Liquid Metal coolants for high power heat transport systems

P. Hosemann,

Contribution from:

David Frazer; Cristian Cionea; Stephen Parker; C. Rose Miroslav Popovic; Ouliana Panova; Mark Asta;

University of California Berkeley

M. De Caro, S.A. Maloy, F. Rubio

Los Alamos National Laboratory

K. Lambrinou SCK CEN

MatISSE/JPNM workshop Nov 25th 2015

OUTLINE

•Introduction; Engineering applications utilizing liquid metals. •Introduction; Selected issues using heavy liquid metals. •Results on stainless steel in static and flowing Lead Bismuth Eutectic at medium temperature •Results of Fe-Cr-Al steels in flowing and static LM at medium and high temperature. •Evaluating the adhesion of oxides on the substrate. •Experimental approach on evaluating the effects of radiation on corrosion.

•Summary

Why Liquid metal technology

Issues with liquid metal technology

LIQUID METAL COOLED POWER SYSTEMS

NUCLEAR FISSION POWER SOLAR CONCENTRATING POWER (CSP)

~0 carbon emission Advanced reactors can close the nuclear fuel cycle and reduce the urge for nuclear fuel storage High power density.

~0 carbon emission Large scale plants feasible (Ivanpah plan in CA) ~130MW/unit

• Fast neutrons • High neutron yield in ADS or spallation

sources • Good thermal properties • Low melting point • High boiling point • Cost effective • Low viscosity

• Good thermal properties • Low melting point • High boiling point • Costs effective • Low viscosity

LM AS FILLER FOR FUEL RODS

Conventional UO2 and He gap have limited thermal properties leading to very high temperatures in the fuel centerline. Other fuel concepts might be considered bypassing some of these issues.

pellet stack

Cladding

He LM

Spring He

gap

UO2 U-ZrH1.6

Conventional fuel rod

Proposed fuel rod

D. Olander, M. Balooch, K. Terrani, P. Hosemann

hydride hydride oxide

characteristic He bond LM bond He bond

pellet OD, mm 10 10 10

LHR, W/cm 375 375 375

fuel centerline, oC 680 555 1505

Tfuel 170 170 995

Tgap (35 m) oC 125 1 125

Tclad oC 46 46 46

Tfluid oC 39 39 39

coolant, oC 300 300 300

OTHER LIQUID METAL APPLICATIONS

NUCLEAR FUSION POWER

Good thermal properties Low melting point High boiling point Fire hazard of Li can be reduced Tritium breeding See Konys talk

ADDITIONAL TECHNOLOGICAL APPLICATIONS OF LIQUID METALS

Liquid metal used to obtain plasma for EUV light

Well controlled cooling rate for gas turbine blades

A. Kermanpur MSE-B 2000

AJ. M. Algots lithography 2005

LIQUID METALS IN NUCLEAR APPLICATIONS

LM’s in nuclear applications have been well established.

Staring in the 50’s several liquid lead bismuth cooled submarines were build

and commissioned

Clementine reactor first fast reactor 1946-1949 Los Alamos, Mercury cooled 25kW

Several sodium cooled reactors have been realized

BOR 60

BN 600

WHY NEW CSP HEAT TRANSPORT FLUIDS?

• Power transported in CSP is f(T,cp,V/t)

• Hydrogen production and process heat generation requires high temperatures.

• High temperatures and high cp allow for thermal storage over night.

Push the temperature, of the solar

concentrator units to >700C! New heat transport fluids are required and proposed Liquid Salt currently temp limited 100 - 550°C nitrate salts Fluoride salts 450 - 1000C Liquid metal 100C ->1000C

Many liquid metals have a low melting point

Liquid metals have excellent heat conduction

Liquid metals have low viscosity

Many decades of experience with various liquid

metals for other applications.

Large facilities have been build and

successfully operated in the past

REVIEW OF POSSIBLE ELEMENTS FOR LM IN CSP Melting point, cost, toxicity, boiling points

Na, K, Mg, Ca, Cu, Zn, Al, Sn, Pb, Sb, Bi

Based on cost, melting temperature and non-toxicity:

Melting point below 350oC Melting point above 350oC

Group 1

Group 2

LIGHT AND HEAVY LIQUID METALS

Group 1 light elements: Large scale facilities have been realized. (Na) Low melting point. Little corrosion issues High vapor pressure at high temperatures. REACTIVE! Group 2 heavy elements: Large scale facilities have been realized Low melting point (with alloying) Not reactive with water Low vapor pressure Corrosion issues exist!!

