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; Kano, Shigeki; Tachi, Yoshiaki; Kawai, Masataka *
JNC TN9410 2000-013, 89 Pages, 2000/09
JNC-TN9410-2000-013.pdf:5.28MB
Lithium is one of goodcoolants because of high boiling point (1317
C), small specific gravity (0.47 at 600C) and large specific heat (1cal/g/C). Therefore if lithium will be used in fast reactor for coolant, the heat efficiency of reactor will largely increase. Here the fundamental properties of lithium and the results of examination on chemical reaction, combustion and extinction are shown. These examinations were also carried out on sodium to compare with lithium. The differences between both are that lithium reacts more moderately with water, not explosive, and is not combustible but after ignition burns at higher temperature and longer.
Tachi, Yoshiaki; Kano, Shigeki; *; *
Journal of Nuclear Materials, 271-272, p.486 - 490, 1999/05
Times Cited Count：6 Percentile：45.48(Materials Science, Multidisciplinary)None
Kaji, Yoshiyuki; Tsuji, Hirokazu; Sakino, Takao*; Fujita, Mitsutane*; Kinugawa, Junichi*; Tachi, Yoshiaki*; Saito, Junichi*; Kano, Shigeki*; Shimura, Kazuki*; Nakajima, Ritsuko*; et al.
JAERI-Tech 99-007, 32 Pages, 1999/02
no abstracts in English
Tsuji, Hirokazu; ; Fujita, Mitsutane*; Kano, Shigeki*; Tachi, Yoshiaki*; Shimura, Kazuki*; Nakajima, Ritsuko*; Iwata, Shuichi*
Advances in Science and Technology, 24, p.417 - 424, 1999/00
no abstracts in English
Tsuji, Hirokazu; ; Fujita, Mitsutane*; Kurihara, Yutaka*; Kano, Shigeki*; Tachi, Yoshiaki*; Shimura, Kazuki*; Nakajima, Ritsuko*; Iwata, Shuichi*
Journal of Nuclear Materials, 271-272, p.486 - 490, 1999/00
no abstracts in English
Saito, Junichi; Kano, Shigeki; *; Morinaga, Masahiko*
Journal of Nuclear Materials, 264, p.216 - 227, 1999/00
Times Cited Count：5 Percentile：40.62(Materials Science, Multidisciplinary)None
Saito, Junichi; Kano, Shigeki; *; Kudo, Hisaaki*
JAERI-Review 98-016, p.164 - 166, 1998/10
None
Saito, Junichi; Tachi, Yoshiaki; ; Kano, Shigeki
PNC TN9410 98-082, 60 Pages, 1998/08
Ceramics possessing high temperature strength are promising matelials for the structural application in severe environment. The development of ceramics has been carried out in order to use them in FBR environment such as liquid sodium. In particular, corrosion behavior of ceramics has been investigated to improve the corrosion resistance in liquid sodium. However, the corrosion mechanism of ceramics was not comprehended in detail even now. Because corrosion products which were deposited on the surface of test pieces a during corrosion test and played an important role in corrosion behavior were not detected distinctly after the corrosion test. In this study, an ion implantation technique was applied to understand the corrosion mechanism of ceramics in the stead of the conventional corrosion test. Sodium ions were implanted in ceramics (100keV, 1.9
10
ions/cm
) and then heat treatment was performed at either 923K or 823K for 36ks in argon atmosphere. After that, products on the surface were analyzed using SEM and TEM observation and X-ray diffraction. Consequently, a kind of the corrosion product was not identified exactly, but the presence of corrosion products was confirmed on the surface. It caused by the amount of corrosion products was only a few. In future, it is necessary to carry systematically out the implantation and heat treatment under various conditions. Therefore, it seems that the beneficial information will be obtained to understand the corrosion mechanism of ceramics.
