Structural and PFC materials for liquid metal concepts · • Introduction – the problem of power exhaust: why study liquid metals in a tokamak environment? • LM experiments in

1M. Iafrati

With contribution by1M. L. Apicella, 2S. Bassini, 2S. Cataldo, 𝟏R. De Luca, 𝟏G. Dose, 𝟑J. P. S. Loureiro, 1 G. Mazzitelli, 𝟒G. F. Nallo, 𝟓P. Rindt, 𝟏S. Roccella

Structural and PFC materials for liquid

metal concepts

6th IAEA DEMO Programme Workshop (DPWS-6) -- October 1-4, 2019

1ENEA-C.R. Frascati, Via E. Fermi 45, 00044 Frascati, RM, Italy3 IPFN, IST, Universidade de Lisboa, 1049-001 Lisboa, Portugal5 Eindhoven University of Technology & DIFFER, Netherlands

This work has been partially carried out within the framework of the EUROfusion

Consortium and has received funding from the Euratom research and training

programme 2014-2018 under grant agreement No 633053. The viewsand opinions

expressed herein do not necessarily reflect those of the European Commission.

2ENEA−C.R. Brasimone, Loc. Brasimone, Camugnano 40032 Bo, Italy4 NEMO Group, Dipartimento Energia, Politecnico di Torino ltaly

Outline

• Introduction– the problem of power exhaust: why study liquid metals in a tokamak environment?

• LM experiments in the world– Analysis of different approaches (i.e. flowing vs static)

• Materials for the liquid PFC design– Retention, evaporation and plasma compatibility, corrosion, cooling

• Proposal for a Liquid Metal Divertor (LMD)– Two WP-DTT1-LMD proposal

• Conclusion

2DPWS-6 Moscow -- October 1-4, 2019





• Conclusion


Introduction: power exhaust challenge

4

One of the main challenges in the European fusion roadmap is to design a power exhaust system able

to withstand the large loads expected in the divertor of a future fusion power plant.

“A reliable solution to the problem of heat exhaust is probably the main challenge towards the realization of

magnetic confinement fusion.”Roadmap to Fusion Electricity - EFDA November 2012

Actual strategy:

• development of plasma facing components

• selection of the divertor geometry and of the

magnetic flux expansion

• removal of plasma energy before it reaches the

target via impurity radiation

• recycling and increase of density, lowering the

temperature close to the target -> detached regime

DPWS-6 Moscow -- October 1-4, 2019

Introduction: EU Roadmap to Fusion Electricity

• As risk mitigation strategy

advanced materials are

under study

• LMs are also included

• WP-DTT1-LMD is devoted

to the Liquid Metal Divertor

development

5

Alternative and

advanced PFCs

solutions


Introduction - Motivations

• Liquid Metals (LM) are self-healing/renewable plasma-facing

material

• LMs are less sensitive/immune to the neutron damage

• LM can be considered a long lifetime plasma-facing

component

• Vapour shielding effect against (e.g. fast transient) increasing

heat load

6

Why study liquid metals in a tokamak environment?


Introduction: Liquid metals in Tokamaks

7

Many subsystems need to be combined to an

integrated component

Cooling system

Structural

materials

Liquid metal

confinement

Safety

Plasma

scenarioClosed loop

Integrated

PFC


Introduction: about the LM choice (Li and Sn)

8

Most relevant LMs and their vapour pressure


• The evaporative flux is one

of the main issue for the

steady state operation

[J.W. Coenen et al.

Phys. Scr. T159

(2014) 014037]




• Proposal for a Liquid Metal Divertor (LMD)

• Conclusion


LM experiments: possible approaches

10

LMs in a fusion reactor, flowing or not flowing?

Flowing Static


Flowing LM approach

• LM could remove heat load and particles

• Many experiments:

– Gallium Jet (ISTTOK)

– LiMIT concept (HT-7, EAST, Magnum-PSI and LTX)

– Flili EAST

• Free cascade vs confined metal flow

11

Several approaches


Flowing LM – Ga jet proposal

12

Liquid-metal tokamak divertorsS.V.Mirnov et al. 1992, J. Nuc. Mat.

Liquid metal sheet possible scheme: (a) and

jet-drop curtain (b) divertor plates.