Almeria solar plant accident, Spain!!

Monju NPP

Thorium NPP India 500MW 2014

Russian alpha class submarines; MHYRRA reactor Belgium

WHAT ARE THE CORROSION ISSUES IN HEAVY METALS (EXAMPLE LBE)? DISSOLUTION

Many metals have a solubility in many heavy liquids. In loop systems, this leads to enhance and uncontrolled corrosion if steps are not taken to prevent it.

-4

-3.5

-3

-2.5

-2

-1.5

-1

-0.5

0

0.5

1

0 500 1000 1500

Fe

Cr

Ni

Temperature [°C]

Lo

g C

S [

wt%

]

-4

-3.5

-3

-2.5

-2

-1.5

-1

-0.5

0

0.5

1

0 500 1000 1500

Fe

Cr

Ni

Material testing

temperature range

Loop saturated with corrosion products cannot

work due to the temperature gradient in the

loop!

WHAT ARE THE CORROSION ISSUES IN HEAVY METALS ? FORMATION OF NEW PHASES

Fe-Cr-Ni in Pb and Bi

Fe-Pb Cr-Pb Ni-Pb

Fe-Bi Cr-Bi Ni-Bi

Pb and Bi form few intermetallic phases with steel elements only solubility issues

ASM phase diagram database

Fe-Sn Cr-Sn Ni-Sn

Fe-Zn Cr-Zn Ni-Zn

WHAT ARE THE CORROSION ISSUES IN HEAVY METALS ? FORMATION OF NEW PHASES

Sn and Zn form a large number of intermetallic phases High corrosion rates may be anticipated danger of clogging due to high temp melting phases

ASM phase diagram database

CORROSION MITIGATION STRATEGY

-8

-7

-6

-5

-4

-3

-2

-1

0

1

0 500 1000 1500 2000

Temperature [K]

Lo

g (

CS)[

wt%

]

Melting point of Pb

Melting point of LBE

Loop operating range

Addition of oxygen allows the formation of a protective film

Not sufficient oxygen available to form an Fe3O4 layer

Fully saturated LBE More oxygen is not soluble

CONSIDERATIONS FOR OPTIMAL OXYGEN CONTENT

D. Frazer, E. Stergar, C. Cionea, P. Hosemann; SolarPACES 2013, energy procedia

Detailed experiments in LBE

LBE corrosion automatic control 700°C 250h

CORROSION TESTING OF CANDIDATE MATERIALS in static envrionment

Static corrosion testing Example UCB

Flowing corrosion testing Example LANL

DELTA Loop

PREVIOUS EXPERIENCE WITH AUSTENTITCS STAINLESS STEEL 3000h AT 550C (FLOWING) IN LBE (SEM)

TEM sample

location prepared

by FIB

EDX Line scan

D9 3000 hr (duplex oxide) all elements

0

10

20

30

40

50

60

70

80

0 5 10 15 20 25 30 35 40

um

wt%

Iron

Silicon

Oxygen

Manganese

Nickel

Chromium

Composition [wt%]

3000h sample

Outer oxide

layer

Inner oxide

layer

Steel

Ni

Cr

O

Fe

others

Composition: Cr 13.5-14.5 %, Ni:14.5-15.5% , Mo 2%, Mn 1.65-2.35%, Si:0.5 -0.75% , C 0.035 - 0.05% P. Hosemann, R Dickerson, P Dickerson, N Li, SA Maloy, Transmission Electron Microscopy (TEM) on Oxide Layers formed on D9 stainless steel in Lead Bismuth Eutectic (LBE), Corr Scie. 66, (2013), 196–202

