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Journal Articles

Effect of re-oxidation rate of additive cations on corrosion rate of stainless steel in boiling nitric acid solution

Irisawa, Eriko; Yamamoto, Masahiro; Kato, Chiaki; Motooka, Takafumi; Ban, Yasutoshi

Journal of Nuclear Science and Technology, 56(4), p.337 - 344, 2019/04

 Times Cited Count:0 Percentile:100(Nuclear Science & Technology)

JAEA Reports

Geopolymers and their potential applications in the nuclear waste management field; A Bibliographical study

Cantarel, V.; Motooka, Takafumi; Yamagishi, Isao

JAEA-Review 2017-014, 36 Pages, 2017/06

JAEA-Review-2017-014.pdf:3.37MB

After a necessary decay time, the zeolites used for the water decontamination will eventually be conditioned for their long-term storage. Geopolymer is considered as a potential matrix to manage radioactive cesium and strontium containing waste. For such applications, a correct comprehension of the binder structure, its macroscopic properties, its interactions with the waste and the physico-chemical phenomena occurring in the waste form is needed to be able to judge of the soundness and viability of the material. Although the geopolymer is a young binder, a lot of research has been carried out over the last fifty years and our understanding of this matrix and its potential applications is progressing fast. This review aims at gathering the actual knowledge on geopolymer studies about geopolymer composites, geopolymer as a confinement matrix for nuclear wastes and geopolymer under irradiation. This information will finally provide guidance for the future studies and experiments.

JAEA Reports

Proceedings of the Research Conference on Post-accident Waste Management Safety (RCWM2016) and the Technical Seminar on Safety Research for Radioactive Waste Storage; November 7th and 8th 2016, LATOV, Iwaki, Fukushima, Japan

Motooka, Takafumi; Yamagishi, Isao

JAEA-Review 2017-004, 157 Pages, 2017/03

JAEA-Review-2017-004.pdf:48.18MB

Collaborative Laboratories for Advanced Decommissioning Science (CLADS) is responsible to promote international cooperation in the R&D activities on the decommissioning of Fukushima Daiichi Nuclear Power Station and to develop the necessary human resources. CLADS held the Research Conference on Post-accident Waste Management Safety (RCWM2016) was held on November 7th, 2016 and the Technical Seminar on Safety Research for Radioactive Waste Storage was held on November 8th, 2016. This report compiles the abstracts and the presentation materials in the above conference and seminar.

Journal Articles

Gas retention behavior of carbonate slurry under $$gamma$$-ray irradiation

Motooka, Takafumi; Nagaishi, Ryuji; Yamagishi, Isao

QST-M-2; QST Takasaki Annual Report 2015, P. 95, 2017/03

We conducted $$gamma$$ ray irradiation test using simulated carbonate slurry to investigate the cause of stagnant water over the high integrity container (HIC). This test was performed at Co-60 irradiation facility in Takasaki Advanced Radiation Research Institute. We observed a rise in water level, air bubbles in the slurry, a supernatant when the carbonate slurry with 95 g/L density was irradiated by $$gamma$$ ray at a dose rate of 8.5 kGy/h. The cause of the rise in water level was regarded as the volume expansion by the gas retention of the carbonate slurry. It was suggested that the cause of stagnant water over the high integrity container might be the volume expansion by the gas retention.

Journal Articles

Seawater effects on the soundness of spent fuel cladding tube

Motooka, Takafumi; Ueno, Fumiyoshi; Yamamoto, Masahiro

Proceedings of 2016 EFCOG Nuclear & Facility Safety Workshop (Internet), 6 Pages, 2016/09

At the Fukushima Daiichi nuclear accident, seawater was injected into spent fuel pools of Unit 2-4 for the emergency cooling. Seawater might cause localized corrosion of spent fuel cladding. This would lead to leakage of not only fissile materials but also fission products from fuel cladding. The behavior, however, is not understood well. In this paper, the effects of seawater on corrosion behavior and mechanical property of were studied by using a spent fuel cladding from a BWR. We immersed the spent cladding tubes in diluted artificial seawater for 300h at 353 K, and conducted their visual, cross-sectional and strength examinations. As a localized corrosion index, the pitting potentials of specimens fabricated from the cladding were measured as functions of chloride ion concentration ranging from 20 to 2500 ppm. The visual examination showed that localized corrosion has not occurred, and cross-sectional examination showed no cracks. The strength of immersed tubes was comparable to that of non-immersed tubes. Additionally, pitting potential could not be measured over 1.0 V; pitting corrosion was hardly occurred. These results suggested that the specimens from the spent fuel cladding tube was very resistant to localized corrosion.

