16th International Workshop on CERAMIC BREEDER BLANKET INTERACTIONS, 8-10 September, 2011 Portland, Oregon, USA. Status of research and development of advanced tritium breeder in BA activities Tsuyoshi HOSHINO Japan Atomic Energy Agency ©2011 JAEA 1/20

Rokkasho BA Site in Aomori, JAPAN ● Aomori prefecture IFERC Rokkasho Village 2/20 Tokyo ● Tokai Village ● Fukushima ● Aomori ●

Obuchi Arito Line (prefectural road) to JNFL (Japan Nuclear Fuel Limited) DEMO R&D Building International Fusion Energy Research Center (IFERC) DEMO R&D Building in IFERC Administration & Research Building Computer Simulation & Remote Experimentation Building IFMIF/EVEDA Accelerator Building 3/20

Handling room in DEMO R&D building Beryllium handling room Lithium handling room 4/20

Introduction –Tritium Breeder- Li 2 OLi 2 AlO 2 Li 2 ZrO 3 Li 4 SiO 4 Li 2 TiO 3 Li Vaporization ( in additional H 2 ) > 600˚C> 900˚C> 800˚C> 700˚C> 800˚C Long period use (2 years) Instability (Li vaporization) StabilityInstability (crack) Instability (Li vaporization) Instability (Reduction of Ti) Tritium release ( easy release ) > 400˚C > 350˚C> 300˚C Optimum operating temp ˚C ˚C ˚C ˚C ˚C Tritium breeding ratio (TBR) HighLowerMiddle Thermal conductivity HighMiddle These tritium breeder are available in DEMO blanket? 5/ ˚C High ˚C Stability

Why we need advanced tritium breeder TBR Stability (high temperature use) Li 2 O Li 2 TiO 3 LiAlO 2 Li 2 ZrO 3 Li 4 SiO 4 Demo Blanket in other parties Development target of advanced tritium breeder is influenced by requirement of DEMO blanket. Where is yellow area? 6/20 Requirement 1) ?˚C 2) ? 3) ? Selection of important item

For Example 1 TBR Stability (high temperature use) Li 2 O Li 2 TiO 3 LiAlO 2 Li 2 ZrO 3 Li 4 SiO 4 DEMO Blanket in ●● Li 4 SiO 4 will be selected the tritium breeder for DEMO blanket in ●●. 7/20 Requirement 1) 300 – 800˚C →Requirement of stability is lower

For Example 2 TBR Stability (high temperature use) Li 2 O Li 2 TiO 3 LiAlO 2 Li 2 ZrO 3 Li 4 SiO 4 DEMO Blanket in ●● LiAlO 2 will be selected the tritium breeder for DEMO blanket in ●●. 8/20 Requirement 1) TBR is enough →Requirement of TBR is lower 2) More stability

Advanced Tritium Breeder in JA TBR Stability (high temperature use) Li 2 O Li 2 TiO 3 LiAlO 2 Li 2 ZrO 3 Li 4 SiO 4 DEMO Blanket in JA Li 2 TiO 3 with additional Li (Li 2+x TiO 3+y ) has higher stability at high temperatures in a reducing atmosphere. Why we need advanced tritium breeder? 9/20 Requirement 1) 300 – 1000˚C 2) 30% 6 Li burn up 3) Use for 2 years

Li 2 TiO 3 with additional Li (Li 2+x TiO 3+y ) Blackened by reduction No change White sample (Li 2 TiO 3 ) With additional Li Li 2 TiO 3 The color of Li 2 TiO 3 has changed from white to black under the H 2 atmosphere at high temperatures. This color-change corresponds to reduction of Li 2 TiO 3. In the case of Li 2 TiO 3 with additional Li, the color has not changed, indicating that this sample is not reduced in the hydrogen atmosphere. Heating in H 2 atmosphere Reduction of Ti in Li 2 TiO 3, namely, the valency change from Ti 4+ to Ti 3+, is accompanied by decrease in the oxygen content of the sample. The result for Li/Ti = 3.9 indicated no presence of oxygen defects, which indicates clearly that this sample is highly resistant to reduction. 10/20

Raw material preparation LiOHH 2 OH 2 TiO 3 Precursors mixed in the molecular ratio of Li/Ti = 2.2 Calcination Sintering Mixture rotated at room temperature Gelation Novel solid phase reactions Separation Water Gel Rotation time: 10h Rotation time: 48h Powders of LiOHH 2 O and H 2 TiO 3 were mixed in a molecular ratio of Li/Ti = 2.2. In addition, the mixture of the starting powders was continuously rotated at room temperature for 48 h in a polyethylene container. The mixture gradually turned into a gel through a solid phase reaction at room temperature. After drying, the gel was calcined in air at 873 K for 5 hr and sintered in N 2 at 1373 K for 2 hr. 11/20

Fabricating pebbles by emulsion method This granulator is composed of two syringes and T-shaped flow path. One syringe is filled with oil. Other syringe is filled with Li 2 TiO 3 slurry. Two flow lines from these syringes are connected in the T-shaped flow path. In this time, Li 2 TiO 3 slurry flow is cut by oil flow from the oil-filled syringe. The emulsion method is known as the technique that can easily produce the uniform submicron particle in large volume. 12/20

