Acoustic sensing technique provides an efficient measure to detect and diagnose incipient failures occurred in plant components. The study reported here investigates the feasibility of adaptive super-directive microphone array technique for detection and localization of anomaly in nuclear power plants. The technique extracts anomaly information of objective components from the acoustic signals obtained at geometrically arranged multiple microphones. A specific signal processing was used to obtain a super-directive sensitivity of the microphone array and to adapt the sensitivity following the acoustic environmental change. Two adaptive sensing algorithms have been developed and implemented in a personal computer, and their abilities to extract the objective acoustic signal have been tested through numerical simulation. For appropriate number of the microphones, the satisfactory performance of the sound extraction has been obtained within reasonable computational load. The practical applicability of this technique to component monitoring in nuclear power plants has been confirmed through the present study.

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A logic verification system for sequence diagrams of power plants has been developed. The system's main function is to verify correctness of the logic realized by sequence diagrams for power plant control systems. The verification is based on a symbolic comparison of the logic of the sequence diagrams with the logic of the corresponding IBDs (Interlock Block. Diagrams) in combination with reference to design knowledge. The developed system points out the sub-circuit which is responsible for any existing mismatches between the IBD logic and the logic realized by the sequence diagrams. Applications to the verification of actual sequence diagrams of power plants confirmed that the developed system is practical and effective.

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Along a wavy interface of a horizontal stratified flow in a closed channel, the gas flow over waves creates lift force on the wave crest due to local static pressure drop. This pressure drop, termed the Bernoulli effect, will prompt the wave growth and the flow regime transition from the stratified-wavy to slug flow slugging. The gas phase pressure during slugging was measured in a large-height (0.7m) rectangular duct for an air-water co-current horizontal two-phase flow under atmospheric pressure. The static pressure drop over waves was evaluated from measurement of air static pressure profile along a wave at different fetches. The pressure drop measured concurrently with the liquid level was comparable to the water static head corresponding to the wave height at vicinity of the crest of the slugging wave. The pressure drop profile along the wave agreed well with the prediction from the Bernoulli equation at the upstream side of the wave crest. Then, a considerable pressure drop occurred across the crest due to loss of air kinetic energy. Meanwhile, significant liquid entrainment occurred in the vicinity of the wave crest and tended to prevent the wave growth into a slug.

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Research and development have been carried out on new heavy duty Ni-Cr-W superalloys for application to the structural components of high-temperature gas-cooled reactors with coolant outlet temperatures of around 1, 000°C. In the first step of the program, the basic chemical composition, i.e. Cr/W contents in the alloy was determined to be Ni-18 to 19 mass% Cr-20 to 22 mass% W. In order to examents the effect of additional alloying elements, i.e. Si, Mn, Y, B, T etc.c. on the hot-workability, a series of high-strain-rate high-temperature tension tests, so-called Gleeble tests, was carried out on 21 heats of the alloys with the basic chemical com-position of Ni-18 to 19 mass% Cr-20 to 22 mass% W. The addition of Si and Mn is extremely harmful to the hot-workability. On the contrary, the addition of Y is very effective in improving the hot-workability. The addition of B and Ti is also beneficial. Neither enrichment of C nor addition of Nb or Fe is significantly beneficial to the hot-workability. The multiple regression analysis technique is applicable to the predic-tion of the hot-workability of Ni-Cr-W superalloys.

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A method is presented for the determination of the dissociation yield of UF₆ in infrared laser isotope separation of uranium. The fluorescence intensity from vibrationally excited HF molecules in the dissociation with 16 μm infrared radiation is related to that in the dissociation with 266 nm ultraviolet radiation for which the absorption cross section and the quantum yield are known. One can calibrate the dissociation yield of UF₆ from the fluorescence intensity in 16 μm irradiation, using the experimental result that the fluorescence signal linearly increases with the pulse energy of the 266 nm beam, and the relation derived theoretically between its energy and the number of dissociated molecules. The authors discuss how the fast thermal-ization of F atoms in both irradiation cases guarantees such a calibration method in spite of the difference in the translational energy of dissociation fragment F atoms.

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The elution behavior of Sr sorbed on zeolite columns was investigated in connection with the distribution coefficient K_d between desired zeolites and aqueous solutions. The K_d values decreased with increasing concentrations of coexisting inorganic cations and EDTA. The retention volume V_R on zeolite column was predicted from the K_d value. An EDTA solution was desirable for the quantitative elution of sorbed Sr from the column owing to the low K_d value reduced by complex formation with EDTA. The column efficiency and the elution per-centage were improved with increasing temperature and decreasing flow rate. The structure of zeolite A remained unaltered after the repetitive use as the column packing.

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The influence on Np(V) migration behaviour through quartz-packed columns brought by the presence of Fe(III) real colloid was studied at pH 6.0 and 9.5. At pH 6.0, NpO₂⁺ -which constituted the dominant species of Np(V) at this pH-proved to move faster in the presence than in the absence of Fe(III) real colloid. Moreover, whereas 25-30% of the supplied NpO₂⁺ was found retained in the column in the absence of Fe(III) real colloid, the presence of this colloid induced about 95% of the NpO₂⁺ to be recovered from the column. It is shown that change in the particle size distribution brought about by the formation of Fe(III) real colloid, and the consequent effect on the filtration of Np(V)-Fe(III) pseudocolloid, vitally influence the migration behaviour of the NpO₂⁺ At pH 9.5, more than 50% of NpO₂CO₃^- -the dominant Np(V) at this pH -remained uneluted in the column, whether or not Fe(III) real colloid was present. The filtration behaviour of NpO2₂CO₃^- -in the forms of Np(V)-Fe(III) and Np(V)-silica pseudocolloidsignificantly affects the migration behaviour of NpO₂CO₃^-. At both pH 6.0 and 9.5, the first stage of contact with eluant was characterized by a small but distinct fraction of Np(V)-Fe(III) pseudocolloid that was eluted from the column faster than HTO, and the rate of Np(V)-Fe(III) pseudocolloid elution was higher at pH 9.5 than at pH 6.0. The rapid elution noted above of a fraction of Np(V)-Fe(III) pseudocolloid is con-sidered attributable to the formation of large pseudocolloid particles.

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The authors furnish a new parametrization of the Fermi-Gas model description of nuclear levet densities at excitation energies corresponding to the neutron binding energy. The model adopted is the standard Fermi-Gas model with pairing and shell-effect corrections. Particular care has been devoted to the inclusion of shell effects and to their parametrization. The pro-cedure for the evaluation of level density parameters has been applied to a data-base of 217 nuclei covering a mass range 41 ?? A ?? 253. A global systematics parametrization has been derived which allows for a derivation of level density parameters for nuclei where experimental information is not available.

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Silicon PIN photodiodes were used to measure the absolute intensity of monoenergetic photons in a synchrotron radiation beam line at 740 keV region. Below 20 keV, the intensity was measured with an accuracy of 5%. Above this energy, the accuracy was about 20% be-cause the photocurrent in the sensitive area was not uniform due to backscattered radiation from backing.

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