Journal Articles

Irradiation experiments of simulated wastes of carbonate slurry

Nagaishi, Ryuji; Motooka, Takafumi; Yamagishi, Isao

Proceedings of 2016 EFCOG Nuclear & Facility Safety Workshop (Internet), 6 Pages, 2016/09

Overflow of water from waste storage tanks of High Integrity Containers (HIC) in the multi-nuclide removal equipment (ALPS) was discovered at Fukushima Daiichi NPS in April of last year. The mechanism of overflow was not understood very much at that time. To elucidate that for chemical safety in the waste storage, irradiation experiments of simulated carbonate slurry by Co-60 $$gamma$$-rays have been conducted in CLADS, JAEA in cooperation with TEPCO, TOSHIBA and KURITA. Hydrogen molecule was the main radiolytic gas product in the slurry, and its amount was enhanced by dissolved species of not only halide ions as seawater components but also carbonate ion as an additive for co-precipitation at a basic condition. The bubbles of molecules were further formed and almost held in the slurry without stirred. These sequentially led to the expansion of slurry, and then to its separation into the shrunk one and supernatant water, which was little accumulated without irradiated.

Journal Articles

Simulation for radiolytic products of seawater; Effects of seawater constituents, dilution rate, and dose rate

Hata, Kuniki; Sato, Tomonori; Motooka, Takafumi; Ueno, Fumiyoshi; Hanawa, Satoshi; Kasahara, Shigeki; Tsukada, Takashi

Journal of Nuclear Science and Technology, 53(8), p.1183 - 1191, 2016/08

 Times Cited Count:5 Percentile:38.13(Nuclear Science & Technology)

Journal Articles

Corrosion rate of carbon steel in NaCl solution with various chloride ion concentration under $$gamma$$-ray irradiation

Motooka, Takafumi

JAEA-Review 2015-022, JAEA Takasaki Annual Report 2014, P. 23, 2016/02

Corrosion rates of carbon steel in chloride aqueous solutions under a low dose rate were investigated by corrosion test using chloride aqueous solutions with different chloride concentrations. The corrosion rate of carbon steel had the maximum value at a certain concentration at a dose rate of 500Gy/h. The oxidants produced by radiolysis of chloride aqueous solution enhanced the corrosion of carbon steel. The dependence of corrosion rate and chloride concentration has a positive correlation with the dependence of oxidant concentration and chloride concentration.

Journal Articles

Effect of nitrous ion on oxidation of oxidizing-metallic ion in nitric acid solution

Irisawa, Eriko; Seki, Masaharu*; Ueno, Fumiyoshi; Kato, Chiaki; Motooka, Takafumi; Abe, Hitoshi

Proceedings of 21st International Conference & Exhibition; Nuclear Fuel Cycle for a Low-Carbon Future (GLOBAL 2015) (USB Flash Drive), p.1108 - 1112, 2015/09

Journal Articles

Effect of chloride concentration on corrosion behavior of carbon steel under $$gamma$$-ray irradiation

Motooka, Takafumi; Ueno, Fumiyoshi

Zairyo To Kankyo, 64(6), p.220 - 223, 2015/06

Corrosion behavior of carbon steel in chloride aqueous solutions under a low dose rate was investigated by corrosion test using chloride aqueous solutions with different chloride concentration at a dose rate of 500 Gy/h. The corrosion rate of carbon steel increased by the irradiation, and the corrosion rate had the maximum value at a certain chloride concentration. The oxidants produced by radiolysis of chloride aqueous solution enhanced the corrosion of carbon steel. The main oxidants were oxygen and hydrogen peroxide, and the diffusion process of oxidants controlled the corrosion of carbon steel under irradiation. There was a positive correlation between the dependence of corrosion rate and chloride concentration and the dependence of oxidant concentration and chloride concentration.

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

Effect of chloride and bromide ion on the concentration of hydrogen peroxide produced from seawater radiolysis

Hata, Kuniki; Hanawa, Satoshi; Motooka, Takafumi; Tsukada, Takashi

JAEA-Review 2014-050, JAEA Takasaki Annual Report 2013, P. 22, 2015/03

Fukushima Daiichi Nuclear Power Plants experienced seawater injection into the cores and spent fuel pools as an emergent measure for a short period after the accident. The injected seawater was exposed to radiation, and radiolytic species were produced. Especially, hydrogen peroxide (H$$_{2}$$O$$_{2}$$) is known as an oxidant which affects corrosion of materials. In order to identify the important factor which results in the high concentration of H$$_{2}$$O$$_{2}$$ in seawater radiolysis, the concentrations of H$$_{2}$$O$$_{2}$$ in $$gamma$$-irradiated artificial seawater was measured and compared with the result of radiolysis calculation. Solutions containing some constituents of seawater were also measured to identify which ion affects H$$_{2}$$O$$_{2}$$ production of seawater radiolysis. The experimental results showed that the H$$_{2}$$O$$_{2}$$ production from seawater radiolysis is mainly attributed to reactions of Cl$$^{-}$$ and Br$$^{-}$$ in water radiolysis, though many kinds of ions are dissolved in seawater.