Saito, Junichi; Morinaga, Masahiko*; Kano, Shigeki
PNC TN9410 98-072, 97 Pages, 1998/07
Research on structural materials which will be utilized even in the severe environment of high-temperature liquid alkali metals has been promoted in order to develop the frontiers of materials techniques. The super-heat resisting alloys which are based on refractory metals, Nb and Mo, are aimed as promising materials used in such an environment. The corrosion resistance in liquid Li and the mechanical properties such as creep and tensile strengths at high temperatures are important for these structural materials. On the basis of many expeliments and analyses of these properties at 1473K, the material design of Nb-based and Mo-based alloys has-been carried out successfully. In this report, all the previous experimental results of corrosion tests in liquid Li were summarized systematically for Nb-based and Mo-based alloys. The corrosion mechanism was proposed on the basis of a series of analyses, in particular, focussing on the deposition mechanism of corrosion products on the surface and also on the initiation and growth mechanism of cracks on the corroded surface of Nb-based alloys. The principal results are as follows. (1)For the deposition mechanism, a reaction took place first between dissolved metallic elements and nitrogen which existed as an impurity in liquid Li and then corrosion products (nitrides) precipitated on the metal surface. Subsequently, another reaction took place between dissolved metalic elements in liquid Li, and corrosion products (intermetallic compounds) precipitated on the metal surface. The composition of deposited corrosion products could be predicted on the basis of the deposition mechanism. (2)For the crack initiation mechanism, the chemical potential diagrams were utilized in order to understand the formation of Li-M-O ternary oxides which caused cracks to be formed on the corroded surface. Consequently, it was evident that not only the concentration of the dissolved oxygen in the alloy but also the concentration of Li which ...
; Kano, Shigeki
PNC TN9410 98-049, 55 Pages, 1998/03
Low speed tribological properties of stainless steel, ceramics and hard metals were investigated in air at room temperature and in nitrogen atmosphere at high temperature for the consideration of sliding type support structure in intermediate heat exchanger of fast reactor. The following results are obtained. (1)In low speed friction measurements in air at room temperature, friction coefficients of ceramics and hard metals were smaller than that of stainless steel. Surface roughness of the specimens increased the friction force and silicon carbide showed the smallest friction coefficient among the specimens with mirror polished surface. (2)From the results of friction measurements at various sliding speeds in air at room temperature, friction coefficients of ceramics and hard metals were always stable and lower than that of stainless steel. Among ceramics, PSZ showed the smallest friction and silicon carbide showed the most stable friction at any sliding speeds. (3)Friction coefficients of silicon carbide and silicon nitride in nitrogen atmosphere at high temperature showed low values as measured at room temperature. On the contrary, friction coefficient of stainless steel measured in nitrogen atmosphere at high temperature were higher than that measured at room temperature, over 1. (4)In the reciprocal sliding tests in nitrogen atmosphere at high temperature, friction coefficient of stainless steel were over 1. On the contrary, the friction coefficients of ceramics were less than 1 instead of chipping during the slidings.
; Hirakawa, Yasushi; Kano, Shigeki; Yoshida, Eiichi
PNC TN9410 98-048, 56 Pages, 1998/03
Planar specimens of functionally gradient material (FGM) for thermal stress relaxation in fast reactor environment were formed and evaluated. FGMs of Al
O
-SUS316L system and YO-SUS316L system were deposited on SUS316L substrates by low pressure plasma spraying. The deposited coatings with 6 layers in which the ratio of ceramics/SUS316FR changes from 0 to 100% by 20% were successfully formed. Cross-sectional observation of the coatings showed no cracks and the hardness in the coating increased continuously from the substrate to the surface. From the results of X-ray diffraction, there were no changes in the structure of SUS316L and YO between the powder and the coating. On the contrary, in the case of AlO, 
- AlO phase was detected in the coating formed from 
_
_
$ powder. The specimens were exposed in liquid sodium at 823K or 923K for 3.6Ms(1000h). The coatings were damaged with many cracks in liquid sodium. It was revealed that the bonding strength between the sprayed particles were not sufficient. To improve the stability in liquid sodium, another specimens were formed with changing the chamber pressure during deposition. From the microstructural inspections of the specimens, the coating formed at higher chamber pressure showed less porosity.
