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面对等离子体材料的研究现状与趋式以及我们今后工作的主要考虑

陈俊凌 , 李建刚

2005/6/1

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Materials Issues in Fusion: Extreme Conditions

Intense Irradiation, e.g. high n fluence

High thermal loads

Complex mechanical loads

Physico-chemical attack

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Fig. 1. Divertor heat sink and terminology

1

23

最高表面温度一般出现在边缘的角点，如点1 位置；

PFM 和热沉连接由于热膨胀系数的不同引起的应力，其最大值一般出现在角点 2 的位置；同时 2 点的位置也是连接界面间温度的最高点；

3 点是冷却水管最高热通量出现点，有可能出现超过 Critical heat flux 所 允值。

CFC or W

CuCr Zr copper alloy

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From JET to ITER

PULSE LENGTH (S)

STORED ENERGY (MJ)

INPUT ENERGY/ SHOT (MJ)

DIVERTOR PARTICLE FLUENCE/ SHOT

JET 40 10 40 1x 1024

ITER 400 350 50000 4 x 1027

x10 x35 x 1000 x 4000

ELMs and

disruptionsLifetime and T- retention

Challenge to Technology and Plasma Wall Interactions

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Fusion devices, parameters

ITER power reactor

relative size 1 1...1.2fusion power (MW) 500 2000power to He-ions (MW) 100 400total thermal power (MW) 2600electric power (MW) 1000efficiency (%) 38neutron damage (dpa) 5 150 in 5y

ITER (fusion power 500 MW, 400 s)

Reactor (DEMO) (fusion power 2000 MW, stationary)

JET (fusion power 16 MW, 2 s)

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Material choice compromise various requirements

Impurity release versus plasma

poisoning

Wall lifetime Tritium retention

Neutron materialdamage

Low Z (Be or C)(High Z, AUG)?

Melt layer loss

CFC on high heat flux areas

Particle erosion

W on baffle & dome

T co-deposition With C

No Carbon as PFC?

Low activationmaterials &

neutrondegradation

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ITER parameter and wall materials

Volume 850m3

PFus 500MW

P 100MW

Paux 50 MW

700m2 Be first wall

Low Z

Oxygen getter

100m2 Tungsten

no erosion by low

energy particles

50 m2 CFC（ NS31)

No melting in

transient heat

losses

Divertor Plasma

Optimised for

Power & Particle

exhaust

ITER

Main plasma

Te 8 KeV

Dens 1020/m3

E 3.5 sec

Present material

choice is the result

of long experiences

in fusion research

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Wall lifetime under steady state plasma bobardment

First wall

Erosion (peak, order of magnitude) derived from ITER calculations:

low Z materials: 3.5 mm/burn year; iron: 1 mm/burn year; tungsten: 0.1 mm/burn year

but: in_depth assessment needed; seed impurity ion erosion may be critical

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T-retention

How to approach the T- retention problem

Develop full metal scenario

Understanding ofT-retention in

present devices

Develop T-removal

technique

Lab work

and proof in

tokamaks

Plasma compatibility

Power exhaust

Melt layer erosion by

transient heat loss

Development of

control schemes to

reduce or mitigate the

T-retention (in

particular T-tailoring

and geometry

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Control of fuel retention and fuel removal will be essential in any wall material scenario and needs more attention in present

research (with and without C walls)

Fuel Removal• Isotope exchange on PFC side

• Thermal desorption on PFC side

• Oxygen venting remote areas?

• Scavenger techniques ??

and Fuel Control• Temperature tailoring

• Carbon traps

• Divertor geometry …

Work in plasma simulators

+

Dedicated lab experiments

+

Tokamak research

Needs detailed understanding of the involved physics

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W-coated PFCs

W-coated graphite tiles inASDEX Upgrade (2003/2004)

Campaign 2002/2003d = 1 m

A = 14.6 m

central column

upper PSL

inner divertor baffle

Campaign 2003/2004additionally:d = 3.5 mA = 7.2 (10.2) mupper divertorouter divertor baffle)protection limiter(Sec 8/9)

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European Power Plant Concept Studies

PPCS

Main Chamber First Wall:

Tungsten

Very low erosion yield,high threshold energy

Component lifetimeconsiderations

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Evaluate the performance of different materials for divertor/FW

• FWM: < 1MW/m2, technically ready

• High-field side: SiC coating on the doped graphite, bolted heat sink;

• Low-field side: W coating on the FS

• Divertor: 4-6MW/m2 (8-12MW/m2)

• SiC/B4C coating on the high performance doped graphite ( inner leg), C brazed to Cu heat sink.

• W coating (0.5mm) on the high performance graphite(out leg), C brazed to Cu heat sink.

• W coating (1-2mm) on the Cu heat sink.

• W coating (mm) on low radioactive steal (CLAN, similar with H82), high Tw operation for T inventory.

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Manufacturing Route of PFC

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Progressive formation of tungsten carbide

XPS investigations of carbon layers on tungsten

Ch. Linsmeier et al.:

CBM 表面上的 W 涂层成为研究热点

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Relatively high strength, highest melting point and low vapor pressure;

‘Promote deposition’ of high Z atoms;

Higher threshold energy of sputtering and low sputtering yield;

Quite favorable thermal mechanical properties (even >100W/m.K at 15000C);

Higher reflection coefficient for heat deposition;

钨作为 PFM 的主要优点 :

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Macrobrush Lamellar Rod

Qabs = 43MW/m2, 10-15s, 2 cyclesQabs = 27MW/m2, 10s, 1500 cycles

Steady state HHF-PFCs

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Shortcomings:Shortcomings:

Poor ductile (DBTT 1500 ～ 4000C), heavy mass, re-crystallization (11500C) ( properties dependent on metallurgical treatment-method of production, machining condition, grain size, temperature of history and impurities.)

