Phenomenological Study of Fuel Relocation Behavior and Formation of Debris Bed in Metal-fueled Sodium-cooled Fast Reactor

Department of Nuclear EngineeringMetallic fuel has been proposed as one of fuel types in sodium-cooled fast reactor (SFR). The metallic fuel has advantages in terms of safety issues. Especially, it has been known that severe accident for metal-fueled SFR might be terminated earlier due to its safety characteristics. Hypothetical core disruptive accidents (HCDA) are considered as the accident which causes fuel melting and cladding failure in SFR. When cladding bleach occurs in initiating phase of HCDA, molten fuel is relocated debris is formed in fuel assembly. Severe accident consequences are determined depending on these phenomena. Thus, it is necessary to study fuel behavior and solidification phenomena in severe accident. However, the studies related to the metallic fuel in severe accident condition were partly performed. There is still a lack of fundamental knowledge about the severe accident phenomena and related physics. Therefore, the present study focuses on fuel relocation behavior and debris formation phenomena, which is in specific accident scenario, with experimental approaches. The fuel relocation behavior has been not studied clearly, especially in initiating phase of HCDA. To understand the phenomena and provide physical insights, there were visual studies for various experimental conditions. The studies were performed as a parametric study so key parameters affecting the fuel relocation behavior were selected. The parameter discussed in the experiment are coolant boiling, channel condition, initial melt temperature, and initial melt ejection pressure etc. In the fuel relocation experiments, simulants were used instead of metallic fuel. Wood???s metal and gallium were used as the simulant for the metallic fuel in most of experiment. Since the fuel behaviors are driven by force balance, Froude and Weber numbers were compared to investigate similarity. High speed video camera was used to observe the fuel relocation behavior and visual analysis methods were applied on the parameter study. There were two steps to conduct the visualization experiments. Firstly, possible fuel relocation behaviors were observed in small-scaled experimental facility. The experimental facility is called UNIST molten core and coolant interaction experimental facility (UNICORN)-B (baby). From the experiments, it was found that sodium boiling could be powerful driving force for fuel dispersal regardless of channel condition. Then, there were additional visual studies using UNICORN-C (child) which was established considering actual scale of fuel assembly in metal-fueled SFR. As a result, it was clarified that debris bed formation was highly dependent on the fuel relocation behaviors. Although fuel is ejected into coolant channel, core could be cooled from hydrodynamic point of view. If high porous debris bed is formed, decay heat would be removed using natural circulation flow. UNICORN-A (adult) was established to simulate actual fuel ejection condition in HCDA. Simultaneous occurrence of unprotected transient over power (UTOP) and unprotected loss-of-flow (ULOF) event was selected as a target scenario. A severe accident code SAS4A was used to calculate initial experimental conditions. Radiographic images were obtained to analyze melt relocation behavior. The experimental results show that melt was not swept out from active core region. Mass fraction of frozen melt was investigated along axial distance. It showed melt was radially dispersed rather than the axial melt dispersal. In addition, most of melt was frozen near cladding failure point where the melt was directly ejected out. Debris bed seemed like agglomerated shape leading to local flow blockage. Since debris bed porosity affects to pressure drop and flow rate of fuel assembly, the porosity was evaluated after the experiment. The porosity was measured with two methods; classical method and post-processing method of radiograph image. The classical method was performed using volume fraction of test section before and after the fuel relocation experiment. Debris bed was measured 0.89 of its porosity with these methods. It could ensure that core has coolability by natural circulation. Thus, it was verified that there was a possibility of early termination of severe accident. The characteristics of debris bed are mainly determined from physical form of individual debris. Especially, debris bed porosity is affected by debris morphology. In severe accident condition in SFR, metallic fuel had ligament-like shape of debris. This morphology made characteristics of debris bed porosity. The metal fuel had relatively high debris bed porosity. In previous research group, quenching experiments were conducted using molten metal droplet. The debris morphology was analyzed quantitatively. It was insufficient to qualitatively investigate the debris morphology. The present study was performed with experimental works based on theoretical model regarding rapid solidification. It is suggested that debris morphology is attributed to freezing point and instantaneous contact interface temperature between melt and coolant. From rapid solidification experiments, it was shown that high porous debris bed would be formed above porosity of 0.83 based on the reactor accident conditions in ULOF.ope

Progressive Processing of Continuous Range Queries in Hierarchical Wireless Sensor Networks

