Refine your search:     
Report No.
 - 
Search Results: Records 1-20 displayed on this page of 54

Presentation/Publication Type

Initialising ...

Refine

Journal/Book Title

Initialising ...

Meeting title

Initialising ...

First Author

Initialising ...

Keyword

Initialising ...

Language

Initialising ...

Publication Year

Initialising ...

Held year of conference

Initialising ...

Save select records

JAEA Reports

Estimation of oxygen consumption amount in LBE-cooled accelerator-driven system

Sugawara, Takanori; Komatsu, Atsushi

JAEA-Research 2020-016, 44 Pages, 2021/01

JAEA-Research-2020-016.pdf:2.94MB

It is required to control the oxygen concentration in lead-bismuth eutectic (LBE) to prevent the corrosion of structures in LBE-cooled nuclear system. This study estimated the oxygen consumption amount in the LBE-cooled accelerator-driven system (ADS). We used the evaluation formula for the oxide layer thickness, which were derived by various experiments, to estimate the oxygen consumption amount. It was found that the maximum oxide layer thicknesses for the fuel assembly and the beam window were about 35 [$$mu$$m] and 20 [$$mu$$m], respectively. Based on these results, the oxygen consumption amount for the ADS plant was estimated as 30 [kg] during one cycle (one year). Through this study, it was indicated that an oxygen supply device which could supply 3-4 [g/h] oxygen in the normal operation, 150 [g/h] in the peak and about 30 [kg] during one cycle was necessary.

JAEA Reports

A Catalog showing distribution and features of lineaments and related landforms in an active shear zone with unclear fault displacement topography; An Example of an active left-lateral shear zone in southern Kyushu Island, southwest Japan (Contract research)

Goto, Akira; Sasaki, Akimichi*; Komatsu, Tetsuya; Miwa, Atsushi*; Terusawa, Shuji*; Kagohara, Kyoko*; Shimada, Koji

JAEA-Research 2020-013, 88 Pages, 2020/11

JAEA-Research-2020-013.pdf:22.86MB
JAEA-Research-2020-013-appendix(CD-ROM).zip:0.18MB

Improvement of the investigation techniques to identify active faults is important for the implementation of geological disposal projects from the viewpoint of avoiding locations where permeability increases due to fault displacement. Generally, the existence of active faults is confirmed by aerial photography interpretation of fault displacement topography, which is a topographical trace of fault movement, and on-site geological surveys. However, the investigation method for cases where the topographical traces are unclear is not sufficiently developed. Therefore, to improve existing topographical methods, this study deciphered lineaments up to the rank of poorly defined features, which are almost neglected in general active fault research. The investigation area is one of the geodetic strain concentration zone, called the southern Kyushu shear zone, where the seismogenic faults of the 1997 Kagoshima northwest earthquakes are concealed. We conducted aerial photography interpretation of 62 sheets of 1/25,000 topographic maps, and obtained 1,327 lineaments. Distribution density, direction and length of lineaments were also investigated with topographic and geologic information. As a result, it was clarified that the east-west lineaments in the south Kyushu shear zone predominate in the western part, and the lineaments are densely distributed in the aftershock distribution area of the Kagoshima northwest earthquake. Along with these results, we have compiled a catalog of typical 13 lineaments based on combinations of clarity, direction, length and geomorphic characters of lineaments.

JAEA Reports

Annual report for research on geosphere stability for long-term isolation of radioactive waste in fiscal year 2018

Ishimaru, Tsuneari; Ogata, Nobuhisa; Hanamuro, Takahiro; Shimada, Akiomi; Kokubu, Yoko; Asamori, Koichi; Niwa, Masakazu; Shimada, Koji; Watanabe, Takahiro; Saiga, Atsushi; et al.

JAEA-Research 2019-006, 66 Pages, 2019/11

JAEA-Research-2019-006.pdf:4.39MB

This annual report documents the progress of research and development (R&D) in the 4th fiscal year during the JAEA 3rd Mid- and Long-term Plan (fiscal years 2015-2021) to provide the scientific base for assessing geosphere stability for long-term isolation of the high-level radioactive waste. The planned framework is structured into the following categories: (1) Development and systematization of investigation techniques, (2) Development of models for long-term estimation and effective assessment, (3) Development of dating techniques. In this report, the current status of R&D activities with previous scientific and technological progress is summarized.