Bulk tungsten

Pure -W ( sintering technique ,electron beam or arc);

PW (W-5Re; W-1%La2O3, W-Cu, W-Cu, W-Cu-Ni, W-Fe-Ni etc.).

PVDPVD CVDCVD IPSIPS VPS VPS

W-coating methods

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Fig. 2. Tungsten has low CTE (coefficient of thermal expansion)

The primary difficulty is cooling the substrate to reduce stresses caused by thermal distortion

In essence, the thicker the coating, the larger the T through the thickness which increases the strains between the hot tungsten surface and the cooled copper substrate and can result in and can lead to cracking in the tungsten coating either during the spraying process, during cooling, or during the actual operation of the component.

A secondary consideration is that the longer it takes to cool the tungsten during plasma spraying, the larger and more columnar the grain structure, which results in a higher DBTT than would be achieved with a finer grain size.

EUROFER

Large mismatch of CTE between W and substrate

J.W. Davis, J. N. Mater. 233-237(1996) 604-608

316LN

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Thermally sprayed coatings formed by the deposition of molten or partially molten particles, propelled onto a substrate where they impact, are flattened and quenched to the substrate temperature within a very short time (few ms), and agglomerate to form a thin layer. RS are expected within the sprayed deposit as a consequence of the release of thermal and kinetic energies.

Residual stresses:

Deposition stress;

Thermal stress;

Temperature gradient stress.

Fig. 5. Schematic diagram of thermal spray process

The shear stress and peeling stress occur near free ends of the coated components…… delaminate the coatings from the free ends;

The in-plane normal stress in the interior region …….may result in the coating layer cracking, spalling, or buckling…

HHFl

mismatchl

depositionl

totall

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2003/05/15, Max-Planck-Institut für Plasmaphysik, Garching bei München, Germany J.L.Chen, MF

Stress induced by temperature profile under full constraint

Once the temperature profile has been obtained from a forgoing thermal analysis, the thermal

stress of the armor tile is determined applying the strain suppression method where full constraint by the heat sink is assumed.

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2003/05/15, Max-Planck-Institut für Plasmaphysik, Garching bei München, Germany J.L.Chen, MF

Final stress levels

nncdCTE

nnndn

wnyddn

wnkkEbh

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The final residual stress levels at the bottom face and top face of the substrate are obtained by adding the contributions represented by

Where . For example, the stress as the midpoint of the n th layer is,nj 1

(38)

(39)

(40)

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W as a plasma facing material:

• low erosion rate • heat resistant, lowest vapor pressure of all metals

VPS offers an industrial coating of first wall to be loaded up to 1MW/m²

Development of 2 mm VPS W coatingson actively cooled steel substrates:

DEMO/ power plant: potentially as FW Covering on EUROFER/ F82H

(ITER: FW, special divertor comp.

made of 316L)

Motivation

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samples after heat load tests

length: 190 mm

Garching-IPP initiated a development program of VPS W layers on cooled steel substrates

mixed W/ steel interlayer

actively cooled substrates reduction of residual stress

Vacuum plasma spraying:

• temperature up to 15.000 K

• velocity of particles: 500 m/s

• no oxidation

PLANSEE AG, 2003:

fabrication of 2 mm W-VPS layers

- 3 mock-ups made of EUROFER

- 3 mock-ups, F82H

- 3 mock-ups, 316L

Manufacturing

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Metallographical examination:• measured properties:

• Coating micro structure, homogeneity of thickness, SEM

• D retention

• Residual stress measurements, hardness, Young’s modulus (Univ. Stuttgart)

VPS-W layer

InterlayerSubstrate

Characterization

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Preliminary results of heat flux tests W-VPS on EUROFER, FZJ 10.02.04,comparison of calclulated and measured temp. distribution, 60 s heating

Incident heat flux, MW/m²

Thermal loading tests- W on EUROFER

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Preliminary results of heat flux tests W-VPS on 316L, FZJ 12.02.04,comparison of calclulated and measured temp. distribution, 60 s heating

Incident heat flux, MW/m²

Thermal loading tests- W on 316L

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tranfered arc cleaning

B4C deposition on flat samples

Sulzer-Metco low pressure plasma spray facility with F4 torch

thick tungsten layers (up to 23mm)

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The ability to study the science of plasma interaction with materials is provided by the DIII-D divertor material evaluation system (DiMES)

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Schematic view of the test limiter in TEXTOR’ 94 device

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Simple ITER-like TZM catellated structures have been used inTEXTOR with TZM in erosion and C-deposition dominated area

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ITER is planned to have tungsten baffles in the first operation phaseand probably a full W wall in its reactor like operation phase

Issues to be addressed:

• Erosion, deposition and migration in a mixed material device

• Behaviour under transient heat loads

• Hydrogen retention and material degradation under high H fluxes

• W diagnostics (spectroscopy)

• Operation must be compatible to W PFCs

• Seed impurity scenarios to replace intrinsic C radiation

• High performance scenario development along W compliant route

• Code simulations for interpretation and extrapolation

issues may be investigated in existing fusion devices as well in

other laboratories

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Installation of W divertor possibly during shut down in 2008

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谢谢大家！ Thanks for your attention!