in-pile behaviour of lithium metatitanatein exotic-9nrg/mmi 13th workshop on ceramic breeder blanket...

NRG/MMI 13th Workshop on Ceramic Breeder Blanket Interactions 1

In-pile behaviour of lithium meta titanate in EXOTIC-9

A.J. Magielsena, J.B.J. Hegemana, M.J.M. Peetersa, J.G. van der Laana, J.D. Lulewiczb, M.P. Stijkela

a NRG Petten, the Netherlands, b CEA Saclay, France


MOM !

In-pile behaviour of lithium meta titanate in EXOTIC-9

A.J. Magielsena, J.B.J. Hegemana, M.J.M. Peetersa, J.G. van der Laana, J.D. Lulewiczb, M.P. Stijkela

a NRG Petten, the Netherlands, b CEA Saclay, France


Outline• Scope of work• Objectives EXOTIC-9/1 • Rig layout & design• Material loading• In-pile operation• Tritium release characterisctics• Status & outlook


Scope of work• Tritium inventory is major item in the safety case for a fusion power

plant: breeding blanket should be designed for minimal inventory:– Fast tritium release up to end-of-life burn-up– Increase the lower value of breeder temperature, and reduce

large low temperature zones

• Tritium breeders under development in EU for HCPB concept:– Li4SiO4 base, new manufacturing process explored– Li2TiO3 base, stretched to smaller & denser pebble, to enhance

effective 6Li density

• Present EFDA HCPB test programme is also addressing effects of pebble-bed thermo-mechanics (e.g. in HICU)


Objectives for EXOTIC*-9/1Tritium release characteristics of latest Li2TiO3 supplied by

CEA• differential inventory from in-pile transients• post-irradiation inventory measurements

• Co-irradiation of small piggy back samples, – New technology OSi samples for post irradiation microscopy and inventory

measurements– OSi with 20% 6Li– MTi with 30% 6Li

• Secundary: Permeation though Eurofer-97 and demonstration of in-situ oxidation for permeation reduction

*EXtraction Of Tritium In Ceramics


Design (1)EXOTIC-9/1 T-release capsules

• Annular breeder pebble-bed, modest radial temperature gradient, 120 mm stack height

• Triple containment for safety • Integrated tritium monitoring.• Electrical heaters, for large

variation in temperature transients(300-500 C)

• Purge gas (He + 5000 ppm - 10 ppm H2 or pure He, all 6.0 quality)

• Eurofer-97 tube permeation rateobtained simultaneously

• Demonstration of in-situ oxidation for permeation reduction

EXOTICEXOTIC--8/98/9


Design (2)

A B C D E F G H I

1 Be Be Be Be Be Be Be Be 1 Be F Fuel element

2 F F F D2 F F2 F H2 2 Be

3 F F C3 F E3 F G3 F 3 I3 CR Control rod

4 F CR F CR F CR F H4 4 Be

5 F F C5 F E5 F G5 F 5 I5 Be Reflectorelement

6 F CR F CR F CR F H6 6 Be

7 F F C7 F E7 F G7 F 7 Be E5 Experiment

8 F F F D8 F F8 F H8 8 Be

9 Be Be Be Be Be Be Be Be 9 Be Hx EXOTIC


Test matrix and loadingCeramic materials:1. Same as 4, approx. 1.2 g2. Li4SiO4 20 % 6Li enr. (FZK, OSi00/2-3-c),

0.2 g3. Li4SiO4 nat 6Li enr. (FZK, OSi03/1-3 ), 0.2 g

4. Li2TiO3 nat 6Li enr. CEA, CTI 273 Ti 1100 CTI), approx. 12.8 g

5. Li2TiO3 , 29,5 % 6Li enr. (CEA, CTI 1233 Ti 1100 CEA), 0.2 g

6. Same as 4, approx 1.2 g


table 1 Characteristics of irradiation specimens after assembly of the test elements

bulk material

Piggyback 1

Piggyback 2

Piggyback 3

Piggyback4

Material Li2TiO3 Li2TiO3 Li4SiO4 Li4SiO4 Be Supplier CEA CEA FZK FZK FZK(NGK)NRG ID NRG 130 NRG 131 NRG 129 NRG132 NRG 2010 6Li enrichment 7.5 % 30% 7.5 % 20 % -- measured density (g·cm-3) by He pycnometry technique

3.280 3.246 2.34 not meas. not meas.

open porosity (%) 1.7 2 3.5 not meas. not meas. closed porosity (%) 5.3 5.8 2.7 not meas. not meas. Smear density (g·cm-3) 1.84 1.84 1.44 1.44 not meas. Theoretical density (g·cm-3) 3.43 3.43 2.25 not meas. not meas. Weight (g) 12.8 0.2 0.2 0.2 0.2 Pebble diameter (mm) 0.6-0.8 0.6-0.8 0.25-0.63 not meas. 0.85-1 grain size (μm) 1-3 1-4 not meas. not meas.

Material loading (1)


Material loading (2)

Li2TiO3, CTI 273 Ti 1100 CTI nat 6Li (NRG 130)

Li2TiO3, CTI 1233 Ti 1100 CEA, 30% 6Li (NRG

131)

FZK, OSi-03/1-3 nat 6Li Li4SiO4 (NRG 129)


Rig assembly

irradiation experiment near completion of assembly

Second containment with heater element ~ 5 m


Beryllium piggy-back

NGK pebbles (0.2 g, NGK 1.0 batch 2003) of diameter 0.85- 1 mm fitted in mini tube, tube loaded to sleeve inside stainless steel support of ceramic bed

to


In-pile tritium release (1)

1st Cycle: 05-04

0

100

200

300

400

500

600

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28Time (days)

Tem

pera

ture

(C)

0

0.2

0.4

0.6

0.8

1

1.2

IC s

igna

l (a.

u.)