• Results on D9

Steel

Inner layer 4

Outer Layer 2

Outer Layer 1 Surface

Row 6

Row 7

Row 8

Row 9

Row 10

Row 11

Row 12

Row 13

8.2

pores

indents

-50nm

50nm Height scale

Row 2

Row 3

Row 4

Row 5

Row 6

Row 7

Row 8

Row 9

11.5

Steel

Steel

Inner layer 4

Inner layer 3

Outer layer 2

Outer layer 1

-8.7V

8.7 V

Magnetic signal scale

0nm

Outer layer 1

Outer layer 2

Inner layer 3

Inner layer 4

Outer layer 1

Outer layer 2

Inner layer 3

Inner layer 4 -25 nm

25 nm 2V

-2V

AFM MFM MEASUREMENTS ON D9 3000h, 550C, 10-6wt% O2

S-TEM & APT ON D9 OXIDE LAYERS

Inner layer Outer layer

Intermediate

layer

500nm 2m

Cr rich phase

200nm

50nm 200nm

P. Hosemann et al. Corr Science 66, (2013), 196–202

N. Bailey, A. Reichard., P. Hosemann unpublished

Yellow – Oxygen Red – Chromium Blue – Nickel

SIMILAR STRUCTURES ON OTHER AUSTENITIC STEELS 316l (3000h, 550C, 10-6wt% IPPE LOOP

STEM AFM

C-AFM

MATERIALS TESTING AT 700°C FOR 300h at 10-5wt% OXYGEN (STATIC) 316l

O Cr

Fe Ni

Pb Bi LBE penetration follows the

oxide penetration.

Fast diffusion at high temperature.

rapid progress of LM

penetration

SEM/EDX ON FERRITIC STEELS HT-9 (0.1C, 8.3Cr, 0.43Si, 0.95Mo) 3000h 550C, 10-6wt% (IPPE LOOP)

Back scattered SEM image (a) and EDX mapping of the same

location on HT-9 exposed to 550C LBE for 3000h.

TEM ON OXIDE LAYERS FORMED ON HT-9

0

2000

4000

6000

8000

1 104

1.2 104

1.4 104

0 5 10-8

1 10-7

1.5 10-7

2 10-7

Cr-K

Ni-KO-K

Fe-K

Cou

nts

Distance [nm]

0

1000

2000

3000

4000

5000

6000

7000

8000

0 5 10-8

1 10-7

1.5 10-7

2 10-7

Cr-K

Si-K

O-KFe-K

Co

un

ts

Distance [m]

0

2000

4000

6000

8000

1 104

0 200 400 600 800 1000 1200 1400 1600

Cr KSi K

O KFe K

C KNi K

Coun

tsDistance [nm]

0

1000

2000

3000

4000

5000

6000

0 10 20 30 40 50

Cr KSi K

O K

Fe K C K

Ni K

Coun

ts

Dsitance [nm]

B

A

A

B

Cr Fe Si O

Cr Fe Si O

Cr Fe Si O

Cr Fe Si O

Characterization of oxide layers formed under oxygen starvation

T-EBSD

26

FIB PROCESSING ON LBE PENETRATED SAMPE; SCK SAMPLE

Standard FIB based lift out and slice and dice can be deployed in order to obtain the best location for a TEM sample. 316l, 450C, 1000h <<10-8wt%

20 m

thin foil location

(a)

5 m

0.5 m

end of LBE

penetration

deformation

twin boundaries

(d) 3 m (c)

2 m

ferritized micro-volumes between twin boundaries

(b) Pt strip

cavities

Orientation map Y FCC

450C 1000h IN LOW OXYGEN LBE 316l SS T-EBSD; SCK SAMPLE

Phase map (red fcc, blue bcc)

In collaboration with K. Lambrinou SCK-CEN P. Hosemann, Submitted.

59.94 degrees

Austenitic matrix (fcc)

LBE

twin boundaries

200 nm 2 m

deformation twin boundaries

Phase transformation fccbcc and LM expansion upon freezing leads to stresses and crack formation

PUSHING THE LIMIT FOR CSP SYSTEMS WITH TEMPERATURE

High temperature; >700C High Flow velocity,

High temperature corrosion even more of an issue in LM

High temperature oxidation on the air side

High temperature creep/strength issues Liquid metal creep issues?

New structural materials selection is needed

Best passivation film formation on common steels is Al containing steels Fe-Cr-Al alloys MA956, PM2000 ODS alloys with 4.5-5.5 wt%Al Kanthal steel series with 3-6wt%Al.

