IN TOKAMAK MAKE Suk-Ho Hong Dusts in plasmas horse head nebula - PowerPoint PPT Presentation

SAFETY ISSUES THE DUSTS IN TOKAMAK MAKE Suk-Ho Hong

Dusts in plasmas horse head nebula ghost head nebula N44C nebula Suk-Ho Hong, IAEA Divertor Concept TM, 29 th Sept.-2 nd Oct. 2015, Vienna, Austria

Dusts in plasmas  From lab to the universe 0,3 CygOB2*5 Gal. Ctr. IRS 6 (High Res.) Bochum analog 0,2 Optical depth Wave propagation Instability induced by dusts 0,1 0,0 2800 2850 2900 2950 3000  / cm -1 Pendleton, Y.J., & Allamandola, L.J. 2002, ApJS 138, 75 Eva Kovacevic, DPG Tagung in Kiel, 2004 Vortex formation Killer particles in semiconductor industry Suk-Ho Hong, IAEA Divertor Concept TM, 29 th Sept.-2 nd Oct. 2015, Vienna, Austria

Dusts in tokamaks ITER definition: solid particles/debris of size about 10 nm-100  m Droplets from arcing (AUG) Flakes Mobilized dusts Nanoparticles (Tore Supra) (Tore Supra) (Tore Supra/JET) Suk-Ho Hong, IAEA Divertor Concept TM, 29 th Sept.-2 nd Oct. 2015, Vienna, Austria

Dusts in tokamaks Suk-Ho Hong, IAEA Divertor Concept TM, 29 th Sept.-2 nd Oct. 2015, Vienna, Austria

What are the problems dusts brings in?  Degradation of plasma performance as “ uncontrolled pellet injection“ from LFS SOL  Damage of in-vessel components by high speed collision or by high temperature  Stress relaxation of layers by incorporated dusts Current tokamaks  Tritium retention and Radioactivity Future tokamaks  Explosion Main question = “Amount of dusts or how often events occur” Suk-Ho Hong, IAEA Divertor Concept TM, 29 th Sept.-2 nd Oct. 2015, Vienna, Austria

Degradation of plasma performance as “uncontrolled pellet injection“ from LFS SOL  Impurity influx  Radiative power loss  Fuel dilution  Disruption (such as killer pellet) S. Hong et al ., “Temporal evolution and spatial distribution of dust Dust influx after plasma touches the wall  creation events in Tore Supra and in ASDEX Upgrade studied by CCD image analysis”, Nucl. Fusion 50 (2010) 035002 at JET (captured by high speed camera) Suk-Ho Hong, IAEA Divertor Concept TM, 29 th Sept.-2 nd Oct. 2015, Vienna, Austria

Degradation of plasma performance as “uncontrolled pellet injection“ from LFS SOL To study influence of dusts on the plasma  performance and to simulate W splashing event in ITER, a gun-type injector has been designed, developed, and fabricated.  Aimed to inject various powder form particles into edge plasmas  For W injection: W 12 μ m in diameter.  Initial velocity ~ 1.5-4.0 m/s in air, up to a factor ~ 2 in vacuum.  2-3 mg per single injection Multi-purpose manipulator First injection of W has made at KSTAR.  International collaboration is ongoing: EAST,  WEST, AUG will perform similar experiments. Suk-Ho Hong, IAEA Divertor Concept TM, 29 th Sept.-2 nd Oct. 2015, Vienna, Austria

Degradation of plasma performance as “uncontrolled pellet injection“ from LFS SOL AUG T. Puetterich et al., Plasma Phys. I p =600 kA, P NBI =5 MW, H-mode discharge Control. Fusion 50 (2008) 085016 “Splashing” of ~ 3 mg W droplets from LFS SOL would not be a problem in current machines. Only transient  effects of W influx into the discharge were observed (no influence of W on discharge after 0.5-1 sec, also on next shot ). “Splashing” from divertor will be performed in next campaign. More detailed, quantitative analyses and comparison with SANCO modelling are ongoing (will be reported  in next PSI). Suk-Ho Hong, IAEA Divertor Concept TM, 29 th Sept.-2 nd Oct. 2015, Vienna, Austria

Damage of in-vessel components by high speed collision  Hyper velocity dust impact on PFCs and diagnostics can cause severe damages. FTU probe head Runaway impact at Tore Supra (captured  by high speed camera) Suk-Ho Hong, IAEA Divertor Concept TM, 29 th Sept.-2 nd Oct. 2015, Vienna, Austria

Damage of in-vessel components by high speed collision  Quantitative measurement of in-vessel dust velocity and its correlation with toroidal rotation of plasmas S. Hong et al ., “Quantitative measurement of in -vessel dust velocity and its correlation with toroidal rotation of plasmas”, Journal of Nuclear Materials 463 (2015) 851 – 855 Suk-Ho Hong, IAEA Divertor Concept TM, 29 th Sept.-2 nd Oct. 2015, Vienna, Austria