Principal scheme of the

jet-drop shaper


Flowing LM – Ga jet in ISTTOK

13

Gallium droplets appearing during

plasma–liquid metal interaction

Liquid gallium jet with the ISTTOK edge plasmaR. Gomes et al., FED 2008


Flowing LM – FLiLi experiment in EAST

14

FLiLi limiter in EAST tokamak (a). SoF DC current OFF

(b). SoF 20 A DC current

(c). EoF 20 A DC current

Experiments with the flowing lithium limiter in EAST Hu J.S.et al., Nuc. Mat. and Energy, 2019


Flowing LM – FLiLi experiment in EAST

15

Comparison of the SS foil surface:

a. after the 2014 experiment → 1st FLiLi limiter

b. after the 2016 experiment → 2nd FLiLi limiter


Flowing LM - LiMIT

16

LiMIT Lithium Metal Infused TrenchesD. Ruzic et al., NF 2011

P. Fiflis et al., NF 2015

LiMIT was tested in the linear

plasma simulator, Magnum

PSI, at heat fluxes of up to 3

MW m−2. Comparisons to

predictions, both analytical and

modelled, are made and show

reasonable agreement.


Static LM approach

Vapor box

17

Take it static


- Heat delivered out of the plasma‐ Evaporation of many l/s required (Li?)‐ Plasma formation on isolated chambers?‐ Alignment issues‐ First wall protection?

CPS-basedCapillary Porous System

‐ Particle and power exhaust‐ Plasma Contamination‐ Material lifetime‐ Neutron activation‐ Target compatibility

Static LM - Vapour boxes

18

Vapour box solution


o Heat exhaust via plasma-

vapor interactions;

o Multiple chambers in Li

vapor-box divertor;

o Large density in lower

boxes, passive differential

pumping in higher boxes.

[Nagayama Y., Fus. Eng. Des. 84 (2009)]: [Goldston R. et al., Nuc. Mat. En. 12 (2017)]:

o Heat exhaust via

latent heat in pool-

type LM divertor;

o Evaporation

chamber (EC)

contains the pool;

o Differential chamber

(DC) intended for

metal vapor and

impurity pumping.

Slide with courtesy of G. F. Nallo

Static LM - New LM confinement strategy


Experiments on T10S.Mirnov et al.

• Confine the LM in a felt

• Close the loop using the emitter-

collector strategy

Static LM - Capillary Pore System - CPS

20

Capillary pressure can prevent splashing and droplet formation


Static LM - CPS withstands high transient heat load

21DPWS-6 Moscow -- October 1-4, 2019 Evtikhin V et al., 2002, Plasma Phys Control Fusion, 44, 955

Li-filled CPS structure: 22 plasma pulses of 4 MJ/m2 and 0.2-0.5 ms duration in a QSPA

Unexposed Exposed w/o Li Exposed with Li

Static LM - Liquid Lithium Limiter

Main aim was to verify the liquid metal compatibility in a tokamak using the CPS in order to

avoid droplets formation and the lithium impact on plasma performances.

22

Since 2006 experiments with LMs have been performed on FTU using CPS


Static LM - Liquid Tin Limiter

• Very flexible and versatile

layout: in principle the

limiter head can be easily

changed

• At high temperature tin is

very corrosive: the liquid

tin limiter layout prevents

copper corrosion

23

A liquid tin limiter has been used for the first time in a tokamak

According with the vapor pressure, tin allow a wide temperature operational window


Static LM - The first LMD?


Li CPS divertor for the Kazakhstan Tokamak - KTM

• Actively NaK cooled

• Adjustable targets

To be tested

Static LM – Li Divertor test in COMPASS

25

Plans for Liquid Metal Divertor in Tokamak CompassJ. Horacek et al., Plasma Physics Reports, 2018, Vol. 44, No. 7, pp. 652–656


Tokamak COMPASS allows testing the liquid

metal divertor concept under ITER relevant

heat fluxes in H-mode with Type-I ELMs

Flowing vs Static – brief summary

26

Flowing


PROS :• Simplicity• No splashing issues• Flexible (choice of geometry, LM)• Small quantities of LM• Concept maturity

CONS:• Heat load must be exhausted by

coolant - Need of a solid support• No particle pumping

PROS:• Active removal of particles and heat loads• Protection of Divertor and FW• Possible shielding vs fusion neutrons

(thick layer)• Possible T breeding

CONS:• Splashing• Need external recycling for T recovery• Flow instabilities

Static





• Conclusion


Material for the LMD design: retention

28

Lithium retention


High retention for low

temperature liquid lithium

Baldwin et al., NF, V42, 2002

• Several investigations has demonstrated that hydrogenic retention on liquid

lithium starts ceasing above T=500ºC. [Oyarzabal et al.]