; Kano, Shigeki; ; Tachi, Yoshiaki; Hirakawa, Yasushi; Yoshida, Eiichi
PNC TN9410 98-021, 68 Pages, 1998/02
Engineering ceramics have excellent properties such as high strength, high hardness and high heat resistance compared with metallic matelials. To apply the ceramic in fast reactor environment, it is necessary to evaluate the sodium compatibility and the influence of sodium on the mechanical properties of ceramics. In this study, the influence of high temperature sodium on the mechanical properties of sintered ceramics of conventional and high purity AlO, SiC, SiAlON, AlN and unidirectional solidified ceramics of AlO/YAG eutectic composite were investigated by means of flexure tests. Test specimens were exposed in liquid sodium at 823K and 923K for 3.6Ms. There were no changes in the flexural strength of the conventional and high purity AlO, AlN and AlO/YAG eutectic composite after the sodium exposure at 823K. On the contrary, the decrease in the flexural strength was observed in SiC and SiAlON. After the sodium exposure at 923K, there were also no changes in the flexural strength of AlN and AlO/YAG eutectic composite. In the conventional and high purity AlO and SiC, the flexural strength decreased and signs of grain boundary corrosion were detected by surface observation. The flexural strength of SiAlON after the sodium exposure at 923K increased instead of severe corrosion. In the specimens those showed no changes in the flexural strength, further exposure in sodium is needed to verify whether the mechanical properties degrade or not. For SiAlON, it is necessary to clarify the reason for the increased strength after the sodium exposure at 923K.
Tachi, Yoshiaki; Hirakawa, Yasushi; Kano, Shigeki; Yoshida, Eiichi
PNC TN9410 98-054, 57 Pages, 1998/01
It has been progressed as the Frontier Materials Research to research and develop ceramics to apply for several components of fast breeder reactor using liquid sodium as coolant instead of metallic materials. Grain boundary of ceramics has peculiar properties compared with matrix because most of ceramics are produced by hardening and firing their raw powders. Some previous researchers indicated that ceramics were mainly corroded at grain boundaries by liquid sodium, and ceramics could not be used under corrosive environment. Thus, it is the most important for the usage of ceramics in liquid sodium to improve corrosion resistance of grain boundaries. In order to develop the advanced ceramics having good sodium corrosion resistance among fine ceramics, which have recently been progressed in quality and characteristics remarkably, sodium corrosion behaviors of typical sintering additives such as MgO, YO and AIN etc. have been examined and evaluated. As a result, the followings have been clarified and some useful knowledge about developing advanced ceramics having good corrosion resistance against liquid sodium has been obtained. (1)Sodium corrosion behavior of MgO depended on Si content. Samples containing large amount of Si were corroded severely by liquid sodium, whereas others with low Si contents showed good corrosion resistance. (2)Both YO and AIN, which contained little Si, showed good sodium corrosion resistance. (3)MgO, YO and AIN ale thought to be corroded by liquid sodium, if they contain some SiO. Therefore, in order to improve sodium corrosion resistance, it is very important for these ceramics to prevent the contamination of matrix with SiO through purity contlol of their raw powders.
