[en] The Reactor vault cooling system (RVCS) is a passive air cooling system located between containment concrete and vessel. The major goal for the RVCS is cooling internal structures in plant, such as a concrete and reactor vessel (RV). The RVCS was not considered in previous safety analysis for the PGSFR. The RVCS can have an influence on the reactor vessel temperature, which is a very important parameter in a RV expansion reactivity feedback during unprotected accident, especially unprotected loss of heat sink (ULOHS). Therefore, in order to study the RVCS effect on accident, the ULOHS event with RVCS is preliminarily analyzed with tentative design parameters. In order to evaluate the effect of the RVCS model in the unprotected event, the ULOHS event is analyzed for the PGSFR plant with and without the RVCS model. When the RVCS model with a closed damper is applied, the peak clad temperature is increased due to larger positive CRDL/RV reactivity feedback. However, when the RVCS model with an opened damper is applied, the peak clad temperature is reduced due to smaller positive CRDL/RV reactivity feedback

[en] In the preliminary specific design, design basis events were classified into the AOO, DBA class-1, DBA class-2, and DEC by the event frequencies based on PRA and the standard review guideline of LWR referring of other SFR safety analysis reports. The conservative assumptions for intial power, fuel condition, hot channel factor, reactivity feedback modeling, DHRS modeling, and loss of offsite power are used in the safety analysis for DBEs. However, the unprotected events belonged to DEC category is analyzed by using the design values of nominal condition and the sensitivity calculation for the most sensitive design parameter like the structural expansion reactivity feedback. The diverse protection system and reactor vault cooling system were designed to play a role of the prevention of severe accident. However, to identify the automatic reactor power reduction by the inherent reactivity feedback and the secure of subcooling margin of the coolant the DEC events(unprotected events) were analyzed not considering the above counter-measures. For the PSA of SFR prototype, the 10 initiating events were selected referring other safety analysis report, PSA reports, and the system designs. The PSA was focussed on the identification of the characteristics of cliff-edge effect through safety function of each safety system and mitigation of event consequency and the not optimistic initial event frequencies were used. The MARS-LMR code is used to analyze the DBEs and DEC events. In this phase the code validation was intensively performed using component tests and integral effect tests.

[en] To confirm the limiting condition, based on the maximum allowable reactivity insertion of 0.3 $, three cases from the end of cycle (EOC) are selected. In addition, assuming the failure of CRSS by earthquake, additional cases is defined at beginning of cycle (BOC). When the CRW occurs, the reactor can be protected by plant protection system (PPS). In this study, PPS mechanism is sequentially studied for all initiating events. For design basis accidents (DBA), the reactor can be scrammed by reactor protection system (RPS). The first and seconds RPS signals are checked during transients. When RPS is failed, so called as anticipated transient without scram (ATWS), the reactor will be protected by diverse protection system (DPS). In this study, in order to analyze various initiating events related control rod withdrawal, four kinds of operating condition is defined. TOP events are analyzed using MARS-LMR. The influence of various plant protection system such as RPS and DPS are investigated

[en] Temperature and time dependences of magnetization of Al-1.0%Zn-4.2%Mg, Al-2.6%Zn-3.2%Mg, Al-4.1%Zn-1.1%Mg, and Al-5%Zn (at.%) alloys were measured in the range between 10 and 310 K after various periods of natural aging and peak-aged heat treatments. Enhanced diamagnetic contributions on the magnetization were observed for the as-quenched Al-Zn-Mg alloys for the first time. The enhanced diamagnetism observed in Al-2.6%Zn-3.2%Mg and Al-4.1%Zn-1.1%Mg were found to largely alter in natural aging, while that of Al-1.0%Zn-4.2%Mg little changed. After peak-aged heat treatments, the diamagnetism of Al-Zn-Mg was largely reduced. The binary Al-5%Zn showed neither enhanced diamagnetism nor natural aging effect on the magnetization. Isothermal time variations of magnetization of Al-Zn-Mg alloys at 300 K were found to be related with solute-vacancy clustering.

[en] A concurrent strengthening process by high-pressure torsion (HPT) and fine precipitation hardening of an Al 2024 alloy has been studied. The HPT was conducted on disks of the alloys under an applied pressure of 6 GPa for 0.75 and 5 turns with a rotation speed of 1 rpm at room temperature. The HPT processing leads to microstructural refinement with an average grain size of ∼240 nm and to an increase in hardness up to a saturation after 5 turns. Aging treatment is performed for sample after 5 turns at temperatures of 423 K for a maximum period up to 256 hours. The hardness increased above the hardness level after HPT processing through the subsequent aging. This study thus suggests that simultaneous hardening due to grain refinement and fine precipitation occurred by a combination of HPT processing and subsequent aging at 423 K

