We have devised the methods to measure a liquid-film thickness distribution and three-dimensional velocity in a large diameter pipe or complex rod bundle geometry.
(1) A pair of an excitation electrode and a working electrode is implemented onto a three-layer printed circuit with a 1.8 mm lengthwise and crosswise apart from each other. This printed circuit can bend to form a cylindrical shape with 12 mm in diameter. The cylindrical printed circuit demonstrates liquid film perturbations in an annuls flow path.
(2) We have proposed the methods to estimate three-dimensional velocity profile in terms of length scale of a two-phase flow mixture on the basis of acquired data with commonly used wire-mesh sensors. We visualize a swirl flow dynamics such that a water flow moves outside and in turn gas shifts to inside of a pipe.
(3) We visualized 121 points of center subchannel in a 10 × 10 rod bundle geometry by inserting a thin wire into each rod gap. In addition, we visualized 400 points of rod gap in the combination of rods as an excitation electrode and thin wires as a measurement electrode. The devised 'subchannel void sensors' were installed in eight layers acquiring 521 points / layer at every 1 ms.

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  Oxide-dispersion-strengthened (ODS) 9Cr ferritic heat resistant steel is a leading candidate for a cladding material used in advanced fast reactor fuels because of its superior radiation resistance and high-temperature strength. In this study, distribution of oxides, which is presumed to be a dominant factor of the high-temperature strength, has been evaluated by three-dimensional (3D) observations using electron tomography. The oxide distribution was classified into two regions, whose number densities were high or low. Dislocation pinning forces caused by the oxides were estimated from the 3D data in each region. A good coincidence was recognized between the force in the low-density region and a threshold stress at which the creep deformation mechanism changes. Therefore, the high temperature deformation behavior of ODS steels is influenced by dislocation motions in the low-density regions of oxides.

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  This paper presents hierarchical and time-varying data visualization techniques for nuclear reactor measurements and simulations. The developed system assumes time-varying values of hundreds or thousands of physical measurement values as input information. It divides the values according to their positions and unit systems, and represents the hierarchy of the values by HeiankyoView. It also represents the time sequence of the values in a thin window. This paper shows examples and user experiences that prove the effectiveness of the visualization techniques.

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  Authors are interested in the flow visualization and in the information visualization. In the present report, authors introduced two topics of our research activities. One is the flow visualization supported by the high speed camera for understanding a physical phenomenon. The other is the information visualization to understand overall data about the accidents in nuclear power plants. The flow visualization was applied to an experiment about the water-sodium reaction. The gas jet injected into water at high pressure was investigated using the high speed camera. Visualizing a huge data of NUCIA was performed and a 2D-3D mixed visualization method was proposed. It was thought that the mixed visualization method could help the public to share the information.

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  In this manuscript, the fundamentals and merits of neutron visual sensing techniques, high-speed consecutive visual sensing technique, high-speed-scanning dynamic 3D visualization technique, multi-beam 3D velocimetry technique and energy-selective neutron imaging technique are summarized. These techniques have been developed mainly for the R&D of the nuclear energy　system using the high-flux research reactors, JRR-3 and JRR-4, and a high-intensity pulsed neutron source, J-PARC. Very unique visualization and measurement, e.g. dynamic 3D velosimetry in JRR-4 were successfully carried out by these neutron visual sensing techniques. An energy-selective neutron imaging, e.g. the neutron resonance absorption imaging in J-PARC is extremely unique and newly developed visualization and measurement technique. Analytical investigation for the feasibility of multiphase flow experiment in J-PARC was also reported using a Monte Carlo neutron simulation code. It was confirmed from the analytical work that the measurement error of the void fraction of two-phase flow can be reduced by the energy-selective neutron imaging technique.

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