In-pile tritium release (2)Cycle 05-07

0

100

200

300

400

500

600

0 5 10 15 20 25time (days)

Tem

pera

ture

(C)

0.0

0.7

1.4

2.1

2.8

3.5

4.2

IC s

igna

l (a.

u.)

High inventory build-up


Effect of purge gas composition

First cycles results suggest:• Surface process (desorption) seems not rate determining• Bulk diffusion is apparently rate determining

0.0

0.5

1.0

1.5

2.0

13.5 14 14.5 15 15.5

time (days)Tr

itium

rele

ase

rate

(mC

i/min

)

0.1 % H2 (ref gas)

1.0 % H2 0.1 % H2 (ref gas)

Later cycle (05-07)

0

100

200

300

400

500

600

0 5 10 15 20 25time (days)

Tem

pera

ture

(C)

0.0

0.8

1.6

2.4

3.2

4.0

4.8

Triti

um re

leas

e ra

te (m

Ci/m

in)

Temperature

Tritium release rate


Tritium residence time from temperature transients

At steady state: Tritium generation rate (G) = Tritium release rate

The surface area represents the difference in inventory: ΔI = I2 - I1

The difference in tritium residence time is calculated from: Δτ = τ2 - τ1 = ΔI / G

GI

=τ

Tritium residence time (τ):

I = tritium inventory (mCi)G = tritium production rate (mCi/min)


Tritium release of Li2TiO3 pebbles in E-9/1

Li2TiO3-extruded (E-9/1)

0.1

1

10

100

1000

1.20 1.30 1.40 1.50 1.60 1.70

Temperature (1000/T(K))

Tritr

ium

Res

iden

ce ti

me

(hou

rs)

cycle_04cycle_05cycle_06cycle_07cycle_09cycle_10fit


Tritium release & microstructureEXOTIC-Capsule E-8/2 E-8/9 E-8/1 E-8/7 E-8/7 E-8/9 E-8/5 E-9/1

CEA CEA CEA CEA CEA CEA CEA CEAsinter spinel agglom agglom extrus extrus extrus-

sinterextrus-spheroid-sinter

pellets crushed bar pebbles pebbles pebbles pebbles pebbles pebbles4.0 - 9.5 0.8 - 1.2 0.7 - 0.9 0.6 - 1.2 1.1 - 1.5 0.9 - 1.2 1.1 - 1.5 0.6 - 0.8

83 90 84 84 89 94 87 931 - 2 ? 1.5 - 2 1 - 2 1.5 - 2.5 1-2.5 1 - 2.5 1 - 315 ? 10 11 6 ? 7 1.72 ? 6.5 4.8 5 ? 5.7 5.3

0.8 1 1.3 1.3 - 4.8 6.4 12.2

Closed porosity

Residence time at 500 C

Size pellets / pebbles

Grain sizeDensity of pebble

Open porosity

Supplier

Fabrication

Shape

Tritium residence time increases with amount of closed porosity


Comparison with EXOTIC-8 results

0.1

1

10

100

1000

1.15 1.25 1.35 1.45 1.55 1.65 1.75Temperature (1000/T(K))

Triti

um R

esid

ence

Tim

e (h

ours

)

E-8/5; extruded; TD= 87; OP= 7

E-8/1;agglomerated; TD= 84; OP= 10

E-8/2; sintered pellets; TD= 83; OP= 15

E-8/7; extruded; TD= 89; OP= 6

E-8/7; agglomerated; TD= 84; OP= 11

E-8/9; extruded; TD= 94

E-9/1; extruded; TD= 93; OP= 1.7

E-8/9; spinel; TD= 90

0

2

4

6

8

10

12

14

16

18

20

0 5 10 15Tau in hrs (at 500 C)

Por

osity

OpenClosedTotal porosityLinear (Total porosity)Linear (Closed)Linear (Open)


Permeation in first few days …

1st Cycle: 05-04

0

100

200

300

400

500

600

0 2 4 6 8Time (days)

Tem

pera

ture

(C)

0

0.2

0.4

0.6

0.8

1

1.2

IC s

igna

l (a.

u.) IC-1

50 x IC-2


Status & outlook• EXOTIC-9/1 now in 6th cycle, continues to Spring 2006; the

experiments runs well with no instrumentation failures• Significant inventory built up is observed in the latest high density

MTi pebbles, attributed to high closed porosity and low fraction ofopen porosity

• P.I.E. starts mid 2006: post-irradiation inventories and microscopy• In-situ oxidation of Eurofer-97 containment in Cycle 05-10, should

provide evidence for effective permeation reduction – This is ongoing for a week: water vapour saturated purge gas through seconsd

containment, with tube at about 400 C. This will be continued for another 2 or 3 weeks, depending on actual effect

• Consequences for breeder material and its specification development will be addressed soon (TBM scope & timing), including a.o. low temperature irradiation effects


End ofEnd of EXOTIC EXOTIC presentationpresentation

in-pile behaviour of lithium metatitanatein exotic-9nrg/mmi 13th workshop on ceramic breeder blanket...

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