Haruo Fujimori

Detection of Fine Particles in Liquids by Laser Breakdown Method

Basic characteristics of a particle detection method using laser breakdown were studied for a system of polystyrene standard particles dispersed in ultrapure water. The method was able to detect 0.02 µm particles. The detection sensitivity decreased with the particle size due to size dependence of the laser breakdown threshold. The plasma emission delay time from the laser pulse decreased with particle size (9.8±0.8 ns for 0.04 µm, 5.7±0.8 ns for 3.0 µm). The above results suggested the possibility of concentration and size measurement of fine particles in liquids by the proposed method.

Effect of Zirconium Addition to Austenitic Stainless Steels on Suppression of Radiation Induced Chromium Segregation at Grain Boundaries under Ion Irradiation

The effect of Zr addition to austenitic stainless steels on the suppression of radiation induced Cr segregation at grain boundaries under 400 keV He+ irradiation was studied. Type 316L stainless steel and steels with addition of 0.07, 0.21 or 0.41 mass% Zr were kept at 1,423K for 30 min, and then they were quenched into the water. Irradiation was done at 773K with the dose rate of 2.4×10−4dpa/s. The total dose was 0.85 or 3.4dpa. After irradiation, profiles of Cr concentration across the grain boundaries were measured using an analytical electron microscope with 1 nm beam diameter. Concentration of Cr at the grain boundary is decreased by radiation induced segregation. However, it increased with the addition of Zr, and the Cr segregation is almost completely suppressed when Zr is added more than 0.21 mass%. The effect of Zr addition on suppression of Cr segregation was analyzed focussing on the interaction between dissolved Zr atoms and point defects. The effect is based on vacancy trapping by the Zr atom...

Noncontact Measurement of Film Thickness by the Photothermal Deflection Method

A noncontact film-thickness measurement method using photothermal deflection was studied from theoretical and experimental results of the film-thickness dependency of the deflection amplitude. The calculated results showed that thicknesses in a range from the skin depth to the thermal-diffusion length of an opaque film could be determined from the deflection amplitude, which increased monotonously in that range. It was shown that the thicknesses of a transparent film could be determined from the vibrational structure of the deflection amplitude due to an interference effect of the excitation beam or from its decrease by an adiabatic effect of the film. Experimental results for NiO films (3–38 µm) and SiO2 films (20–110 nm) revealed the possibility of noncontact film-thickness measurements in air and water.

Particle Size Dependence of Correlation between Plasma Emission Delay Time and Plasma Emission Intensity of Laser Breakdown Induced by a Particle

Plasma emission delay time and plasma emission intensity of laser breakdown induced by a polystyrene particle in water were measured simultaneously. Short plasma emission delay time tended to correspond to high plasma emission intensity, as expected from the spatial and temporal profiles of the laser pulse power density. Particle size dependence of the correlation between the two parameters may serve in the measurement of the particle size.

Simultaneous Determination of Uranium and HNO3 Concentrations in Solution by Laser-Induced Fluorescence Spectroscopy

A simultaneous determination method of U and HNO3 concentrations by fluorescence spectroscopy was proposed. In the method, the former was determined from UO2 2+ fluorescence intensity which is proportional to UO2 2+ ion concentration and the latter from UO2 2+ fluorescence spectrum profile which depends on the NO3 − ion configuration around the UO2 2+ ion. The UO2 2+ fluorescence spectra were measured by a laser-induced fluorescence spectrometer which was capable of remote measurement by utilizing fiber optics. The fluorescence spectrum profiles were evaluated by normalized integrated fluorescence intensities in the wavelength region of 510∼650 nm. The U and HNO3 concentrations were determined in the ranges of 1∼200 mg/dm3 with an accuracy of 0.5 mg/dm3, and 0.75∼6.0 mol/dm3 with an accuracy of 0.1 mol/dm3, respectively.