JAEA Reports

Annual report for research on geosphere stability for long-term isolation of radioactive waste in fiscal year 2017

Ishimaru, Tsuneari; Ogata, Nobuhisa; Shimada, Akiomi; Asamori, Koichi; Kokubu, Yoko; Niwa, Masakazu; Watanabe, Takahiro; Saiga, Atsushi; Sueoka, Shigeru; Komatsu, Tetsuya; et al.

JAEA-Research 2018-015, 89 Pages, 2019/03

JAEA-Research-2018-015.pdf:14.43MB

This annual report documents the progress of research and development (R&D) in the 3rd fiscal year during the JAEA 3rd Mid- and Long-term Plan (fiscal years 2015-2021) to provide the scientific base for assessing geosphere stability for long-term isolation of the high-level radioactive waste. The planned framework is structured into the following categories: (1) Development and systematization of investigation techniques, (2) Development of models for long-term estimation and effective assessment, (3) Development of dating techniques. In this report, the current status of R&D activities with previous scientific and technological progress is summarized.

JAEA Reports

Research plan on geosphere stability for long-term isolation of radioactive waste (Scientific Program for fiscal year 2018)

Ishimaru, Tsuneari; Ogata, Nobuhisa; Shimada, Akiomi; Asamori, Koichi; Kokubu, Yoko; Niwa, Masakazu; Watanabe, Takahiro; Saiga, Atsushi; Sueoka, Shigeru; Komatsu, Tetsuya; et al.

JAEA-Review 2018-020, 46 Pages, 2019/01

JAEA-Review-2018-020.pdf:1.25MB

This report is a plan of research and development (R&D) on geosphere stability for long-term isolation of high-level radioactive waste (HLW) in Japan Atomic Energy Agency, in fiscal year 2018. The objectives and contents in fiscal year 2018 are described in detail based on the outline of 7 years plan (fiscal years 2015-2021). Background of this research is clarified with the necessity and the significance for site investigation and safety assessment, and the past progress in this report. In addition, the plan framework is structured into the following categories: (1) Development and systematization of investigation techniques, (2) Development of models for long-term estimation and effective assessment, (3) Development of dating techniques.

Journal Articles

In-situ measurement of electrical conductivity of solution within crevice of stainless steel in high temperature and high purity water

Soma, Yasutaka; Komatsu, Atsushi; Ueno, Fumiyoshi

Zairyo To Kankyo, 67(9), p.381 - 385, 2018/09

In-situ measurement of electrical conductivity of solution within crevice of SUS316L stainless steel in 288$$^{circ}$$C water has been conducted with newly developed electrochemical sensor system. The sensor measures local electrical conductivity of crevice solution beneath the electrode ($$kappa$$$$_{crev}$$) with electrochemical impedance method. The sensors were installed at different positions within tapered crevice of SUS316L stainless steel. The crevice specimen with the sensors were immerged into 288$$^{circ}$$C, 8 MPa, pure oxygen saturated high purity water for 100 h. $$kappa$$$$_{crev}$$ at a position with crevice gap of $$approx$$59.3$$mu$$m was 8-11$$mu$$S/cm, least deviate from conductivity of 288$$^{circ}$$C pure water (4.4$$mu$$S/cm) and no localized corrosion occurred. On the contrary, $$kappa$$$$_{crev}$$ at a position with crevice gap of $$approx$$4.4$$mu$$m increased with time and showed maximum value of $$approx$$1600$$mu$$S/cm at 70 h. Localized corrosion occurred in the vicinity of this position. Thermodynamic equilibrium calculation showed $$kappa$$$$_{crev}$$ of 1600$$mu$$S/cm being equivalent to pH of 3 to 3.7. It can be concluded that acidification occurred in tight crevice even under high purity bulk water and resulted in localized corrosion.

Journal Articles

Oxidation characteristics of lead-alloy coolants in air ingress accident

Kondo, Masatoshi*; Okubo, Nariaki; Irisawa, Eriko; Komatsu, Atsushi; Ishikawa, Norito; Tanaka, Teruya*

Energy Procedia, 131, p.386 - 394, 2017/12

 Times Cited Count:2 Percentile:11.38

The chemical behaviors of lead (Pb) based coolants in the air ingress accident of fast reactors were investigated by means of the thermodynamic considerations and the static oxidation experiments for Pb alloys at various chemical compositions. The results of the static oxidation tests for lead-bismuth (Pb-Bi) alloys indicated that Pb was depleted from the alloy due to the preferential formation of PbO in air at 773K. Pb-Bi oxide and Bi$$_{2}$$O$$_{3}$$ were formed after the enrichment of Bi in the alloys due to the Pb depletion. The oxidation rates of the alloys were much larger than that of the steels, and became larger with higher Pb concentration in the alloys. The compatibility of Pb-Bi alloys with stainless steel was worse when the Pb concentration in the alloys became low, since the dissolution type corrosion was promoted by the Bi composition in the alloy. The Pb-Li alloys were oxidized as they formed Li$$_{2}$$PbO$$_{3}$$ and Li$$_{2}$$CO$$_{3}$$. Then, Li was depleted from the alloy.

