Mitglied der Helmholtz-Gemeinschaft Materials for Future Fusion Reactors under Severe Stationary and Transient Thermal Loads J. Linke, J. Du, N. Lemahieu, Th. Loewenhoff, G. Pintsuk, B. Spilker, T. Weber, M. Wirtz Forschungszentrum Jülich, Institut für Energie- und Klimaforschung, 52425 Jülich HELSMAC Symposium - Downing College, Cambridge 7th-8th April 2016
Mysterious fusion
Mysterious fusion deuterium helium (3.5 MeV) tritium neutron (14.1 MeV)
Mitglied der Helmholtz-Gemeinschaft Outline: A Thermal loads on plasma facing components B Simulation of intense thermal loads C Hydrogen and helium effects D Material degradation by energetic neutrons HELSMAC Symposium - Downing College, Cambridge 7th-8th April 2016
A Thermal loads on plasma facing components
Energy conversion in a thermo-nuclear reactor
Steps towards the reactor JET ITER DEMO n-dose: 10-9 dpa 1 dpa 100 dpa inertially cooled wall
ITER and the plasma facing components first wall divertor
The ITER blanket design Be
The new ITER divertor cassette W 54 cassettes (six per vacuum vessel sector) weight approx. 9 tons / cassette W CFC # W CFC # # CFC replaced by W L max 100 mm source: M. Merola, ISFNT-9, Dalian, China, 2009
B Simulation of intense thermal loads on plasma-facing components
power density [MW/m 2 ] Expected heat loads on the ITER divertor 10 5 10 4 disruptions irreversible material degradation 10 3 VDEs 10 2 10 1 ELMs: 1 GW/m 2, 0.5 ms, n >> 10 6 divertor: 5-20 MW/m 2, 450 s, n ~ 10 4 off-normal normal 10 0 10-4 10-3 10-2 10-1 10 0 10 1 10 2 10 3 duration of event [s] R. A. Pitts, et al., Journal of Nuclear Materials 438 (2013) S48-S56 J. Linke, Transactions of fusion science and technology 49 (2006) 455-464 A. Loarte et al., Plasma Physics and Controlled Fusion 45 (2003) 1549-1569
power density [MW/m 2 ] Expected heat loads on the ITER divertor 10 5 10 4 10 3 irreversible material degradation 10 2 10 1 10 0 ELMs: 1 GW/m 2, 0.5 ms, n >> 10 6 divertor: 5-20 MW/m 2, 450 s, n ~ 10 4 normal 10-4 10-3 10-2 10-1 10 0 10 1 10 2 10 3 duration of event [s] R. A. Pitts, et al., Journal of Nuclear Materials 438 (2013) S48-S56 J. Linke, Transactions of fusion science and technology 49 (2006) 455-464 A. Loarte et al., Plasma Physics and Controlled Fusion 45 (2003) 1549-1569
surface temp. Wall loading in a toroidally confined plasma (Tokamak) mitigated transient thermal loads < 1GWm -2, Δt 500 µs pulsed stationary thermal loads < 10 MWm -2, Δt = minutes - hours 0 time thermal shock cracking/melting of PFM-surface thermal fatigue joints between PFM and heat sink
Loads on plasma facing components very high thermal loads plasma exposure neutrons
Loads on plasma facing components Steady state heat loads: up to 20 MWm -2 in ITER (lower loads in DEMO) recrystallization failure of joints very high thermal loads Transient thermal loads: up to 60 MJm -2 (disrupt., ELMs, VDEs) crackings melting dust formation plasma exposure neutrons Plasma loads: sputtering hydrogen helium Neutrons: up to 14 MeV defects transmutation
High heat flux test facilities Electron beam facility JUDITH 1 Electron beam facility JUDITH 2 max. power 60 kw acceleration voltage < 150 kv EB diameter ~1 mm FWHM loaded area 10 x 10 cm 2 max. power 200 kw acceleration voltage 30 60 kv EB diameter 5 mm FWHM loaded area 40 x 40 cm 2
High heat flux test facilities Linear Plasma Device PSI-2 Electron beam facility JUDITH 2 plasma source target positions target exchange & analysis chamber linear manipulator plasma diameter 60 mm particle flux 10 23 m -2 s -1 incident ion energy (bias) 10 300 ev Nd:YAG laser 1064 nm laser energy 32 J max. power 200 kw acceleration voltage 30 60 kv EB diameter 5 mm FWHM loaded area 40 x 40 cm 2
High heat flux test facilities Linear Plasma Device PSI-2 Quasi Stationary Plasma Accelerator (QSPA) plasma source target positions target exchange & analysis chamber linear manipulator plasma diameter 60 mm particle flux 1023 m-2s-1 incident ion energy (bias) 10 300 ev Nd:YAG laser 1064 nm laser energy 32 J heat load 0.5 2 MJ/m 2 pulse duration 0.1 0.6 ms plasma diameter 5 cm magnetic field 0 T ion impact energy 0.1 kev electron temp. < 10 ev plasma density 10 22 m -3
Simulation of ELMs in QSPA 20 mm