• The observed effects allow to be optimistic about this phenomenon that

appears as a key problem within the tritium inventory limitation issues.[Alfonso de Castro Calles – Ph.D. Thesis]

Material for the LMD design: retention

29

Tin retention


Tin sample exposed in GyM facility (1024 ions 𝑚−2) has

been analysed by ion beams in the IPFN in Lisbon:

D concentration of 0.18at% has been detected only

in the first few hundreds nm of the sample surface.

• The result from the previous sample has been confirmed

• The magnitude in deuterium retention for the analyzed range of fluences

remains in the same range.

There is no evidence of

the time decay

phenomena in term of

deuterium content, at

least for the time scale

considered

Tin retention experiment from Jülich and DIFFER indicate more detailed analysis are needed.





• Conclusion


Material for the LMD design: plasma pollution

31

When evaporation becomes dominant the UV

spectrum is dominated by Li or Sn lines. From

the Zeff measurements we can respectively

infer a concentration of

MoFe

O

Li

Sn

𝑛𝐿𝑖𝑛𝑒

≈ 1 ∙ 10−2

𝑛𝑆𝑛𝑛𝑒

≈ 5 ∙ 10−4

Li

Sn


Results from FTU

Material for the LMD design: plasma performances

32

Confinement time from JETTO simulation

on FTU pulses.

Starting from the bottom:

• Metals dominating spectra (Mo, Fe, O)

• Tin main impurity after many shots with

tin limiter

• Lithium main impurity after the

“lithization campaign”

• After a fresh boronization


The liquid metal choice will depend

on the plasma scenario





• Conclusion


Material for the LMD design: corrosion


1200°C

Material for the LMD design: corrosion


Structural

material

compatibility

with fusion

relevant LMs

LMs are extremely

corrosive at high

temperature

F. Tabares on behalf of the ISLA International Committee

?X ?

??

X

Material for the LMD design: anticorrosion layer


Material for the LMD design: anticorrosion layer


SEM-EDS analysis on Pristine coating

200 µm 50 µm

Elmt Wt% At%

O 44.21 57.20

Al 55.79 42.80

Elmt Wt% At%

Mo 01.43 00.83

Cr 09.48 10.17

Fe 89.09 89.00

Al2O3 layer appears homogeneous and uniform

It is up to 90 µm thick, very compact and with low porosity

SEM micrographs EDS analysis

Courtesy of S. Cataldo





• Conclusion


Cooling the static LM PFC


We need “low” surface temperature to avoid evaporation,

particularly if lithium is used

Thermal resistance, 𝑅𝑡 , is a key parameter. At the steady state we can consider:

𝑄 =𝑇𝑠𝑢𝑟𝑓 − 𝑇𝑐𝑜𝑜𝑙𝑎𝑛𝑡

𝑅𝑡

• LM allow to reduce the thickness O(mm) -> lower 𝑅𝑡• Different cooling system are under study

Cooling the static LM PFC: liquid vs gas

40

Liquid


Gas

PROS :• Safety (?)• High thermal efficiency of the

power conversion systems

CONS:• Relatively low SF - limited CHF• Low convective heat transfer

coefficient • Advanced engineering solution

PROS:• High achievable CHF • Assessed technology• Ideally “low” surface temperature

CONS:• Coolant activation• Water leak can be dangerous if Li is used

P. Norajitra et al., NF 2005


Cooling the static LM PFC: tin based divertor


Water has been chosen due to high remove heat

capability. Practical question for the developing

of a tin based PFC:

It is possible to keep tin below the limit of 1300°C

with Incident Heat Flux (IHF) of 20 MW/m2 ?

The main issue is to prevent the

critical heat flux (CHF)





• Conclusion


Flowing LM - Sn based LMD → See Poster P08

43

The second concept from WPLMD uses gravity

driven Sn flow through a CPS.

This approach…

• Is needed because the required height of

700 mm is too high for a static liquid column.

• Makes sure all leading edges are avoided.

• And allows for easier re-wetting of the PFS

in case of dry-out.

steel bath

3D-printed

texturegra

vit

y d

rive

n

flo

w

PLASMA

cooling

channelsDesigned by Peter Rindt – Eindhoven University of Technology & DIFFER, Netherlands


Proposal for a Liquid Metal Divertor


• The elementary liquid metal units can fit the

standard DEMO cassette scheme.

