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Japanese tap water is Ca2+-poor and SiO2-rich in comparison with that of other counties. Thus, there have been few studies on its corrosivity. We sampled tap waters at 70 different sites and in different seasons in Japan, subjected the samples to chemical analysis and measured localized corrosion depth and the total corrosion loss of carbon steel placed in these waters. The average corrosion rate vavg and maximum localized corrosion rate vmax were calculated. The ratio of vmax to vavg, which was defined as localized corrosion factor LCF (=vmax/vavg), was also studied. The multiple regression method was applied to obtain the dependence of vavg (objective variable) on concentrations of chemical species (explanatory variables). In the same manner, the relation of vmax and LCF to concentrations of chemical species was derived. As a result, we showed that SiO2 and SO42− mainly dominate the corrosivity of Japanese tap water. In particular, as SO42− increased, vavg became larger and vmax became smaller. Also, as SiO2 increased, vmax became larger and vavg became smaller. The behavior of LCF was similar to that of vmax. The findings of this study will be useful for estimating the corrosivity of tap waters that have low Ca2+ and high SiO2 concentrations. [ABSTRACT FROM AUTHOR]

Coronavirus disease pandemic has led to a shortage of disinfectant alcohol (DA; 76.9-81.4% ethanol solution) in Japan. This study investigated the availability of hypochlorous acid (HA) as an alternative disinfectant to DA in clinical environment. HA is a safe and economical disinfectant with a broad antibacterial spectrum and low risk of hand irritation, which is used worldwide. In this study, HA and sodium hypochlorite solution (SH) were degraded over time and the degradation was accelerated by temperature and lighting. Results of bactericidal effects of HA revealed that the realistic effective concentration should be 200 ppm. Compared with DA, the dental carbon steel burs were more severely rusted by SH and HA. These results indicated that high concentration of HA generated on-site could be an effective and safe disinfectant for use immediately after generation with consideration of object materials in clinical environment, as an alternative to DA. [ABSTRACT FROM AUTHOR]

For the geological disposal system in Japan, a vitrified waste will be contained in a metal overpack, which, in turn, will be surrounded by a thick bentonite buffer. The overpack is aiming to prevent the contact of groundwater to vitrified waste during the high radioactivity and heat generation period of the first 1,000 years at least after emplacement. Within the Japanese program, consideration for overpack candidate materials has included carbon steel, copper–steel composite, and titanium–steel composite. Within the extensive safety assessment conducted in 2000, steel was selected. This selection was partly based on the manufacturability of carbon steel, as well as its well‐understood corrosion behavior. However, the understanding of copper corrosion and welding/manufacturing technologies have greatly progressed over the past two decades. In this study, we focus on the copper‐coated container developed by the Nuclear Waste Management Organization, because this technology is seemingly effective to maintain very long‐term containment of hundreds of thousands of years, with a low cost of manufacturing within the Canadian program. We are investigating the applicability of the copper‐coating technologies in terms of the corrosion allowance and mechanical design. [ABSTRACT FROM AUTHOR]

Current designs for the geological disposal of high‐level radioactive waste in Japan use carbon steel overpack containers surrounded by a mixed bentonite/sand buffer material, which will be located in a purpose‐built repository deep underground. Though there are many suitable sites for a repository in Japan, the coastal areas are preferable from a logistical point of view. It is, therefore, important to evaluate the long‐term performance of the carbon steel overpack and the mixed bentonite/sand buffer material in the saline groundwaters of coastal areas. In the current study, the passivation behavior and initial corrosion rates of carbon steel with and without mixed bentonite/sand were tested as a function of the pH and salt concentration in representative saline groundwaters. The main findings indicate that the passivation of carbon steel encapsulated in a buffer material will be unlikely in a saline environment, even at high pH (12), and that the corrosion rate of carbon steel is more strongly affected by the presence of the buffer material than by the salt concentration. [ABSTRACT FROM AUTHOR]

