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Nuclear power generation is now one of the most important technologies in the energy supply in Japan. The operational experience of nuclear power plants for more than 20 years in Japan has shown that water chemistry is a key technology for safer and more economical operation of nuclear power plants. Extensive efforts have been made in the field of water chemistry to achieve the targets of radiation field control, to keep the integrities of piping and fuel elements and to reduce the radioactive waste generation. This paper briefly describes the present status of Japanese water chemistry technology with the main emphasis placed on BWRs.

Medium-chain fatty acids (MCFA) such as caproic, heptanoic, and caprylic acids are monocarboxylic acids, which can be used as precursor molecules to synthesize biodiesel, bioplastics, antimicrobials, and corrosion inhibitors.

Abstract Continuous bio-methanization of an energy crop, namely the beet silage, was investigated in this laboratory-scale work as mono-substrate, using a mesophilic biogas digester controlled by a fuzzy logic control (FLC) technique and without using any supplementing or buffering agent, despite the low pH of the substrate around 3.80. The temperature, pH, redox potential (ORP), daily biogas production and composition of digester biogas were continuously measured online. During the operation, the hydraulic retention time (HRT) varied between 24.8 and 9 days, as the organic loading rate (OLR) ranged from 2.6 to 4.7 g L −1 d −1 . The average pH, specific gas production rate (spec. GPR) and volumetric gas production rate (vol. GPR) were determined to be 7.12, 0.31 L g VS −1 d −1 and 1.084 L L −1 d −1 , respectively. The average methane (CH 4 ) content of digester biogas was about 56%. The FLC technique, which was developed at HAW Hamburg for anaerobic conversion of acidic energy crops to methane, determined the daily feeding volume (∼ OLR/HRT) for the biogas digester, depending on the feedback from online pH and methane measurements, and on the calculation of the spec. GPR. The spec. GPR was calculated by the corrected daily biogas production. Through online monitoring of pH, biogas production rate and composition, and by use of the FLC technique, the acidic beet silage could continuously be converted to biogas, without using manure or any other kind of buffering or supplementing agent(s). The lab-scale anaerobic biogas digester performed stable and safe, without encountering any problems of instability, as indicated by an adequate amount of buffering capacity, a VFA content below 0.5 g L −1 and a neutral pH range throughout the study.

Abstract Experimental study on the concentration difference cell between seawater and river water (dialytic battery) has been made with special attention to the transient change in the power output. The cell consists of 59 compartments made with 29 ion-exchange membrane pairs, each of which has an effective area of 80 cm 2 per sheet. It has been found that the voltage drop across the load decreases exponentially with two different short and long time constants, of which values are about 50 and 800 s, respectively. Accordingly the power also decreased to about one fourth (from 259 to 68.9 mW/m 2 pair) after sufficient time passed. These transient behaviors have been successfully interpreted by the capacitor-type equivalent circuit model. From comparisons between the experimental and the model results, values of the internal resistance and two kinds of capacitor were determined, of which values were 114 Ω, 1.35 and 66.4 F, respectively. It was suggested that the short and long time constants came from charge double layers formed at the cathode and the anode, respectively. Measurements of potential difference between saline water compartments in the case with and without external current by reference electrodes showed that voltage losses occurred due to the concentration polarization near the ion-exchange membranes and the activation polarization at the electrode surfaces.

In order to relieve the suppression problems of methanogenesis with microorganisms surrounded by undegraded lipids in food waste, hydrothermal alkali pretreatment was utilized to degrade lipids for promoted methane production through the co-production process of hydrogen with methane. GC-MS results demonstrated that oleic acids and hexadecanoic acids derived from degraded glycerol trioleate increased (from 43.29% to 58.22%, and from 1.06% to 8.25%, respectively) when the pretreatment temperature was increased from 160 °C to 220 °C. SEM, TEM and FTIR analyses showed that the pre-treatment at 220 °C effectively degraded 87.56% of glycerol trioleate and drastically relieved the covering of methanogens by non-degraded lipids. The methane yield and the production peak rate of glycerol trioleate also increased (from 636.85 to 877.47 mL CH4/g-total volatile solid (VS), and from 32.60 to 51.22 mL CH4/g-VS/d, respectively), which led to an increased energy conversion efficiency from 48.05% to 66.21% through the co-production of hydrogen with methane.

