Yoshiyuki Satoh

Effects of Hydrogen Peroxide on Corrosion of Stainless Steel, (V) Characterization of Oxide Film with Multilateral Surface Analyses

In order to understand corrosion behavior of stainless steel in BWR reactor water conditions, characteristics of oxide films on stainless steel specimens exposed to H2O2 and O2 in high temperature water were determined by multilateral surface analyses, i.e., SEM (scanning electron microscope), LRS (laser Raman spectroscope), SIMS (secondary ion mass spectroscope) and STEM-EDX (scanning transmission electron microscope). The following points were experimentally confirmed. 1. Oxide layers were divided into inner and outer layers: Outer layers of the specimen exposed to 100ppb H2O2 consisted of larger corundum type hematite (α-Fe2O3) particles, while inner layers consisted of very fine Ni rich magnetite (Fe3O4). Outer layers of the specimen exposed to 200 ppb O2 consisted of larger magnetite mixture particles, while inner layers consisted of fine Cr rich magnetite. 2. Outer oxide layers consisted of oxide particles. The oxide particles depositing on the specimens exposed to 100ppb H2O2 were divided into two groups, i.e., a larger particle group and a smaller particle group. For other specimens, the diameter distribution of depositing particles was a single peak. Particle density and size were changed by oxidant concentration. The average diameter of the particles (that of the smaller group only for the specimen expose to 100 ppb H2O2) decreased with [O2] and [H2O2]. 3. Total oxide film thickness decreased with [H2O2] and increased with [O2]. 4. A larger dissolution rate at higher [H2O2] resulted in a thinner oxide film with smaller particles and larger hematite particles.

Determination of Hydrogen Peroxide in Water by Chemiluminescence Detection, (I) : Flow Injection Type Hydrogen Peroxide Detection System

A flow injection type hydrogen peroxide detection system with a sub-ppb detection limit has been developed to determine hydrogen peroxide concentration in water sampled from a high temperature, high pressure hydrogen peroxide water loop. The hydrogen peroxide detector is based on luminol chemiluminescence spectroscopy. A small amount of sample water (20 μl) is mixed with a reagent mixture, an aqueous solution of luminol and Co2+ catalyst, in a mixing cell which is installed just upstream from the detection cell. The optimum values for pH and the concentrations of luminol and Co2+ ion have been determined to ensure a lower detectable limit and a higher reproducibility. The photocurrent detected by the detection system is expressed by a linear function of the hydrogen peroxide concentration in the region of lower concentration ([H2O2]≤10ppb), while it is expressed by a quadratic function of [H2O2] in the region of higher concentration ([H2O2]>10ppb). The luminous intensity of luminol chemiluminescence is the highest when pH of the reagent mixture is 11.0. Optimization of the major parameters gives the lowest detectable limit of 0.3 ppb.

Effects of hydrogen peroxide on intergranular stress corrosion cracking of stainless steel in high temperature water, (V) characterization of oxide film on stainless steel by multilateral surface analyses

The difference in electrochemical corrosion potential of stainless steel exposed to high temperature pure water containing hydrogen peroxide (H2O2) and oxygen (O2)is caused by differences in chemical form of oxide films. In order to identify differences in oxide film structures on stainless steel after exposure to H2O2 and O2 environments, characteristics of the oxide films have been examined by multilateral surface analyses, e.g., X-ray diffraction (XRD), Rutherford back scattering spectroscopy (RBS), secondary ion mass spectroscopy (SIMS) and X-ray photoelectron spectroscopy (XPS). Preliminary characterization results of oxide films confirmed that the oxide film formed under the H2O2 environment consists mainly of hematite (α-Fe2O2), while that under the O2 environment consists of magnetite (Fe3O4). Furthermore oxidation at the very surface of the film is much more enhanced under the H2O2 environment than that under the O2 environment. It was speculated that metal hydroxide plays an important role in oxidation of stainless steel in the presence of H2O2. The difference in electric resistance of oxide film causes the difference in anodic polarization properties. It is recommended that several anodic polarization curves for specimens with differently oxidized films should be prepared to calculate ECP based on the Evans diagram.

A particle energy determination with an imaging plate

Abstract It is shown that the stimulation spectra of Eu 2+ luminescence in BaFBr:Eu 2+ based imaging plates are strongly dependent on the energies of the incident charged particles and the ratios of the luminescences stimulated by two different light wave lengths, e.g. of 600 and 500 nm, indicate simply the energies. This additional feature enables us to determine the incident particle energies by the imaging plate itself, keeping all the high performances of the imaging plate intact.

Measurements of mobilities and longitudinal diffusion coefficients for Li+ ions in some molecular gases

The transport coefficients for Li+ ions in some moleculars gases have been measured over a wide range of E/N with a conventional drift tube at temperatures close to 300 K. The zero‐field reduced mobilities are found to be 3.91±0.11, 4.44±0.12, 3.64±0.10, 2.46±0.07, and 3.44±0.10 cm2/V s in N2, O2, CO, CO2, and CH4 gas, respectively, and these values except in O2 gas significantly deviate from the Langevin limit. In N2, CO, and CO2 gas, the resulting mobility curves show clear minima at intermediate E/N, but the depressions in O2 and CH4 gas are slight. The drop of the zero‐field values in N2, CO, and CO2 gas is explained in terms of an effective ion–quadrupole interaction which provides the r−6 attractive behavior. From the mobility calculations with using n−4–6(γ) potential, it is suggested that the depression of the mobility curve is developed by the addition of a sufficient r−6 term and is partly attributed to inelastic collisions as expected even at intermediate E/N. The experimental diffusion data ar...

