Current Status of Lithium Ceramic Pebble Manufacturing in Korea

Yi-Hyun Park1, In-Keun Yu1, Mu-Young Ahn1, Seungyon Cho1,Duck Young Ku1, and Sang-Jin Lee2

1 National Fusion Research Institute, Daejeon, Korea2 Mokpo National University, Jeonnam, Korea

CBBI-16, Sep. 8-10, 2011, Red Lion on the River, Portland, OR, USA

Contents

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Background

R&D Status-1 : Synthesis of Li4SiO4 Powder

R&D Status-2 : Fabrication of Li4SiO4 Pebble Compression Molding Method Slurry Droplet Drying Method Slurry Droplet Wetting Method

Summary and Future Works

CBBI-16, Sep. 8-10, 2011, Red Lion on the River, Portland, OR, USA

Background

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Korea Helium Cooled Solid Breeder TBM (KO HCSB TBM)

• Reduced Activation Ferritic/Martensitic steel as structural material

• Li4SiO4(LS) or Li2TiO3(LT) pebble as breeder• Be pebble as multiplier• Graphite pebble as reflector

SiC coating is necessary to avoid air/water contact, to enhance pebble strength, and to handle easily.

Parameter Values

FW heat flux Average 0.3 MW/m2

Peak 0.5 MW/m2

Neutron wall load 0.78 MW/m2

Thermal Power 1.01 MWTritium Breeding

Ratio 1.1

Structural material RAFM (< 550 oC)

BreederLi4SiO4 pebble bedLi2TiO3 pebble bed (optional)< 920 oC

Multiplier Be pebble bed< 650 oC

Reflector Graphite pebble bedSize 1208x710x600 (mm)

Coolant

8 MPa He0.973 kg/sFW ( 300 oC / 390 oC ) Breeding Zone(390 oC/500 oC )

Purge He with 0.1 % H2

FirstWall

BreedingZone

TopPlate

BackManifold

CBBI-16, Sep. 8-10, 2011, Red Lion on the River, Portland, OR, USA

Required Properties for Li-ceramic

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Material Property Requirement Remarks

Powder

Particle Size < 0.5 μm success (LS)

Crystalline Phase > 98.5 % success (LS)

Impurities Co : < 1 ppmAl : < 35 ppm

from activation/waste

Pebble

Particle Size < 10 μm need to control

Diameter 1.0 mm need to control

Porosity < 20 % need to control

Sphericity < 1.05 -

Crush Load > 15 N -

Quality Controllability, Mass Production,High-yield, Good Reproducibility,

Reprocessing (Recycling)

CBBI-16, Sep. 8-10, 2011, Red Lion on the River, Portland, OR, USA

Contents

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Background

R&D Status-1 : Synthesis of Li4SiO4 Powder

R&D Status-2 : Fabrication of Li4SiO4 Pebble Compression Molding Method Slurry Droplet Drying Method Slurry Droplet Wetting Method

Summary and Future Works

CBBI-16, Sep. 8-10, 2011, Red Lion on the River, Portland, OR, USA

Synthesis Process of Li4SiO4 powder

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Synthesis Process for Li4SiO4 powder by PVA Solution Route

• Lithium Nitrate (LiNO3)

• Silica sol (SiO2)

D.I. water

PVA

5 wt.% PVA solution

D.I. water

Mixing (entrapment)

Drying (Li4SiO4 ceramic precursor)

Calcination & Crystallization

CBBI-16, Sep. 8-10, 2011, Red Lion on the River, Portland, OR, USA

Thermal Analysis of Li4SiO4 Precursor

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Thermo Gravimetry (TG) / Differential Thermal Analyzer (DTA)

The calcination process was finished below about 800 oC.

Crystallization Process : >800 oC

CBBI-16, Sep. 8-10, 2011, Red Lion on the River, Portland, OR, USA

Synthesized Li4SiO4 Powders

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Effects of Crystallization Temperature

800oC

1000oC

900oC

Primary Particle Size : about 200 nm

CBBI-16, Sep. 8-10, 2011, Red Lion on the River, Portland, OR, USA

Synthesized Li4SiO4 Powders

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Low Mw

High MwLow Mw High Mw

Effects of PVA Type

Effects of PVA Content

5 wt.% 10 wt.%

5 wt.%

10 wt.%

CBBI-16, Sep. 8-10, 2011, Red Lion on the River, Portland, OR, USA

Contents

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Background

R&D Status-1 : Synthesis of Li4SiO4 Powder

R&D Status-2 : Fabrication of Li4SiO4 Pebble Compression Molding Method Slurry Droplet Drying Method Slurry Droplet Wetting Method

Summary and Future Works

CBBI-16, Sep. 8-10, 2011, Red Lion on the River, Portland, OR, USA

Fabrication of Pebble : Compression Molding Method

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PVA solutionLi4SiO4 powder

Mixing

Pressing using Compression Mold

Sintering

Granulation

Fabrication Process of Compression Molding Method

Li4SiO4 Granules

Compression Mold for Pebble

Dia. : about 0.3mm

PVA cont.: 5~10wt.%

Punch SphericalGreen Body

CBBI-16, Sep. 8-10, 2011, Red Lion on the River, Portland, OR, USA

Strength Properties

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0 0.02 0.04 0.06 0.08 0.1 0.120

20

40

60

80

100No.1No.2No.3No.4No.5

Displacement (mm)

Load

(N)

No. Dia. (mm) Crush Load (N) Max. Contact Pressure (GPa)1 2.10 67.4 5.602 2.17 93.9 6.133 2.12 66.8 5.554 2.13 72.5 5.695 2.12 75.9 5.80

• Equipment : Micro-force Material Tester• Cross-head Speed : 0.5 mm/min• Test Temperature : R.T.

