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Journal Articles

Burial environment of bronze artifacts and behavior of bronze metal components at Yanagisawa archaeological site in Nagano Prefecture

Mitsui, Seiichiro; Murakami, Ryu*; Ueda, Norio*; Hirabayashi, Akira*; Hirota, Kazuho*

Bunkazai Kagaku, (77), p.1 - 14, 2018/10

Well-preserved bronze artifacts comprising five bells and eight halberds from the Yayoi Period were excavated at the Yanagisawa archaeological site in Nakano City, Nagano Prefecture in 2007. Comprehensive analysis of soil and groundwater samples at the site was carried out and geochemical calculations were made to better understand the local conditions that led to the artifacts being so well preserved. Analysis of the soil surface adjacent to the bronze artifacts identified cuprite (Cu$$_{2}$$O) as the main corrosion product. Migration behavior of the bronze metal components, copper, tin, and lead, both inside and outside of the burial pit, was also investigated. Copper and lead had migrated 2 m from the burial pit, whereas tin was confined to the immediate vicinity of the bronze artifacts. The difference in migration behavior of these elements can be explained in terms of the chemical stability of the solid phases. The main factor contributing to the well-preserved state of the bronze artifacts was the tin content, which is thought to have formed a protective layer of cassiterite (SnO$$_{2}$$) on the outer surface of the bronze artifacts.

Journal Articles

Utilization of the knowledge of excavated archaeological artifacts for research and development of geological disposal

Mitsui, Seiichiro

Maizo Bunkazai Nyusu, (171), p.10 - 17, 2018/03

As part of research and development of geological disposal, "natural analogues" have been applied to validate concept of models and evaluation methodologies for performance assessment. By introducing domestic and overseas research results on natural analogues, this paper presents how we have utilized knowledge of excavated archaeological artifacts for geological disposal studies.

Journal Articles

Expectations for corrosion science and technology from the viewpoint of long-term prediction

Taniguchi, Naoki

Zairyo To Kankyo, 65(9), p.363 - 364, 2016/09

no abstracts in English

Journal Articles

Burial environment and corrosion of socketed iron axe excavated from Yoshida Nakamichi site in Tottori City, Tottori Prefecture

Mitsui, Seiichiro

Koeki Zaidan Hojin Tottoriken Kyoiku Bunka Zaidanhen 2014 "Yoshida Nakamichi Iseki" Tottoriken Kyoiku Iinkai, p.221 - 230, 2015/03

An ancient socketed iron axe was excavated from Yoshida Nakamichi site in Tottori City, Tottori Prefecture. To understand reasons of corrosion state of the axe, we studied relationship between burial environment and corrosion. As environmental conditions, we investigated groundwater chemistry and corrosion rate with iron probe monitor, etc. As for corrosion state, we analysed corrosion depths with a X-ray CT and corrosion products with a portable XRD/XRF. As results, we found that the redox potential and dissolved oxygen level as environmental conditions were very low, and that the maximum corrosion rate (2$$times$$10$$^{-3}$$ mm/y) evaluated from measured corrosion depths was smaller than the probe corrosion rate (5$$times$$10$$^{-2}$$ mm/y) by two orders of magnitude and identified siderite (FeCO$$_{3}$$) as a corrosion product. The results suggested that the siderite precipitated on the surface of the iron sword inhibited corrosion reaction.

Journal Articles

Burial environment and corrosion of iron artifacts excavated from Mukibanda archaeological remains

Mitsui, Seiichiro

Mukibanda Iseki Hakkutsu Chosa Kenkyu Nempo 2014, p.27 - 44, 2015/03

AA2014-0727.pdf:4.39MB

A number of ancient iron artifacts were excavated from Mukibanda archaeological remains in Tottori Prefecture. To obtain detailed information on corrosion state of the iron artifacts, we analysed corrosion depths with a X-ray Computer Tomography (X-ray CT) and corrosion products with a portable X-ray diffractometer equipped with X-ray fluorescence spectrometer (XRD/XRF). As reference information for relationship between corrosion and environmental conditions, we also measured some environmental parameters. As results, we found that the maximum corrosion rates evaluated from measured corrosion depths was smaller than the probe corrosion rate by one to two orders of magnitude. The results suggested that the corrosion products precipitated on the surface of the iron artifacts inhibited corrosion reaction.

