No abstract available

[en] Japan Power Engineering and Inspection Corporation (JAPEIC) is managing many national RD projects in the field related to inspection, welding and integrity evaluation according to the policy of the Ministry of International Trade and Industry (MITI) on the safety and reliability of operating nuclear power plants. The Plant Life Management Technology Project (PLIM), one of these RD projects, has newly started from 1996 to develop the evaluation methodologies for the neutron irradiation embrittlement in the upper shelf region of the reactor pressure vessel (RPV) and the thermal embrittlement of duplex stainless steel components, and to develop the technology for reconstitution of RPV surveillance test pieces. For the first item of these three, the development of evaluation method in the upper shelf region, the detailed scope of test program has been recently settled and the neutron irradiation of test specimens is scheduled to start this year using the Halden Boiling Water Reactor (HBWR) in Norway. This paper presents the RD scope for the development of evaluation method for the neutron irradiation embrittlement in the upper shelf region in the PLIM project of JAPEIC (author) (ml)

No abstract available

[en] Detailed examinations of the changes in particle size during the course of WO₃ reduction were conducted. In this report, a detailed examination has been conducted of the changes at each stage of reduction from WO₂ to W. (author)

[en] Full text: Recently, we have established tritium (T) tracer techniques to visualize depth profiles of hydrogen (H) loaded into fusion reactor materials by gas absorption and ion/plasma implantation. Wide dynamic range of T detection up to 5 digits makes detailed depth profiling possible in comparison with conventional H detection in solid. Observing changes of the depth profiles by annealing and/or during storage after the hydrogen loading, H release mechanism and behaviors of H (diffusion and trapping) in the F82H steel and pure tungsten (W) were investigated. It was found that the depth profiles of loaded H were composed of four components in depth as follows; 1) H in surface adsorbates: Any materials surfaces adsorb H atoms and its compounds like water and hydrocarbon molecules. Although some of H in the surface adsorbates is easily replaced with loaded T by isotopic exchange reactions, their behavior was hardly correlated with that of the loaded H. Instead, a T amount retained in the surface adsorbates significantly changed during the storage after the loading by the isotopic exchange with H in ubiquitous water molecules and moisture in surrounding atmosphere. 2) H in intrinsically modified surface layers: Separate from the surface adsorbates, surfaces of metals are easily oxidized as often appears as protective or passive oxide layers or coverage of some other precipitates (like carbides, sulfides, nitride and their mixtures) with thickness of a few tens nm. Mechanical works make any surfaces defective. Some of the loaded H was found to be retained in the modified surface layers probably by making OT, CT bonds and/or defects-assisted trapping. Because of large binding energy or trapping energy, H retained in the modified layers hardly moved at room temperature. But their effect on release of the loaded H in further deeper region was not clear. It should be noted that distinction of H in the modified surface layers from H in the adsorbates is quite hard but the T tracer technique enabled us to distinguish them. 3) H in defects/impurities induced by H loading behind the modified surface layers: H is trapped at defects or damages and segregated impurities induced by energetic H loading in the damaged region. This region was saturated by H trapping in the defects (probably stabilized by self-trapping) during the H loading. In the case of pure W, the thickness of this region anomalously increased by continuous H loading. Since the amount of trapped H in this region was very large, most of the previous investigations on behaviors of ion/plasma-implanted H in pure W have simply observed the trapped H in the damaged region. 4) H in far deeper region: H penetrated in the deeper region by diffusion. Most of H was in solution but some could be trapped at intrinsic defects such as dislocations and grain boundaries. Observing time sequences of the depth profiles in the deeper region, reliable bulk H diffusion coefficients were determined both for the F82H steel and pure W. (author)

[en] Short communication. 3 refs

[en] The low-lying structure of the C isotopes is investigated using the Antisymmetrized Molecular Dynamics (AMD) Multi-Slater Determinant model. The calculated 2⁺ energies of the even-even isotopes indicate the change from spherical to deformed structure at N = 8. This is consistent with the isotope change of the single particle energy deduced from recent experiments. Binding energies and r.m.s. radii are also calculated and compared with the experimental data

[en] In this paper the possible modes of M1 excitation in deformed even-even nuclei are studied in terms of the particle-number-conserved Nilsson + BCS formalism with the standard parameters. The spurious motion with respect to the rotation is removed. In addition to the Scissors mode, the Unique-Parity Spin and Normal-Parity Spin modes are suggested, although the latter may be fragmented to a large extent. The Scissors mode carries most of the orbital strength, while the others the spin strength. The proton Unique-Parity (i.e. Oh_11/12) Spin mode for ¹⁶⁴Dy is obtained just below Ex = 3 MeV with B(M1) ∼ 0.2 μ²_N) in the sum rule limit. This is in a good agreement to the recent experimental data

No abstract available

[en] Rotational states are investigated in terms of the interacting boson model. A ground-state rotational band is built from a shell-model many-nucleon system. It is shown that the S and D collective nucleon pairs play dominant roles in low-spin states of the band, and that this S-D dominance is broken in high-spin states. The intrinsic hamiltonian is constructed from the effective nucleon-nucleon interaction used in the shell model calculation, and the intrinsic state of the rotational band is shown to be comprised primarily of S and D pairs. We introduce a lambda boson which is a linear combination of s, d and higher angular momentum bosons, and the boson intrinsic state is given by the lambda boson condensate state. The s and d bosons constitute approximately 90% of the lambda boson, and the boson intrinsic state reproduces very well the energy and the intrinsic quadrupole moment of the nucleon intrinsic state. The s-d boson hamiltonian is constructed from the S and D pairs, while effects of non S-D pairs are also included by renormalization of the boson hamiltonian. The renormalization is made by using the lambda boson. The s-d boson quadrupole operator is derived similarly. The boson hamiltonian and quadrupole operator thus derived reproduce well the exactly calculated values for low-spin states of the rotational band, although the accuracy decreases in high-spin states. It is shown that the IBM possesses the same physical picture of the rotational states at the Nilsson scheme with pairing correlations. It is therefore concluded that the IBM is capable of describing low-lying rotational states. (orig.)