Current status on lithium ceramic breeder development in India Paritosh Chaudhuri

1. Current status on lithium ceramic breeder development in India Paritosh Chaudhuri Institute for Plasma Research Gandhinagar, INDIA CBBI-16, 8- 10 Sept. 2011, Portland, USA

2. Outline • Indian Blanket Concept for ITER TBM program • Requirements of Ceramic breeders in TBMs • Development of Li ceramics from different routes • Solid state method • Solution Combustion Synthesis Process • Sol-Gel method • R&D Issues for Solid breeder materials in TBM • Characterizations • Li6 enrichment process development • Critical Issues & Future Work

3. Indian Blanket Concepts • 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)

4. Requirement of Li2TiO3 in LLCB and HCPB Based on the present design

5. Development of Ceramic Breeder Pebbles In India three different routes have been used to develop the ceramic breeder pebbles: • Solid state method • Solution Combustion Synthesis Process: • Sol-Gel method

6. 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 Solid state reaction, extrusion, spherodization & sintering process 900o C 900o C 900o C 6

7. 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.

8. Solution Combustion Synthesis Process (SCSP) • The conventional synthesis process needs • - Higher Calcination Temperature Results in coarser particle size • Higher Sintering Temperature Results in Large grain Ceramic, Lithium • evaporation, difficult to sinter and maintain • stoichiometry • 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.

9. 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. Combustion during reaction

10. Products of combustion synthesis are highly reactive Contain minimum levels of impurities Can be prepared rapidly at a low temperature (500-600oC) Solution Combustion Synthesis Process (SCSP) Aqueous-based citrate-nitrate autocombustion process is a promising technique Li2(CO3) Citric Acid NH4NO3 TiO2 (NH4 )2SO4 Ti-Nitrate solution H2SO4 Constant heating & stirring pH, Fuel/Oxidant ratio Constant Stirring and Heating Ti- sulphate NH4OH Yellow Viscous gel Ti-Hydroxide Calcination at 600°C washing XRD Particle Size Surface Area Particle Morphology Sintering behaviour Sulphate free precipitate Li2TiO3 1:1 HN03 Combustion Ti-Nitrate solution Preparation of Ti-Nitrate solution Flow sheet of Li2TiO3 Preparation

11. 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 PowderExtruder-SpherodizerLi2TiO3 pebbles (~1 mm)

12. 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

13. Solution Combustion Synthesis Process (SCSP) Thermal Conductivity MEASURED BY Laser Flash Method (Li2iO3 pellet by SCSP)

14. Li2TiO3 Synthesis & Pebble Fabrication by Sol-Gel Method 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. 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 )

15. Fabrication of Mixed Oxide [BeO + Li2TiO3] • 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 15

16. Design of effective thermal conductivity measurement equipment

17. Specs. of effective thermal conductivity measurement equipment Heater type : Cartridge Heater Heated length : 500 mm; Heating element : kanthal A-1 grade alloy wounded on hollow mullite tube Max 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 °C sheath material : Inconel 600 alloy Typical response : 0.3 sec

18. Location of thermocouples in effective thermal conductivity measurement equipment

19. Summery and Future Work • Development of ceramic breeder by different routes and some of their characterizations have been done • Design of pebble bed apparatus have been starred. • 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

20. Thank you 20

21. Back-up slides 21

22. Conclusions 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). 22

23. HCSB Concept