Fluorometry of UO2+2 ion in nitric acid solutions

The UO2 2+ fluorescence spectra were measured for solutions whose conditions, except for coexisting species, corresponded to high level waste (HLW) solutions in the nuclear fuel reprocessing plants. From these spectra it was ascertained that the U concentration can be determined in the range of 2–200g/m3 with an accuracy of 1g/m3 at 30–40°C. The UO2 2+ fluorescence was influenced significantly by the temperature. The apparant activation energy of the temperature effect was 35.7 kJ/mol. The fluorescence intensities increased with nitric acid concentration in the range of 0.75–4.5mol/dm3. The temperature effect was considered to be caused by a chemical process concerned with water molecules.

Effects of Coexisting Ions upon UO2+2 Fluorescence in Fuel Reprocessing Solutions

The UO2 2+ fluorescence spectra were measured for solutions simulating the raffinate of the codecontamination process in nuclear fuel reprocessing plants, including 27 kinds of coexisting ionic species. When the coexisting ion concentration was equal to that of the raffinate, the U concentration was determined in the range of 2∼100 mg/dm3 and detection sensitivity was only l/6 that in the reference solution containing no coexisting ions. The UO2 2+ fluorescence intensity decreased with increasing coexisting ion concentrations for the following three reasons. The first was absorption of the excitation beam by these ions. The second was absorption of fluorescence by these ions. The last was fluorescence quenching by interactions between UO2 2+ and the coexisting ions. The respective ratios of fluorescence reduction attributed to these reasons at the raffinate were estimated as 0.26, 0.87 and 0.59, based on comparison of experimental results with calculations for absorption of the excitation beam and fluores...

Chemical State and Deposition Rate of Nickel Ion Deposit Produced on Heated Surface in High Pressure Boiling Water

Nickel ion deposit was produced on a heated rod surface in high pressure boiling water (150–285°C, 0.4–7.0 MPa). The deposit under the same temperature and pressure conditions as those for BWR reactor water (285°C, 7.0 MPa) was identified as NiO by spectrum profile analysis of the NiLα, NiLβ and 9th-order NiKα1 lines. Deposition rate was obtained from in situ measurements of deposit thickness, by a photoacoustic method, and from chemical analysis of deposit amount. The deposition rate coefficients obtained in temperature and pressure ranges of 150–250°C and 0.4–4.0 MPa were 2 × 10−3–5 × 10−2, which were 0.15–0.45 times as large as those of iron crud. This was attributed to a dissolution effect of Ni ion from NiO. The deposition rate coefficient at 285°C, 7.0 MPa was estimated to be 4.4 × 10−2–1.3 × 10−1.

In Situ Thickness Measurement of Nickel Ion Deposits on Heated Surface in Water by Thermal Wave Methods

Thermal wave signals from nickel ion deposits produced on a heated rod surface in boiling water at atmospheric pressure was measured by two kinds of thermal wave methods, photothermal deflection and photoacoustics. Thickness of the deposits was determined from calibration curves for NiO which was their possible chemical state. It was revealed that the methods served as useful tools for in situ thickness measurement in high temperature water. Nickel ion was deposited in circular patterns (about 1 mmφ) at boiling nucleation sites. The deposit thickness (0.1 − 1.1 μm) was proportional to time (0 − 20 h) and nickel ion concentration (20 − 50 ppm). This indicated that nickel ion was deposited by the evaporation-dryout mechanism, the same as for iron crud deposition in BWRs. The deposition rate for nickel ion (2.7 × 10−3) was about 1/6 of that for iron crud. The difference was attributed to dissolution of nickel ion from NiO.

Micro-State Analysis of Iron Compounds Using the 9th-Order FeKα1 Line

The X-ray spectra of 9th-order FeKα1 (FeKα19), FeLα and FeLβ lines were measured for metallic iron, FeO, Fe3O4, Fe2O3, FeF2 and FeF3 with an excitation potential of 20 kV using an electron probe microanalyzer (EPMA). The micro-state analysis of these iron compounds using EPMA was greatly improved by observation of the FeKα19 line, because its intensity relative to the FeLα line varied with the chemical state and its peak position became a marker to measure the wavelength shift of the FeLα line (ΔLα). Factors influencing the absorption effect on the measured spectra were evaluated by calculating the absorption correction factors. The wavelength shift, ΔLα did not exhibit substantial changes in electron binding energy, though it showed correlation with the valency of iron.