Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – CIEMAT 29-31 – 10 – 2007 1

EFDA Plasma Edge Technology ProgrammeMonitoring of 2006 Activities

Alberto LoarteEuropean Fusion Development Agreement

Close Support Unit – Garching

Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – CIEMAT 29-31 – 10 – 2007 2

Activities within Plasma Edge Technology Programme

Programme supports various types of activities :

Well defined laboratory experiments/modelling to identify/model important PWI processes in conditions relevant to ITER

Analysis of samples/components exposed to tokamak plasmas (and/or in dedicated experiments) to quantify processes relevant to ITER

Modelling/experiments to determine influence of ITER components specifications on their behaviour under plasma exposure (transient loads, influence on T retention and removal, etc.)

Development of measurement/removal techniques for PWI-related issues which affect the licensing of ITER (Dust, Tritium)

EFDA Plasma Edge Technology Programme is coordinated with EU PWI Task Force (Voluntary Physics Research Programme)

TW6-TPP budget = 3364 k€ (art. 5.1.a), 285 k€ (art. 5.1.b), 340 k€ (UT)

Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – CIEMAT 29-31 – 10 – 2007 3

Tasks in 2006 (I)

Tasks finished/running in 2006

1. Material erosion behaviour and transport in tokamaks

TW4-TPP-TRIDEP, Studies of hydrocarbon formation and redeposition in ITER-relevant divertor chamber

TW5-TPP-TILCAR, Characterisation of erosion/deposition balance in ITER-relevant divertor tokamaks and of PFCs after hydrocarbon removal by oxidative methods

TW5-TPP-CARWBER, Erosion/Deposition studies of the Carbon-Beryllium-Tungsten system in PISCES-B (EU-US collaboration)

UT_W_Brush2005_TP, Characterization of Reactor relevant W Plasma Facing Components  

UT_W_PFC2005_TP, Characterization of Reactor relevant W Coatings TW6-TPP-CARTIL, Characterisation of erosion/redeposition balance in ITER-

relevant divertor tokamaks TW6-TPP-ERDEP, Studies of material erosion and redeposition in ITER-relevant

divertor target temperatures, plasma impact energies and divertor target geometries TW6-TPP-CNDMSTICK, Determination of reflection properties of hydrocarbon

radicals for ITER-like divertor conditions

Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – CIEMAT 29-31 – 10 – 2007 4

Tasks in 2006 (II)

2. Fuel retention and removal TW4-TPP-TRIREMA, Study of Oxidizing Agents for Tritium Removal in ITER-

compatible Conditions: Ozone   TW4-TPP-TRIREMB, Study of Oxidizing Agents for Tritium Removal in ITER-

compatible Conditions: Alternatives to Oxygen and Ozone TW5-TPP-HEGLO, Optimisation of oxidising glow discharges for removal of

hydrocarbon deposits TW6-TPP-RETMIX, Characterisation of fuel retention in ITER-relevant mixed-

materials TW6-TPP-GAPOX, Study of Tritium removal from macrobrush structures by

oxidative methods TW6-TPP-RETMET, Determination of fuel retention in metallic materials for ITER UT06_TPP_LASRAD, Characterization of the In-Vessel Components Treated by

Laser IPPLM__TPP_UT1, Application of pulsed laser light for the removal of co-deposited

deuterium/tritium from in vessel components OEAW_UT06_TPP_Be, Dependence of hydrogen retention in Beryllium on the

thickness of the oxidised surface layer and its carbon content

Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – CIEMAT 29-31 – 10 – 2007 5

3. Transient heat loads and control TW3-TPP-MATDAM, Characterisation of Material Damage for EU W and CFC ITER Divertor

Materials under Repetitive Plasma Energy Fluxes by Modelling and Experimental Validation (EU-RF collaboration)

TW4-TPP-TARCAR, Characterisation of W and CFC targets exposed to ITER-relevant Type I ELM and disruption loads in plasma gun facilities (EU-RF collaboration)

TW5-TPP-ITERTRAN, Modelling of ITER divertor target damage and plasma contamination following ELMs and disruptions (part. EU-RF collaboration)

TW5-TPP-BEDAM, Modelling of Material Damage to Be-clad and Be-coated ITER Plasma Facing Components under Type I ELMs, Disruptions and Mitigated Disruptions and Scoping Studies for its Experimental Validation (EU-RF Be-studies contract)