JAEA Reports

Passivation condition of carbon steel in bentonite/sand mixture

Taniguchi, Naoki; Kawakami, Susumu; *

JNC-TN8400 2001-025, 27 Pages, 2002/03

JNC-TN8400-2001-025.pdf:0.82MB

It is essential to understand the corrosion type of carbon steel under the repository conditions for the lifetime assessment of carbon steel overpack used for geological isolation of high-level radioactive waste. According to the previous study, carbon steel is hard to passivate in buffer material assuming a chemical condition range of groundwater in Japan. However, concrete support will be constructed around the overpack in the case of repository in the soft rock system and groundwater having a higher pH may infiltrate to buffer material. There is a possibility that the corrosion type of carbon steel will be influenced by the rise of the pH in groundwater. In this study, anodic polarization experiments were performed to understand the passivation condition of carbon steel in buffer material saturated with water contacted with concrete. An ordinary concrete and a low-alkalinity concrete were used in the experiment. The results of the experiments showed that the carbon steel can passivate under the condition that water having pH $$>$$ 13 infiltrate to the buffer material assuming present property of buffer material. If the low-alkalinity concrete is selected as the support material, passivation can not occur on carbon steel overpack. The effect of the factors of buffer material such as dry density and mixing ratio of sand on the passivation of carbon steel was also studied. The results of the study showed that the present property of buffer material is enough to prevent passivation of carbon steel.

JAEA Reports

The Activity of sulfate reducing bacteria in bentonite and the effect of hydrogen sulfide on the corrosion of candidate materials for overpacks

Taniguchi, Naoki; Kawasaki, Manabu*; *

JNC-TN8400 2001-011, 62 Pages, 2001/03

JNC-TN8400-2001-011.pdf:6.42MB

The corrosion of metallic materials used in natural environment are sometimes affected by microbial action. It is apprehended that microorganism living in deep underground or brought from ground surface during excavation makes an impact on overpack material for geological disposal of high-level radioactive waste. Sulfate reducing bacteria (SRB) is known to be one of the most representative microorganism which affects the corrosion of metals. In this study, the behavior of growth of SRB was investigated at first under the presence of bentonite as a main component of buffer material which encloses the overpack. The results of the tests showed that the population of SRB after the culture in synthetic sea water mixed with bentonite decreased with increasing the ratio of bentonite/solution. SRB was hardly grown in medium whose bentonite/solution ratio exceeded 1000g/l. As a conservative case, the effects of sulfide on the corrosion of overpack materials were also studied assuming high activity of SRB. Carbon steel, copper and titanium specimens were immersed in synthetic sea water purging 0.1MPa H$$_{2}$$S gas and the corrosion behavior was compared with the results in N$$_{2}$$ gas purging environment. Obvious effect of sulfide on the corrosion of carbon steel was not observed, but the corrosion rates of copper specimens were accelerated several hundred times by purging H$$_{2}$$S gas. The absorption of hydrogen into titanium specimens was not affected by purging H$$_{2}$$S gas, but the difference of hydrogen absorption between pure titanium and titanium alloy containing 0.06%-Pd was observed.

JAEA Reports

Effect of magnetite as a corrosion product on the corrosion of carbon steel overpack

