Progress of fusion nuclear technologies in the broader approach framework

In the Broader Approach framework, the International Fusion Materials Irradiation Facility/Engineering Validation and Engineering Design Activities (IFMIF/EVEDA) project, the International Fusion Energy Research Center (IFERC) project, and the Satellite Tokamak project are implemented. In the IFMIF/EVEDA project, engineering design of IFMIF and engineering R&D include the construction and tests of an IFMIF prototype accelerator system up with a 9 MeV and CW deuteron beam, a liquid lithium test loop with free surface flow, and full scale irradiation test module including temperature control instrumentation. The commissioning of the EVEDA lithium test loop was completed in March 2011, and a lithium flow of ～5 m/s was obtained. As a part of the IFERC project, R&Ds on reduced activation ferritic/martensitic steels as blanket structural material, SiC_f/SiC composites as a flow channel insert material and/or alternative structural material, advanced tritium breeders and neutron multipliers, and tritium technology are carried out. At the beginning of 2011, the integrated DEMO design team was established among the IFERC project team and EU/JA home teams, where the design criteria, other design basis are discussed as an initial work. A high performance supercomputer with the peak performance of 1.3 Pflops is under installation at the Rokkasho BA site.     

Development of an Evaluation Methodology for Fuel Discharge in Core Disruptive Accidents of Sodium-Cooled Fast Reactors

The purpose of the present study is to develop a methodology to evaluate fuel discharge through the CRGT （control-rod guide tube） during CDAs （core-disruptive accidents） of SFRs （sodium-cooled fast reactors）, since fuel discharge will decrease the core reactivity and CRGTs have a potential to provide an effective discharge path. Fuel discharge contains multi-component fluid dynamics with phase changes, and, in the present study, the SFR safety analysis code SIMMER （Sn, implicit, multifield, multicomponent, Eulerian recriticality） was utilized as a technical basis. First, dominant phenomena affecting fuel discharge through the CRGT are identified based on parametric calculations by the SIMMER code. Next, validations on the code models closely relating to these phenomena were carried out based on experimental data. It was shown that the SIMMER code with some model modifications could reproduce the experimental results appropriately. Through the present study, the evaluation methodology for the molten-fuel discharge through the CRGT was successfully developed.     

A 38-ns 4-Mb DRAM with a battery-backup (BBU) mode

The authors describe a DRAM with a battery-backup (BBU) mode, which allows automatic data retention with extremely reduced power consumption. The circuit techniques for reducing the refresh current and the back-bias-generator current are shown. The dissipated current required for data retention of 44 μA is achieved under typical conditions. This DRAM was fabricated with quad-poly and double-metal CMOS process technology. The memory array is divided into 4×32 subarrays. The finely divided array architecture is suitable for the fast access time and the multibit test mode     

Use of taxol and collagenase for better three-dimensional visualization of microtubules in the enterocyte and Brunner's gland cell, with special reference to their relation to the Golgi apparatus

Cytoskeletal microtubules were visualized in the mouse duodenal mucosa by an improved immunofluorescence method using a microtubule-stabilizing reagent, Taxol, and collagenase as an enzymatic epitope retriever. The improvement in immunostaining was shown morphologically and statistically by comparing fluorescence intensities of specimens prepared with or without Taxol and collagenase treatment. In free cells in the epithelium and in the lamina propria, microtubules radiated from the gamma-tubulin-immunostained organizing center. Enterocytes and Brunner's gland cells double-stained with an anti-alpha-tubulin antibody and a lectin (Helix pomatia agglutinin, soybean agglutinin or Ulex europaeus agglutinin-I) showed that microtubules ran along the cell axis and were abundant between the Golgi apparatus and the apical surface. The microtubules appeared to provide a structural support to hold the Golgi apparatus in position and to act as railways for secretory granules, which are transported towards the apical surface. In addition, gamma-tubulin-like immunoreactivity was associated with the Golgi apparatus in the enterocytes. These results show that the method using Taxol and collagenase is effective for visualizing microtubules in epithelial cells, and that microtubules may play important roles in both positioning of the Golgi apparatus and transport of secretory granules. Our results also support the idea that the Golgi apparatus may act as an organizing center for microtubules.     

Release of short-lived noble gases from HTGR fuel with failed coated fuel particles and contaminated matrix

Fuel compacts of the high-temperature gas-cooled reactor may contain a fraction of exposed uranium as defective coated fuel particles and a contamination of graphite matrix. Releases of short-lived noble gases were measured on the fuel compacts containing artificial failed particles as well as those having a highly contaminated matrix. The results were compared with the prediction by the JAERI model of short-lived gas release, which has been generated from previous irradiation testings. The release from the compacts with artificial failed particles agreed with the prediction except at lower temperatures where the fission-induced diffusion would predominate. The release from the matrix-contaminated compacts was different from the model prediction: The model fairly accurately predicted R/B of Xe, but significantly overpredicted that of Kr.     