TW6-TPP-REPELM, Material damage for CFC and W under large cycle under-threshold ITER ELM-like loads simulated with an e-beam

TW6-TPP-BECOAT, Coating of EU CFC/W targets with Beryllium for exposure to ITER-like transient loads in plasma gun facilities (EU-RF Be-studies contract)

TW6-TPP-ANABE, Analysis of Be-coated and Be-clad targets for exposure to ITER-like transient loads in plasma gun facilities (EU-RF Be-studies contract)

TW6-TPP-DAMTRAN, Modelling of ITER plasma facing component damage and consequences for plasma evolution following ELMs and disruptions (EU-RF Be studies contract)

UT-PWI-2006, Analysis of irradiation effects and thermal shock resistance on tungsten and beryllium for plasma facing components

EFDA  05-995, Design and R&D work with Kurchatov Institute Moscow on effects of ELMs and disruptions on Be-coated and Be-clad PFCs for ITER

Tasks in 2006 (III)

Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – CIEMAT 29-31 – 10 – 2007 6

4. Dust in production in fusion devices and removal TW6-TPP-DUSTGEN, Evaluation of dust generation mechanisms at the ITER SOL and

divertor plasma TW6-TPP-DUSTMEAS, Demonstration of diagnostic techniques for time resolved dust

measurements in tokamaks5. Modelling of plasma-wall interaction processes for ITER TW5-TPP-TUNMOD, Modelling of Tungsten Erosion and Edge Plasma Transport in

ITER TW5-TPP-ITERNEUT, Modelling of neutral-photon and neutral-neutral effects on ITER

edge and divertor plasma conditions   TW6-TPP-BETUNCMOD, Molecular dynamics simulations of mixed-material formation at

the ITER divertor TW6-TPP-ERITERA, Modelling of Erosion/Redeposition for ITER Limiter Ramp

up/down and Reference Scenarios including Macrobrush & Gap Geometries, Temperatures and Surface Composition

TW6-TPP-ERITERB, Improvement of Surface Processes Modelling in the ERO Code for Advanced Description of mixed Material Formation in ITER Reference Scenarios

TW6-TPP-SOLITER, Self-consistent modelling of plasma-wall interactions and SOL transport with real 3-D PFC geometries for ITER reference scenarios

Tasks in 2006 (IV)

Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – CIEMAT 29-31 – 10 – 2007 7

TRIREMA : O3 oxidation of hydrocarbon deposits in ITER-relevant conditions

Oxidation in ozone achieves rates near the ITER requirements (0.5-5.0 mh-1) and operating temperature (T < 250 oC) for TEXTOR flakes (variability of 3-4 depending on impurity content) Oxidation of base material (EK98) is very large cleaning restricted to few cycles

Major results in 2006 (I)

Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – CIEMAT 29-31 – 10 – 2007 8

TRIREMB : Removal of fuel with alternative methods and comparison to O2

Oxidation by O2/ Nitric Oxide (NO) of Hard Films & TEXTOR flakes (H/D>>1) shows that NO oxidation is slower than O2 and does not produce H2 (260 oC @ 2 torr)

Isotope interchange on flakes from ASDEX Upgrade activated by H2O2 does not occurActivation of samples

with H2O2 + H/D interchangeCandidate reaction :

NO + H NOH + H NO + H2 Some

production of CO with NO but

no enhanced production of H2

H2O2 treated AUG flakes in H2 1 bar atmosphere show release of H2, DH and D2

at similar temperatures than in TDS

H2O

H2

D2DHO

D2O

HD

TDS

T(K

)

HD D2

H2

Major results in 2006 (II)

Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – CIEMAT 29-31 – 10 – 2007 9

TRIDEP : CxHy formation and deposition in remote areas (PSI-2) Deposition experiments show that H plasmas lead to much larger deposition than Ar/He plasmas and is accompanied by different hydrocarbon production from CH4

Experiments to quantify H erosion of C-H re-deposits in remote locations carried out Effect of N2 to avoid deposition demonstrated

Major results in 2006 (III)

Measured conversion of C2H2 to HCN

Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – CIEMAT 29-31 – 10 – 2007 10