EXPERIMENTS ON PM2000 IN FLOWING LBE (600h, 535C°)

0

20

40

60

80

100

0 50 100 150 200 250

Cr

O

Y

Fe

Al

0

20

40

60

80

100

450 650 850 1050 1250 1450 1650 1850 2050

Cr 2p

O 1s

Y 3d

Fe 2p

Al 2s

80

60

40

20

0

100

0

10

20

30

40

50

60

70

80

90

100

450 650 850 1050 1250 1450 1650 1850 2050

Cr 2p O 1s Y 3d Fe 2p Al 2s

0 50 100 150 200 250 450 650 850 1050 1250 1450 1650 2050

The shallow Sputter Depth

Profile (SDP) and the deep

SDP using the XPS of the

material PM2000 is

presented. The oxide layer

is Al enriched and very thin

(200nm)

Composition [At.%]

Distance [nm]

The Al-alloyed ODS steel (5.5wt%Al; 20wt%Cr; 0.5wt%Y2O3) did not show any kind

of oxide layer when analyzed in cross section using SEM. Therefore a Sputter Depth

Profiling (SDP) using X Ray Photoelectron Spectroscopy (XPS) was performed to

determine the composition of the very thin oxide layer on the surface of this material.

P. Hosemann, H.T. Thau, A. L. Johnson, S. A. Maloy, N. Li, “Corrosion of ODS Steels in Lead-Bismuth-Eutectic” J. Nucl. Mat. 373, 1-3 (2008) 246-253

CORROSION TESTING OF CANDIDATE MATERIALS AT HIGH TEMPERTURE

Materials selected for corrosion testing

Sample Cr Al Fe Ni

316l 16-18 - Bal 10-14

ALK 14-16 4.3 Bal -

APM 20-23 5.8 Bal 5.8

316L steel

LBE

oxide

ALK steel

LBE

oxide

APM steel

LBE

oxide

16-18% Cr, 10-14% Ni; 14-16% Cr, 4.3% Al 20-23% Cr, 5.8% Al

Bi

O

Cr

Fe

Ni

Typical double layer was found on 316l as reported in the literature

Thin Al and O rich surface near region was formed as expected. APM has too thin of a layer to detect the passivation film

CORROSION TEST RESULTS 600°C 10-7

at% 500h

O

Cr Bi

Al

Fe

Test 4: 750°C for 200 h 10-7 wt%

316L steel

LBE

oxide

ALK steel

LBE

oxide

APM steel

LBE

oxide

CORROSION TEST RESULTS IN LBE 750°C FOR 200h 10-7wt%

Bi Al

Pb O

Fe Cr

Passivation layer formed on 316l is not protective any more under this condition. Passivation layer on Al containing steels appears to be sufficient.

STRAIN UNDERNEATH THE OXIDE LAYER AFTER COOLING THE SAMPLE STUDIED USING LAUE MICRO DIFFRACTION

Strain map

Peak shape change as a function of location

Unstrained lattice Strained lattice

inte

nsi

ty

2Θ

Kanthal ALK 700°C 500h

Flow conditions

T [C] 488

Velocity [m/s] 3.5

Oxygen concentration [wt%] 3.2 x 10-5

Samples Oxide thickness

APM 1 μm

APMT 5 μm

MA956 5 μm

EP823 10 μm

G92 10 μm

HT-9 (not polished) 20 μm

ALK14 15 μm

ALK720 10 μm

PM2000 1 μm

316L 3 μm

Alloy 8 5.5 μm

HT-9 18 μm

G92 Cross X Weld 12 μm

PM2000 (not polished) 12 μm

SiFe "A" 13 μm

SiFe"B" 20 μm

SS420 A 12 μm

Alloy 4

HIGH VELOCITY FLOW EXPERIMENT AT LANL (LBE)

The DELTA Loop

We were able to provide samples for the LANL corrosion loop

M. De Caro, S.A. Maloy, F. Rubio Los Alamos National Laboratory

0 5 10 15 20 25

APM

APMT

MA956

EP823

G92

HT-9 (not polished)

ALK14

ALK720

PM2000

316L

Alloy 4

Alloy 8

HT-9

G92 Cross X Weld

PM2000 (not polished)

SiFe "A"

SiFe"B"

SS420 A

Depth (um/1000h)

RESULTS OF HIGH VELOCITY TESTING OF VARIOUS STEELS LBE 535°C 1000h

Hi Cr and high Al alloys perform the best even at high flow velocity

Investigating the strengths of the passive layers. A parameter of mechanical adherence

MECHANICAL STABILITY OF PASSIVE LAYERS FORMED IN LBE

In-situ testing in the SEM using a Hysitron PI85 picoindenter

The PI 85 software package includes integrated test setup,

data analysis, sample positioning, and synchronization of

mechanical data with SEM video. Automated routines are also

incorporated for the tip/sample approach and for hands-off

execution of indent arrays.