Each liquid metal elementary unit should be

provided by:

• Coolant

• LM reservoir and refill line

• Heating system

• Anti-corrosion layer

Proposal for a Liquid Metal Divertor


Water hydraulic parameters

Tbulk = 140°C

p= 5 MPa

v= 12m/s

Gas temperature

T = 350°C

Proposal for a LMD – Thermal analysis


Heat flux = 10 MW/m2 Heat flux = 20 MW/m2

In both cases evaporation is negligible because the CPS surface temperature is “low”

Summary of the proposed LMD


All the requirements for the PFU are fulfil:

1. “Acceptable” operational range for CuCrZr

2. Acceptable operational range for EUROFER

3. Acceptable operational range for Tin

4. Acceptable CHF margin (1.4 ITER CHF Margin)

Copper would not be low activation, but the relatively small volume of waste arising from the target

plates is taken to be acceptably low.T. R. Barrett, et al, 2016.

In this component there is 75% more Copper than in the ITER- like reference

design

LMD proposal: W70%-Cu30% advanced material


W MonoblockDEMO (yes swirl)

Tbulk = 120°Cv = 12 m/sp = 40 bar

Dint = 12 mm↓

CHF 45.3 MW/m2

↓CHF incident

on the PFC (fp = 1.7)

26.8 MW/m2

CHF Margin1.33

LMD (CuCrZr)(yes swirl)

Tbulk = 140 °Cv = 12 m/sp = 50 bar

Dint = 8 mm↓

CHF 40 MW/m2

↓CHF incident


28.5 MW/m2

CHF Margin1.42

LMD (W-Cu)(yes swirl)

Tbulk = 120 °Cv = 12 m/sp = 50 bar

Dint = 8 mm↓

CHF 46 MW/m2

↓CHF incident


32.6 MW/m2

CHF Margin1.6

LMD Mock-up under construction for tests in LDs


Experiments are needed

A small mock-up will be ready

within few months to be tested

in linear plasma devices.

Divertor Tokamak Test Facility

50

DTT Objectives

The DTT facility will test the physics and

technology of various alternative divertor

concepts under conditions that can

confidently be extrapolated to DEMO.

First wall

• Cooled replaceable W coating panels

• Working temperature 300°C

Standard W divertor

• compatible with advanced magnetic

configurations

A liquid metal module divertor is under design.





• Conclusion


Conclusion


• LM seem a viable solution for the power exhaust problem

• The experiments are supporting the LM as mitigation risk solution

• The LM community is growing

Future work

• Validate the LM divertor concept design in linear devices as foreseen

from the WP-DTT1-LMD

• Test the LM divertor in a real integrated scenario: COMPASS-U, DTT?

6th INTERNATIONAL SYMPOSIUM ON LIQUID METALS APPLICATIONS FOR FUSION (ISLA-6) University of Illinois, Urbana-Champaign, Illinois, USA

September 30 – October 3, 2019.

Thank you for your attention


Liquid metals as Plasma Facing Material

• T-3, T-11 performed experiments with liquid Ga at the beginning of the Russian (and worldwide) program. Flowing gallium limiter

was used and successful tested in T-3. The gallium curtain limiter performances have been compared with that from a graphite

limiter.

• T-11M, T-10 operated with CPS based liquid lithium limiters for many hundreds shot; lithium collector concept has been tested,

some experiments have been performed with cryogenic collector as well

• T-15MD foreseen experiments are planed for the oncoming Russian upgraded tokamak.

• ISTTOK used a gallium jet limiter; H trapping and saturation effect have been studied. Recently a manipulator if available for small

liquid metal surface exposure experiments; system improvements and CPS exposition are foreseen.

• TJ-II exposed a CPS-LLL with positive or negative bias to the plasma; devoted experiments on recycling have been performed. The

eutectic allow Sn-Li has been exposed too.

• HT-7 deployed two flowing lithium modules developed by US researchers plus other ways to expose liquid Li to plasmas. Free Li

surfaces produced high Li emission. Many shots disrupted likely from JxB induced droplet. HT-7 operated also with modular CPS-

LLL, developed by Russian researchers.

• CDXU the 1st tokamak operated with a large area of liquid Li. It used heated SS trays as a floor limiter filled from an injector nozzle.