Determination of Hydrogen Peroxide in Water by Chemiluminescence Detection, (II): Theoretical Analysis of Luminol Chemiluminescence Processes

The authors previously developed a flow injection type hydrogen peroxide detection system based on chemical photoluminescence spectroscopy. This system has the lowest detectable limit of 0.3 ppb. The relationships between the hydrogen peroxide concentration and luminous intensity were expressed as a linear function and a quadratic function of the H2O2 concentration. In the present study, the chemiluminescence processes were theoretically evaluated by analyzing the chain radical reactions to confirm the effect of major parameters on the chemiluminescent intensity and to understand the complex relationship between H2O2 concentration and luminous intensity. Then delay in luminescence was empirically analyzed by calculating diffusion of chemical species in the sample water and mixed reagent solution. The calculated results showed dependencies of the chemiluminescent intensity on luminol concentration and pH of the mixed reagent were mainly determined by a balance between OH radical concentration and luminol concentration. Furthermore the presence of O2 - radicals in the mixed reagent might explain the linear relation between chemiluminescent intensity and H2O2 concentration at low values.

Effects of hydrogen peroxide on corrosion of stainless steel (II) ; Evaluation of oxide film properties by complex impedance measurement

A high temperature high pressure water loop, which can control H2O2 concentration with minimal oxygen (O2) coexistence, has been fabricated. In order to evaluate the effects of hydrogen peroxide (H2O2) on intergranular stress corrosion cracking. Not only static responses, i.e., electrochemical corrosion potential (ECP), of the stainless steel specimens exposed to H2O2 and O2 at elevated temperatures but also their dynamic responses, i.e., frequency dependent complex impedances (FDCI), were measured. The conclusions obtained by the experiments are as follows. 1. The ECP measured for the SUS 304 specimen exposed to 100ppb H2O2 reached the saturated level in 50h, showed a larger value than the specimen exposed to 200 ppb O2 and kept the same ECP level when the H2O2 concentration was decreased to 10ppb. 2. The FDCI measured for the specimen exposed to 100 ppb H2O2 showed saturation in the low frequency semicircles; this behavior was determined by the electric resistance of the oxide film and caused by saturation of oxide film thickness. Behavior for the specimen exposed to 200 ppb O2 was determined by the resistance of oxide dissolution, which was much larger than that for the specimen exposed to H2O2 3. The ECPs of the specimens exposed to 200 ppb O2 after 200-h exposure to 100 ppb H2O2 were higher than those exposed to only 200 ppb O2 due to memory effects on oxide films. The specimens with pre-exposure to 200 ppb O2 did not show these memory effects.

Effects of hydrogen peroxide on corrosion of stainless steel, (I) improved control of hydrogen peroxide remaining in a high temperature high pressure hydrogen peroxide loop

In order to evaluate the effects of hydrogen peroxide (H2O2) on intergranular stress corrosion cracking, a high temperature high pressure water loop, which can control H2O2 concentration with minimal oxygen (O2) co-existence, is required. This loop is characterized by 1. A once-through type loop to prevent accumulation of decomposed O2 in the loop 2. Minimized autoclave volume to prevent bulk thermal decomposition of H2O2 3. A polytetrafluoroethylene (PTFE) lining to prevent surface decomposition of H2O2, and 4. A H2O2 monitoring system with an off-line H2O2 detector to determine concentration in the sampled water which is combined with an in-line dissolved O2 detector to determine the decomposed O2 concentration. The authors developed such a loop previously. In the present work, performance tests were carried out and measured data were evaluated by comparing with predicted values to verify whether the target characteristics were met. The measured H2O2 remaining in the sampled water agreed with the predicted amount within 5%. It was confirmed that the ratio of H2O2 remaining in the loop autoclave was more than 90% and the concentration could be monitored continuously with the in-line dissolved O2 detector installed after the cooler in the loop. Electrochemical corrosion potential (ECP) and frequency dependent complex impedance were measured successfully by changing H2O2 concentration.

Identification of Ionizing Radiation with an Imaging Plate Using Two-Wavelength Stimulation Light

Imaging plates are widely used in various fields. However, ordinary reading instruments give no information on the type of radiation. We proposed that radiation type can be identified by stimulation with light of two wavelengths. Recently, we have carried out further investigation and found that the intensity ratio of photostimulated luminescence (PSL) between two wavelengths depends on particle properties. Imaging plates were irradiated with 3.2 MeV protons, 40 kVp X-rays, 200 keV electrons and Co-60, and stimulation spectra were observed for each type of radiation. We compared the PSL intensities at 500 nm with those at 600 nm 18 hrs after irradiation. The PSL intensities at 600 nm normalized by those at 500 nm were observed to decrease in order of irradiation with 3.2 MeV protons, 40 kVp X-rays, 200 keV electrons and Co-60.

Emission characteristics of zeolite A ion source

An easy method to prepare alkali ion emitters has been realized by using the ion‐exchange technique. The thermionic emission characteristics of zeolite A alkali ion sources have been studied. Experimental results indicate that ion transport process within zeolite plays an important role in the emission mechanism.