In this paper, we study the problem of processing continuous range queries in a hierarchical wireless sensor network. Contrasted with the traditional approach of building networks in a "flat" structure using sensor devices of the same capability, the hierarchical approach deploys devices of higher capability in a higher tier, i.e., a tier closer to the server. While query processing in flat sensor networks has been widely studied, the study on query processing in hierarchical sensor networks has been inadequate. In wireless sensor networks, the main costs that should be considered are the energy for sending data and the storage for storing queries. There is a trade-off between these two costs. Based on this, we first propose a progressive processing method that effectively processes a large number of continuous range queries in hierarchical sensor networks. The proposed method uses the query merging technique proposed by Xiang et al. as the basis and additionally considers the trade-off between the two costs. More specifically, it works toward reducing the storage cost at lower-tier nodes by merging more queries, and toward reducing the energy cost at higher-tier nodes by merging fewer queries (thereby reducing "false alarms"). We then present how to build a hierarchical sensor network that is optimal with respect to the weighted sum of the two costs. It allows for a cost-based systematic control of the trade-off based on the relative importance between the storage and energy in a given network environment and application. Experimental results show that the proposed method achieves a near-optimal control between the storage and energy and reduces the cost by 0.989~84.995 times compared with the cost achieved using the flat (i.e., non-hierarchical) setup as in the work by Xiang et al.Comment: 41 pages, 20 figure

Satisfaction with food policies for consumer

노트 : Selected paper prepared for presentation at the Agricultural & Applied Economics Association’s 2016 AAEA Annual Meeting, Boston, Massachusetts, July 31-August 2, 201

Laminaria japonica Extract Enhances Intestinal Barrier Function by Altering Inflammatory Response and Tight Junction-Related Protein in Lipopolysaccharide-Stimulated Caco-2 Cells.

In the normal physiological state, intestinal epithelial cells act as a defensive frontline of host mucosal immunity to tolerate constant exposure to external stimuli. In this study, we investigated the potential anti-inflammatory and gut permeability protective effects of Laminaria japonica (LJ) water extract (LJE) and three types of fermented Laminaria japonica water extracts (LJE-F1, LJE-F2, and LJE-F3) in lipopolysaccharide (LPS)-stimulated Caco-2, human intestinal epithelial cells. All four extracts significantly decreased the production of nitric oxide and interleukin-6 induced by LPS stimulus. In addition, LJE and the three types of LJE-Fs also inhibited LPS-induced loss of monolayer permeability, as assessed by changes in transepithelial electrical resistance. All four LJ extracts significantly prevented the inhibition of the protein levels of occludin, whereas LJE, LJE-F1, and LJE-F3 significantly attenuated the reduction in phosphorylation of adenosine monophosphate-activated protein kinase compared with the LPS-treated group in Caco-2 cells. In conclusion, LJE and its fermented water extracts appear to have potential gut health-promoting effects by reducing inflammation and partially regulating the tight junction-related proteins in human intestinal epithelial cells. Thus, additional studies are warranted to evaluate Laminaria japonica as a therapeutic agent for inflammatory bowel diseases

First record of the genus Pseudaeginella Mayer, 1890 (Crustacea, Amphipoda, Caprellidae) with a new species from Korean waters

A new species of the genus Pseudaeginella Mayer, 1890 belonging to the family Caprellidae Leach, 1814 was collected from the South Sea in Korea. Pseudaeginella carinaspinosa sp. nov. is morphologically similar to related congeners belonging to the genera Paradeutella Mayer, 1890 and Pseudaeginella, in having dorsal projections on pereonites, triarticulate mandibular palp, small or absent molar, and uniarticulate pereopods 3 and 4. However, this new species is distinguished from its congeners by the position and size of dorsal projection. This is the first record of Pseudaeginella from the Northwest Pacific region, including Korea, and a key to species of the genus Pseudaeginella is also provided

Effects of exercise on obesity-induced mitochondrial dysfunction in skeletal muscle