• Flow simulation of hydrate re-formation in actual offshore gas hydrate production. • Quantitative estimation of hydrate volume fraction along water production line. • Mass transfer model of hydrate growth in water-dominant, turbulent flow in pipes. • Hydrate reservoir production systems heat transfer limited. • Use of uninsulated carbon steel may exacerbate hydrate re-formation. Natural gas hydrates are a potential new energy resource, however, challenges for stable, long-term gas hydrate production remain. This study examines the flow assurance risk of hydrate re-formation in production lines during gas hydrate production, which is a key issue in designing reliable production systems and operations. The focus of this study is the second offshore methane hydrate production test conducted in the Nankai trough area of Japan in 2017, where the depressurization method with a pump, wellbore gas separation, and two production lines for gas and water was applied. In this field test, separation inefficiencies caused significant quantities of gas to be produced from the water production line, posing a risk of hydrate re-formation. To understand and aid in management of this risk, we have developed models of hydrate growth and dissociation in water-dominant flow and conducted flow simulations that were compared to field data from the water production line in this field case. The simulation predictions suggest that the hydrate re-formation was not significant in this production test due to use of flexible hoses with a low overall heat transfer coefficient. The thermal insulation of the flexible hoses contained the heat generated by hydrate formation inside the production lines, resulting in a heat transfer limited system with low hydrate volume fractions (<5.2 vol%). Further simulations were conducted to estimate the sensitivity of such systems to insulation and materials choice, where a system with the flexible hoses replaced with carbon steel pipes was predicted to experience volume fractions four times greater (<19.8 vol%). Given hydrate production test systems typically take the form of short vertical lines, this indicates that pipe insulation may be critical in managing the risk of plugging due to re-formation. This insight is particularly important given the widespread use of carbon steels in subsea production facilities. Simulations enabled by the algorithm presented in this work will inform design choices for future methane hydrate production facilities. The use of thermal insulators will likely limit the degree of hydrate re-formation in such systems, and enable the deployment of management strategies that minimize or eliminate chemical injection. [ABSTRACT FROM AUTHOR]

Dose response functions (DRFs) are examined in terms of applicability to the data of outdoor exposure tests in Japan (JWTC data) in order to improve estimation methods for assessing the domestic atmospheric corrosivity of carbon steel and zinc. ISO9223DRF is selected from a literature survey as a suitable DRF. The corrosion rate estimated by the ISO9223DRF shows insufficient agreement with the measured rate from the JWTC data. The ISO9223DRF coefficients are redetermined by a nonlinear least-squares regression model based on the JWTC data (fitted DRF). The corrosion rate estimated for the fitted DRF shows better agreement with the measured rate from the JWTC data in terms of correlation with the measured one and the fraction of the estimated one within errors of --50...+100%. [ABSTRACT FROM AUTHOR]

Elemental iodine is produced in Japan from underground brine (fossil salt water). Carbon steel pipes in an iodine production facility at Chiba, Japan, for brine conveyance were found to corrode more rapidly than those in other facilities. The corroding activity of iodide-containing brine from the facility was examined by immersing carbon steel coupons in 'native' and 'filter-sterilized' brine samples. The dissolution of iron from the coupons immersed in native brine was threefold to fourfold higher than that in the filter-sterilized brine. Denaturing gradient gel electrophoresis analyses revealed that iodide-oxidizing bacteria (IOBs) were predominant in the coupon-containing native brine samples. IOBs were also detected in a corrosion deposit on the inner surface of a corroded pipe. These results strongly suggested the involvement of IOBs in the corrosion of the carbon steel pipes. Of the six bacterial strains isolated from a brine sample, four were capable of oxidizing iodide ion (I) into molecular iodine (I), and these strains were further phylogenetically classified into two groups. The iron-corroding activity of each of the isolates from the two groups was examined. Both strains corroded iron in the presence of potassium iodide in a concentration-dependent manner. This is the first report providing direct evidence that IOBs are involved in iron corrosion. Further, possible mechanisms by which IOBs corrode iron are discussed. [ABSTRACT FROM AUTHOR]