Pebble fabrication trial setup (a) Overview of the granulator Gel particles (d) Gel particles of Li 2 TiO 3 in oil-filled container Cutting (c) T-shaped flow path for cutting the slurry Oil Li 2 TiO 3 (b) Oil and Li 2 TiO 3 syringes The size of Li 2 TiO 3 gel particles was controlled by the relative flow speeds of the oil and the Li 2 TiO 3 slurry. The Li 2 TiO 3 gel particles were kept in a container filled with oil. 13/20

Design of emulsion granulation equipment Top View Side View Front View Emulsion granulation equipment will be completed in syringes T-shaped flow path 14/20

Fabricating Li 2 TiO 3 pebbles Slurry (Li 2+x TiO 3+y with binder) Emulsion method Gel-spheres Sintered pebbles Pebble Fabrication Calcination The XRD patterns of the sintered Li 2 TiO 3 pebbles matched the pattern of the Li 2 TiO 3 listed in the JCPDF card. The molar ratio (Li/Ti) of the sintered Li 2 TiO 3 pebbles was 1.99, as evaluated by ICP- AES, which was nearly identical to the original mixing ratio of starting materials. in air at 873 K for 5 h in air at 1373 K for 2 h 15/20 ● Li 2 TiO 3 2θ (deg) ● ● ● ● ● ● ● ● ● XRD

Characteristics Li 2 TiO 3 pebbles 16/20 SEM Optical microscope The average diameter of the sintered Li 2 TiO 3 pebbles was 0.95 mm, as measured by optical microscopy. The average grain size of the sintered Li 2 TiO 3 pebble was < 5 μm, as measured by SEM The diameter of the pebbles and the grain size after sintering were 1 mm and < 5 μm, respectively, indicating that the pebbles were be suitable for the DEMO blanket.

Fabricating Li 2+x TiO 3+y pebbles Slurry (Li 2+x TiO 3+y with binder) Emulsion method Gel-spheres Sintered pebbles Pebble Fabrication (a) Pebbles at the top of the calcined pebbles. (b) Pebbles under those shown in (a). Calcination in container The color change was due to the residual binder. Because pebbles at the top were in contact with air during calcination, they could be removed. Therefore, it was necessary to calcine the sample in enough air to remove the binder. Only the white calcined pebbles were sintered to make the final pebbles. in air at 873 K for 5 h in 1%H 2 -He at 1373 K for 2 h 17/20

Sintered Li 2+x TiO 3+y pebbles 200μm 5μm (a)Surface (b)Cross-section Photo of sintered Li 2+x TiO 3+y pebbles SEM emages of sintered Li 2+x TiO 3+y pebbles 1) Average diameter was 1.4 mm. 2) Average grain size on the surface and the cross section was < 5 μm and 5 – 10 µm, respectively. Considering the tritium release characteristics and the packing factor of the blanket, the desired pebble diameter and grain size after sintering were 1 mm and < 5 μm, respectively. Therefore, the next step was to optimize the granulation conditions to reach these target values. 18/20

Sintered Li 2+x TiO 3+y pebbles 2θ (deg) ● Li 2 TiO 3 ● ● ● ● ● ● ● ● ● XRD patterns of sintered Li 2+x TiO 3+y pebbles The XRD results of the sintered Li 2+x TiO 3+y were almost the same as those of the Li 2 TiO 3 listed in the JCPDF. No other phases or impurities were observed. Molar ratio of Li 2+x TiO 3+y pebbles Fabrication processMolar ratio (Li/Ti) Original mixing ratios of LiOHH 2 O and H 2 TiO Powder of the raw material (Li 2+x TiO 3+y ) 2.2 Gel-spheres2.18 Calcined Li 2+x TiO 3+y pebbles Sintered Li 2+x TiO 3+y pebbles The loss of Li was likely because the Li evaporated with the binder during calcination. The molar ratio of the sintered Li 2+x TiO 3+y was smaller than the ratio in the original mixture of LiOHH 2 O and H 2 TiO 3 (Li/Ti = 2.2) but higher than the stoichiometric value of Li 2 TiO 3 (Li/Ti=2.0). 19/20

Summarizes the characteristics Diameter (mm)1.40 Sphericity1.02 Grain size (μm) < 5 (Surface) 5 – 10 (Cross section) Ratio of Li/Ti Crystal structureSingle phase of Li 2+x TiO 3+y Summarizes the characteristics of the sintered Li 2+x TiO 3+y pebbles The emulsion method was suitable for fabricating the advanced tritium breeder pebbles. 20/20

Conclusion We developed an emulsion method to fabricate Li 2 TiO 3 pebbles with additional Li (Li 2+x TiO 3+y ) as an advanced tritium breeder. The average diameter and the sphericity of the pebbles were 1.40 mm and 1.02, respectively. The molar ratio (Li/Ti) of the pebbles made by the emulsion method decreased from 2.2 to , but the ratio was still higher than that in the stoichiometric Li 2 TiO 3 (Li/Ti = 2.0). Thus, the emulsion method is a promising method for the fabrication of advanced tritium breeder pebbles. 21/20