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Journal Articles

Study of optimum composition of extra high purity Ni-Cr-W-Si alloy for advanced reprocessing plant

Ioka, Ikuo; Suzuki, Jun; Kiuchi, Kiyoshi; Nakayama, Jumpei*

Proceedings of 2nd International Workshop on Structural Materials for Innovative Nuclear Systems (SMINS-2), p.391 - 400, 2012/12

Optimization of composition for high Cr-W-Si Ni base alloy has been studied to apply to a nitric acid with high oxidation-reduction potential of advanced reprocessing plants. The corrosion resistance of the Ni base alloy is superior to that of conventional stainless steels. In addition, The Ni base alloy has an excellent resistance of weld crack and ability of plastic deformation caused by extra high purity (EHP) refining technology. However, the Ni base alloy has a technical limitation in hot working and welding for practical use. Several Ni base EHP alloys with different content of Si and W were manufactured to choose an optimum composition range without losing corrosion resistance. High strain rate tensile tests at high temperature, corrosion tests and weldability tests were carried out to examine the optimum composition range of Ni base EHP alloy.

Journal Articles

Microstructural evolution and void swelling in extra high purity Ni-base superalloy under multi-ion irradiation

Kim, G.; Shiba, Kiyoyuki; Sawai, Tomotsugu; Ioka, Ikuo; Kiuchi, Kiyoshi; Nakayama, Jumpei*

Proceedings of 2nd International Workshop on Structural Materials for Innovative Nuclear Systems (SMINS-2), p.273 - 279, 2012/12

Journal Articles

Study of optimum composition of extra high purity Nb-W alloy for reprocessing condition with boiling nitric acid

Ioka, Ikuo; Suzuki, Jun; Kiuchi, Kiyoshi; Nakayama, Jumpei*

Proceedings of 19th International Conference on Nuclear Engineering (ICONE-19) (CD-ROM), 5 Pages, 2011/10

An Extra high purity Nb-W alloy (Nb-W EHP) that is superior to current Zr for cracking in severer environment is developed for reprocessing plants. Nb-W EHP has a technical limitation in weldability for practical use. To choose an optimum composition range of W, Nb-W EHP with different content of W were manufactured. Weld joint specimens were prepared by TIG welding. Tensile, corrosion and Charpy impact tests were carried out to examine the effect of W on chemical and mechanical properties of Nb-W EHP. There was little effect of W on corrosion rate of weld joint of Nb-W EHP. The increase in W improves ultimate tensile strength of Nb-W EHP. A ductile-brittle transition temperature (DBTT) of Nb-W EHP increased with an increase in W. The increase in DBTT is a problem as a structural material. Moreover, DBTT of the weld joint was high about 150K in comparison with the base metal. It is necessary to adjust W content to 8wt% or less in Nb-W EHP from the obtained results.

Journal Articles

Application of extra high purity austenitic stainless steel to weld overlay

Ioka, Ikuo; Suzuki, Jun; Kiuchi, Kiyoshi; Nakayama, Jumpei*

Proceedings of 18th International Conference on Nuclear Engineering (ICONE-18) (CD-ROM), 6 Pages, 2010/05

An Extra High Purity austenitic stainless steel (EHP alloy) was developed with conducting the new multiple refined melting in order to suppress the harmful impurities less than 100 ppm. EHP alloy has great intergranular corrosion resistance. It is considered that intergranular corrosion becomes initiation of SCC. So, we try to apply EHP alloy to weld overlay materials to prevent from SCC. EHP alloy was melted by the new multiple refined method. The conventional weld metals were also prepared as comparisons. Specimens were machined from the welded metal of each material. Intergranular corrosion tests were performed in boiling 8 kmol/m$$^{3}$$ HNO$$_{3}$$ solutions containing 1 kg/m$$^{3}$$ Cr(VI) ions. The intergranular corrosion of conventional weld metals was severer than those of EHP alloys. Crevice Beam bending tests to evaluate susceptibility of SCC were carried out in high temperature water of 561 K with saturated oxygen for 1000 h. Cracks and intergranular corrosion of conventional weld metals were much more than those of EHP alloys. It was confirmed that EHP alloy had excellent SCC resistance in comparison with conventional materials when EHP alloy was used as a weld metal.

