Current status on lithium ceramic breeder development in India

Paritosh ChaudhuriInstitute for Plasma Research

Gandhinagar, INDIA

CBBI-16, 8- 10 Sept. 2011, Portland, USA

Outline

Indian Blanket Concept for ITER TBM program

Requirements of Ceramic breeders in TBMs

Development of Li ceramics from different routesSolid state methodSolution Combustion Synthesis ProcessSol-Gel method

R&D Issues for Solid breeder materials in TBMCharacterizationsLi6 enrichment process development

Critical Issues & Future Work

Lead-Lithium cooled Ceramic Breeder (LLCB) Tritium Breeder: Pbli, Lithium Ceramic pebbles; Coolant: PbLi (multiplier and breeder); FW coolant: Helium Gas; Structural Material: Reduced Activation FMS Purge gas: Helium T extraction from CB

(To be tested in one half of ITER port no-2)

Helium Cooled Ceramic Breeder (HCCB)

Tritium Breeder: Lithium Ceramic pebbles; Multiplier : Beryllium Pebbles; Coolant : Helium gas; Structural Material: Reduced Activation FMS

Purge gas: Helium T extraction from CB

(to participate as TBM Partner)

Indian Blanket Concepts

LLCBLead Lithium cooled Ceramic Breeder

HCPBHelium Cooled Pebble Bed

Vol (m3) Mass (kg)

CB1 - 0.0070 8 87CB2 - 0.0096 18.91

CB3 - 0.0096 18.91

CB4 - 0.0127 25.21

CB5 - 0.00159 31.52 Total ~ 103 kg

Vol (m3) Mass (kg)

1 CB Canister 0.0012 2.39

1 unit cell 0.0048 9.56(4 CB Canister )

In HCPB TBM 0.048 95.64 (10 unit cell)

Total ~ 96 kg

Requirement of Li2TiO3 in LLCB and HCPBBased on the present design

Development of Ceramic Breeder Pebbles

Solid state method

Solution Combustion Synthesis Process: Sol-Gel method

In India three different routes have been used to develop the ceramic breeder pebbles:

Process Steps

1. Step-1: Reaction in Solid State: Li2CO3 + TiO2 Li2TiO3

2. Step-2: Classification, (Particle size < 45μ)

3. Step 3: Addition of binder (PVA) and Extrusion

4. Step 4: Spherodization

5. Step-5: Calcination & Sintering Li2TiO3 Pebbles

900o C

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900o C

900o C

Solid state reaction, extrusion, spherodization & sintering process

A lab scale preparation of Li2TiO3 of capacity 1 kg per day has been developed.

Fabricated pebbles was characterized. The properties of the fabricated pebbles meet almost all the desired properties.

Future Action: A production facility of 20 kg and more per day is under consideration.

Solid state reaction, extrusion, spherodization & Solid state reaction, extrusion, spherodization & sintering processsintering process

- Higher Calcination Temperature Results in coarser particle size- Higher Sintering Temperature Results in Large grain Ceramic, Lithium evaporation, difficult to sinter and maintain stoichiometry

The conventional synthesis process needs

Alternative techniques:

Solution combustion technique and sol-gel technique for Li2TiO3

Melt Spraying technique for Li4SiO4 where hygroscopic LiOH is used as one of the precursor material.

Solution Combustion Synthesis Process (SCSP)

In this SCSP methoad we have used the cheaper source of Ti (e.g. TiO2) as the precursor material instead of conventional Ti source of TiCl4 or Ti-isopropoxide.

Precursor for Li2TiO3 are: - Lithium carbonate: for lithium ; - Titanium oxy-nitrate for Ti;

- Citric acid as chelating agent as well as fuel for the combustion reaction.

Able to Lower the calcination temperature in the range of 200-600 C to and got nanosized powder.

Solution Combustion Synthesis Process (SCSP)

Combustion during reaction

TiO2 (NH4 )2SO4

H2SO4

Constant heating & stirring

Ti- sulphate

Ti-HydroxideNH4OH

Sulphate free precipitate

washing

Ti-Nitrate solution

1:1 HN03

Preparation of Ti-Nitrate solution

Ti-Nitrate solution

Constant Stirring and Heating

Yellow Viscousgel

Calcination at 600°C

Combustion

NH4NO3

Citric

Acid

Li2(CO3

)

Li2TiO3

Flow sheet of Li2TiO3 Preparation

pH, Fuel/Oxidant ratio

XRD Particle SizeSurface Area

Particle MorphologySintering behaviour

Solution Combustion Synthesis Process (SCSP)Aqueous-based citrate-nitrate autocombustion process is a promising technique

Products of combustion synthesis are highly reactiveContain minimum levels of impuritiesCan be prepared rapidly at a low temperature (500-600oC)

Solution Combustion Synthesis Process (SCSP)

Li-based Pebble are prepared by extrusion-spherodisation-sintering process;

Optimization of process parameter for formulation of the extrusion paste consist of Li-based powder/binder/plasticiser;

Optimization of extruder nozzle diameter to get desired spherisity;

Optimization of sintering condition to get desired densification and porosity .