Earlier experiments had a mesh-covered rail limiter fed with Li by a tube.

54

Brief list of LMs experiments around the world [1/2]

For more information see:

R.E.Nygren, F.L.Tabarés

Nuclear Materials and Energy

Volume 9, December 2016, Pages 6-21DPWS-6 Moscow -- October 1-4, 2019

Liquid metals as Plasma Facing Material

• LTX the only device in the world with fully covered liquid lithium wall, the results on confinement are extremely encouraging.

• NSTX operated with the Liquid Lithium Divertor (LLD). It was coated using two previously developed LITER Li evaporators. The

upgraded NSTX-U plans to install a new dedicated CPS based LLD.

• EAST used Li injection for ELM control and various methods to expose liquid Li to the plasma, i.e. the liquid flowing lithium

experiment also used to evaporate lithium for wall conditioning purpose.

• KTM the Kazakhstan tokamak is still not in operation. It is equipped by a CPS divertor module cooled with the liquid allow Na-K.

Hopefully it will confirm the reliable operation over temperature range of 20 -- 200 °C.

• RFX-mod studied the electron density control using Li evaporation to cover the graphite wall before the discharges or injection of

single or multi-pellets. CPS module like the one used in FTU operated in the RFP.

• FTU started worked with CPS based lithium limiter inertially cooled, tested the water-cooled liquid lithium limiter. It is the first

tokamak in the word, unique up to now, has used a liquid tin limiter.

• GyM it is a linear plasma device, the tests performed until now include liquid metals exposure to plasma in order to characterize the

retention.

• Magnum-PSI linear plasma machine deeply involved in the liquid metals' experiments. A lot of interesting feature are studied in

such device, i.e. vapour shields, heat removal capability, PFCs plasma compatibility.

55

Brief list of LMs experiments around the world [2/2]


For more information see:

R.E.Nygren, F.L.Tabarés

Nuclear Materials and Energy

Volume 9, December 2016, Pages 6-21

BACK-UP Slides


Introduction: Liquid metals in Tokamaks

We need to:

– Confine the LM

– Power removal

– Provide the LM refill if needed

– Provide safety (in case of lithium)

– Find out the proper plasma scenario (i.e. high or low

evaporation regime, closed loop)

57

LMs in a fusion reactor?


Liquid metals in Tokamaks


• Comparable heat flux handling capability in steady state

• Resilience to transients• Self-healing surface

Material constraints analysis for the LMs solution

59

From concept to the material and structural choice


[1] G. G. van Eden et al., ISLA 2017

[2] G.G. van Eden et al., Nature Communications, 2017

[3] A. Vertkov et al., preprint for the 2018 IAEA FEC

conference

[4] G. Mazzitelli et al., internal report for WPDTT1-LMD

substrate

[2]

LM-filled capillary-porous structure (CPS):o Prevents droplet ejectiono Provides passive surface

replenishment

ENEA design of Sn divertor moduleo Water cooling for plasma-

facing surfaceo Gas heating for LM

reservoir

TRINITI (RF) design of Li divertoro Water spray coolingo Thin plasma-facing

surface

Material constraints analysis for the LMs solution


Incoming plasma

flux

Evaporation

Multiphysics problem: tight coupling between SOL

plasma and target conditions

• Li/Sn emissiono Physical sputteringo Temperature-enhanced

sputteringo Evaporation

• Plasma-vapor interactions → plasma coolingo Li ionizationo Line radiationo Bremsstrahlung

• Other phenomena (surface physics/chemistry)o LiD formation if T<500C → T retentiono Sn can corrode CPS mesh materialo Li can react with water coolant in case of leaks

e-e- e-

[1] T. Abrams, Ph.D. thesis, Princeton (2015)[2] G. F. Nallo, G. Mazzitelli, L. Savoldi, F. Subba, R. Zanino, Nucl. Fus. 59 (2019) 066020

Surface metal choice

LM target model development strategy


[1] J. H. You et al., Fus. Eng. Des. 109-111, pp.1598-1603 (2016)

Sn

Poloidal

direction

Toroidal

direction

(take into

account

enthalpy of

replenishing

LM)

Li

• 2D model (FE)