PI 85 SEM PicoIndenter®

PI 85 SEM PicoIndenter

Quantitative nanomechanical testing interfaced with your SEM.

The PI 85 is a depth-sensing indenter that can be interfaced

with a scanning electron microscope (SEM). With this system

it is possible to perform quantitative nanomechanical testing

while simultaneously imaging with the SEM. Coupling these

two techniques allows the researcher to position the probe

extremely accurately and to image the deformation process

throughout the test.

This system is designed for exceptional performance in the

electron microscope, with a vacuum-compatible transducer and

an electrically conductive probe. With Hysitron’s capacitive

transducer, force is applied electrostatically and displacement

is measured capacitively. This low-current design provides low

thermal drift and industry-leading stability and sensitivity.

The PI 85 system is ideal for characterizing fracture onset and

crack propagation, delamination, and pile-up. Also, time-sensitive

phenomena such as viscoelastic behavior can be observed in

real time. The pairing of these two high-resolution techniques

provides unique insight into the mechanisms responsible for

materials behavior.

Designed for Performance

With the compact design of Hysitron’s capacitive transducer,

the PI 85 can be mounted directly onto the SEM stage without

platform of the instrument allows for maximum stage tilt and

minimum working distance for imaging during testing. The

system is designed to accommodate samples up to 10 mm

thick, with XYZ translation stages to provide precise sample

positioning with >3 mm range in three dimensions.

The PI 85 instrument is driven by the newly designed

performech™ DSP-embedded controller, which boasts an

addition, the mechanical coupling of the sample stage and the

transducer provides a stable, rigid platform for nanomechanical

testing.

Mechanical data from the PI 85 is fully synchronized with the SEM video, providing

a complete understanding of the deformation process.

PI-SERIES

9 6 2 5 W EST 76 TH ST. M IN N EA PO LIS, M N 5 5 3 4 4 TEL: 1 -9 5 2 -8 3 5 -6 3 6 6 FA X: 1 -9 5 2 -8 3 5 -6 1 6 6 W W W . H YSITRO N . C O M

Indenter Tip Sample Holder Transducer

Indenter Tip

Bend bar

Additional questions raised: Mechanical strength of the oxide layers? Interface strength between steel and passive layers? Fracture surface and fracture mode of the passive layers? Initial experiments were designed to evaluate the questions above.

M. D. Abad et al; Oxid. Met. 2015

Fe3O

4

FeC

r 2O

4

Micro Cantilevers milled at the University of California, Berkeley Milled using a FEI Quanta 3D FEG Focused Ion beam instrument Ferritic/martensitic steel HCM12A after exposure to LBE. Sample provided by K. Kikuchi

INVESTIGATING MECHANICAL STABILITY OF PASSIVE FILMS, BRITTLE FRACTURE

IN-SITU FRACTURE TEST C cantilever 1 = 1423 MPa

C cantilever 3 = 1046 MPa

0

500

1000

1500

0 0.002 0.004 0.006 0.008 0.01

Stre

ss [

MP

a]

Strain [-]

Cross Section cross section # 7

Cross section # 6

Cross section # 5

0

200

400

600

800

1000

1200

1400

1600

1800

0 0.002 0.004 0.006 0.008 0.01 0.012 0.014

Stre

ss [

MP

a]

Strain [-]

Inner Oxide inner oxide # 4

inner oxide #3

inner oxide # 2

Inner layer outer layer

POST FRACTURE ANALYSIS

Fracture Surface

Fe O

Cr

Steel Diffusion zone

oxide

High porosity region Fracture region

Fracture occurs in the porous area not directly at the interface!

M. D. Abad et al; Oxid. Met. 2015

Other liquid metals may be considered for CSP

0 5 10 15 20 250.4

0.5

0.6

0.7

0.8

0.9

1.0

EM

F [

V]

wt% Sn

550 C

600 C

650 C

700 C

750 C

800 C

Sn in Bi-Pb

(Bi:Pb = 2:1)

SMALL AMOUNTS OF ADDITIONAL ELEMENTS AFFECT OXYGEN POTENTALS.

Pb-Bi-Sn phase diagram: 96C melting point

The irradiation and corrosion experiment (ICE)

Beam: 5 MeV protons, 0.5 µA current, 80 hour run Target: Concaved HT-9 foil, 40 um at the center, 350 ºC Damage level: 0.3 to 1.4 dpa LBE chemistry control: no oxygen sensor Corrosion rate change due to irradiation is not important/noticeable

Hosemann et al. , J. Nucl. Mat. 376 (2008) 392.

