Search

A bionic concept originating from the mechanism of gastric mucosa protecting a gastric wall from corrosion by gastric acid is creatively proposed, with the intention of finding a new way to reduce the corrosion of insulation coatings in liquid metal blankets. A compatible fluid barrier that mimics the function of gastric mucosa is used to prevent the flowing liquid metal from contacting the inner wall of a loop pipeline. The design of the bionic structure and the control of the barrier fluid are the most critical and difficult. A single-channel simulation is performed using Computational Fluid Dynamics (CFD) analysis to evaluate the effect of a compatible fluid barrier on separating the liquid lithium and insulation coating. The results show that the compatible fluid barrier can completely cover the inner wall of the pipeline within which the liquid metal is flowing, indicating that the bionic design can eliminate the corrosion of insulation coatings with flowing liquid lithium. Based on this, a compatible fluid barrier is investigated with multiple conditions, including the coverage area and film thickness, by changing the velocity ratio of the lithium to the barrier fluid, the shape of the inlet port, and the curvature radius of the bend pipes. In addition, an S-shaped pipe is confirmed to be completely corrosion free. This bionic concept is aimed at all corrosive liquid metals, and this work only starts with the extreme case of pure lithium. This work is expected to provide a preliminary feasibility basis for anti-corrosion design for a pipeline with dual fluids. [ABSTRACT FROM AUTHOR]

The 4mm thick plate of V–4Ti–4Cr alloy (NIFS-HEAT-2) was bead-on-plate welded by electron beam (1.5kW) under high vacuum atmosphere. The samples were placed in V–5Ti capsule subsequently filled by liquid Li (8g) in glove box under high-purity He atmosphere in order to avoid contamination of Li by O and/or N. Static corrosion tests were carried out at 700°C for 500h utilizing vertical water cooling furnace placed in the same glove box. During the test, liquid Li contacted with recirculating helium which was continuously purified with respect to O (4–30wppm). After the test, the samples were cleaned against adhered Li in 30%H2O2 at 5°C in order to avoid hydrogenation of V-alloy. After the welding, the impact properties of the weld metal measured at 77K remained high enough (9.5J) while fracture mode was ductile in spite of the solid-solution hardening by O released from Ti–C,O,N precipitates during high temperature electron beam welding. In contrast, impact properties of weld metal degraded after exposure to liquid Li (2.2J) and post welding heat treatment (1.8J) both carried out at 973K. Character of fracture mode also changed to brittle due to the re-precipitation assisted hardening caused by aging effect. [ABSTRACT FROM AUTHOR]

The promising way to mitigate magneto-hydrodynamic (MHD) pressure drop in self-cooled Li/V-alloy blanket is to use electrical insulating coating. The chemical formation of Er2O3 layer on V–4Cr–4Ti during exposure in liquid Li doped with Er was explored. V–4Cr–4Ti specimens were oxidized at 973 K for 0.5–8 h, annealed at 973 K for 16 h, and finally exposed for 20–300 h at 873 K. The Er2O3 layer formed on V–4Cr–4Ti specimens that were oxidized plus annealed, but did not form on either as-received or oxidized only specimens. The resistivity of V–4Cr–4Ti coated with Er2O3 is ∼1013 Ω cm at room temperature which is much larger than the minimum requirement. The Er2O3 layer is stable in liquid Li after 300 h at 873 K. The results indicate that the oxygen source to form Er2O3 layer is the pre-charged oxygen in V–4Cr–4Ti, and that annealing after oxidation to homogenize the oxygen distribution in specimen is necessary. [Copyright &y& Elsevier]

• Oxide and SiC materials are developed for MHD insulators in liquid metal blanket. • Electrical insulating performances at high temperatures could satisfy requirements. • Radiation induced conductivity phenomenon would not be an issue in development. • In addition to irradiation damage, there is concern about injection of recoil atoms. Various oxides and SiC have been proposed as candidate materials for electrical insulation coatings and inserts to suppress the magnetohydrodynamic (MHD) pressure drop in liquid metal fusion blanket systems. From the early stage of the MHD insulator development, the magnitudes of the radiation-induced conductivities (RICs), i.e., increases in conductivities by radiation excitation, have been evaluated on bulk and coated specimens by using several radiation sources. While the insulating performances of the oxide coated and SiC plate specimens are inferior to those of high quality and purity bulk materials due to cracks, pits, sintering additives, etc., the results indicate that the RIC phenomenon would not prevent the MHD insulators from achieving the required performances (10−3–10−2 S/m for coatings, 102 S/m for inserts) at the first wall of the blanket (500–700 °C, several kGy/s). The recent design investigation of blanket modules for DEMO reactor conditions provides more precise information for prediction of the performances in reactors and conditions to be simulated in the future irradiation damage studies. In the case of the coatings, the suppression of recoiled Li from the liquid metal breeder/coolant might be an issue to be considered in the development. [ABSTRACT FROM AUTHOR]

