP: gas-driven permeation PDP: plasma-driven permeation SP-W: sputtering-deposited W Deuterium concentration depth profile measurements by SIMS (secondary ion mass spectrometry). 14