Taniguchi, Naoki; ; Kawasaki, Manabu*; *

JNC-TN8400 2001-001, 56 Pages, 2000/12

JNC-TN8400-2001-001.pdf:1.48MB

It is necessary to clear the effects of corrosion products on the corrosion life time of carbon steel overpack for geological isolation of high-level radioactive waste(HLW). Especially, it is important to understand the effects of magnetite because magnetite as a simulated corrosion product is reported to accelerate the corrosion rate of carbon steel. In this study, corrosion tests to reproduce the acceleration of corrosion due to magnetite was performed and the mechanism of the acceleration was investigated to evaluate the effects of magnetite as a corrosion product. Based on the results of experiments, following conclusions are obtained ; (1)Magnetite powder accelerates the corrosion rate of carbon steel. The main reaction of corrosion under the presence of magnetite is the reduction of Fe(III) in magnetite to Fe(II), but the reaction of hydrogen generation is also accelerated. The contribution of hydrogen generation reaction was estimated to be about 30% in the total corrosion reaction based on the experimental result of immersion test under the presence of magnetite. (2)Actual corrosion products containing magnetite generated by the corrosion of carbon steel protect the metal from the propagation of corrosion. The corrosion depth of carbon steel overpack due to magnetite was estimated to be about 1 mm based on the results of experiments. Even if the effect of magnetite is taken into the assessment of corrosion lifetime of overpack, total corrosion depth in 1000 years is estimated to be 33 mm, which is smaller than the corrosion allowance of 40 mm described in the second progress report on research and development for the geological disposal of HLM/ in Japan. It was concluded that the effect of magnetite on the corrosion life time of carbon steel overpack is negligible.

JAEA Reports

Development of the evaluation methodology for earthquake resistance of the engineered barrier system (III)

Mori, Koji*; Neyama, Atsushi*; Nakagawa, Koichi*

JNC-TJ8400 2000-064, 175 Pages, 2000/03

JNC-TJ8400-2000-064.pdf:5.23MB

In this study, the following tasks have been performed in order to evaluate the stability of earthquake resistance for the engineered barrier system(EBS) of High Level Waste (HLW) geological isolation system. (1)validation studies for the liquefaction model. The function of single-phase analysis without interaction between soil and pore water in three-dimensional effective stress analysis code, which had been developed in this study, have been verified using by actual vibration test data. This fiscal year, some validation studies for the function of liquefaction analysis was conducted usig by actual measured data through the laboratory liquefaction test. (2)Supplemental Studies for JNC Second Progress Report. Through the JNC second progress report, it was considered that the stability of earthquake resistance of the engineered barrier system would be maintained under the major seismic event. At the same time we have recognized that several model parameters for joint-crack element, which takes into account for the response behavior of material discontinuous surface such as between overpack and buffer material, will become important in the response behavior of the whole EBS. This year, we have studied about several topics, which arise from technical discussion on JNC second progress report and we have discussed about total seismic stability of EBS. (3)Supplemental Studies for joint study with NRIDP. At this fiscal year, the joint study with National Research Institute for Disaster Prevention (NRIDP) will be final stage. UP to this day, incremental validation studies had been continued using by mesuared data obtained from vibration test. In this final stage, validation analysis has been conducted again using by current version new analysis code and maintained the validation data which will be contribute to the joint study mentioned above.

JAEA Reports

Natural analogue of alteration of bentonite contacting with concrete

Imai, Jun*

JNC-TJ8400 2000-008, 113 Pages, 2000/03

JNC-TJ8400-2000-008.pdf:20.79MB

The objective of this research is to make clear long-term alteration processes of bentonite contacting with concrete under a repository condition for radioactive waste. The Uzu tunnel in yamagata prefecture in Japan, constructed during the term of December of 1963 to July 1967, was selected as an appropriate natural analogue: the tunnel wall was made of portland cement and which has been contacting with a bentonite bed during $$geq$$ 32 years. Sample analyses indicated that the original bentonite was Na$$^{+}$$-type and it changed to Ca$$^{2+}$$-type in the range of a few millimeters from the contact. Although a Ca$$^{2+}$$ leaching was also observed from the concrete near the contact, neither transformation to zeolite nor to illite was recognized. On the other hand, sulfur increased and ettringite (3CaO $$cdot$$ Al$$_{2}$$O$$_{3}$$ $$cdot$$ 3CaSO$$_{4}$$4 $$cdot$$ 32H$$_{2}$$O) was recognized in the concrete within the depth about 30 mm from the contact.

JAEA Reports

Research on engineering procedure and models on buffer materials

Amemiya, Kiyoshi*; TRAN DUC PHI OAN*; Yamashita, Ryo*

JNC-TJ8400 2000-056, 487 Pages, 2000/02

JNC-TJ8400-2000-056.pdf:16.24MB

JNC presented the 2$$^{nd}$$ progressive reports on HLW disposal system. The documents impressed the importance of developing the engineering procedures and the model evaluating the thermo-hydro-mechanical phenomena in waste disposal system. In this research, the methods filling the gap between buffer and rock or buffer and overpack were examined. Bentonite pellets were tested as the filling materials. In order to assess the full-scale system performance, the Japanese experiences of buffer mass experiments were compared with the Prototype Repository Project of SKB in Sweden. Father more, the thermo-hydro-mechanical (THM) code named TRAMES was validated at the international co-research programs of DECOVALEX II.

