Upload
schuyler
View
69
Download
1
Tags:
Embed Size (px)
DESCRIPTION
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. Outline. Indian Blanket Concept for ITER TBM program Requirements of Ceramic breeders in TBMs - PowerPoint PPT Presentation
Citation preview
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
6
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.
15
• 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.
20
Back-up slidesBack-up slides
21
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).
22
HCSB Concept