[en] This research project addresses a fundamental problem in turbulence theory, the relation between Lagrangian and Eulerian statistics, by carrying out, analyzing, and interpreting a set of field experiments in the coastal waters off the south shore of Long Island. The study will not only provide information on the relation between the Lagrangian and Eulerian autocorrelations but also between the various experimental methods for quantitatively estimating turbulent diffusion. Two experiments, one in summer and one in winter, consisting of simultaneous measurements of dye diffusion, drogue dispersion, and Eulerian current velocities in a typical coastal locale were planned. In order to ensure a match between the Lagrangian (drogues, dye) scales of motion and the Eulerian (current meters) scales, however, a preliminary experiment, consisting of a 6 mooring current meter array and a short (approx. 3 hours) drogue experiment, was conducted during March 1980. Results of this preliminary experiment and their implications to the experimental program are discussed. The principal results were an improved design of our current meter array, and a wider variety of drogue experiments, i.e., multi-level, multi-scale, and continuous source simulation

[en] Nuclear forensics is the analysis of intercepted illicit nuclear or radioactive material and any associated material to provide evidence for nuclear attribution by determining origin, history, transit routes and purpose involving such material. Nuclear forensics activities include sampling of the illicit material, analysis of the samples and evaluation of the attribution by comparing the analysed data with database or numerical simulation. Because the nuclear forensics methodologies provide hints of the origin of the nuclear materials used in illegal dealings or nuclear terrorism, it contributes to identify and indict offenders, hence to enhance deterrent effect against such terrorism. Worldwide network on nuclear forensics can lead to strengthening global nuclear security regime. In the ESARDA Symposium 2015, the results of research and development of fundamental nuclear forensics technologies performed in Japan Atomic Energy Agency during the term of 2011-2013 were reported, namely (1) technique to analyse isotopic composition of nuclear material, (2) technique to identify the impurities contained in the material, (3) technique to determine the age of the purified material by measuring the isotopic ratio of daughter thorium to parent uranium, (4) technique to make image data by observing particle shapes with electron microscope, and (5) prototype nuclear forensics library for comparison of the analysed data with database in order to evaluate its evidence such as origin and history. Japan’s capability on nuclear forensics and effective international cooperation are also mentioned for contribution to the international nuclear forensics community.

[en] In the paper, the results of the nuclear forensics questionnaire provided for Asian countries are introduced and the experience of the regional training course on nuclear forensics organized by ISCN is reported. (author)

[en] In the paper, current status and future prospects on nuclear forensics technology development in ISCN-JAEA are discussed. (author)

[en] Full text: There is an increasing interest in the distribution and fate of natural and artificial radionuclides in the marine environment. Their existence and accumulation in the marine environment raises an irradiation threat to human health. On the other hand, radionuclides have served as geochemical tracers for the study of fundamental issues, such as water mass movement, particle scavenging and sediment mixing processes. Over the years, using the highly sensitive ICPMS technique, we identified Pu contamination sources and proposed its transport mechanism, investigated particle scavenging using Pu, ²⁴¹Am and ²³⁰Th, and for the first time, obtained vertical distribution profiles of ⁹⁹Tc. (author)

[en] An analytical method for the determination of ²³⁹Pu and ²⁴⁰Pu in marine particle samples by sector field high-resolution ICP-MS was developed. The method was applied for large and small particle samples (particle diameter: >70 μm and 1-70 μm, respectively, collected with a large volume in situ filtration and concentration system at different depths in the water column off Rokkaho, Japan, where the spent nuclear fuel reprocessing plant of Japan Nuclear Fuel Ltd. has started test operation since March 2006. (author)

[en] Some acceptor-doped perovskite type oxides exhibit proton conduction. These materials are of special interest because of their potential application as a solid electrolyte used in H₂O₂ fuel cells. In order to increase the power density as well as to reduce the operation temperature of the fuel cells, development of the electrolyte materials with high proton conductivity is required. In the present study, we measure dc conductivity on the compositionally graded proton conducting oxides, and reveal the existence of the compositionally gradient effect in these oxides. That is the dc conductivity for the downhill configuration, with respect to the chemical potential for the hydration, is about three times larger than that for the uphill configuration. Moreover, the internal resistance of the fuel cells based on the compositionally graded electrolyte of the downhill configuration is reduced 25∝30% compared with that of the uphill configuration. (orig.)

[en] The interface magnetism between Co₂FeGe Heusler alloy layers and MgO layers was investigated using ⁵⁷Fe Mössbauer spectroscopy. Interface-sensitive samples, where the ⁵⁷Fe isotope was used only for the interfacial atomic layer of the Co₂FeGe layer on the MgO layer, were prepared using atomically controlled alternate deposition. The ⁵⁷Fe Mössbauer spectra of the interface-sensitive samples at room temperature were found similar to those of the bulk-sensitive Co₂FeGe films in which the ⁵⁷Fe isotope was distributed throughout the films. On the other hand, the tunnel magnetoresistance effect of magnetic tunnel junctions with Co₂FeGe layers as the ferromagnetic electrodes showed strong reduction at room temperature. These results indicate that the strong temperature dependence of the tunneling magnetoresistance of magnetic tunnel junctions using Heusler alloy electrodes cannot be attributed simply to the reduction of the magnetization at the interfaces between the Heusler alloy and insulator layers.

[en] Magnetic properties and phase stability of the L2₁ phase in Co₂(Ti_1-xMn_x)Ga alloys were investigated by magnetic and DSC measurements. The order-disorder phase transition temperature from the L2₁ to the B2 phase T_t^L2₁/B2 was found to increase linearly with increasing Ti composition and its linear extrapolation to x = 0.0 accords with the reported value of T_t^L2₁/B2 for the Co₂TiGa alloy. The Curie temperature T_C increases with increasing Mn composition, exhibiting an upward convexity, but is rather independent of composition in the high Mn region. It is concluded that the Co₂(Ti_1-xMn_x)Ga alloys located in the middle composition range possess both a high T_C and a high T_t^L2₁/B2.

[en] Highlights: • Phase diagram was first established in Co₂Cr(Ga_1−xSi_x) Heusler alloys. • Existence region of the single phase in the L2₁-type was confirmed in x ⩽ 0.5. • Magnetic measurements predict Co₂Cr(Ga,Si) are half-metallic ferromagnets if the order degree is completely controlled. -- Abstract: The phase diagram, magnetic properties and the region over which the Heusler alloys Co₂Cr(Ga_1−xSi_x) occur as a single phase have been established. A single phase was obtained in the composition range of x ⩽ 0.5, in which the order–disorder phase transition temperature from the L2₁ to the B2 phase, T_t^L21/B2, increased almost linearly with increasing x. The value of T_t^L21/B2 for the L2₁-type Co₂CrSi Heusler alloy, estimated by linear extrapolation from its concentration dependence, was about 1450 K, and therefore higher than that of Co₂CrAl and Co₂CrGa. The Curie temperature, T_C, also increased with increasing x becoming 600 K at x = 0.5, thus reflecting an increase in the magnetic moment caused by the change in the number of the valence electrons. The concentration dependence of the spontaneous magnetic moment, M_s, measured at 5 K increased with increasing x, almost following the generalized Slater–Pauling (S.P.) rule predicted by Galanakis et al