JAEA Reports

Research on engineering procedure and models on buffer materials

Amemiya, Kiyoshi*; TRAN DUC PHI OAN*; Yamashita, Ryo*

JNC-TJ8400 2000-055, 49 Pages, 2000/02

JNC-TJ8400-2000-055.pdf:4.15MB

JNC presented the 2$$^{nd}$$ progressive reports on HLW disposal system. The documents impressed the importance of developing the engineering procedures and the model evaluating the thermo-hydro-mechanical phenomena in waste disposal system. In this research, the methods filling the gap between buffer and rock or buffer and overpack were examined. Bentonite pellets were tested as the filling materials. In order to assess the full-scale system performance, the Japanese experiences of buffer mass experiments were compared with the Prototype Repository Project of SKB in Sweden. Father more, the thermo-hydro-mechanical (THM) code named THAMES was validated at the international co-research programs of DECOVALEX II.

JAEA Reports

A Study on design methods for overpack welds; Acquisition of basic data to quantify welding quality

*; *; *; *; Sago, Hiromi*; *; *

JNC-TJ8400 2000-049, 175 Pages, 2000/02

JNC-TJ8400-2000-049.pdf:7.54MB

In this study basic data on welds of overpack structures for HLW were acquired and a predictive destruction analysis was performed usig the data acquired, in order to examine the viability of weld design methods. The results are summarized as follows: (1)Investigation of Design and Welding Condition for Welded Joint Models. Three welding methods--EBW, TIG and MAG--were selected, and welding conditions were determined so that the welding quality almost equivalent to that of an actual over-pack was ensured. (2)Fabrication of Welded Joint Models. Three welded joint models, one for each of EBW, TIG and MAG, were fabricated. It was confirmed that these models satisfied the quality requirements for Class I specified in JIS Z3104. (3)Sampling and Machining of Strength Test Specimens. Test specimens were taken from each welded joint model, and models for corrosion tests were delivered to the Japan Nuclear Cycle Development Institute (JNC). (4)Strength Test and Micro/macro Structure observation. Tensile tests were conducted at room temperature and at 150$$^{circ}$$C, and fracture toughness tests at 0$$^{circ}$$C and 150$$^{circ}$$C, in order to obtain stress-strain curves, J-R curves and Vickers hardness. In addition, an observation of micro and macro structures was performed. (5)Evaluation. Using the data on the welds obtained from the tests, a fracture prediction analysis and an evaluation of unstable fracture due to weld flaws were performed on the over-pack design described in the second progress report. The following conclusions were obtained: (a)For the overpack design examined, the effects of welds (material property and residual stress) and fabrication tolerance on fracture loading are negligible. (b)In addition, it was decided that even in a design with reduced wall thickness, welds have an insignificant effect on fracture loading because fracture initiates in the center of the shell of the overpack. (c)The size of flaws leading to unstable fracture is on ...

JAEA Reports

A Study on design methods for over pack welds; Acquisition of basic data to quantify welding quality