THE IRRADIATION AND CORROSION EXPERIMENT (ICE) DESIGN

Specimen concave shape allows to hold the pressure of the corrosive medium

Sample cross section

77 m thick

Preparation of HT-9 concave specimens requires thinning of disks

Dose profile shows maximum value at the edges of the specimen

(T. Wynn, 2011)

Schematic machining:

SPECIMEN DESIGN AND FACILITY

LBE Side on HT-9

~60 hours 430C, 2.5dpa

INITIAL INVESTIGATION OF ICE SAMPLE

Out of the beam spot

In the beam spot

STEM ON ICE SPECIMEN (HT-9)

steel

oxide

The ion beam irradiation enhances the oxidation significantly and leaves lesser dense oxides on the sample surface

SUMMARY

• Introduction to selection of heavy liquid metals in CSP and nuclear applications. • Significant synergistic problems between the different engineering applications. • Phenomenon LM corrosion and structural materials selection • Oxide layer formation on austenitic and ferritic stainless steels as well as Fe-Cr-Al

alloys in LM static and flowing conditions. -flow of 3.5m/sec is acceptable. -low oxygen content fosters the development of ferrite zones in austenitic materials -Fe-Cr-Al shows better corrosion properties at higher temperatures. • Adherence of oxides on the substrate material can be sampled directly.

• Introduction to the ICE experiment. accelerated oxidation in the beam spot.

Thank you for your attention!

OXIDATION STAGES OF PM2000 in LBE

0 50 100 150 200

0

100

200

300

400

500

600

0 500 1000 1500 2000 2500

Measured O2 in the

oxide layer

Calcualted O2 in the

oxide layer

Y2O3+

Al2O3+

Cr2O3+

Fe3O4

Y2O3+

Al2O3+

Cr2O3+ Y2O3+

Al2O3+

Oxygen content [counts] Measured Oxygen

content

Calculated Oxygen

content

Based on the published electron binding energy of each element, XPS allows the determination of the

oxidation state of the element. Here the measured oxygen in the layer is compared with the calculated oxygen

for the material.

Experiment

temperature

0 50 100 150 200 Distance [nm]

0

100

200

300

400

500

0 2000 4000 6000

Oxygen

final sum

0

100

200

300

400

500

0 200 400 600

Oxygen

final sum

Distance [nm]

Y2O3+

Al2O3+

Cr2O3+

Fe3O4

Y2O3+

Al2O3+

Cr2O3+

Y2O3+

Al2O3+

Measured Oxygen

content

Calculated Oxygen

content

Oxygen content [counts]

MA956Fe, 20Cr, 4.5Al, 0.3Y2O3

PM2000

Fe, 20Cr, 5.5Al,

0.3Y2O3

LBE

LBE

LBE

LBE

Holes

FIB PROCESSING AND STEM ON LME TEST SAMPLE (T91); SCK SAMPLE

In collaboration with E. Stergar, SCK

LBE penetrates at GB

A large number of intermetallic phases can be formed between Bi, Pb and Zr. While no ternary phase diagram is available the binary systems show significant formation of intermetallic phases

Since in an encapsulated system no new oxygen supply is possible intermetallics may form

The pre-irradiation tests did show that LM-Zr cladding is not a concern due to passivation layers formed and constant fresh supply of oxygen.

OM comparison (capsule 1)

100 µm

SEM OF THE IRRADIATED CAPSULE 1 SAMPLE

• Zr in the LM, • Some U is found at the Zr interface. • Cracks in the LM? • Multi phase mixtures in the LM

AFM/MFM/C-AFM ON HT-9

Outer layer

Inner layer

Outer layer

Inner layer

HT-9 bulk HT-9 bulk

Pores

Crack

Interface Interface -20 nm

Outer layer

Inner layer

Interface

Steel

10-25pA 0pA 10-40pA

GB Grain Current line profile through the boundaries identified

Grain

Cu

rren

t (n

A) Cr2O3 lower

electrical conductivity than Fe3O3

HOW DOES THIS OXIDE LAYER FORM in a Ni containing materials IN LIQUID METAL?

P. Hosemann, et al. J. Nucl. Mat. 375, 3, 30 (2008)323-330

Oxide layer growth: leaching and oxidation takes place: