Author's works on an evaluation formula for the radiation duct streaming are reviewed.
The formula, which describes the direct and albedo components, is derived in a generic straight duct geometry. It is expressed by the product of spatial distributions which are represented by twice and eight-time reflected components, and power of an albedo matrix. The computational method of the spatial distributions is outlined.
The application of the formula to bent ducts is then described. The inflow of radiations to downstream at a corner of multibent ducts is formulated with the flux in the upstream leg. Using the obtained inflow current as the source term to the downstream, the formula predicts the radiation flux in the downstream leg.
The estimation of the leakage component is made by a simple point kernel method. When the streaming effect of radiations of the leakage component is important, the formula is combined with the point kernel method.
The formula is then extended to more general duct geometries, where a straight duct penetrating two material zones and a bent duct with general crossing angle are taken up. The estimation method of the flux in these ducts is briefly outlined.
The formula has been tested through the application to a variety of streaming problems, and showed to be highly applicable.

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Designs of large test facilities of nuclear fusion research succeeding the current large Tokamaks such as TFTR, JET and JT-60 show that huge pulsed power is required to operate the new test facilities ; 700 MW for 10 s to excite poloidal coils. The present paper proposes three steps of application of MHD power generation to fusion to provide such large pulsed power. The first step is to design and construct a small scale MHD generator which excites the Demo poloidal superconducting magnet (SCM) coil being under construction in JAERI. The operating current is 30 kA with the stored energy of 40 MJ. As the working gas of MHD generator, H₂-O₂ combustion product is selected, seeded with 5 w/o K. The second and third steps are to construct an intermediate MHD channel of 100 MWe and a large channel of 800 MWe. Much improved designs are obtained in the present study, compared with the previous designs. For the large 800 MW generator, the maximum magnetic field becomes 3.5 T with the load current of about 100 kA, while the stored energy in the MHD magnet is estimated to be less than 0.5 GJ which is much smaller than 58 GJ of planned poloidal coils. The small MHD channel designed for the Demo poloidal coil is 4 m long with the peak field of 1.8 T. The cryogenic magnet can be self-excited within 20 s. The Demo poloidal coil is charged in about 4 s.

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It is generally difficult to insert a position sensitive proportional counter (PSPC) with a conventional charge division in a narrow space, or to work the counter under special environments, such as in water or in a reactor. We improved the position signal readout to make it possible to use a PSPC under such environments. A position signal was extracted from only one end of an anode wire by grounding the other end through a capacitor and a total charge signal was obtained from twelve cathode wires stretched parallel to the anode wire, so that two pre-amplifiers were able to be connected at only one end of the counter. The character-istics of the PSPC with the improved signal readout were examined with X-rays. The position resolution was 1.3 mm with an effective length of 550 mm, and depended on the X-ray injection position. A non-linearity of position signals was less than 0.2%.

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The vaporization behavior of fission-produced noble metal system (Mo-Ru-Pd, Mo-Ru-Rh and Mo-Tc-Pd) in vacuum and oxidative atmosphere at high temperatures was investigated by the thermodynamic calculation on the basis of the regular solution model and the available experimental data. The palladium and rhodium in the alloys, and molybdenum and ruthenium in the alloys vaporize preferentially at high temperature in vacuum and in air, respectively. At low temperature below 385 K in air, ruthenium and technetium in the alloys vaporize predominantly by oxidation.

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The deposition of Ni and Co ions on a heated surface of simulating fuel rods has been studied in water at atmospheric and 70 atm pressures during nucleate boiling.
The effects of various factors, including heat flux of the heated surface, concentration of coexisting iron oxide (α-Fe₂O₃) and concentration of Ni and Co ions, on their deposition rate have been investigated. The model for iron oxide deposition which is based on microlayer evaporation and drying out phenomena in the nucleate boiling bubble was shown to be applicable to the deposition of Ni and Co ions. That is, dW/dt=K•Q•C/L<•I>, where dW/dt is the deposition rate, K the deposition rate coefficient, Q the heat flux, C the ion concentration, and L the latent heat of vaporization. The K value of Ni ion is about 0.1 and independent of iron oxide concentration. On the other hand, the K value of Co ion increases with iron oxide concentration and seems to approach that of iron oxide (0.3). The Co ion deposited with iron oxide forms Co ferrite. Solubility of Co ferrite is small compared with that of Co deposits without iron oxide (CoO or Co(OH)₂). The increase in the K value of Co ion with iron oxide concentration is attributed to the change in chemical form of Co deposits into more stable species not favoring Co release.

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Reactions of Ni and Co ions with amorphous iron (III) hydroxide, which was synthesized by electrolysis of iron electrode, have been studied in high temperature water using an in situ method of a modified magnetic balance and using a reaction model. Formation of NiFe₂O₄ and CoFe₂O₄ from the amorphous iron (III) hydroxide were explained by the reaction model incorporating two phenomena, i.e. dehydration of the iron (III) hydroxide and diffusions of Ni and Co ions into it. The dehydration rate followed Avrami's equation. Apparent activation energy of the dehydration was 4.39×10⁴ J/mol for the amorphous iron (III) hydroxide used in the experiments. The diffusions of Ni and Co ions into the particle were evaluated from the diffusion equation for spherical coordinates. The diffusion coefficient of Ni ion into the amorphous iron(III) hydroxide was much higher than that of Co ion, while its apparent activation energy was about 5.5×10⁴ J/mol, a value close to that of Co ion. However, the diffusion rate of Co ion into α-Fe₂O₃ was faster than that of Ni ion. Calculated values from the reaction model showed good agreement with experimental values.

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The sorption behavior of cesium on a variety of minerals and rocks has been investigated by batch equilibration using ¹³⁷Cs. The distribution coefficient (K_d) of cesium increased with decreasing concentration of cesium and approached a constant value in dilute regions. The distribution coefficients determined at a trace level (K_{d, tr}) differed more than four orders of magnitude strongly depending on the kinds of samples, for example, about 30 on quartz and 10⁵ on tuffs. The values of K_{d, tr} are related to the cation exchange capacity (CEC ; meq/g) determined from the saturated sorption of cesium for individual samples as : log K_{d, tr}=log CEC +constant. Most K_{d, tr} values were found to approximately follow this linear relationship.

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