Abstract: Corrosion experiments of 9Cr-ODS steel were carried out in static Li at 873K for 250h and compared with those of 9Cr-ODS in Pb–Li at the same exposure conditions. After exposure to liquid Li, 9Cr-ODS showed slight weight loss and decrease in hardness near surface. The tensile property exhibited a negligible change at 973K and the creep property degraded at 973K. By metallurgical analyses, 9Cr-ODS demonstrated a non-uniform corrosion behavior by preferential grain boundary attack and pronounced nodule-like morphology. The slight depletion of Cr was detected to about 15μm in depth by chemical composition analyses. According to the calculation of free energy of formation, the nano-scale oxide particles of TiO2 in 9Cr-ODS were thermodynamically less stable while Y2O3 were more stable compared with those of Li2O in Li environment. However, Y2O3 may be reacted with Li to form YLiO2. The mechanism of corrosion was proposed as the slight dissolution of Cr and Fe in matrix into liquid Li, chemical interaction of nano-scale oxide particles with Li, preferential grain boundary attack and penetration of Li, and finally development of extreme nodule-like structure during cleaning of Li. On the contrary, 9Cr-ODS showed much larger weight loss and depletion of Cr near surface but less marked corroded morphology in Pb–Li than in Li, which may be derived from higher solubility of Cr and Fe and lower activity of Li in Pb–Li than in Li. [Copyright &y& Elsevier]

Abstract: The corrosion of reduced activation ferritic martensitic steel, JLF-1 (Fe–9Cr–2W–0.1C), in high-purity Li was quite small. However, carbon in the steel matrix was depleted by the immersion to the Li. The depletion caused the phase transformation of the steel surface in which the morphology of the steel surface changed to ferrite structure from initial martensite structure. The phase transformation degraded the mechanical property of the steel. However, the carbon depletion and the phase transformation of the steel were suppressed in carbon doped Li. The carbon in the steel was chemically stable and did not dissolve into the Li when the carbon potential in the Li was high. The concentration of nitrogen and oxygen must be kept as low as possible because the corrosion was larger when the concentration of oxygen or nitrogen in the Li was higher. The chemical reaction between the steel and the Li compounds of Li3N and Li2O was also investigated. The corrosion of the JLF-1 steel in Pb–17Li was summarized as the dissolution of Fe and Cr from the steel into the melt. The corrosion of the specimen with Er2O3 coating fabricated by metal organic decomposition process in the Li and the Pb–17Li was investigated. The coating was deformed, cracked and partially exfoliated in the liquid metals, though the oxide itself was chemically stable in the liquid breeders. The damage was probably made by the stress, which was generated by a large difference of the thermal expansion ratio between the solidified Li or Pb–17Li and the coating during a heat up and a cool down process of the corrosion test. [Copyright &y& Elsevier]

Abstract: This paper reports a measurement technique for surface waves on a liquid lithium jet, and its experimental results for the purpose of study on a Li target of the International Fusion Materials Irradiation Facility (IFMIF). The statically characteristic of the waves was successfully clarified by a contact-type liquid level detector and an analysis method of the obtained data newly proposed in this paper. The detail procedure of the measurement method is described in this paper. As the results, it was found that the wave distributions in the all jet velocity range up to 15m/s were conformed each other in normalized form and Rayleigh distribution which is one of popular model to show irregular water waves, and found that the mean wave height increased with increasing of the flow velocity. [ABSTRACT FROM AUTHOR]

Abstract: Hydrogen permeation window is candidate not only for tritium recovery system from molten lithium, but also for hydrogen monitor for molten lithium because hydrogen permeation rate is dominated by hydrogen concentration. In this study, in-situ observation of deuterium hot trapping by yttrium in molten lithium was performed, measuring HD and D2 permeation through an iron wall at 773, 823 and 873K. Deuterium permeation showed good agreement with deuterium concentration in lithium and iron permeation wall was found to be reliable for deuterium monitoring for liquid lithium around a hundred wppm. As a result of in-situ observation, gettering rate for deuterium was 6×10−5 mol/m2/sec at 773K, 5×10−4 mol/m2/sec at 823K and 4×10−4 mol/m2/sec at 873K. Oxidation or nitridation at the surface of yttrium may suppress gettering rate at 873K. [Copyright &y& Elsevier]

Abstract: International Fusion Materials Irradiation Facility (IFMIF) employs liquid lithium as D+ beams target. The liquid Li target is formed as flat plane free-surface flow by a nozzle and flows at high speed around 15m/s. This paper focuses on flatness of the liquid Li target. The Li flow experiment was conducted in Osaka University Li Loop with a test section which was 1/2.5 scaled model of IFMIF. The thickness of the Li flow was measured and obtained by a contact method which was developed for the measurement. Analytical study on Kelvin wake and numerical calculation on the wake near the side wall of the flow channel were also conducted and compared with the experimental results. As a result, the positions of the wake crest obtained from both of the experiment and numerical calculation assuming contact angle 140° agreed well with the iso-phase line of the analytical model. The generation of the wake likely depends on wettability between Li and the structural material which is 304SS in the present study. [Copyright &y& Elsevier]

Nitrogen concentration in liquid lithium was controlled by the method of hot trapping. V–Ti alloy and chromium were used as nitrogen gettering materials. Chromium is known to form ternary nitride with lithium. Gettering experiments were conducted at 823 K for 0.8–2.2 Ms. Under high nitrogen concentration in liquid lithium, above 10−2 mass%, nitrogen gettering effect of chromium was found to be larger than that of V–10at.% Ti alloy. Nitrogen gettering by chromium at 823 K reached a limit at about 6.5×10−3 mass% of nitrogen concentration in liquid lithium. Instability of ternary nitride of chromium and lithium below this nitrogen concentration in liquid lithium was considered to be the reason for this limit. The composition of the ternary nitride that was formed in this study was considered to be Li6Cr(III)3N5. In addition, immersion experiments of yttrium with V–10at.% Ti alloy were performed. It was found that nitriding of yttrium in liquid lithium is controlled by nitrogen gettering effect of V–10at.% Ti alloy. [Copyright &y& Elsevier]