Bridging of gaps due to melt motion 100 pulses @ E = 1.6 MJ/m 2, = 500 µs H HF = 71 MW/m 2 s 0.5 Source: A. Zhitlukhin et al., SRC RF TRINITI, Troitsk
Bridge formation between tungsten tiles W4,L3, 10 exposures W4,L3, 20 exposures W4,L3, 50 exposures w = 1.6 MJ/m 2 1mm 1mm 1mm H HF = 71 MW/m 2 s 0.5 W3,R3, 20 exposures W3,R3, 50 exposures W3,R3, 100 exposures w = 1.0 MJ/m 2 1mm Plasma stream direction 1mm 1mm H HF = 44.7 MW/m 2 s 0.5 t = 500 µs Source: A. Zhitlukhin et al., SRC RF TRINITI, Troitsk
Simulation of ELMs in QSPA H HF = 44.7 MW/m 2 s 0.5 W 3 plasma stream tungsten target E = 1.0 MJm -2 t = 500 µs 100 pulses T 0 = 500 C
W3 melt motion melt motion starts at vertical cracks plasma stream
cracking threshold Thermal shock tests on tungsten Experimental setting Sample size 12 12 5 mm³ Loaded area 4 4 mm² Base temperature: RT up to 1000 C Power densities: 0.19 to 1.51 GW/m² transversal recrystallized longitudinal damage threshold 100 pulses with a duration of 1 ms; absorption coefficient 0.55
Crack Formation loaded surface cross section Plansee pure tungsten according to ITER specifications ( IGP ) L abs = 0.38 GW/m 2 (F HF = 12 MW/m 2 s 1/2 ), T base = RT transversal longitudinal recrystallized
ELM simulation using e-beams with high repetition rates in JUDITH 2 power density [GW/m²] 0.82 0.68 0.55 0.41 damage threshold 0.27 0.14 Th. Loewenhoff et al., Physica Scripta T145 (2011) 014057
ELM simulation using e-beams with high repetition rates in JUDITH 2 power density [GW/m²] 0.82 0.68 0.55 0.41 damage threshold 0.27 0.14 Th. Loewenhoff et al., Physica Scripta T145 (2011) 014057
ELM simulation using e-beams with high repetition rates in JUDITH 2 recrystallization melting 50 µm recrystallization around crack edges original grain structure Th. Loewenhoff, et al., Fusion Engineering and Design 87 (2012) 1201-1205 100 µm
W CFC Threshold values for ELM loads damage threshold cracking of pitch fibres PSI 2010 PAN eros. >100 shots PAN erosion > 50 shots PAN erosion > 10 shots 0 0.5 1.0 1.5 energy density* E / MJm -2 heat flux factor P Δt / MWm -2 s 1/2 0 20 40 60 melting of tile edges melting of tile surface droplets bridging of tiles crack formation source: PSI 2006 / 2010 * Δt = 500 µs T 0 = 500 C CFC: NB31 W: forged rod material
Thermal shock testing of beryllium 5 ms Benjamin Spilker PFMC-15 Aix-en-Provence electron beam tests with 100 cycles
Repeated thermal shock testing of Be n = 100 n = 1000 n = 10000 2 mm 2 mm 2 mm power density P =1.0 MJ/m 2 pulse duration t = 5 ms P ( t) = 14 MW/m 2 s 1/2 base temperature T 0 = 250 C
C Hydrogen and helium effects
Thermal shock and He-loading Simultaneous 0.19 GWm -2 Simultaneous 0.38 GWm -2 1 µm 1 µm Only He-Plasma Simultaneous 0.76 GWm -2 1 µm 1 µm
Thermal shock and He-loading Simultaneous 0.19 GWm -2 Simultaneous 0.38 GWm -2 600 nm 600 nm Only He-Plasma Simultaneous 0.76 GWm -2 600 nm 200 nm
D Materials degradation by energetic neutrons
Neutron-induced material degradation High Flux Reactor (HFR) Petten, The Netherlands Neutron induced effects: activation of plasma facing and structural materials e.g. Co, Ag transmutation due to 14 MeV neutrons W Re Os Be He, T degradation of thermal and mechanical properties thermal conductivity, hardening, embrittlement
thermal conductivity (W m -1 K -1 ) thermal conductivity / W/m thermal th. conductivity conductivity / W/mK (W m -1 K -1 ) n-irradiation effect on thermal conductivity 350 300 250 200 un-irradiated 0.2 dpa 1 dpa 150 100 CFC (NB31) 50 0 0 200 400 600 800 1000 temperature temperature / C ( C) 350 300 250 200 tungsten un-irradiated 0.1 dpa 0.6 dpa 150 Laser-flash-apparatus (schematic) 100 50 0 0 250 500 750 1000 1250 1500 temperature / C temperature ( C)
t e m p e r a t u r e / C HHF performance of neutron irradiated divertor modules Dunlop Concept 1 (12 mm) / CuCrZr 3 0 0 0 2 5 0 0 IR - 551_11~1.IMG 2100,0 C 1500 1000 T irr = 350 C / 0.3 dpa 2000 b e s t r a h l t u n b e s t r a h l t 2 0 0 0 1 5 0 0 25:09:97 09:59:34 500 400,0 1 0 0 0 IR - DZ150SS.IMD 2100,0 C 2000 5 0 0 0 0 1 0 2 0 3 0 t h e r m a l l o a d / M W m - 2 1500 1000 500 400,0 Zykliertests an CFC-Modulen vom Type N07.08.96
Future fusion materials research in HML very high thermal loads hot cell JUDITH 1 1 plasma exposure neutrons JULE-PSI hot cell 1