[en] The synthesis of nanostructured materials without any hazardous organic chemicals and expensive capping reagents is one of the challenges in nanotechnology. Here we report on the L-arginine (a biomolecule)-assisted synthesis of single crystalline cubic In(OH)_3 nanocubes of a size in the range of 30–60 nm along the diagonal using hydrothermal methods. Upon calcining at 750 °C for 1 h in air, In(OH)_3 nanocubes are transformed into In_2O_3 nanoparticles (NPs) with voids. The morphology transformation and formation of voids with the increase of the calcination temperature is studied in detail. The possible mechanism of the voids’ formation is discussed on the basis of the Kirkendall effect. The photocatalytic properties of In(OH)_3 nanocubes and In_2O_3 NPs are studied for the degradation of rhodamin B and alizarin red S. Furthermore, the CO oxidation activity of In(OH)_3 nanocubes and In_2O_3 NPs is examined. The photocatalytic and CO oxidation activity are measured to be higher for In_2O_3 NPs than for In(OH)_3 nanocubes. This is attributed to the lower energy gap and higher specific surface area of the former. The present green synthesis has potential for the synthesis of other inorganic nanomaterials. (paper)

[en] Graphical abstract: - Highlights: • Eu(III) and Tb(III) activators were doped in La(OH)_3 and La_2O_3. • La(OH)_3 nanowires were synthesized by a hydrothermal method. • La_2O_3 were obtained by a post-annealing method. • Photoluminescence imaging profiles were fully obtained and assigned. • La_2O_3 was unstable and changed to La(OH)_3. - Abstract: Understanding the role of the host oxide material is very important for developing phosphor materials. Here, Eu(III)- and Tb(III)-doped La(OH)_3 nanowires were prepared by a facial hydrothermal method, and Eu(III)- and Tb(III)-doped La_2O_3 nanostructures were obtained by a post-thermal treatment. Their physicochemical characteristics were examined by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and ultraviolet-visible absorption spectroscopy. The photoluminescence (PL) counter mapping profiles were obtained to understand the photoluminescence mechanism. All the emission profiles were assigned based on the "5D_0 → "7F_J (J = 0–4) transitions of Eu(III) and the "5D_4 → "7F_J (J = 6, 5, 4, 3) transitions of Tb(III) ions. The hygroscopic La_2O_3 host is unstable under ambient conditions and changed slowly to more stable La(OH)_3. PL decay lifetime was observed be longer for the annealed sample with lower doping concentration due to a higher crystallinity.

[en] Muon spin relaxation has the unique ability to detect very low concentrations of vacancies and vacancy–solute complexes in solids. In this work, we investigate quaternary Al-Mg-Si-Cu alloys and show that after quenching to room temperature from 848 K (575 °C), vacancies gradually become incorporated into clusters in the Al matrix. The total amount of vacancies in the material increases as small vacancy-rich clusters are formed, which is the opposite of the behavior in Cu-free Al-Mg-Si alloys.

[en] Er_2O_3 is a high potential candidate material for tritium permeation barrier and electrical insulator coating for advanced breeding blanket systems with liquid metal or molten-salt types. Recently, Hishinuma et al. reported to form homogeneous Er_2O_3 coating layer on the inner surface of metal pipe using Metal Organic Chemical Vapor Deposition (MOCVD) process. In this study, the influence of thermal history on microstructure of Er_2O_3 coating layer on stainless steel 316 (SUS 316) substrate by MOCVD process was investigated using SEM, TEM and XRD. The ring and net shape selected-area electron diffraction (SAED) patterns of Er_2O_3 coating were obtained each SUS substrates, revealed that homogeneous Er_2O_3 coating had been formed on SUS substrate diffraction patterns. Close inspection of SEM images of the surface on the Er_2O_3 coating before and after thermal cycling up to 700degC in argon atmosphere, it is confirmed that the Er_2O_3 particles were refined by thermal history. The column-like Er_2O_3 grains were promoted to change to granular structure by thermal history. >From the cross-sectional plane of TEM observations, the formation of interlayer between Er_2O_3 coating and SUS substrate was also confirmed. (author)

[en] Highlights: • We have studied the effect of the grain refinement on the superconductivity in Nb. • The bulk nanostructured Nb samples have been prepared by high-pressure torsion (HPT). • The critical temperature T_c and the critical current density Jc increase after HPT. • The enhancement of T_c is consistent with the size effect for nanoscale superconductors. • The increase of J_c can be explained by the enhanced vortex pinning. -- Abstract: We have measured the magnetization M(T, H) and the resistivity ρ(T) in bulk nanostructured Nb prepared by high-pressure torsion (HPT) and studied the effect of the grain refinement on the superconducting properties. With increasing revolution numbers N of HPT, the critical temperature T_c and the critical current density J_c increase. The enhancement of T_c is consistent with the size effect for nanoscale superconductors. The increase of J_c can be explained by the enhanced vortex pinning due to the introduction of lattice defects such as dislocations and grain boundaries