Identification of transfer function matrices in a feedback system is discussed by using the singular value decomposition of Hankel matrix from the viewpoint of inverse problems. A method of model reduction is considered, and selection criteria are proposed for identification of them. Transformation formula between open loop and closed loop transfer function matrices are determined from the feedback loop structure, and they are needed for identification of open loop transfer function matrices under such a condition where the feedback system is in a minimum phase. Though the identifiability of open loop transfer function matrices can be examined in the framework of innovation model equivalent to the feedback system, there are pole-zero cancellations in the identification of them. The method to reduce a model order of an open loop transfer function is discussed by using the singular value decomposition of a gramian given by the open loop transfer function with higher degree. To check reliability of the present algorithm, a simulation study is performed for an example.

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Thermal detonation theory, has been increasingly applied to vapor explosions. However, there are many questions and interrogations in previous works due to the lack of detailed explanation of the basis of the calculations and due to the incomplete interpretations or internally inconsistent discussions. Therefore, the present study calculates the Hugoniot curves for water and CFC12 systems to discuss again the applicability of the ZND detonation model to vapor explosion. The results reveal that a solution of detonation may be obtained in a wide range of initial void fraction if steady, one-dimensional and homogeneous two-phase flow is assumed. Three types of solution of C-J point can be obtained, depending on the initial void fraction: the two-phase condition, the kink-point condition and the condensed-phase condition. However, the assumptions involved in the two-phase condition and the condensed phase condition solutions are not always satisfied. On the other hand, the kink-point condition, which has been often excluded from the discussion in previous works, provides a solution that may be actualized.

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The characteristics, that is, morphology, size distribution, alloy phase and microstructure of U₃Si and U₃Si₂ powders, solidified rapidly by a centrifugal atomization, were investigated. The atomized powders consist of spherical particles with a relatively narrow size distribution independent of the alloy composition. The particle size distribution can be controlled by adjusting the atomization parameters such as feeding rates of the melt and revolution speeds of the disk. The major phases of atomized U₃Si and U₃Si₂ powders are α-U and U₃Si₂ and U₃Si₂, respectively. The atomized U₃Si powder has a dendritic structure of very fine and non-faceted U₃Si₂ precipitates with less fibric and eutectic U₃Si₂ structure. The microstructure of U₃Si₂ powder shows a cellular structure with fine U₃Si₂ grains and finely dispersed silicon-rich precipitates. The time for complete peritectoid reaction of the atomized U₃Si particles and the resulting grain size are greatly reduced, due to the refinement of primary U₃Si₂ precipitates.

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In order to examine the effect of oxalic acid(H₂ox) on the exchange reaction of n-octyl(phenyl)-N, N-diisobutylcarbamoylmethylphosphine oxide (oφcmpo) in U(VI) nitrato complex with oφcmpo, structural and kinetic studies have been carried out for the solutions prepared by dissolving UO₂(NO₃)₂(oφcmpo), oφcmpo, and H₂ox in CD₃COCD₃ using ³¹P and ¹³C NMR method. The number of coordinated oφcmpo was determined to be 2 by the area integration of ³¹P NMR signals of free and coordinated oφcmpo. From the area integration of ¹³C signals of free H₂ox and coordinated oxalate(Cox), the number of Cox was estimated to be 1. Hence, the complex with composition ratio of UO²⁺₂:oφcmpo: Cox=1:2:1 was supposed to be formed in the present solution system. The exchange rate of oφcmpo in this complex was found to show a first-order dependence on the free oφcmpo concentrations and to decrease with increasing free H₂ox concentrations. From these results, it is proposed that the exchange reaction of oφcmpo proceeds through the interchange(I) mechanism and that the retardation effect of free H₂ox is due to the formation of outer-sphere complex.

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A containment function of transport and/or storage casks of radioactive materials is essential to prevent the materials from being released excessively into the environment. It is not practical for containment tests to measure directly the radioactivity release so that gas volumetric leakage rates are usually assessed and gas pressure decrease or increase method is usually applied. As gas flow model for evaluation, the ISO standards has deleted the concept of choked flow which is adopted by ANSI N14.5. Provided that the choked flow is not adopted to the leakage rate evaluation, the criteria of the test should be severer, and a new leakage rate measuring system with high accuracy and reasonable measuring time is required. Transport casks are often inspected in a temporary cask-storage facility where simultaneous measurement of many casks is required. In a storage cask system, multiple casks are monitored on their containment function during a storage period, and the method for simultaneous monitoring at many points for long term is required. In this study, two kinds of small gas leakage rate measuring systems are developed. One is to measure gas leakage rates directly and is called "flow measuring system", which can measure gas leakage rate of 10^-4 to 10^-2cm³/s with high accuracy and short measuring time. The other is to measure the pressure decreasing rate and is called "pressure decreasing rate measuring system", which can monitor the pressure change at many points simultaneously.