*; *; *; *; Sago, Hiromi*; *; *

JNC-TJ8400 2000-048, 30 Pages, 2000/02

JNC-TJ8400-2000-048.pdf:1.64MB

In this study basic data on welds of overpack structures for HLW were acquired and a predictive destruction analysis was performed using the data acquired, in order to examine the viability of weld design methods. The results are summarized as follows: (1)Investigation of Design and Welding Conditions for Welded Joint Models. Three welding methods--EBW, TIG and MAG-were selected, and welding conditions were determined so that the welding quality almost equivalent to that of an actual over-pack was ensured. (2)Fabrication of Welded Joint Models. Three welded joint models, one for each of EBW, TIG and MAG, were fabricated. It was confirmed that these models satisfied the quality requirements for Class I specified in JIS Z3104. (3)Sampling and Machining of Strength Test Specimens. Test specimens were taken from each welded joint model, and models for corrosion tests were delivered to the Japan Nuclear Cycle Development Institute (JNC). (4)Strength Test and Micro/macro Structure observation. Tensile tests were conducted at room temperature and at 150$$^{circ}$$C, and fracture toughness tests at 0$$^{circ}$$C and 150$$^{circ}$$C, in order to obtain stress-strain curves, J-R curves and Vickers hardness. In addition, an observation of micro and macro structures was performed. (5)Evaluation. Using the data on the welds obtained from the tests, a fracture prediction analysis and an evaluation of unstable fracture due to weld flaws were performed on the over-pack design described in the second progress report. The following conclusions were obtained: (a)For the overpack design examined, the effects of welds (material property and residual stress) and fabrication tolerance on fracture loading are negligible. (b)In addition, it was decided that even in a design with reduced wall thickness, welds have an insignificant effect on fracture loading because fracture initiates in the center of the shell of the overpack. (c)The size of flaws leading to unstable fracture is on the ...

JAEA Reports

Study on migration behavior of radionuclides in engineered clay barrier (II)

*; *; *

JNC-TJ8400 2000-018, 79 Pages, 2000/02

JNC-TJ8400-2000-018.pdf:2.09MB

As a basic research for geological disposal of high-level radioactive wastes, diffusion behavior of radionuclides and corrosion behavior of overpack materials in clay buffer materials (bentonite) were studied. In the study on the diffusion behavior of radionuclides, basal spacing and water content were determined for water saturated, compacted Na-montmorillonite that is major clay mineral of bentonite. The apparent diffusion coefficients of Na$$^{+}$$, Sr$$^{2+}$$, Cs$$^{+}$$ and Cl$$^{-}$$ ions and their activation energies were also determined at different dry densities of montmorillonite. For all kinds of ions, the activation energies were found to increase as the dry density increased. These findings suggest that the diffusion mechanism of ions in compacted montmorillonite changed with increasing dry density. As a reasonable explanation for the changes in the activation energy, we proposed a multiprocess diffusion model, in which predominant diffusion process is considered to change from pore water diffusion to interlayer diffusion via surface diffusion when the dry density increases. The Na-montmorillonite is expected to alter by the ion exchange with Ca$$^{2+}$$ ions, which could be introduced from groundwater and/or cementitious materials in a repository. The apparent diffusion coefficients of Na$$^{+}$$ and Cs$$^{+}$$ ions and their activation energies were studied for Na/Ca montmorillonite mixtures in order to know the effect of this kind of alteration on the diffusion behavior of ions. It was found that the alteration of montmorillonite affected diffusion coefficients and the activation energies for both kinds of cations. These effects cannot be explained only by the pore water diffusion. The multiprocess diffusion model proposed in this study is suggested as the most reasonable explanation for the effects. The oxidation behavior of pyrite in bentonite during drying process was studied for understanding corrosion behavior of overpack materials in bentonite. There ...

JAEA Reports

Study on cathodic reaction control efficiency by low alloy steels

Akashi, Masatsune*; Fukaya, Yuichi*; Asano, Hidekazu*

JNC-TJ8400 2000-015, 46 Pages, 2000/02

JNC-TJ8400-2000-015.pdf:2.01MB

Difference of hydrogen generation phenomena on the surface of the Steels were not observed between carbon steel, atmospheric corrosion resisting steel and 5%-Ni steel. Rust layer was formed on these three-type of steels by steam oxidation method. And the chemical composition of the rust for the steels were basically two (2) layers structure for the previous two steels as hematite (Fe$$_{2}$$O$$_{3}$$) based for the outer layer and magnetite (Fe$$_{3}$$O$$_{4}$$) based for the inner layer. And for the last steel, it had three (3) layer in the rust as hematite (Fe$$_{2}$$O$$_{3}$$) based for the outer layer, magnetite (Fe$$_{3}$$O$$_{4}$$) based for the intermediate layer and Ni based layer for the inner layer. These steels showed mostly same Tafel gradient in their cathodic polarization curves compare with that for no rust specimens. However, the exchange current density which reaction is assumed as a hydrogen generation reaction was largely increased. The cathodic reaction for each steels whose surface is covered by magnetite layer might be accelerated, then the corrosion rate was considered as accelerated, too.