Abstract A range-adjusted measure (RAM) of efficiency, as recently developed in data envelopment analysis (DEA), is used to evaluate the performance of entities that supply water services in Japan. Its robustness properties are tested and pointed up for uses in improved accountability, and are further pointed up in terms of the potential for help in conducting performance and efficiency audits. The results from DEA are also joined with the Mann–Whitney rank order statistic to show how the two techniques may be jointly used in addressing issues of general policy. The Kanto Region and Kanagawa Prefecture in Japan are used for an illustration.

Electricity generation and treatment of sweet potato-shochu waste, acidic and organic-rich slurry, was examined using cassette-electrode microbial fuel cells (CE-MFCs). Among CE-MFCs with raw (73 g-chemical oxygen demand chromium CODCr/L) and different concentration of diluted sweet potato-shochu waste (0.5, 1, 5, 10, and 20 g-CODCr/L) without pH control, the maximum power density (1.2 W/m3) and CODCr removal efficiency (67.4 ± 1.8%) were observed in the CE-MFCs with 10 g-CODCr/L shochu waste. The concentration of organic acid was decreased to below the quantification limits during the 9-day operation in the CE-MFC with 10 g-CODCr/L shochu waste. During the same period, the electrolyte pH was increased from 4.2 to 6.6. Microbial community analysis revealed that the genus Clostridium (75.4%) was predominant in the CE-MFCs with raw shochu waste, whereas Bacteroides (65.3%) and Clostridium (12.1%) were predominant in the CE-MFCs with 10 g-CODCr/L shochu waste.

Photosynthetic bacteria produce hydrogen from lactate and acetate that are products of hydrogen producing bacteria in the dark. Thus, their coculture is a promising method for hydrogen production. However, the hydrogen production yield from acetate of Rhodobacter sphaeroides RV, which has been shown to possess the highest yield and hydrogen production rate, is low as compared to that from lactate. Photosynthetic bacteria that produce hydrogen from acetate as well as lactate were screened from lakes and swamps in the Tokyo and Chiba areas in Japan. Seventy-six strains of photosynthetic bacteria were obtained and the analysis of their 16S rRNA gene sequences revealed that they belong to R. sphaeroides. Among the isolated bacteria, R. sphaeroides HJ produced the highest amount of hydrogen from acetate and lactate. The HJ strain produced a 2300±93ml/L-broth of hydrogen from 75mM acetate consumed during for 120h of fermentation. The amount of hydrogen and the yield from acetate were 1.9 and 2.1 times higher, respectively, than those of R. sphaeroides RV. The amount and yield of hydrogen, produced by R. sphaeroides HJ from lactate were similar to those produced by R. sphaeroides RV. Since the amount and yield of produced hydrogen by the HJ strain were similar regardless of the substrate (acetate or lactate), its metabolic pathway could have a key to increasing hydrogen production from acetate.

An analytical investigation of a high-temperature heat pump system was developed to estimate the thermal cycle and to assess the thermal fluids for their high-temperature delivery (up to 180°C) capacities without decomposition or the use of lubricant mechanisms. Then, a screw-type compressor was applied in the above conditions. Furthermore, a screw expander was also used as a replacement for the throttle valve [Taniguchi et al. J. Engng Gas Turbine and Power (ASME) 110, 628–635 (1988). In order to assess the performance of the heat pump system, leakage and friction effects had to be determined and simulated when using the screw machines. Numerical results of system tests are presented from cases where steam-water (for higher temperatures) and ammonia (for lower temperatures) were used as thermal fluids instead of normally used fluids such as halogenated chlorofluorocarbon, which has been implicated in the depletion of stratospheric ozone.