Journal Articles

Electrochemical impedance analysis on solid electrolyte oxygen sensor with gas and liquid reference electrodes for liquid LBE

Adhi, P. M.*; Okubo, Nariaki; Komatsu, Atsushi; Kondo, Masatoshi*; Takahashi, Minoru*

Energy Procedia, 131, p.420 - 427, 2017/12

 Times Cited Count:0 Percentile:100

The ionic conductivity of solid electrolyte may insufficient, and the sensor output signal will deviate from the theoretical one in low temperature. The performance of oxygen sensor with Ag/air reference electrode (RE) and liquid Bi/Bi$$_{2}$$O$$_{3}$$ RE was tested in low-temperature LBE at 300$$sim$$450$$^{circ}$$C and the charge transfer reactions impedance at the electrode-electrolyte interface was analyzed by electrochemical impedance analysis (EIS). After steady state condition, both of the sensors performed well and can be used at 300$$sim$$450$$^{circ}$$C. Bi/Bi/Bi$$_{2}$$O$$_{3}$$ RE has lower impedance than Ag/air RE. Therefore, the response time of the oxygen sensor with Bi/Bi/Bi$$_{2}$$O$$_{3}$$ RE is faster than the oxygen sensor with Ag/air RE in the low-temperature region.

Journal Articles

Estimation of corrosion amounts for carbon steel in $$gamma$$-ray irradiated neutral water condition

Yamamoto, Masahiro; Komatsu, Atsushi; Sato, Tomonori; Nakano, Junichi; Ueno, Fumiyoshi

Proceedings of 17th Asian Pacific Corrosion Control Conference (APCCC-17) (USB Flash Drive), 8 Pages, 2016/01

In Fukushima-Daiichi Nuclear Power Station, decommissioning procedures are continuing more than 30 years until fuel debris removal. It is important to keep soundness of primary container vessel (PCV), made of carbon steel, during these procedures. Corrosion of carbon steel is well-known to be controlled by cathodic reaction, in usual, oxygen reduction reaction. Corrosion of carbon steel could be mitigated by nitrogen injection procedure. However, a lot of radioactive materials exist in cooling water, an effect of radiolysis product on corrosion is an important problem. Clarifying an irradiation effect for corrosion of carbon steel, corrosion test was conducted in $$^{60}$$Co $$gamma$$-ray irradiated condition. Electrochemical measurements were conducted to determine cathodic current density of samples. Corrosion rates of carbon steel decrease with time in both $$gamma$$-ray irradiated and non-irradiated conditions. Measured values of cathodic current density gradually decreased with time and then stayed at constant value.

Journal Articles

Estimation method for corrosion rate of carbon steel in water with $$gamma$$-ray irradiated condition

Yamamoto, Masahiro; Sato, Tomonori; Komatsu, Atsushi; Nakano, Junichi; Ueno, Fumiyoshi

Proceedings of European Corrosion Congress 2015 (EUROCORR 2015) (USB Flash Drive), 7 Pages, 2015/09

In Fukushima-Daiichi Nuclear Power Station, decommissioning procedures are continuing and it will take more than 30 years. As some structures are made of carbon steel, degradation by corrosion is large problem for structural reliability. To clarify an irradiation effect for corrosion of carbon steel, corrosion test was con-ducted in $$^{60}$$Co $$gamma$$-ray irradiated condition. Corrosion test results showed that corrosion rates of $$gamma$$-ray irradiated condition increased with $$gamma$$-ray dose rates. The oxidant concentrations were also increased with $$gamma$$-ray dose rate. From these results, a new estimation method for corrosion rate of carbon steel in water with $$gamma$$-ray irradiated condition using radiolysis calculation is introduced and discussed.