JAEA Reports

Study on cathodic reaction control efficiency by low alloy steels

Akashi, Masatsune*; Fukaya, Yuichi*; Asano, Hidekazu*

JNC-TJ8400 2000-014, 22 Pages, 2000/02

JNC-TJ8400-2000-014.pdf:0.75MB

Difference of hydrogen generation phenomena on the surface of the Steels were not observed between carbon steel, atmospheric corrosion resisting steel and 5%-Ni steel. Rust layer was formed on these three-type of steels by steam oxidation method. And the chemical composition of the rust for the steels were basically two(2) layers structure for the previous two steels as hematite(Fe$$_{2}$$O$$_{3}$$) based for the outer layer and magnetite(Fe$$_{3}$$O$$_{4}$$) based for the inner layer. And for the last steel, it had three(3) layer in the rust as hematite(Fe$$_{2}$$O$$_{3}$$) based for the outer layer, magnetite(Fe$$_{3}$$O$$_{4}$$) based for the intermediate layer and Ni based layer for the inner layer. These steels showed mostly same Tafel gradient in their cathodic polarization curves compare with that for no rust specimens. However, the exchange current density which reaction is assumed as a hydrogen generation reaction was largely increased. The cathodic reaction for each steels whose surface is covered by magnetite layer might be accelerated, then the corrosion rate was considered as accelerated, too.

JAEA Reports

None

Shibata, Toshio*; *; *; Tsuru, Toru*; Inoue, Hiroyuki*

JNC-TJ8400 2000-013, 38 Pages, 2000/02

JNC-TJ8400-2000-013.pdf:3.25MB

None

JAEA Reports

Corrosion of iron buried in clay

Sumiyama, Morio*

JNC-TJ8400 2000-009, 138 Pages, 2000/02

JNC-TJ8400-2000-009.pdf:3.0MB

To evaluate corrosion behavior of carbon steel, a candidate materials of overpack, buried in soil for a long time, the water pipes buried in freshwater clay for a long time we digged out and the soil environment and the corrosion weight loss of pipes have been researched. From the results, a corrosion model (an empirical equation), an oxygen reduction reaction rate-determing step type, of carbon steel buried in soil was introduced. The corrosion data of under ground pipe collected by the Japan Community Gas Associations was used to increase reliability of the corrosion model equation. These data are one of researches of corrosion behavior of carbon steel buried in soil for a long time studied by at home and abroad. 38 samples buried freshwater clay were selected in 171 samples. With estimating the corrosion velocities and the soil environment factors of the above data, the maximum depth of pit corrosion was calculated by the statistical method of the extreme values using the area of overpack as the recurrent time. The correlation between the soil environment factors and the corrosion weight loss was obtained by the correlation analysis. The corrosion model of the maximum depth of pit corrosion at 0.99 of cumulative probability was compared between the under ground pipe data and the above data. On the reference data and the above data, the corrosion model equation; H = aY$$^{n}$$ was compared with the maximum depth of pit corrosion at 0.99 cumulative probability. The data of water pipes and community gas pipes at 0.99 cumulative probability showed the reasonable values when these data were compared with the reference data. So that the model was proved as a good corrosion model m the neutral low dissolved oxygen environment.

JAEA Reports

Inspection about the corrosion of metallic archaeological artifacts in ground

Honda, Takashi*; *

JNC-TJ8400 2000-007, 200 Pages, 2000/02

JNC-TJ8400-2000-007.pdf:14.84MB

In general, it is very difficult to evaluate the residual state of metallic iron and the original shape of iron-base archaeological artifacts, as these are covered by thick oxide films formed in the ground during over several hundred years. The purpose of this research is to quantify the corrosion of an artifact such as base, knife, and nail, which was digged out of the relics about 500-1,000 years old. (1)The outer oxide film layer and the inner metallic iron can be quantitatively divided by using X-ray CT method. Furthermore, the original surfaces of artifacts can be estimated from the obtained images, even if the metallic iron has corroded completely. The X-ray CT images were also compared with those obtained by X-ray transmission inspection. (2)The corrosion amounts and rates were evaluated on the basis of thicknesses, densities, and iron concentrations of oxide films. (3)The characteristic differences between ancient iron and modern carbon steel were evaluated by analyzing the ancient iron slag.

66 (Records 1-20 displayed on this page)