ReNeW PMI Theme PFC Panel Report

Panel team members :C. Wong ( GA), B. Lipschultz (MIT), T. Leonard (GA), R. Majeski (PPPL), D. Youchison (SNL), B. Merrill (INL)R. Doerner (UCSD), S. Milora (ORNL)

US Department of Energy

OFES Research Needs Workshop (ReNeW)

University of California, Los Angeles

March 2–6, 2009

• Organization

• First question at the beginning: What are we doing?

• Technologists to physicists: What heat fluxes will the DEMO have?

• Physicists to technologists: What are your design limits?

• Both sides agreed: We have significant challenges ahead.

• The team then worked on requirements and issues of different areas.

• Generated the PFC Matrix showing issues and needs for different areas.

• We do have a draft PFC related research thrusts

PFC is a Tier 1 priorityGreenwald Priority Tier 1: solution not in hand, major extrapolation from current

state of knowledge, need for qualitative improvements and substantial development

for both short and long term

• Plasma Facing Components

• Materials

Plasma Facing Components: Understand the materials and processes that

can be used to design replaceable components that can survive the enormous

heat, plasma and neutron fluxes without degrading the performance of the

plasma or compromising the fuel cycle.

ReNeW PMI PFC Organization

Panel member focused areas:• Physics (Lipschultz and Leonard)• Solid surface and design (Wong)• Liquid metal and design (Majeski)• Surface heat transfer and components

testing and analysis (Youchison)• Tritium, safety and RAMI (Merrill)• Surface materials (Doerner)• Maintenance and development program (Milora)

Review…requirements…development… thrusts… …for the next 15-20 years

ITER design asan initial example

To project robust PFC design and development we created the ~ 1000 MWe DEMO key PFC parameters:Mid-plane Γn-max =3 MW/m2

FW φ-max= 0.5-4.0 MW/m2 (TBD)Div φ-max = 10 MW/m2 (steady state)

+ 20 MW/m2(10-100s) (pulses TBD)

EU Roadmap Divertor Development towards ITER & DEMO

[P. Norajitra et al.]

constant load

for DEMO

*

**

For DEMO:

ELMs have to be supressed,

VDEs and disruption

„unlikely events“

(Vertical Displacement Events)

(Edge Localized Modes)

Intro (6): Assumptions for DEMO Design from EU

* Number of events in ITER

[T. Ihli, Summer School 2007, Karlsruhe,

Germany]

Intro (5): Example Divertor Cassette for Model C from EU

Replacement

scheme

[P. Norajitra et al.]

1-Finger module

10 MW/m2

Divertor cassette

Dome and structure

(ODS RAFM)

Outboard

Inboard

Divertor target plates

with modular thermal

shield (W/W alloy)

9-Finger module

Reference Design:

He-cooled modular divertor with jet cooling (HEMJ)

(DBTT, irr.)

1300°C

700°C

600°C

300°C

600°C inl.

700°C outl.

(RCT, irr.)

WL10

Thimble

creep rup.strength

(DBTT, irr.)

He coolant

ODS Euro

Structure

Temperature

windows

18

} 5

[T. Ihli]

HEMJ-J1c

• W-tile: Non-castellated, russ. W• WL10 thimble• W/W joint: STEMET 1311• W-Steel joint by Cu castingHe data:• 10 MPa• 13.5 g/s (∆P 0.31 MPa*)• Tin = 520-570°C• Tout = 550-600°CResults:• 10 cycles each at 4,6,10,11

MW/m2 ok• Failure in W/W joint after 6 cycles

at ~13 MW/m2• He Loop and thimble still intact

W-tile

Detached area

W-thimble

Steel ring

Conical Cu-

cast lock

*) about 0.085 MPa equivalent

at 6.8 g/s nominal

EF

RE

MO

V u

nd

er

FZ

K c

on

tra

ct

Overall results:

No suddenly

and/or completely

broken mock-up,

i.e. no brittle

failure.

Nor was a

recrystallisation of

the thimble

observed in any

mock-up.

2006 HHF test results (mockup #4)

Crack in thimble, growing from inside

Test conditions:

• 10 MW/m2

• 30s / 30s sharp power ramp

THe,in 550°C, 10 MPa, mfr 7 g/s

• Tile temperature rise after 89 cycles*

--> tile probably partially detached.

• He Loop and thimble still intact.