Li2TiO3 Powder Extruder-Spherodizer Li2TiO3 pebbles (~1 mm)

Solution Combustion Synthesis Process (SCSP)• Up-scaling of the solution combustion synthesis process can be done by spray pyrolysis technique. • Compared with other synthesis techniques of powders, spray pyrolysis has several advantages such as high purity of powders, excellent control of chemical uniformity and stoichiometry in multi-component system, simplicity in manufacturing equipment, and as a continuous process. • It involves passing a precursor solution through a graded temperature reactor, in which the individual droplets are thermally decomposed to form oxide particles.

Spray pyrolyzer, Jars containing coarse and Spray pyrolysed fine Li2TiO3 powder Li2TiO3 powder

Solution Combustion Synthesis Process (SCSP)

Thermal Conductivity MEASURED BY Laser Flash Method (Li2iO3 pellet by SCSP)

Li2TiO3 Synthesis & Pebble Fabrication by Sol-Gel Method

Process Steps: TiOCl2+ 2LiCl+NH4OH Ti(OH)2+ 2LiOH+NH4Cl (Gel formation) (CH2)6N4+10H2O 6 HCHO+4 NH 4 OH (Hydrolysis of HMTA)

Ti(OH)2+ 2LiOH Li2O+TiO2 (Calcination at 1000oC) Li2O+TiO2 Li2TiO3 pebble (Sintering at 1000oC )

In this process, gel of Ti(OH)2 and Li2O is prepared from aqueous solution of TiOCl2, LiNO3, Hexa-methylene-tetra-amine (HTMA) and urea at 0 C-4 C. The gel is then washed with aqueous solution of NH4OH and gel is dried. The dried gel is calcined and sintered at 1000 C.

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• India has a dedicated plant for beryllium production;

• Capability to produce Nuclear grade Be, BeO, Be alloy

• Production has been stepped up for high temp.fusion reactor materials;

• Started activities in mixed oxide ceramic materials [BeO + Li2TiO3];

- Grain size ~ 2- μm;

- TBR is not affected; - Th. Cond. of Be pebble: 36 to 14 W/m/K with the increase in

temperature from 127 C to 927 C.

- Coefficient of thermal expansion (CTE): 18.9 x 10-6 / C

Fabrication of Mixed Oxide [BeO + Li2TiO3]

Design of effective thermal conductivity measurement equipment

Heater type : Cartridge HeaterHeated length : 500 mm; Heating element : kanthal A-1 grade alloy wounded on hollow

mullite tubeMax temperature : 850°C.Sheath Material : Inconel 600 alloy.

Thermocouple Type : Type-K.Temperature range : 95 to 1260 °C TC probe OD : 1/25 inch Junction type : Ungrounded type TC accuracy : ± 2.2 °Csheath material : Inconel 600 alloyTypical response : 0.3 sec

Specs. of effective thermal conductivity measurement equipment

Location of thermocouples in effective thermal conductivity measurement equipment

Summery and Future Work

Standardization of Li2TiO3 synthesis process (Qualification criteria)

Detailed study the densification behavior of synthesized powder in terms of Phase purity, Density, Pore size and pore structure Thermo-mechanical test of pebble bed Alternative Ceramic breeder (other than Li2TiO3) Activation and recycling Reprocessing strategies Li6 enrichment Irradiation experiment

Development of ceramic breeder by different routes and some of their characterizations have been doneDesign of pebble bed apparatus have been starred.

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Back-up slidesBack-up slides

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Conclusions from solid StateConclusions from solid State

The temperature at which the reaction is completed and single phase-Li2TiO3. obtained is 900oC

The extruded, spherodized and sintered pebbles having desired density ( i.e. 85-90% TD) range for TBM material of Fusion Rector can be fabricated using solid state reaction and spherodization technique

Extruded and spherodized spheres after sintering at 900oC for eight hours, can produce adequate density, shape, open and closed porosity.

The SEM analysis shows that grain size of the fabricated Li2TiO3 pebbles is in the desired range (1-6 µ). The microstructure of the pebbles was influence by the sintering temperature. It was suggested that the pebbles should be sintered at 900oC in order to obtained favorable microstructure and relatively high density (85-90%T.D).

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HCSB Concept