• Material constraints

• Effect of particular

divertor design can

be considered

• HTC specified at

coolant pipe

boundary

Courtesy of G. F. Nallo

Static LM - LM choice impact on the VB solution

62

Vapour box solution


No-Corona Cooling rate for Li and Sn

Courtesy of G. F. Nallo

• Li• High evaporation rate

• Relatively benign to core plasma

• Radiative loss function 𝐿𝑧 strongly dependent on plasma

electron temperature 𝑇𝑒 and particle dwell time 𝜏

• Sn:• Lower evaporation rate

• BUT stronger effect, should it reach the core plasma

• For a LM divertor:• Non-coronal radiation and evaporation/condensation can

be exploited to spread the localized plasma load on a larger

surface (chamber walls) if confined in the divertor region

• But excessive metal vapor efflux would contaminate the core

plasma

Choice of LM

is not straightforward

CHF: Water performance as coolant


Flexible divertor: liquid alternative

64

As regarding liquid metals divertor, the first hypothesis is to design a divertor

by using the capillary technology…But we are even thinking

quite different solutions,

like the possibilities to

have liquid metal pool

and vapor confinement

by “boxes” of liquid

metal.

R. Zanino et al., «2D self-consistent

modelling of a box-type liquid metal

divertor for the DTT facility»DPWS-6 Moscow -- October 1-4, 2019

LMs overview


FTU and the liquid metal limiters

Immagine FTU• Compact high magnetic field

device:

𝐵𝑡 ≤ 8T, 𝐼𝑝 ≤ 1,6MA

• R = 0,935 m

• a = 0,335 m

• Fully metallic circular limiter

machine:

- vacuum vessel (SS)

- toroidal limiter (TZM)

- poloidal limiter (TZM)

- liquid metal limiter (Li or Sn)


The liquid metal limiters during the FTU pulse

67

LiUp to 1.5cm

from the LCMS

SnClosed the

LCMS


Fast IR-Camera: temperature evolution

68

LiSn

Sn

Li


Tin surface temperature simulation with ANSYS


Explored temperature window

70

• The difference, after 1s, between ANSYS calculation and experimental surface

temperature could be explained by “vapour shield” phenomena.

2𝑀𝑊/𝑚2

18𝑀𝑊/𝑚2

LiSn


Liquid Tin corrosion of on W wire

Weight and surface morphology after treatment @1000°C, 200 h

71

# PRISTINE TREATED DIFFERENCE

[mg] [mg] [mg]

31 78,56 78,54 -0,02

32 73,92 73,98 0,06

33 73,34 73,33 -0,01

34 71,80 71,83 0,03

35 78,44 78,45 0,01

36 76,33 76,33 0,00

37 73,44 73,40 -0,04

38 74,50 74,50 0,00

39 80,13 80,13 0,00

40 72,96 72,96 0,00

41 76,87 76,84 -0,03

42 75,99 75,99 0,00

MEAN 75,52 75,52 0,00

Samples masses are practically unchanged before and

after corrosion treatment.

The weigh difference is well in the error range of the scale

W

Residual

Sn

W and Sn do not combine,

surface appears straight with no

sign of corrosion

Cleaned sample

350 µm350 µm


Flowing LM - Sn based LMD

72

The cooling channels are made out of W/Cu and

have a 3D-printed W CPS armor. The armor thickness is chosen because:

• In normal steady-state operation 2

mm W/Sn armor is thin enough to

keep 𝑇 < 1250 °𝐶, the evaporation

limit.

• In off-normal operation, 2 mm armor

is thick enough to cause vapor

shielding before the coolant critical

heat flux (CHF) is reached.

Designed by Peter Rindt – Eindhoven University of Technology & DIFFER, Netherlands

180 oC

150 Bar

Water

3D-printed W

texture soaked

in liquid tin.

W- corrosion

barrier

W-reinforced

copper pipe

2 mm

10 mm

10 mm


Flowing LM - Sn based LMD

73

Operational limits exceed those of the tungsten MBs

Designed by Peter Rindt – Eindhoven University of Technology & DIFFER, Netherlands

An FEM analysis, taking into account vapor shielding shows:

• Up to ~24 MW/m2 allowed in steady state

– Onset of nucleate boiling and evaporation limit are reached.

– ~17 MW/m2 with SF of 1.4.

• Up to ~60 MW/m2 allowed during slow transients,

– CHF of the water is reached.

Surviving disruptions is uncertain… but plausible.


Documents

Structural and PFC materials for liquid metal concepts · • Introduction – the problem of power exhaust: why study liquid metals in a tokamak environment? • LM experiments in