Abstract: Railway axles are one of the most important components in railway systems since a fail-safe design is not available. In the present paper, the fatigue tolerance of the high-speed railway axle in Japan is reviewed. To maintain the safety, the fatigue strength of the axle has been extensively studied. Theses case histories and consequent improvements in manufacturing process are presented. The crack propagation behavior of the induction hardened axle is studied based on the fracture mechanics. Concerning the powered railway axles, the fatigue design method in Japan is compared with that in Europe and the effect of the train velocity on the allowable load is discussed. [Copyright &y& Elsevier]

Abstract: This paper dynamically analyzes the Japanese material flow of stainless steel. The substance flow analysis of Cr and Ni associated with stainless steel was conducted by classifying the material flow of stainless steel into two main alloy types: ferritic and austenitic. The substance flow covered more than 80% of Cr and Ni consumption in Japan. In mass balances of Cr and Ni, the production of not only stainless steel but also other alloying steels containing Cr and/or Ni was taken into account. The mass balances of three elements (Fe, Cr, and Ni) provided complementary information for confirmation of our estimations. As a result of dynamic analysis, the in-use stock of ferritics and austenitics at the end of the year 2005 was 4Tg and 14Tg, respectively, which converts to 3Tg of Cr and 1Tg of Ni. In addition, the recycling flow was closely analyzed. From the result for the year 2005, the recycling rates as stainless steel scrap were estimated as 21–38% for ferritics and 94–100% for austenitics. The amount of ferritics scrap to be recycled as carbon steel was quantified as well. By comparing our results with those in previous studies, we found that applying parameters obtained in other countries may be misleading, especially in recycling flows. [Copyright &y& Elsevier]

• Scale formation is a major problem that hinders geothermal power plant operation. • Method to imitate MgSiO 3 scale structure developed and scaling properties evaluated. • Scales in Obama Hot Spring, Japan were considered for the study. • Synthesis in CO 2 yielded scales similar to real samples, with high scaling property. • The method will aid in future experimental research on silicate antiscaling. To shorten the development period of suitable anti-scaling technology for individual geothermal plants, it is necessary to improve the precision in evaluating the scaling technology through laboratory testing. Therefore, in this study we investigated a method to imitate the structure of magnesium silicate scale that has precipitated in Obama Hot Spring in Nagasaki Prefecture, Japan. Magnesium silicate hydrates were synthesized in an artificial solution at 100°C under different environments (i.e., carbon dioxide, nitrogen, and atmosphere). The synthesized solutions with magnesium silicate hydrates were flowed to the inner surface of a carbon steel pipe, and the scaling propensity of magnesium silicate was evaluated. Among the samples, the ones synthesized under the carbon dioxide environment have a similar structure with the field magnesium silicate scale and exhibited high scaling propensity. We believe that the findings are useful to eliminate the gap between the characteristics of field scaling and laboratory testing. [ABSTRACT FROM AUTHOR]

• New strength design and evaluation rules were developed for railway axles. • Fatigue damage was evaluated by variations in the in-service conditions. • Safety assessment involved comparing equivalent stress with past proven values. • Full-scale fatigue tests of railway axles were performed to clarify the S–N curve. • Inverse values of S–N curve slope were specified for different axle types and parts. Fatigue-limit-based designs were employed for railway axles in Japan, and new strength design and evaluation rules were developed to achieve more reasonable designs. Design specifications for strength were introduced to describe the detailed processes, whereas other specifications were introduced to propose a method for the estimation of the fatigue damage caused by variations in in-service conditions. Further, safety assessments were implemented by comparing the equivalent stress with the reference values obtained from past safe-operation records. The proposed assessment method is superior to previously used techniques for railway axles because of its low safety risk. To clarify the S–N curve of axles, full-scale fatigue tests were performed on railway axles used in Japan. The slopes of the S–N curve were specified in the damage evaluation rules. [ABSTRACT FROM AUTHOR]