Journal Articles

Development of extra high purity stainless steel for advanced reprocessing process

Ioka, Ikuo; Kiuchi, Kiyoshi; Nakayama, Jumpei*

Materia, 49(3), p.122 - 124, 2010/03

In reprocessing plants, it is known that the corrosion environment for structural materials is extremely severe to be used boiling nitric acid with oxidized ions related to fission products (FP). Ultra low carbon stainless steels (SUS304ULC) were developed from the experience of corrosion troubles in foreign plants and the operation of domestic plant. In an advanced reprocessing plant, it is predicted that the corrosion environment will be more severe because of the advanced spent fuels which contain much FP than an existing spent fuel. Therefore, it is necessary to develop the new stainless steel with excellent corrosion resistance in comparison with SUS304ULC. We developed an extra high purity stainless steel (EHP alloy) having superior corrosion resistance in the strong acid environment for the advanced reprocessing plant. In the production process of EHP alloy, the practical use was taken into consideration. This report introduces the present conditions of EHP alloy.

Journal Articles

Correlation between intergranular corrosion and impurities of extra high purity austenitic stainless steels

Ioka, Ikuo; Suzuki, Jun; Motooka, Takafumi; Kiuchi, Kiyoshi; Nakayama, Jumpei*

Journal of Power and Energy Systems (Internet), 4(1), p.105 - 112, 2010/02

An intergranular corrosion is an important degradation mechanism of austenitic stainless steels for use in a nuclear fuel reprocessing plant. The intergranular corrosion is caused by the segregation of impurities to grain boundaries. An extra high purity austenitic stainless steel (EHP) was developed with conducting the new multiple refined melting to suppress the impurities less than 100ppm. The intergranular corrosion behavior of EHP alloys added various impurities was examined in boiling nitric acid solution with highly oxidizing ions. A multi regression analysis was performed using the obtained data. The degree of influence of the impurities on intergranular corrosion was shown from the analysis. The influence on corrosion rate became small in order of B, P, Si, C, S and Mn. There is little effect of Mn on corrosion rate of EHP-SSs in case of 10000appm or less.

Journal Articles

Influence of impurities on intergranular corrosion of extra high purity austenitic stainless steels

Ioka, Ikuo; Suzuki, Jun; Motooka, Takafumi; Kiuchi, Kiyoshi; Nakayama, Jumpei

Proceedings of 17th International Conference on Nuclear Engineering (ICONE-17) (CD-ROM), 5 Pages, 2009/06

An intergranular corrosion is an important degradation mechanism of austenitic stainless steels for use in a nuclear fuel reprocessing plant. The intergranular corrosion is caused by the segregation of impurities to grain boundaries. An extra high purity austenitic stainless steel (EHP$$^{TM}$$) was developed with conducting the new multiple refining to suppress the impurities less than 100 ppm. The intergranular corrosion behavior of EHP alloys with various impurities was examined in boiling nitric acid solution. The intergranular corrosion was observed in impurity doped EHP alloys, although no intergranular corrosion was observed in EHP alloy. From the obtained results, an empirical equation between susceptibility of intergranular corrosion and impurities was established by means of the regression analysis. The degree of influence of the impurities on intergranular corrosion was shown.

Journal Articles

Intergranular corrosion for extra high purity austenitic stainless steel in boilng nitric acid with Cr(VI)

Ioka, Ikuo; Kato, Chiaki; Kiuchi, Kiyoshi; Nakayama, Jumpei

Journal of Power and Energy Systems (Internet), 3(1), p.31 - 37, 2009/00

Austenitic stainless steels suffer intergranular attack in boiling HNO$$_3$$ with oxidants. The intergranular corrosion is mainly caused by impurities at the grain. An extra high purity austenitic stainless steel (EHP alloys) was developed with conducting the new technique in order to suppress harmful impurities less than 100 ppm. The corrosion behavior of type 310 EHP alloy in HNO$$_3$$ with highly oxidants was investigated. The straining, aging and recrystallizing (SAR) treated type 310 EHP alloy showed superior corrosion resistance for intergranular attack than solution annealed (ST) type 310 EHP alloy with same impurity level. Boron segregation at the grain boundary was detected in only ST specimen using a FTE method. It is believed that the segregated boron along the grain boundaries in type 310 EHP alloy was one of main factor of intergranular corrosion. The SAR treatment was effective to restrain the intergranular corrosion for type 310 EHP alloy with B up to 7 ppm.

Journal Articles

Susceptibility of intergranular corrosion for extra high purity austenitic stainless steel in nitric acid

Ioka, Ikuo; Kato, Chiaki; Kiuchi, Kiyoshi; Nakayama, Jumpei

Proceedings of 16th International Conference on Nuclear Engineering (ICONE-16) (CD-ROM), 5 Pages, 2008/05

Austenitic stainless steels suffer intergranular attack in boiling nitric acid with oxidants. The intergranular corrosion is mainly caused by the segregation of impurities to grain. An extra high purity austenitic stainless steel (EHP alloys) was developed with conducting the new multiple refined melting technique in order to suppress the total harmful impurities less than 100ppm. The basically corrosion behavior of type 310 EHP alloy with respect to nitric acid solution with highly oxidizing ions was investigated. The straining, aging and recrystallizing (SAR) treated type 310 EHP alloy showed superior corrosion resistance for intergranular attack. The segregated boron along the grain boundaries was one of main factor of intergranular corrosion from fission track etching results. The SAR treatment was effective to restrain the intergranular attack for type 310 EHP alloy with B less than 7ppm.