Journal Articles

Study of corrosion rate of carbon steel in diluted artificial seawater under simulated irradiation condition

Komatsu, Atsushi; Tsukada, Takashi; Ueno, Fumiyoshi; Yamamoto, Masahiro

Proceedings of 23rd International Conference on Nuclear Engineering (ICONE-23) (DVD-ROM), 4 Pages, 2015/05

Effect of oxygen and hydrogen peroxide on corrosion rate of carbon steel in diluted artificial seawater was investigated by electrochemical methods. Diffusion coefficient and thickness of diffusion layer for oxygen and hydrogen peroxide were measured to estimate the diffusion limiting current density. Corrosion tests of carbon steel were also conducted in diluted artificial seawater containing oxygen and/or hydrogen peroxide at 323K. The diffusion coefficient of hydrogen peroxide was about 0.8 times lower than that of oxygen, and the thickness of diffusion layer was almost equivalent between oxygen and hydrogen peroxide. Diffusion limiting current density of hydrogen peroxide was estimated to be 0.4 times lower than that of oxygen in the same concentration at 323K. Plot of corrosion rate with the addition of concentration of oxygen and 0.4 times concentration of hydrogen peroxide showed good correlation.

Journal Articles

Effect of $$gamma$$ radiolysis on pit initiation of Zircaloy-2 in artificial seawater

Motooka, Takafumi; Komatsu, Atsushi; Tsukada, Takashi; Yamamoto, Masahiro

JAEA-Review 2014-050, JAEA Takasaki Annual Report 2013, P. 18, 2015/03

The effect of changes in water by $$gamma$$-ray irradiation on the pit initiation of Zircaloy-2 in artificial seawater was investigated. Surface analysis and electrochemical test were conducted. They showed that the hydrogen peroxide produced by $$gamma$$ irradiation forms a passive film and the passive film is resistant to the pit initiation.

Journal Articles

Three dimensional computational modelling and simulation of intergranular corrosion propagation of stainless steel

Igarashi, Takahiro; Komatsu, Atsushi; Motooka, Takafumi; Ueno, Fumiyoshi; Yamamoto, Masahiro

Proceedings of 19th International Corrosion Congress (19th ICC) (CD-ROM), 7 Pages, 2014/11

We constructed three dimensional computational model using cellular automata method to simulate the intergranular corrosion propagation of stainless steel. By the simulation using the model, we verified the relationship between surface roughness during corrosion and dispersion of dissolution rate of grain boundaries (GB). The relationship was investigated by the simulation applying constant dissolution rate for GB cells and distributed dissolution rate of GB cells. Our simulations revealed that the surface roughness calculated by the model adopted distributed dissolution rates of GBs was greater than that adopted constant dissolution rates of GBs. The cross-sectional images obtained by our simulation were comparable with that obtained by corrosion tests. These results indicate that the surface roughness during corrosion relates the distribution of corrosion rate.

Journal Articles

Effect of $$gamma$$-ray irradiation on corrosion of low alloy steel in neutral water

Yamamoto, Masahiro; Nakano, Junichi; Komatsu, Atsushi; Sato, Tomonori; Tsukada, Takashi

Proceedings of 19th International Corrosion Congress (19th ICC) (CD-ROM), 6 Pages, 2014/11

Corrosion protection of RPV and PCV is an important issue for the long term maintenance until the end of the decommissioning procedures. One of the uncertain factors for the issue is an effect of radioactivity on corrosion of LAS and CS. Corrosion tests using LAS and CS were conducted in $$gamma$$-rays irradiated condition. Oxygen and hydrogen peroxide concentrations in the water were measured after the tests. Corrosion test results indicated that the amounts of corrosion increased by $$gamma$$-rays irradiation both air and nitrogen atmosphere. And also corrosion amounts increased with $$gamma$$-ray dose rates. Electrochemical analyses indicated that cathodic reaction of Hydrogen peroxide was controlled by diffusion process. The measured diffusion constant of H$$_{2}$$O$$_{2}$$ was about 0.75 times to that of oxygen. From these results, it is estimated that corrosion of LAS and CS in $$gamma$$-ray irradiated condition was evaluated by the cathodic reduction reaction of oxidant.

Journal Articles

Study on the effect of phosphorous concentration on intergranular corrosion of stainless steel in boiling nitric acid solution

Ueno, Fumiyoshi; Komatsu, Atsushi; Igarashi, Takahiro; Yamamoto, Masahiro

Proceedings of European Corrosion Congress 2014 (EUROCORR 2014) (USB Flash Drive), 10 Pages, 2014/09

In this paper, the effect of phosphorous concentration in grain boundary (GB) on intergranular corrosion (IC) progress was studied to understand GB corrosion behavior of stainless steels in boiling nitric acid solution. Phosphorus (P) added extra high purity type 310 stainless alloy was corroded in boiling nitric acid solution, and P in GB was detected by three-dimensional atom probe. IC progress considering with P profile in GB was studied by numerical simulation using cellular automaton method. As the results, we concluded that P concentration change around 1.4at% in GB of the alloy caused IC rate change in boiling nitric acid solution. The developed numerical method could simulate GB corrosion change with P distribution in GB.