MATDAM : Validation of ELM damage modelling by experiments in plasma-gunsTARCAR : Characterisation of ELM-disruption damage in experiments in plasma-gunsITERTRAN : Development of material damage models and application to ITER

[PEGASUS (for CFC and W), PHEMOBRID (CFC), MEMO-S (W), FOREV] Experiments carried out in TRINITI plasma guns under EU-RF collaboration CFC, W, WLa2O3 targets exposed to 100 pulses at 0.5, 1.0, 1.5 and MJ/m2 and 5 at

2.5 MJm-2 t = 500 s (experiments almost completed) Analysis of target damage almost complete

Major results in 2006 (IV)

Plasma flow

Target

Diagnostic windows

Vacuumchamber

600

Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – CIEMAT 29-31 – 10 – 2007 11

Mechanism of CFC damaged under loads identified by experiments and modelling (PAN fibre erosion):

Decrease of threshold for damage but larger protection by vapour shielding at larger energies Fibre orientation can decrease damage

Major results in 2006 (V)

ELM

CFC fibers erosion as a function of surface energy density

Modelling of PAN fibre erosion without/with

vapour shieldingExperiments in Judith (FZJ)

Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – CIEMAT 29-31 – 10 – 2007 12

Mechanisms of W damage : Melting and molten layer displacement + droplet formation and ejection (& cracking) modelling of molten layer in macro-brush geometry + criteria for droplet formation developed and crack modelling started

Major results in 2006 (VI)

500 µm

200 µm

100 µm

WELM = 1 MJm-2

Pestchanyi

Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – CIEMAT 29-31 – 10 – 2007 13

The Rayleigh-Taylor instability is responsible for

The flow is stable if the Taylor criterion OKV melt velocity surface tension melt densityh melt thickness.

the formation of jets at melt layer edges

the formation of bridges between brushes and jets at brush edges

Metal [din/cm]

[cm-3]

h

[m]

Vmax

[m/s]

comment Bulk

armour

Brush

armour

W 2.2 103 17 20-80

200-400

3.5-1.8

1.1-0.8

ELM

disruption

Splashing possible

Splashing

No

No

Be 1.2 103 1.75 20-80

200-400

8.4-4.3

2.8-2

ELM

disruption

Splashing

Splashing

Splashing possible

Splashing possible

The Kelvin-Helmholtz instability is responsible for the droplet formation and melt layer losses

Pla sm a strea m

V Pl

W-b rush

M e lt la ye r Vm

W armourRdroplet~ 10-15 µmVdroplets~15-17 m/sVelocity of mass losses 50-300 g/(cm2s)During 1 ms Splashing thickness up to 150 µm

Be armourRdroplet~ 20-25 µmVdroplets~9-11 m/sVelocity of mass losses 50-100 g/(cm2s)During 1 ms Splashing thickness up to 500 µm

Major results in 2006 (VII)

Bazylev

Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – CIEMAT 29-31 – 10 – 2007 14

T retention within CFC in ITER-like conditions (Tsurf = 1070 K, incident ion energy of 30 eV and plasma fluence ~1027 Dm-2) in PISCES-B

Retained fuel in CFC amounts is very small & independent of Be (3g in ITER) Transient Tsurf increases lead to increased Be2C and low C erosion but

increased D retention (although it remains low)

Major results in 2006 (VIII)

Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – CIEMAT 29-31 – 10 – 2007 15

Conclusions

EFDA TPP Technology Programme well coordinated with EU-PWI

Research Programme (5th year of existence)

Key PWI R & D issues for ITER being addressed

Three major international EURATOM collaborations supported by this area :

(Be mixed-materials) with US (UCSD)

W/CFC target damage under ELMs & disruptions with RF (TRINITI)

Be-clad and Be-coated (W/CFC) PFC damage under ELMs & disruptions with RF (Kurchatov-TRINITI)

Reasonable number (15) of associations involved in running tasks in 2006 : CEA, CIEMAT, ENEA-F, ENEA-CNR, FZJ, FZK, FOM, IPP, IPP.CR, IPPLM, IST, MEdC, MHST, ÖAW, SCK-CEN & TEKES

Special effort to increase participation from “new” countries bearing fruit (IPP.CR, IPPLM, MEdC, MHST)

EU-PWI TF under the new EFDA and the EU Domestic agency will need to coordinate work to maintain an effective contribution to ITER in this area