Pebble

Upper anvil

Lower anvil

CBBI-16, Sep. 8-10, 2011, Red Lion on the River, Portland, OR, USA

Fabrication of Pebble : Slurry Droplet Drying Method

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Fabrication Process of Droplet Drying Methodby using Hydrophobic Cloth

D.I. waterLi4SiO4 powder

Mixing (1:2 wt.%)

Dropping on Hydrophobic Cloth

Drying (24h)

Rolling

Sintering

CBBI-16, Sep. 8-10, 2011, Red Lion on the River, Portland, OR, USA

Photographs of Green Bodies

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slurry droplets

as-dried green body rolled green body

rolling(3h, 100 rpm)

Average diameter of rolled green body was about 1 mm.

It could be easily controlled by changing of rolling conditions.

CBBI-16, Sep. 8-10, 2011, Red Lion on the River, Portland, OR, USA

Fabrication of Pebble : Slurry Droplet Wetting Method

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Fabrication Process of Dropping Wetting Methodby using Hydrogen Peroxide Solution

PVA solution

D.I. waterLi4SiO4 Powder

PVA

Mixing

Dropping into 34%-H2O2 solution

Drying (R.T., 12h)

Sintering

Li4SiO4

powder10wt.%

PVA solution

slurry

syringe needle

H2O2 solution

gel-sphere

CBBI-16, Sep. 8-10, 2011, Red Lion on the River, Portland, OR, USA

Photographs of Gel-spheres

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Dropped and Floating Gel-spheres

gel-sphere

gel-sphere

bubble

after30 seconds

After about 30 seconds settling at the bottom, Li4SiO4 gel-spheres came up to the surface of the H2O2.

Decomposition Reaction of H2O2 : 2 H2O2 (aq) 2 H2O (l) + O2 (g)

Flat surface was not observed at the gel-sphere.

CBBI-16, Sep. 8-10, 2011, Red Lion on the River, Portland, OR, USA

Photographs of Green Body and Pebble

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Spherical Green Bodies and Sintered Li4SiO4 Pebbles

sintering(1000oC, 4h, in air)

spherical green bodies sintered Li4SiO4 pebbles

average diameter : 2.5 mm average diameter : 1.5 mm

CBBI-16, Sep. 8-10, 2011, Red Lion on the River, Portland, OR, USA

XRD Patterns of Powder and Sintered Pebble

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2θ (o)

Inte

nsity

(co

unts

)

pebble

powder

Li2Si2O5 and SiO2 included in starting powder were reacted and removed by sintering process.

CBBI-16, Sep. 8-10, 2011, Red Lion on the River, Portland, OR, USA

Crush Load and Microstructure

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-0.02 0.03 0.080

5

10

15

20

25

30

35

40

Displacement (mm)

Com

pres

sive

Loa

d (N

)

50μm

10μm

Diameter : about 1.5 mm

0.5 mm/min

Room Temp.

Crush Load : 15 N ~ 35 N Particle Size < 10 μm

CBBI-16, Sep. 8-10, 2011, Red Lion on the River, Portland, OR, USA

Contents

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Ⅰ

Ⅱ

Ⅲ

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Background

R&D Status-1 : Synthesis of Li4SiO4 Powder

R&D Status-2 : Fabrication of Li4SiO4 Pebble Compression Molding Method Slurry Droplet Drying Method Slurry Droplet Wetting Method

Summary and Future Works

CBBI-16, Sep. 8-10, 2011, Red Lion on the River, Portland, OR, USA

Summary and Future Works

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Pure and stable Li4SiO4 powder was successfully synthesized by

polymer solution route employing PVA as an organic carrier.

Li4SiO4 pebbles with relatively high sphericity, high strength and

fine grain size could be successfully fabricated by a compression molding method, a slurry droplet drying method, and a slurry droplet wetting method.

It is expected that these methods are easily-controllable and high-yield process for solid breeder pebbles.

These methods should be constantly improved for high perfor-mance of Li-ceramic pebbles such as high-temperature properties, irradiation properties, and recycling process.

CBBI-16, Sep. 8-10, 2011, Red Lion on the River, Portland, OR, USA 22

Thank you for Your Attention !!!

CBBI-16, Sep. 8-10, 2011, Red Lion on the River, Portland, OR, USA 23

(a) Excess or not enough polymer results in large particle size distributions. (b) the optimal amount should give a more uniform distribution.

O : cation ion~ : polymer chain

PVA type and mixing amount

Two types of PVA High degree of polymerized PVA

:D.P. value = 1625 (monomers/polymer)molecular weight = 153,000

Low degree of polymerized PVA: D.P. value = 428(monomers/polymer)

molecular weight = 40,000

PVA content The proportions of the PVA to cation sources in the

solution were adjusted in such a way that there were 0.5~1 times more positively charged valences from the cations than from the potentially nega-tively charged –(OH) functional groups of the

polymers.

PVA amount of polymer controls the particle size distribution