Stress corrosion cracking countermeasure observed on Ni-based alloy welds of BWR core support structure

The effect of hydrostatic test on the residual stress re-distribution was simulated by experiment to confirm the residual stress behavior of the cone-shaped shroud support to reactor pressure vessel (RPV) weld, where a number of cracks due to stress corrosion cracking (SCC) were observed on the inner side only. Test specimen with tensile residual stress was loaded and unloaded with axial plus bending load, which simulates the hydrostatic test load, and the strain change was measured during the test to observe the residual stress behavior. The results verify that the residual stresses of the shroud support to the RPV weld were reduced and the stresses on inner and outer sides were reversed by the hydrostatic test. As the SCC countermeasure, the shot peening (SP) technology was applied. Residual stress reduction by SP on the complicated configuration, and improvement of SCC resistance and endurance of the compressive residual stress were experimentally confirmed. Then, SP treatment procedures on the actual structure were confirmed and a field application technique was established.     

Dependence of electronic stopping powers on incident ions using new Firsov formula

The dependence of the electronic stopping powers on the incident ions of the atomic number Z₁ in the materials of carbon, aluminum, nickel, silver and gold has been evaluated by using the new Firsov formula included the Sugiyama potential for the Firsov model and the screening length with the shell effect of electrons. It was found that the calculated results based on the new Firsov formula show the experimentally well-known Z₁-oscillation in the electronic stopping powers. The electronic stopping powers measured in carbon, aluminum, nickel and silver are reasonably reproduced by the new Firsov formula for the ZBL potential.     

Catalytic oxidative dimerization of methane to form C2-compounds over Arppe's phase oxychlorides of Bi,La and Sm

Three distinct examples of Arppe's phase (M₂₄O₃₁Cl₁₀; M = Bi, La, Sm), which has a structure related to that of the layered oxychloride BiOCl, have been used as monophasic catalysts for the oxidative dehydrogenation of CH₄. The stability and performance of these rival those of the best catalysts previously reported.     

Swelling response behavior of palladium during hydrogen absorption and discharge

Swelling characteristics of hydrogen storage alloy (HSA) with hydrogen content change were experimentally determined. Its kinetic behavior is important for an HSA actuator which is driven by the volume change of the HSA in a hydrogen atmosphere. Although hydrogen absorption characteristics of the alloy are expected to be strongly related to the actuator performance, it is difficult to clarify the relationship using the previous HSA actuators which consist of plural materials. In this paper, the authors investigated the swelling ratio and the response time of palladium powder in a hydrogen atmosphere. As a result, the swelling ratio increased with hydrogen absorption amount. The response time increased with hydrogen pressure during pressurization, while it was independent of pressure. It was revealed from reaction kinetics that a rate-limiting step was diffusion and interfacial reaction during the pressurization and the evacuation, respectively. Thus, the swelling property of palladium is determined from its hydrogen absorption behavior, which suggests the HSA actuator can be designed based on hydrogen storage characteristics.     

Application of an ecosystem model for aquatic ecological risk assessment of chemicals for a Japanese lake.

The Lake Suwa version of the comprehensive aquatic systems model (CASM-SUWA) was developed using field data from Lake Suwa and evaluated to examine the utility of CASM-SUWA for assessing the ecological risk of chemicals for aquatic ecosystems. The calibration of the parameters for the model provided that the established reference model simulation could reproduce complex seasonal biomass behavior of populations that were not significantly different from the general seasonal pattern for the Lake Suwa ecosystem. The sensitivity analyses revealed the potential importance of indirect effects and demonstrated that the parameter values of all the trophic levels were important in determining the biomass of each trophic level in the model. The risk estimation of linear alkylbenzene sulfonates (LAS) demonstrated that the model estimated the risks of direct toxic effects on each population and the indirect ecological effects that propagate through the food-web in the model ecosystem. The CASM-SUWA-derived benchmark levels were approximately one order of magnitude less than the field-derived NOECs in literature. The analyses of the comparison implied that the model could provide a good basis in determining an ecological protective level of a chemical of concern in aquatic ecosystem. This modeling study demonstrated that the model can be used to provide additional information for the decision-making process in the management of the aquatic ecological risk of chemicals.     

Spectro-electrochemical studies of the corrosion inhibition of copper by mercaptobenzothiazole

The mechanism of the corrosion inhibition of Cu by mercaptobenzothiazole (MBT) was investigated by in situ measurements of u.v.-visible reflection spectra of films formed on potentiostatically polarized Cu electrodes. Infrared reflection and X-ray photoelectron spectroscopy were also used. These methods permit microscopic observation of reactions at the liquid/solid interface. It is shown that water-insoluble thin polymeric film of mercaptobenzothiazolato-Cu(I) (Cu^IMBT) is formed on the surface by a surface reaction of cuprous ion with adsorbed MBT and that this film acts as a barrier against corrosive environments.     

A Homogeneous Catalyst for Reduction of Optically Active Esters to the Corresponding Chiral Alcohols without Loss of Optical Purities

A ruthenium complex was found to catalyze the hydrogen reduction of esters under mild and neutral conditions. A variety of optically active esters can be reduced to the corresponding alcohols in excellent yield without loss of their optical purity or causing undesirable side reactions. Hydrogen reduction needs such simple operations – reaction, concentration, and purification – that the violent quench step and extraction step, which accompany conventional sodium borohydride or lithium aluminum hydride reduction, can be omitted.