No abstract available

No abstract available

[en] We are considering with the necessity of the fuel management system on the site of the reactor which is used to follow up the fuel rod behavior under operation. A large size fuel performance code FIBER-2 has been developed, but this code is not suitable for repeated analyses of a large number of fuel pins. For the purpose of the evaluation of fuel integrity in the fuel management system, a simplified code FIBER-H is under development. A simplification of PCMI and restructuring models is one of main tasks in the development of FIBER-H. For a simplification of PCMI evaluation, the quantitative relation between cladding strain and PCMI parameters are obtained by parametric survey using FIBER-2. And the statistical analyses of PIE data performed to deduce empirical equations for fuel resturcturing. 9 figures

[en] The role of near-surface on the reactivity of metal oxide powders in solid-solid reactions increases with a decrease in particle size. Emanation thermal analysis (ETA) using a surface impregnation method with ²²⁶Ra parent isotope was applied to the investigation of the thermal characterization of the near-surface of various inorganic powders with different preparation histories. Further, in order to consider the surface reactivity of these materials, the thermal behaviour of the labelled species in solid-solid mixed systems were were followed by means of the ETA under the working state at high temperatures. The ETA results for single powders, Al₂O₃ and Fe₂O₃, and mixed systems, Fe₂O₃-ZnO, BaCO₃-TiO₂ and Fe₂O₃-Al₂O₃, were represented as typical examples. ETA provided useful informations on the surface characterization of oxide powders, and on the phase-boundary processes taking place in the initial reaction step for the mixed systems. (author) 25 refs., 11 figs., 1 tab

[en] A first-principles fully relativistic multielectron method based on molecular orbital (MO) theory is applied to the analysis for the 4f5d configurations of Pr³⁺-doped LaF₃, LiYF₄ (YLF), and CaF₂ crystals. The formation of MOs between the Pr 5d orbitals and the ligand fluorine 2p orbitals is considered using a (PrF₁₁)^8- and (PrF₈)^5- molecular models. The energy of the lowest level of 4f5d configuration decreases in the order LaF₃, LiYF₄, and CaF₂ (O_h symmetry). The high energy in Pr³⁺:LaF₃ is ascribed to the smaller ligand-field splitting due to the large coordination number. The analysis of many-electron wave functions shows the mixtures between the spin-orbit splitting of the 4f-level MOs and the ligand-field splitting of the 5d-level MOs. Configuration interaction with one-electron excitations gives transition probability to the originally forbidden two-electron excitations, which produce satellite structures in spectra

[en] During the hypothetical core disruptive accident (HDCA) of a fast breeder reactor (FBR), the temperature of the fuel would rise above 3000 K. The experimental data concerning the saturated fuel vapor pressure are necessary for the analysis of the HCDA. In this study, the UO₂ containing Cs, Ba, Ag, or Sn was used to simulate the irradiated fuel in the FBR. The saturated vapor pressure of pure UO₂ and UO₂ containing Cs, Ba, Ag, or Sn at 3000 to 5000 K was measured dynamically with a pulse laser and a torsion pendulum. The surface of a specimen on the pendulum was heated to eject vapor by the injection of a giant pulse ruby laser beam. The pressure of the ejected vapor was measured by both the maximum rotation angle of the pendulum and the duration of vapor ejection. The saturated vapor pressure was theoretically calculated by using the ejected vapor pressure. The surface temperature of the specimen was estimated from the irradiated energy density measured with a laser energy meter. The saturated vapor pressure of UO₂ at 3640 to 5880 K measured in this study was near the extrapolated value of Ackermann's low temperature data. The vapor pressure of UO₂ containing Cs, Ba, Ag or Sn was higher than that of UO₂. The saturated vapor pressure of UO₂ and a solid fission products system was calculated by using these experimental data. (orig.)

[en] We have tested the zig-zag delay lines for z-readout of the TOPAZ inner drift chamber. Using the delay line of 69 cm long and 10 cm wide having the characteristic delay of 5.9 ns/cm, spatial resolution of 8.5 mm in FWHM is obtained for the minimumionizing particles with the gas mixture of 50% argon and 50% ethane. (author)

[en] We had being used wire spark chamber (WSC) system to determine particle tracks behind the analyzer magnet in high energy experiments at 1.3 GeV electron synchrotron. But they sometimes caused troubles such as spark noises, consumption of the Krytron pulser and so on. Then we have replaced the WSC system with drift chamber (DC) system for the experiment to measure angular distributions of the differential cross section in proton Compton scattering. These DC's are of two dimensional readout type based on the drift time measurement and the charge division method. In this paper, we will describe the structure, the readout electronics and the results of the beam test of the DC's. (author)

[en] Cross sections for γd → π⁰d are presented in the photon energy range from 500 to 1000 MeV. As the photon energy increases, the cross sections decrease monotonically with small structures. A significant discrepancy between experimental and theoretical cross sections is found over the range from 600 to 850 MeV. The difference is indicative of dibaryon resonances around 2.5 GeV. (author)

[en] An Inner Drift Chamber (IDC) has been constructed for the TOPAZ e⁺e^- experiment at TRISTAN. The IDC has a cylindrical shape with dimensions of 20 cm in inner diameter, 60 cm in outer diameter and 150 cm long. The IDC is equipped with 1024 anode wires grouped into 10 layers. For the position readout along the anode wires, eight delay-line layers are placed on coaxial cylinders made of Normex honeycomb. The chamber is operated with a gas mixture of Ar(89 %)/CO₂(10 %)/CH₄(1 %) at an atmospheric pressure. In this paper, details of the mechanical structure and the fabrication procedures are described. (author)