Journal Articles

Effect of $$gamma$$ radiolysis on pit initiation of zircaloy-2 in water containing sea salt

Motooka, Takafumi; Komatsu, Atsushi; Tsukada, Takashi; Yamamoto, Masahiro

Journal of Nuclear Science and Technology, 51(7-8), p.987 - 995, 2014/07

AA2013-0829.pdf:0.83MB

 Times Cited Count:6 Percentile:46.7(Nuclear Science & Technology)

Journal Articles

Simulations of intergranular corrosion feature for stainless steel using cellular automata method

Igarashi, Takahiro; Komatsu, Atsushi; Motooka, Takafumi; Ueno, Fumiyoshi; Kaji, Yoshiyuki; Yamamoto, Masahiro

Zairyo To Kankyo, 63(7), p.431 - 437, 2014/07

In order to obtain the relation between an intergranular corrosion behavior and an impurities for stainless steel, cellular automata modeling and simulation of intergranular corrosion was carried out. From intergranular corrosion simulation considering non-uniform phosphorus component distribution on grain boundary, it suggested that complicated intergranular corrosion shape as in experimental data was caused by the large precipitation of phosphorus compounds in part of grain boundary.

Journal Articles

Effect of local segregation of phosphorous on intergranular corrosion of type 310 stainless steel in boiling nitric acid

Komatsu, Atsushi; Motooka, Takafumi; Makino, Masashi; Nogiwa, Kimihiro; Ueno, Fumiyoshi; Yamamoto, Masahiro

Zairyo To Kankyo, 63(3), p.98 - 103, 2014/03

The effect of phosphorous on intergranular corrosion of type 310 stainless steel at transpassive potential was investigated using phosphorous added ultra high purity type 310 stainless steel. Intergranular corrosion depth was measured by scanning electron microscopic observation. Grain boundaries were observed using three dimensional atom probe. Intergranular corrosion was observed on phosphorous added stainless steel. The sample heat treated at 600$$^{circ}$$C showed severe integranular corrosion morphology. Observation by three dimensional atom probe revealed that grain boundary with high dissolution rate had segregated zone of chromium and phosphorous about 5nm in width, on the other hand, grain boundary with low dissolution rate had no segregated zone. From these results, it is suggested that intergranular corrosion of phosphorous added type 310 stainless steel at transpassive potential is affected by segregation of phosphorous and chromium along grain boundaries.

Journal Articles

Pitting potential of zircaloy-2 in artificial seawater under $$gamma$$-ray irradiation

Motooka, Takafumi; Komatsu, Atsushi; Tsukada, Takashi; Yamamoto, Masahiro

ECS Transactions, 53(21), p.25 - 32, 2013/05

 Times Cited Count:2 Percentile:18.12

Journal Articles

Reduction mechanism of nitate on titanium

Komatsu, Atsushi; Ishijima, Yasuhiro; Motooka, Takafumi; Ueno, Fumiyoshi; Yamamoto, Masahiro

Zairyo To Kankyo, 62(5), p.198 - 203, 2013/05

Reduction mechanism of nitrate ion on titanium electrode was investigated using electrochemical method. Cathodic polarization curve of titanium was measured in nitric acid with different concentrations of ions (H$$^{+}$$,NO$$_{3}$$$$^{-}$$,HNO$$_{2}$$). Reduction mechanism of nitrate ion on titanium was investigated from Tafel slope and reaction order of each ions. It was considered that reduction of titanium oxide was involved in reduction mechanism of nitrate ion on titanium, and reduction mechanism was suggested as follows. NO$$_3^{-}$$ $$rightleftharpoons$$ NO$$_{3ad}^{-}$$ (QE), TiO$$_{2}$$ + H$$^{+}$$ + e$$^{-}$$ $$rightleftharpoons$$ TiOOH (QE), NO$$_{3ad}^{-}$$ + TiOOH $$rightarrow$$ (NO$$_3^{-}$$ - TiOOH)$$_{ad}$$ (RDS), (NO$$_3^{-}$$ - TiOOH)$$_{ad}$$ + H$$^{+}$$ + e$$^{-}$$ $$rightarrow$$ NO$$_{2ad}^{-}$$ + TiO$$_{2}$$ + H$$_{2}$$O

54 (Records 1-20 displayed on this page)