Widespread expression of chondroitin sulfate-type serglycins with CD44 binding ability in hematopoietic cells

Serglycin is a family of small proteoglycans with Ser-Gly dipeptide repeats and is modified with various types of glycosaminoglycan side chains. We previously demonstrated that chondroitin sulfate-modified serglycin is a novel ligand for CD44 involved in the adherence and activation of lymphoid cells. In this study, we investigated the production and distribution of CD44 binding serglycins in various hematopoietic cells and characterized their carbohydrate side chains. Immunoprecipitation analysis using CD44-IgG and polyclonal antibody against the serglycin core peptide demonstrated that various serglycin species capable of binding CD44 are produced by a variety of hematopoietic cells including lymphoid cells, myeloid cells, and a few tumor cell lines. Glycosaminoglycans on these serglycins, which are essential for CD44 binding, are composed of chondroitin 4-sulfate or a mixture of chondroitin 4-sulfate and chondroitin 6-sulfate, but no heparin or heparan sulfate side chain was detected. The serglycins are also secreted by normal splenocytes, lymph node lymphocytes, and bone marrow cells, whereas they are secreted in very small amounts by normal thymocytes. Secretion of serglycins is greatly enhanced by mitogenic stimulation with concanavalin A or lipopolysaccharide. Our results showed that serglycin, unlike hyaluronate, is produced and secreted in a functional (CD44 binding) form by many members of the hematopoietic system including various lymphocyte subsets. Our data suggest that serglycin may serve as a major ligand for CD44 in various events in the lymphohematopoietic system.     

Influence of fabric on liquefaction and densification potential of cohesionless sand

For simple shearing under constant pressure, the effects of fabric on liquefaction and densification potentials of saturated cohensionless granular materials are examined theoretically and experimentally. The fabric is identified with the distribution of the dilatancy angles (the angle between the sliding and the macroscopic shearing directions), and the influence of prestraining on this distribution and hence on the macroscopic sample behavior is studied. It is shown that prestraining with zero residual stress can reduce resistance to liquefaction by one or even two orders of magnitude, although the sample density and other conditions are kept the same. The micromechanical features responsible for this and related behaviors are examined in some detail. Finally, some tentative results on the effect of the inherent anisotropy that is produced during sample preparation are reported, showing that a method which yields samples more resistive in triaxial cyclic tests may provide samples less resistive in cyclic shearing.     

Dynamic behavior of a solid particle bed in a liquid pool: SIMMER-III code verification

Dynamic behavior of solid particle beds in a liquid pool against pressure transients was investigated to model the mobility of core materials in a postulated disrupted core of a liquid metal fast reactor. A series of experiments was performed with a particle bed of different bed heights, comprising different monotype solid particles, where variable initial pressures of the originally pressurized nitrogen gas were adopted as the pressure sources. Computational simulations of the experiments were performed using SIMMER-III, a fast reactor safety analysis code. Comparisons between simulated and experimental results show that the physical model for multiphase flows used in the SIMMER-III code can reasonably represent the transient behaviors of pool multiphase flows with rich solid phases, as observed in the current experiments. This demonstrates the basic validity of the SIMMER-III code on simulating the dynamic behaviors induced by pressure transients in a low-energy disrupted core of a liquid metal fast reactor with rich solid phases.     

Survey report on damage caused by 2019 Typhoon Hagibis in Marumori Town,Miyagi Prefecture,Japan

Typhoon Hagibis struck Japan on October 12–13, 2019. There was substantial damage over a wide area including the Tohoku region. In particular, Marumori Town, an urban area in Miyagi Prefecture that includes a town hall, was flooded due to heavy rain. The maximum cumulative rainfall and hourly rainfall measured in the town were over 600 and 70 mm, respectively. Heavy rain caused river flooding and landslides throughout the town, resulting in 10 deaths and one missing person. There was also substantial damage to the infrastructure, such as roads, railways, and river levees. The authors performed a field survey immediately after the disaster, and analyzed the observed data. Most levee breaches occurred due to overflow. A breached levee that failed in an unusual direction, namely, a failure which took place from the landside toward the waterside, was also observed. Landslides were not only caused by the amount of rainfall, but also by geological and topographical factors. Roads and railways were damaged by both river flooding and landslides. While both river flooding and landslides occurred in the Usudaira community, which is in the middle reaches of the Gofukuya River, there were no deaths or missing persons. This should be an important case for future disaster mitigation.