Papers by Keyword: High Temperature Water

Abstract: A transient photoelectrochemical analysis method is improved to investigate the semiconductor properties of oxide films on stainless steel 316L oxidized in high-temperature water. A minute amount of ZnO was added to the high-temperature water environment to alter the semiconductor properties of the oxide film deposited on stainless steel 316L. Characteristic phases in the oxide were investigated using the improved photoelectrochemical analysis method, and the semiconductor properties of the oxide film on stainless steel 316L suggested the presence of an n-type semiconductor. The photoelectrochemical dephasing angle showed movement of the flat band potential in the negative direction after ZnO addition.

Abstract: Hydrolysis of corn residue, one of major by-products after the extraction of starch, in sub-critical water to produce amino acids was conducted in this paper. The quality and quantity analysis of amino acids in hydrolysate were carried out by Amino Acid Analyzer (Biological Liquid Chromatography), and the main amino acid of arginine were obtained. The effects of Solid-water ratio, reaction temperature and time on the yield of the arginine were investigated. It was found that the optimum hydrolysis conditions for arginine preparation from the corn residue in sub-critical water are as follows: solid-water ratio 0.05, reaction temperature 473K and reaction time 1h, and the yield of arginine 10.23%. The results show that the sub-critical water hydrolysis process has the advantages of high efficiency, simple process and friendly to environment.

Abstract: The semiconductor properties of passive film formed on 304L stainless steel (SS), 316L SS and Alloy 800HT in high-temperature and high-pressure water with zinc addition have been investigated by using Polarization curve, Mott-Schottky analysis and photocurrent method. The donor density, flat band and band gap of semiconductor behavior are analyzed to investigate the impact of zinc addition to the passive film. Analysis of the experimental results indicated that passive film formed on 316L and 800HT with zinc addition showed different electrochemical, photo-electrochemical and semiconductor properties. The results indicated that corrosion resistance of passive film from in high-temperature and high-pressure water with zinc addition was obviously better than that without zinc addition.

Abstract: Organic acids (acetic and formic acid) are produced by the decomposition of ETA (Ethanol Amine, C2H7NO) used as pH controller of secondary water in nuclear power plants. Corrosion Fatigue (CF) tests (R=0.2, 0.1Hz) were conducted to evaluate the effect of acetic acid on the CF crack growth rate in high temperature water at 150°C. Acetic acid significantly influenced the environmental cracking behavior of turbine disc steels in high temperature water. The CF crack growth rates of turbine disc steels increase as the organic acid concentration increase to a critical saturation pH value (~pH 4). Beyond the saturation value of pH, the CF crack growth rates decrease significantly. The higher CF crack growth rate of the higher pH solution in water of intermediate content range (pH 4~pH 5) of acetic acid is due to the higher content of H+ enhancing the reduction reactions. Crack tip blunting prevents the CF cracks from growing with increasing rate in the solution of organic acid concentrations beyond the critical value.

Abstract: In this study, the variation of spring characteristics with increasing temperature was examined and the effect of their variations on the wear behavior of a nuclear fuel rod in both room and high temperature (300°C) water conditions was evaluated. From the results of the load-displacement tests, the spring stiffness was remarkably varied with increasing temperature. The results of the wear tests indicated that the wear damages are decreased at high temperature water when compared with the room temperature result. These results indicated that the removal mechanisms of wear debris at high temperature water are dependent on not only the formation of the wear particle layer but also on the changed contact conditions such as the contact length or area due to the stiffness drops.

Abstract: Low cycle fatigue tests were conducted in high temperature water for A533B pressure vessel steels with sulfur contents of 0.013, 0.025 and 0.038 wt.% respectively. Cyclic stress amplitude response and fatigue resistance as well as influence of strain rate, temperature and dissolved oxygen concentration in water were investigated. Fatigue cracking/fractograhpic features were examined. Sulfide-related environmentally assisted cracking mechanism is discussed.

Abstract: The electronic properties of the interfacial oxide film formed on 304L stainless steel in high temperature water are investigated by contact electric resistance (CER) measurements. Tests are performed in pure water with a wide range of dissolved oxygen (DO) content at 200, 250, and 288°C. The electrochemical potential (ECP) moves in the noble direction and CER increases when increasing DO. Results show that DO content has a dominant effect on the electronic properties of oxide film. The change of oxide film properties can also be attributed to the variation of the electrochemical potential, which is directly affected by DO content. Critical potentials exist for the formation and reduction of oxide films in high temperature water. Multiple steps are found for the reduction of oxide films due to de-aeration in 200, 250, and 288°C water, implying the presence of multiple-layer interfacial oxide films. The film reduction process is relatively slower than the film formation process. Present results show that even in high purity water, a moderate change of DO content can result in different surface conditions. Dissolved hydrogen has a moderate effect on interfacial surface films in deaerated water. In-situ monitoring of the oxide film properties by CER technique provides information on the interfacial reactions that are related to the SCC behavior of materials in high temperature water environments.