Obesity is known to induce inhibition of glucose uptake, reduction of lipid metabolism, and progressive loss of skeletal muscle function, which are all as- sociated with mitochondrial dysfunction in skeletal muscle. Mitochondria are dy- namic organelles that regulate cellular metabolism and bioenergetics, including ATP production via oxidative phosphorylation. Due to these critical roles of mitochon- dria, mitochondrial dysfunction results in various diseases such as obesity and type 2 diabetes. Obesity is associated with impairment of mitochondrial function (e.g., decrease in O2 respiration and increase in oxidative stress) in skeletal muscle. The bal- ance between mitochondrial fusion and fission is critical to maintain mitochondrial homeostasis in skeletal muscle. Obesity impairs mitochondrial dynamics, leading to an unbalance between fusion and fission by favorably shifting fission or reducing fusion proteins. Mitophagy is the catabolic process of damaged or unnecessary mito- chondria. Obesity reduces mitochondrial biogenesis in skeletal muscle and increases accumulation of dysfunctional cellular organelles, suggesting that mitophagy does not work properly in obesity. Mitochondrial dysfunction and oxidative stress are reported to trigger apoptosis, and mitochondrial apoptosis is induced by obesity in skeletal muscle. It is well known that exercise is the most effective intervention to protect against obesity. Although the cellular and molecular mechanisms by which exercise protects against obesity-induced mitochondrial dysfunction in skeletal mus- cle are not clearly elucidated, exercise training attenuates mitochondrial dysfunction, allows mitochondria to maintain the balance between mitochondrial dynamics and mitophagy, and reduces apoptotic signaling in obese skeletal muscle

Kinematics Characteristic of Lower Extremity during Simulated Skiing Exercise

We analyze the kinematic factors of sectional and total movements in healthy participants to providing group dependent information during simulated exercise. Participants in this study's experiment were 26 male adults, the elapsed times in each phase, the difference in the lower extremity angles, and muscle activity were computed through analysis of kinematic factors. We revealed that motions of the experts took shorter to perform than non-experts, and showed larger variation of lower limb joint angle in most events during simulated skiing. There were also significant group dependent differences in the peak and mean EMG values during simulated skiing. Referring to these results, such a non-expert's posture leads to enhance muscle activity to keep the lower body in balance. Non-experts should maintain appropriate ROM with lower-intensity exercise to improve muscle endurance initially, and it can be useful in providing preliminary data for future training and rehabilitation studies, as well as improvements in muscle strength

Trib2 regulates the pluripotency of embryonic stem cells and enhances reprogramming efficiency

Embryonic stem (ES) cells are pluripotent cells characterized by self-renewability and differentiation potential. Induced pluripotent stem (iPS) cells are ES cell-equivalent cells derived from somatic cells by the introduction of core reprogramming factors. ES and iPS cells are important sources for understanding basic biology and for generating therapeutic cells for clinical applications. Tribbles homolog 2 (Trib2) functions as a scaffold in signaling pathways. However, the relevance of Trib2 to the pluripotency of ES and iPS cells is unknown. In the present study, we elucidated the importance of Trib2 in maintaining pluripotency in mouse ES cells and in generating iPS cells from somatic cells through the reprogramming process. Trib2 expression decreased as ES cells differentiated, and Trib2 knockdown in ES cells changed their colony morphology while reducing the activity of alkaline phosphatase and the expression of the pluripotency marker genes Oct4, Sox2, Nanog and Klf4. Trib2 directly interacted with Oct4 and elevated Oct4 promoter activity. During the generation of iPS cells, Trib2 knockdown decreased the reprogramming efficiency of mouse embryonic fibroblasts, whereas Trib2 overexpression significantly increased their reprogramming efficiency. In summary, our results suggest that Trib2 is important for maintaining self-renewal in ES cells and for pluripotency induction during the reprogramming process

The Paradoxical Protective Effect of Liver Steatosis on Severity and Functional Outcome of Ischemic Stroke

Background: There is very limited information on the relationship between non-alcoholic fatty liver disease (NAFLD) and the severity or functional outcomes of ischemic stroke or transient ischemic stroke (TIA). We investigated the correlation between NAFLD and stroke outcomes.Methods: NAFLD was assessed in 321 patients with first-ever acute ischemic stroke or TIA, who underwent transient elastography from January 2014 to December 2014. The association of liver steatosis with stroke severity, assessed using the National Institute of Health Stroke Scale (NIHSS), was investigated using robust regression analysis. We also compared the functional outcome at 90 days according to the presence or burden of liver steatosis.Results: NAFLD was observed in 206 (64.2%) patients. Patients with NAFLD had less severe stroke (median NIHSS score 2 vs. 3, P = 0.012) and more favorable functional outcome at 90 days (85.3 vs. 70.5, P = 0.004). Patients with NAFLD were likely to have a 23.3% lower [95% confidence interval (CI), −39.2 to −3.2%, P = 0.026] NIHSS score and a 2.5-fold higher (95% CI, 1.08–5.67, P = 0.033) possibility of favorable functional outcome in multivariate analysis.Conclusions: Our study shows that a higher burden of liver steatosis seems to be associated with less severe stroke and better functional outcome after ischemic stroke or TIA