JAEA Reports

Design study of the low level Radioactive waste retrieval facility (II)

Asahina, Kiyoshi*; Soya, Masataka*; Ogawa, Hikaru*; Akasaka, Takayuki*; Iwata, Toshio*; Fukutome, Yutaka*; Nakayama, Jumpei*

PNC TJ4058 89-005, 178 Pages, 1989/06

PNC-TJ4058-89-005.pdf:27.12MB

None

Oral presentation

Study of optimum composition of extra high purity Ni-Cr-W-Si alloys for reprocessing condition with nitric acid

Ioka, Ikuo; Suzuki, Jun; Maruyama, Nobutoshi*; Kiuchi, Kiyoshi; Nakayama, Jumpei

no journal, , 

Optimization of composition for high Cr-W-Si Ni base alloy has been studied to apply to a nitric acid with high oxidation-reduction potential of advanced reprocessing plants. The corrosion resistance of the Ni base alloy is superior to that of conventional stainless steels. In addition, The Ni base alloy has an excellent resistance of weld crack and ability of plastic deformation caused by extra high purity (EHP) refining technology. However, the Ni base alloy has a technical limitation in hot working and welding for practical use. Several Ni base EHP alloys with different content of Si and W were manufactured to choose an optimum composition range without losing corrosion resistance. High strain rate tensile tests at high temperature, corrosion tests and weldability tests were carried out to examine the optimum composition range of Ni base EHP alloy.

Oral presentation

Study of optimum composition of extra high purity Nb-W alloys for reprocessing condition with nitric acid

Ioka, Ikuo; Yonekawa, Kazuo; Maruyama, Nobutoshi*; Kiuchi, Kiyoshi; Nakayama, Jumpei

no journal, , 

Nb-W binary alloy which is superior to current zirconium for corrosion and cracking in severer environment is developed for advanced reprocessing plants. Ductility of Nb-W binary alloy is improved by an application of extra high purity (EHP) refining technology, but mechanical strength deteriorates. A ductile-brittle transition temperature (DBTT) of Nb-W binary alloy rises, though the increase in W improves mechanical strength. DBTT of the weld tends to be high in comparison with the base metal, and a rise of DBTT by increase in W becomes the problem. Nb-W EHP alloys with different content of W were manufactured to choose an optimum composition range. Tensile, corrosion and Charpy impact tests were carried out to examine the optimum composition range of Nb-W EHP alloy.

Oral presentation

Influence of impurities on intergranular corrosion of extra high purity austenitic stainless steels

Ioka, Ikuo; Suzuki, Jun; Motooka, Takafumi; Kiuchi, Kiyoshi; Nakayama, Jumpei

no journal, , 

An extra high purity austenitic stainless steel (EHP) was developed with conducting the new multiple refined melting to suppress the impurities less than 100ppm. The intergranular corrosion behavior of EHP alloys added various impurities were examined in boiling nitric acid solution to obtain a relationship between intergranular corrosion and impurity content. The intergranular corrosion strongly depended on corrosion rate. An empirical equation between susceptibility of intergranular corrosion and impurities was established by means of the regression analysis. The prediction obtained from the empirical equation was in agreement with experimental data. The influence of B and P was comparatively large to the intergranular corrosion.

Oral presentation

Development of the SUS310EHP stainless steel having superior corrosion resistance, 2; Inter-granular corrosion tests at the SUS310EHP stainless steel

Kato, Chiaki; Soma, Yasutaka; Ueno, Fumiyoshi; Okada, kiyotaka*; Ebina, Tetsunari*; Kano, Yoichi*; Nakayama, Jumpei

no journal, , 

no abstracts in English

Oral presentation

Development of the SUS310EHP stainless steel having superior corrosion resistance, 1; Overview of development of the SUS310EHP stainless steel

Sugiyama, Hiroshi*; Okada, kiyotaka*; Ebina, Tetsunari*; Kano, Yoichi*; Soma, Yasutaka; Kato, Chiaki; Ueno, Fumiyoshi; Nakayama, Jumpei*

no journal, , 

no abstracts in English

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