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Growth of spatial nonuniformity of laser beam propagating in the near-resonant atomic vapor was numerically studied for atomic vapor laser isotope separation (AVLIS). The simulation results well reproduced the linear and nonlinear growth and the beam breakup. The growing region of nonuniformity and the maximum growth rate were analyzed in relation to the spatial wavenumber of ripple and the nonlinear refractive index of the near-resonant atomic vapor. And the effects of ripple growth on AVLIS were discussed.

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Sorption behavior of uranium (VI) during crystallization of amorphous iron (A.Fe) minerals to crystalline iron (C.Fe) minerals have been investigated. Two different sorption conditions are applied for the experiments. One is the condition in which uranium is sorbed on A.Fe minerals before the crystallization (dynamic condition). The other is the condition in which uranium is sorbed on the A.Fe minerals and C.Fe minerals of goethite (static condition). Associations of uranium with the iron minerals are examined by a selective extraction test using a 1M CH₃COOK solution at pH 7, 1M CH₃COONa solution at pH 5 (Morgan's solution), and TAO solution (10.9g•l^-1 oxalic acid+16.1g•l^-1 ammonium oxalate).
Under the static condition, the fraction of uranium desorbed by a 1M CH₃COOK solution at pH 7 from A.Fe minerals is lower than that from goethite. And all of uranium are desorbed by the TAO solution from both A.Fe minerals and goethite. Contrary, under the dynamic condition, fractional uranium is remained after the TAO solution extraction. The fractional uranium remained after the TAO solution extraction from the iron minerals increases with increase in the crystallinity of the iron minerals. The concentrations of uranium in the solutions are less than 1%. These show that during the crystallization of amorphous to crystalline iron minerals most of uranium associated with the amorphous iron minerals is not released into the solution, and some fractional uranium move to be fixed to crystalline iron minerals.

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In this paper we show the feature of the microwave heated oxygen plasma torch which we designed and apply it to the conversion method of metal chloride wastes in a pyrochemical reprocessing into oxides. For this purpose oxygenation experiments of several typical metal chlorides were carried out by using this plasma device and thermodynamic equilibrium diagrams of each metal chloride and oxygen system were calculated. Consequently, it was found that our oxygen plasma has a possibility to realize such a oxygenation reaction, the equilibrium diagrams can predict the oxygenation characteristics of metal chlorides by oxygen plasma and the chlorides have conversion characteristics according to their oxygenation difficulties. Finally, we classified chlorides into three categories by predictions from the calculated thermodynamic equilibrium diagrams.

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Neutron nuclear data of stable mercury isotopes (¹⁹⁶Hg, ¹⁹⁸Hg ¹⁹⁹Hg, ²⁰⁰Hg, ²⁰¹Hg, ²⁰²Hg and ²⁰⁴Hg) have been evaluated in the energy range of 10^-5eV20MeV. Evaluated quantities are the total, elastic and inelastic scattering, capture, (n, 2n), (n, 3n), (n, p), (n, d), (n, α), (n, np), (n, nα) reaction and γ-ray production cross sections, the resonance parameters, and the angular and energy distributions of emitted neutrons and γ-rays. The evaluation is mainly based on nuclear reaction model calculations. Statistical-model calculation played a significant role in the determination of the reaction cross sections. The evaluated data have been compiled in the ENDF-6 format, and are used for the design study of a mercury target system proposed at the Neutron Science Research Center, Japan Atomic Energy Research Institute.

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Experimental data usable for evaluating cross sections of main fission product elements (Rh, Cs, Nd, Sm, Eu and Gd) in the epithermal energy range were measured. A cadmium-covered vessel containing a pure water or an aqueous solution of a fission product element was inserted at the center of TCA (Tank-type Critical Assembly) core. Reactivity effects were obtained by the difference in the critical water levels between a pure water and an aqueous solution in the vessel. The measured reactivity was more than 1¢ and it was greater than the experimental uncertainties. Since the adjoint thermal flux below the cadmium-cutoff energy are largely depressed in the vessel, the reactivity effects in epithermal energy range could be measured. The analyses for the experiments were performed using the SRAC code system and neutron transport calculation code TWOTRAN. The exact perturbation theory was applied to calculate the reactivity effects of fission product elements. The calculated reactivity effects using JENDL-3.2 and ENDF/B-IV cross-section libraries were compared against the measured values. The analyses using JENDL-3.2 gave reasonable results for these measurements.

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