Journal Articles

Evaluation of hydrazine injection effect on spent fuel pools in Fukushima Daiichi Nuclear Power Plant

Motooka, Takafumi; Sato, Tomonori; Yamamoto, Masahiro

Nippon Genshiryoku Gakkai Suikagaku Bukai Bukaiho (Internet), 2 Pages, 2015/03

At the Fukushima Daiichi Nuclear Power Plant, the seawater was injected into Spent Fuel Pool (SFP) after the accident in March 2013. It is considered that corrosion in SFP will be accelerated by the seawater injection. To prevent the corrosion, Tokyo Electronic Power Company injected hydrazine into SFP. We confirmed the hydrazine injection effect in a short time by irradiation test.

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 oxide film formed during $$gamma$$-ray irradiation on pitting corrosion of fuel cladding in water containing sea salt

Motooka, Takafumi; Tsukada, Takashi

Proceedings of 2014 Nuclear Plant Chemistry Conference (NPC 2014) (USB Flash Drive), 9 Pages, 2014/10

In Fukushima Daiichi Nuclear Power Station (1F), seawater was injected into spent fuel pools in March 2011. Zircaloy-2 is adopted for the fuel cladding at 1F. Zirconium alloys including Zircaloy-2 are susceptible to pitting corrosion in oxidizing chloride solutions. In this study, we investigated the effect of oxide film formed during $$gamma$$-ray irradiation on pitting corrosion of fuel cladding in water containing sea salt. The pitting potentials of Zircaloy-2 were measured using the water containing artificial sea salt. Changes in the composition of water containing sea salt were analyzed before and after $$gamma$$-ray irradiation. The characteristics of the oxide films formed on Zircaloy-2 were evaluated by X-ray photoelectron spectroscopy. Solution analyses for water containing sea salt showed that hydrogen peroxide was generated by the irradiation. The pitting potential of Ziracloy-2 with oxide film formed under $$gamma$$-ray irradiation was higher than that with oxide film formed without irradiation. X-ray photoelectron spectroscopy indicated that the oxide film was composed of zirconium oxide and the growth of oxide film was enhanced during the irradiation. It could thus be explained that the enhanced growth of oxide film under $$gamma$$-ray irradiation caused the higher pitting potential.

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:45.36(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.

JAEA Reports

Development of specimen preparation techniques for pitting potential measurement of irradiated fuel cladding tubes

Suzuki, Kazuhiro; Motooka, Takafumi; Tsukada, Takashi; Terakawa, Yuto; Ichise, Kenichi; Numata, Masami; Kikuchi, Hiroyuki

JAEA-Technology 2014-004, 29 Pages, 2014/03

JAEA-Technology-2014-004.pdf:3.66MB

By the effect of the Great East Japan Earthquake, seawater was injected into spent fuel pools in unit 2, 3 and 4 at Fukushima Daiichi Nuclear Plant in order to cool spent fuels. It is known that chloride ion contained in seawater could cause pitting corrosion for metallic materials. It was concerned that radioactive products inside of fuel cladding tubes might be escaped through the pits. Therefore we have investigated the pit initiation condition of fuel cladding tubes by measuring pitting potential in order to evaluate stability of the enclosure function of fuel cladding tubes in spent fuel pools containing sea salt. In this report, we describe the development of specimen preparation techniques for pitting measurement of spent fuel cladding tubes having high radioactivity. By accomplishing of the development of the specimen preparation techniques, we could evaluate pit initiation condition of spent fuel cladding tubes in water containing sea salt.

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

Stress corrosion cracking behavior of zirconium in boiling nitric acid solutions at oxide formation potentials

Ishijima, Yasuhiro; Kato, Chiaki; Motooka, Takafumi; Yamamoto, Masahiro; Kano, Yoichi*; Ebina, Tetsunari*

Materials Transactions, 54(6), p.1001 - 1005, 2013/06

 Times Cited Count:4 Percentile:65.99(Materials Science, Multidisciplinary)

Zirconium has been utilized in nuclear fuel reprocessing plants because of its superior corrosion resistance in nitric acid solutions. However, stress corrosion cracking (SCC) susceptibility of zirconium has been reported in boiling nitric acid solutions at the passivity breakdown potential. However, it has not been clear the SCC initiation and propagation behavior of zirconium. In this study, to clarify the SCC initiation and propagation behavior of zirconium, constant load tensile tests were carried out in boiling nitric acid solutions. From the results, many cracks were initiated under the oxide film and maximum crack led to rupture in the potentials that nobler than passivity breakdown potential. These results showed that the SCC of zirconium in boiling nitric acid solutions is due to the oxide formation. And this SCC behavior suggests that the SCC behavior of zirconium can be attributed to tarnish rupture model.

126 (Records 1-20 displayed on this page)