Nakajima, Ritsuko*; Shimura, Kazuki*; Fujita, Mitsutane*; Tsuji, Hirokazu; ; Tachi, Yoshiaki*; Kano, Shigeki*; Iwata, Shuichi*
Joho Chishiki Gakkai Dai-6-Kai Kenkyu Hokokukai Koen Rombunshu, p.43 - 46, 1998/00
no abstracts in English
Tsuji, Hirokazu; ; Fujita, Mitsutane*; Kano, Shigeki*; Tachi, Yoshiaki*; Shimura, Kazuki*; Nakajima, Ritsuko*; Iwata, Shuichi*
Materials for Advanced Power Engineering 1998, p.1739 - 1745, 1998/00
no abstracts in English
Tachi, Yoshiaki; Kano, Shigeki
Nihon Genshiryoku Gakkai-Shi, 40(6), p.495 - 500, 1998/00
Times Cited Count：0 Percentile：0.01(Nuclear Science & Technology)None
Shimura, Kazuki*; Nakajima, Ritsuko*; Fujita, Mitsutane*; Kurihara, Yutaka*; Tsuji, Hirokazu; ; Tachi, Yoshiaki*; Kano Shigeki*; Iwata, Shuichi*
JAERI-Tech 97-047, 22 Pages, 1997/10
no abstracts in English
Saito, Junichi; Kano, Shigeki
PNC TN9410 97-073, 69 Pages, 1997/07
In order to understand the effect of implanted atom in ceramics and metals on the sodium corrosion, the electronic structures of un-implanted and implanted materials were calculated using DV-X
cluster method which was one of molecular orbital calculations. The calculated materials were 
-SiN
, -SiC and -SiC as ceramics, and f.c.c.Fe, b.c.c.Fe and b.c.c. Nb as metals. An Fe, Mo and Hf atom for ceramics, and N atom for metals were selected as implanted atoms. It is known that these metallic elements have exhibited the excellent corrosion resistance against liquid sodium in previous experiments. The summary of results is shown as follows. Energy levels of implanted atom appeared in or near energy band gap in ceramics. The change of ionicities of each element which showed amount of transferred charges and bond order which showed the covalent bond strength between atoms depended on substrates and implanted atoms. The strength of ionic bonding between atoms reduced in -SiN, as ionicities of constituent atom decreased by the implanted atom. The decreases of ionicity depended on implanted atoms and Hf implantation showed the largest decrease in implanted atoms. The bond order in -SiN and -SiC decreased by the implantation. When the implanted atom occupied at substitutional site in -SiC, the ionicities decreased but the bond order increased. Electron state densities of s and p components of implanted N atom appeared lower energy level than that of d component of constituent Fe (or Nb) atoms. The charge transfer took place to N atom from surrounding Fe (or Nb) atoms. Thus the ionicity of N atom was larger than mother metal. The bond order between mother elements reduced by N implantation. In particularly, there were significant decreases of bond order in b.c.c. Fe and b.c.c. Nb. Hence, the bond order in whole cluster decreased largely except for f.c.c. Fe. Consequently, it is ...
Tachi, Yoshiaki; *; Kano, Shigeki
PNC TN9430 97-003, 13 Pages, 1997/05
The database system named "Data Free Way (DFW)" has been constructed in collaboration with PNC, NRIM, JAERI and JST, and a lot of materials data have been stored in DFW with its improvements. Experimental and literature data on corrosion behaviors of ceramics and refractory metals based alloys against alkali metals have been inputted in DFW of PNC site. The DFW system and the network situation around it have been improved to retrieve distributed database by using Internet. The WWW server has been set in DFW machine for client-server system and user's interface has been developed in order to retrieve the database through WWW browser. The DFW server machine of PNC has been set outside of seculity system called firewall for access from other organizations directly, and the local area network of DFW (DFW-LAN) has been constructed to be possible to use and maintain DFW system through the PNC main network. This consists of some personal computers, which play part in preparation, input and analysis of database, instead of engineering workstation. These improvements have brought more effective value to DFW as a advanced material database system.
Kano, Shigeki; Tachi, Yoshiaki; Fujita, Mitsutane*; Kurihara, Yutaka*; Tsuji, Hirokazu*; Shindo, Masami*; Yokoyama, Norio*; Shimura, Kazuki*; Nakajima, Ritsuko*
PNC TY9449 97-001, 109 Pages, 1997/04
None
