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AlN/Er 2 O 3 multi-layer coatings, as a novel hydrogen isotope permeation barrier for nuclear reactor and hydrogen energy field, were prepared by magnetron sputtering coupled with metal-organic decomposition on the surface of reduced activation ferrite/martensitic steel. The thickness of the Er 2 O 3 layers was adjusted by spin coating several times, the adhesion of the layers was tested with a micron scratch tester, and the microstructure and surface composition of the layers were analyzed by TEM and XPS. The results indicate the absence of evident crack holes on the coating surface, uniform distribution of elements without segregation, and satisfactory densification. In comparison with the individual Er 2 O 3 coating, the multi-layer coating incorporating AlN as the interlayer exhibits enhanced adhesion strength, which could effectively mitigate the thermal mismatch phenomenon of Er 2 O 3 under high temperature conditions. Electrochemical hydrogen permeation and high temperature gas pressure driven deuterium permeation tests demonstrated that the permeability resistance of the AlN/Er 2 O 3 coating does not linearly increase with its thickness. The hydrogen permeation reduced factor of the coating reaches its maximum value when the thickness of the Er 2 O 3 coating is 1500 nm. [ABSTRACT FROM AUTHOR]

Helium-Cooled Pebble-Bed (HCPB) will be chosen as the preferred Test Blanket Modules (TBMs) in International Thermonuclear Experimental Reactor (ITER) and DEMO fusion reactor. Lithium metatitanate (Li 2 TiO 3) ceramic pebbles are proposed as one of promising candidates of solid-type breeder blanket for the outstanding comprehensive performance. Previous fabrication methods still need to be improved on the mild preparation condition, uniform diameter, and high sphericity. In this paper, an improved wet process for pebble fabrication based on polymer-assisted sedimentation is employed. Gel pebbles are formed by dropping the slurry droplets into hot viscous liquid, and the spherical drops are solidified by polymerization reaction inside the droplet during sedimentation. In sintering process, the relationship between the sintering condition and crystalline structure of Li 2 TiO 3 is carefully discussed. Li 2 TiO 3 condensation and phase transitions are studied in particular. Finally, the optimal sintering temperature and time have been determined. This method could meet requirements for industrial mass production of the Li 2 TiO 3 pebbles, due to the mild preparation conditions, simplified transfer and purification process. [ABSTRACT FROM AUTHOR]

Tritium breeder is an important functional material in d-T fusion reactor blanket serving the purpose of tritium re-production and energy conversion. Presently, Li 2 TiO 3 ceramics is considered as the most promising solid tritium breeder for its good chemical stability, high mechanical strength and excellent tritium release performance. However, low lithium content and lithium evaporation at high temperature lead to a low tritium breeding ratio. In the paper the neutron multiplier element, Pb, is introduced into Li 2 TiO 3 to obtain lithium lead titanate (Li 2 Pb x Ti 1-x O 3) as tritium breeder, which combined the advantages of Pb and Li 2 TiO 3 ceramic. Li 2 Pb x Ti 1-x O 3 powders were synthesized via a sol-gel method, employing lithium acetate, tetrabutyl titanate, and lead acetate, with varying lead contents. The characterization results indicate that at a molar ratio of titanium to lead of 1:2, Li 2 TiO 3 -Li 2 PbO 3 eutectic phase could be formed. The tritium breeding ratio (TBR) of Li 2 Pb x Ti 1-x O 3 materials were evaluated by Monte Carlo Code, which was notably influenced by the lead content, exhibiting a continuous increase with higher Pb content and neutron energy. The Li 2 Pb x Ti 1-x O 3 pebbles were prepared by freeze-drying route. The mechanical strength of Li 2 Pb x Ti 1-x O 3 pebbles could be affected significantly by the lead content. Compared to the conventional Li 2 TiO 3 ceramics, the Li 2 Pb 0.4 Ti 0.6 O 3 ceramics exhibits a higher crushing load of 25.33 N. [ABSTRACT FROM AUTHOR]

• A modified freeze-granulation method with great efficiency is developed for fabricating Li 2 TiO 3 tritium breeding pebbles. • The mechanism of pebbles fabrication with good sphericity is provided in detail. • The relationship between the mechanical performance of pebbles and the sintering condition is carefully discussed. Lithium metatitanate (Li 2 TiO 3) ceramic is an important candidate for tritium breeding material in fusion reactor blanket. Nevertheless, mass production has become an important factor restricting the application of Li 2 TiO 3 pebbles. In this paper, freeze-granulation method is innovatively modified by drying frozen pebbles in acetone. The principle of modified freeze-granulation method is explained in detail. Influence of PVA content, sintering temperature and sintering time on mechanical performance of frozen pebbles dried in acetone are carefully discussed. The modified process could shorten the drying time in 30 min under the premise of good crushing load and thus conducive to improve the efficiency of mass production of tritium breeding ceramic pebbles potentially in the future. Finally, the Li 2 TiO 3 pebbles present good sphericity, high average crushing load (38 N), abundant and uniform pores which are beneficial to tritium release. [ABSTRACT FROM AUTHOR]