• Post examination underway

Current Distribution of the Heat Flux used in Efremov

0

2

4

6

8

10

12

0 10 20 30 40 50 60 70

time in [s]

heat

flu

x i

n [

MW

/m^

2]

heat flux

2007: HHF test of optimized HEMJ mockup

*n required ~ 100 - 1000 Post-examined

at FZJ [T. Hirai,

G. Ritz]

2007 overall

results:

successful HHF

tests of optimized

HEMJ mockup 10

MW/m2

(survived 100

thermal cycles,

30s-30s sharp

ramp, w/o

damages)

Castellation: cracks parallel to heat flux, W defect

Wall loads on plasma facing components in ITER

Thermal load during ELMS: 1 GWm-2, t = 500 µs, 1 Hz high cycle thermal fatigue

critical area

flat tile design

W

monoblock

CFC

M. Roedig

ELM induced erosion of CFC and W with the 0.5 MJ/m2 limit

CFC

W

energy density* E / MJm-2

0.5 1.0 1.50

heat flux factor P ·Δt / MWm-2s1/2

20 400 60

melting of tile surface

dropletsbridging of tiles

melting oftile edges

crack formation

cracking of pitch fibres

PAN eros.> 100 shots

PAN erosion> 50 shots

PAN erosion> 10 shotsn

egl

igib

lee

rosi

on

negligibledamage

unmitigated ELMs in ITER

mitigated ELMs in ITER

* Δt = 500 µs

M. Roedig

PFC team went through a detailed identification of PFC requirements and issues

Seven PFC panel areas: 1. Physics, 2. Solid surface and design, 3. Liquid metal and design4. Surface heat transfer and components testing and analysis 5. Tritium, safety and RAMI, 6. surface materials, 7. maintenance and development program

ReNeW PMI PFC Solid surface & design: Wong

Requirements:

• Configure surfaces to reduce peak heat flux, material erosion and deposition• Components life time: FW 4years (TBD), divetor 2 years (TBD)• Disruption and transient events tolerance (TBD) even for unlikely events• Robust components to withstand all Demo operating scenarios, including all

operational & transient E&M loads and structural and thermal stresses (including effects from neutron irradiation, cyclic fatigue, thermal creep, fracture toughness, fracture mechanics effects), while providing a design margin of 1.3 (TBD)*

• Adjust to major divertor configuration change if recommended?• Divertor design to maximize flexibility, surface can be shifted back and forth by ± 5°

when required by operation. • Design with removable chamber first wall (TBD)?• Assess the renewable low-Z surface on W option?• Design with high thermal efficiency• Develop predictive capability via modeling and analysis

(Not covered or provided in the Greenwald report)

Review…requirements…development… thrusts …for the next 20 years

ReNeW PMI PFC Solid surface & design: Wong

Review…requirements…development… thrusts…for the next 20 years

Development needs:

•Demo design: Use a projected Demo design to define the pre-conceptual design with

gradual increase of details: including physics, configuration, segmentation, routing,

maintenance, structural support…etc.

• Industrial connection: Establish connections with industry on PFC components design,

fabrication and testing of different scale of PFC components

• Modeling: If necessary develop PFC relevant design codes, coupled with dedicated

analysis codes and commercial design codes

• Fusion materials design codes

• Connections: Continue to work with physicists, first wall material designers, heat transfer

and components developers and testing professionals

PFC team went through a second round on PFC requirements and issues

PFC requirements and issues

were prepared for different areas

We found that the two VG format was

too limiting, two page write-ups of issues on each

of the seven PFC related areas were generated.

Seven PFC panel areas: 1. Physics, 2. Solid surface and design, 3. Liquid metal and design4. Surface heat transfer and components testing and analysis 5. Tritium, safety and RAMI, 6. surface materials, 7. maintenance and development program

PFC MatrixPFC Gaps: To Develop Understanding for the Construction of Robust PFC Components

Thoeory &

Modeling

Existing/Upgrade/

New Test stands

Existing Upgraded

Confinement

facilities

New Confinemet

Facility

Chamber & Div. heat flux

Steady state

Transient

Example 1

Solid surface design

Liquid surface design Example 2

Tritium in solid,

mix materials

Example 3

Maintenance

Innovations Example 4

• Possible temperature range: RAF/M-350 to 550 C, ODFS Tmax-700-800 C, W-alloy 700-1300 C