Damage of in-vessel components by high speed collision 100 90 80 Cumulative probability 70 60 Ohmic 2010 50 L-mode 2010 H-mode 2010 40 Ohmic 2011 30 L-mode 2011 H-mode 2011 20 Ohmic 2012 10 L-mode 2012 H-mode 2012 0 0 100 200 300 400 500 Velocity (m/s) 2010 2011 2012 R.D. Smirnov et al. J.Nucl.Mater. 390-391 (2009) 84-87 Ohmic 0% 0% 0% L-mode 0.51% 0% 0% m   (5 events) carbon V V tungten carbon m H-mode 0% 0.66% 1.89% tungten (4 events) (14 events) Impact of carbon dust with a velocity of 316m/s • on Beryllium wall is equivalent to an impact of a NBI power 1.3 MW 1.5 MW 3.2 MW tungsten dust with a velocity of 100 m/s. Probability and the number of dusts over 316m/s Number of dust with speed higher than 316 m/s increases as a function of input power  Suk-Ho Hong, IAEA Divertor Concept TM, 29 th Sept.-2 nd Oct. 2015, Vienna, Austria

Damage of in-vessel components by hot dust  Modeling of dust behavior in conventional operation range of a tokamak shows that the temperature of a dust can reach several 1000 K.  Such hot dust can cause Diagrams showing temperature of a spherical carbon dust particle at thermal equilibrium in a deuterium plasma with melting of metal PFCs. temperature T e = T i and with fraction  c = 1% of carbon impurity ions. R D Smirnov et al, ” Modelling of dynamics and transport of carbon dust particles in tokamaks”, Plasma Phys. Control. Fusion 49 (2007) 347 – 371 Suk-Ho Hong, IAEA Divertor Concept TM, 29 th Sept.-2 nd Oct. 2015, Vienna, Austria

Damage of in-vessel components by hot dust Broken BN cover The same type probe used for the campaign afterwards. Broken BN cover after plunging, but not melted. Melted Mo probe head With a crater Primary dusts impact on lower passive stabilizer, cause second generation, are that impinging on fast reciprocating Langmuir Melted spot of a quarts window nearby FRP due to hot dusts probe (FRP) in KSTAR Suk-Ho Hong, IAEA Divertor Concept TM, 29 th Sept.-2 nd Oct. 2015, Vienna, Austria

Stress relaxation of layers by dusts Layers deposited on a substrate build  internal stress. Once the stress overcome adhesion,  layers peel off resulting in mobilization, become dusts. If dusts are incorporated in layers, they  actively relax the stress, leading to thick layers up to several hundred  m. (by a factor 4 in figure) Such layers with incorporated dusts  inside are observed in KSTAR, Tore KSTAR Supra, TEXTOR. This might be one of reasons why  redeposited layers in tokamaks have no ‘well defined” critical thickness before they peel off. This is universal, the same for metal layers.  Suk-Ho Hong, IAEA Divertor Concept TM, 29 th Sept.-2 nd Oct. 2015, Vienna, Austria

Tritium retention and Radioactivity  Retention in co-deposited layers and dusts cannot be separated, since “mobilized” layers will become automatically dusts (dust conversion factor).  Dust conversion factor is hard to measure and not exactly known. Estimated values are 7-8 % in Tore Supra (C. Grisolia et al, JNM 390-391 (2009) 53-56), 43  10% in JET (J. Likonen et al., JNM 463 (2015) 842 – 846).  T inventory in metal machines, e.g. JET with ITER-like wall, is very low, and main retention mechanism is long term retention via co-deposition in Be layers (S. Brezinsek et al., Nucl. Fusion 53 (2013) 083023)  Concentrate on retention in tungsten nano- to micron-size dusts. Suk-Ho Hong, IAEA Divertor Concept TM, 29 th Sept.-2 nd Oct. 2015, Vienna, Austria

Tritium retention and Radioactivity T inventory varies with type and  size of dust. Smaller dusts have trapped much  more tritium than larger ones. Tritium trapping in powder  triggered by surface effects (rough and defected surface). C. Grisolia et al., “Tritium absorption and release from relevant tokamak tungsten dust”, ISFNT-12, 14-18 Sept., Juju, Korea Suk-Ho Hong, IAEA Divertor Concept TM, 29 th Sept.-2 nd Oct. 2015, Vienna, Austria

Tritium retention and Radioactivity LHD LHD V. Rohde et al., dust CRP, IAEA, Vienna, Dec 2011 K. A. McCarthy et al., “Tokamak dust in ITER – Safety issues and R&D supporting dust limits”, 3 th topical meeting on fusion energy (1998) 20 200 Daily collection at midplane 150 in KSTAR count 15 100 count 50 10 0 0 1 2 3 4 5 6 7 8 9 10 effective radius (  m) 5 Campaign integrated 0 0 10 20 30 40 50 60 70 80 90 100 2 ) area (  m S. – H. Hong et al., ITPA div/SOL meeting, Aachen, Jan 2012 J.P. Sharpe et al. / Journal of Nuclear Materials 337 – 339 (2005) 1000 – 1004 Suk-Ho Hong, IAEA Divertor Concept TM, 29 th Sept.-2 nd Oct. 2015, Vienna, Austria

Tritium retention and Radioactivity S. Ciattaglia, IAEA CRP(2008-2012): Characterization of Size, Composition and Origins of Dust in Fusion Devices C. Skinner, “TFTR experience with tritium accounting and tritiated dust”, ITER/PPPL conference call, 24 th June 2014 Suk-Ho Hong, IAEA Divertor Concept TM, 29 th Sept.-2 nd Oct. 2015, Vienna, Austria