Lithium titanate pebbles are proposed as one of promising candidates of tritium breeder for the outstanding comprehensive performance, but the low lithium density and lithium vaporization still need to be overcome. In this paper, phase transitions and lithium loss under different Li/Ti ratio are studied in particular. The relationship between Li/Ti ratio and mechanical performance is carefully discussed. Finally, excessiveness of lithium source in raw materials is optimized about 5%, in order to compensate lithium loss in sintering process and further improve the phase purity. A suitable Li/Ti ratio about 2.1 could balance the requirements of high lithium content and excellent mechanical strength. [ABSTRACT FROM AUTHOR]

• Long-term corrosion behavior in flowing liquid PbLi is studied by a rotating corrosion testing facility. • Flowing situation will accelerate the chemical corrosion and physical erosion of Al 2 O 3 by mechanical flushing action. • Non-oxide ceramics with outstanding corrosion resistant are proposed as tritium permeation barriers for PbLi blanket. Liquid PbLi blanket is one of the promising designs for fusion reactor, which requires tritium permeation barriers (TPBs) with higher corrosion resistance. The corrosion behavior under flowing PbLi is more reasonable for it is closer to the actual working condition of the liquid blanket. In this paper, long-term corrosion behavior of three ceramics for TPB in flowing PbLi are studied using a rotating corrosion facility. Results show that flowing situation will accelerate the chemical corrosion and physical erosion of Al 2 O 3. AlN and SiC present outstanding corrosion resistance which are proposed as the tritium permeation barriers for liquid PbLi blanket. [ABSTRACT FROM AUTHOR]

• A compact apparatus was built to study the compatibility of blanket materials. • The coupling effect of the corrosion and erosion accelerates the process. • The compatibility of RAFMS is slightly better than that of 316 L and ODS. A rotating corrosion test device has been developed to study the compatibility between liquid tritium breeder material and structure materials for fusion facility. The corrosion behaviors of three samples made of reduced activation ferritic/martensitic steel (RAFMS), 316 L stainless steel and oxide dispersion strengthened steel (ODS), are studied in liquid Pb-17Li at 500℃ for an exposure of 1000 h. The weight changes of the specimens are obtained before and after test. The analyses of surface morphology and component are characterized by SEM, EDS and XRD methods. Results show that weight-loss rate of RAFMS is lower than that of 316 L and ODS in the experiment. It indicates that the corrosion mechanism is governed by some or all dissolution of alloy elements (such as Cr, Ni) from the sample surface into liquid Pb-17Li and the exfoliation from the corroded surface by the flowing Pb-17Li. Specifically, the dispersed Al 2 O 3 particles in ODS is easy to be corroded in liquid Pb-17Li and then provide corrosion points to accelerate dissolution of Ni-Fe austenite. The compatibility of RAFMS with liquid Pb-17Li is slightly better than that of 316 L and ODS in the current experimental period. [ABSTRACT FROM AUTHOR]

• Thermodynamic calculations predict chemical stabilities of ceramics in liquid lithium. • Experiments of static compatibility between liquid lithium and four ceramics are carried out. • The tritium permeation barriers adapted to liquid lithium or alloy fluids should employ rare earth oxides, metallic nitrides and other non-oxide ceramics. For the design of liquid lithium first wall in future fusion reactor, chemical compatibility between the tritium permeation barrier (TPB) and liquid lithium should be studied preferentially. The redox reaction is studied from the perspective of thermodynamics at different temperature, which indicates that metallic nitrides and rare earth oxides are predictable to provide higher stability in lithium corrosion situation. Then static compatibilities of Al 2 O 3 , AlN, SiC and Er 2 O 3 ceramics with liquid lithium are tested. The surface analysis of TPB and lithium droplets shows that Al 2 O 3 ceramic could react with molten Li, though it is considered as the preferred candidate of TPB for its easy fabrication, low cost, and self-repair ability. However, the other three ceramics did not show any reduction product peak, indicating the high stability with liquid lithium. These results provide meaningful compatibility with liquid Li and valuable reference in engineering design of structural and TPB materials for future fusion device. [ABSTRACT FROM AUTHOR]