• Design guidelines: FW heat flux ~0.5 MW/m2, Max. heat flux ~10 MW/m2,

ELMs with rise time of 125-250 µs, energy flux ~0.5 MJ/m2

• Inputs to be developed jointly with PWI and other panels

• Inputs to be developed jointly with other panels

PFC Matrix Example 1 (physics)PFC Gaps: To Develop Understanding for the Construction of Robust PFC Components

(Physics) Theory & ModelingDefine chamber spatial and temporal heat loads

1st principles modelingChamber & Divertor heat flux

ConventionalExtended channel(s) (e.g. SXD, snowflakes)

Divertor physics, integrated with PMI effects,1st principles modeling

Transients:

Startup/shutdown Define start/up & shutdown parameters

Model suppression and elimination of high

ELMs power ELMs

Disruption Model disruption avoidance and mitigation,

Other off normal events: eliminate off normal events

MARFE, Improve neutral and photon modeling

H-L transition Model avoidance of MARF, H-L transition heat load

Heat dumps Define occasional ELMs and heat dump locations and parameters by 1st principles modeling

PFC Matrix Example 2

PFC Matric Example 1

PFC Gaps: To Develop Understanding for the Construction of Robust PFC Components

Existing/Upgraded/New Test Stands

Liquid surface design issues

Configuration

(Ext. chan., e.g. SXD,snowflakes) Construct high B-field facilities for

In chamber MHD effects fast flow and capillary flow

Fluid flow MHD Perform high heat flux LM experiments

Heat flux limits at tokamak-relevant high B-field

Liquid surface substrate design Study feed, drain manifolds

Thermal limits Study eroion and corrosion lifetime

Engineering design margin Study T retention/migration

Impurity control and cleanup IFMIF to test substrate material

Plasma performance modifications Study impurity control and cleanup

PFC Matrix Example 3

PFC Gaps: To Develop Understanding for the Construction of Robust PFC Components

Existing/Upgraded Confinement Facilities

Tritium in solid, mix materials

Tritium permeation/migration Validate understanding of tritium

transport and inventory on PFC materials

Materials/irradiation Experiments with innovative and

irradiated PFC materials

Safety limits Testing of tritium diagnostics

Accountancy Develop and test permeation barriers

Test interface joining materials, initiate

material qualification

PFC Matrix Example 4

PFC Gaps: To Develop Understanding for the Construction of Robust PFC Components

Theory & Modeling

Innovations:

Advanced structural materials Model advanced materials: SiC/SiC, refractory alloys (e.g. W, Mo..)

Surface materials innovation Model C, B coating and BW-surface

Advanced heat removal designs Model new innovative heat removal proposals, e.g. liquid metal heatpipes

Potential PFC panel recommended Research Thrusts, version 5, 2/19/09

Small Medium Large

1. Liquid surface options 1,3,5,4 2,6*

2. W surface option 2,3,6,1,4

3. Helium heat transfer 1,2,8,5

4. PFC diagnostics

development

1,2,3,8,5,4 6*

5. Existing/Upgraded/New

Test Stands: He-

loops, heat flux,

materials

2 1,3,8,5,4

6. New confinement

facility (Does it need

to be DT?)

1,3,8,5,6,4

7. Upgrade existing

confinement device

for hot walls

3,6,4

8. Modeling for predictive

capability

1,6,4

Very rough range: Small $2-3 M, medium $10-30 M, large ~$100M per year

*Some of the research thrusts could cost in the small scale but they will need a medium

cost device to work on or demonstrate

1. Wong, 2. Majeski, 3. Doerner, 4. Merrill, 5. Milora, 6. Leonard, 7 Lipschultz ,8. Youchison

Conclusions• We have identified that with presently available materials for ITER water cooled PFC

components are already pushed to the edge of acceptable performance

• When extended to DEMO with RAFM steel as structural material and He as the coolant, disruptions will have to be avoided and ELMs will have to be mitigated or eliminated. Generation of robust PFC design will be a significant challenge, and could be by itself a major Research Thrust.

• Requirements and issues for physics, solid and liquid surface design, heat transfer and components testing and analysis, tritium, safety and RAMI, PFC surface material, maintenance, RAMI and development program areas have been identified.

• Innovative approaches on structural material, PFC material and heat removal will be needed

• A PFC matrix and a first collection of research thrust have been generated.

• We will continue to assess research thrust as a tool to meet our goal of have robust DEMO PFC components.

PFC remains a Greenwald Priority Tier 1 area: solution not in hand,

major extrapolation from current state of knowledge, need for qualitative

improvements and substantial development for both short and long term