Search

The effect of the material hardening model of the canister on a finite element vertical cask drop simulation is investigated for the strain-based acceptance evaluation. Three different hardening models are considered in this paper: the isotropic hardening model, the strain rate-dependent Johnson-Cook (J-C) hardening model, and the modified J-C model which are believed to be the most accurate. By comparing the results using the modified J-C model, it is found that the use of the J-C model provides similar or larger stresses and strains depending on the magnitudes of the strain and strain rate. The use of the isotropic hardening model always yields larger stresses and strains. For the strain-based acceptance evaluation, the use of the isotropic hardening model can produce highly conservative assessment results. The use of the J-C model, however, produces satisfactory results.

Evidence has emerged that a pretreatment immune profile in rectal cancer is associated with response to chemoradiotherapy (CRT) and recurrence after CRT. However, few studies have evaluated the immune profile differences after CRT regarding recurrence and nonrecurrence.We included patients with advanced rectal cancer treated with CRT and surgery with recurrence within 1 year in a recurrence group. After sex and age matching with the recurrence group, patients with no recurrence for 3 years after CRT were included in a nonrecurrence group. We extracted the immune profile, including CD3 and CD8, from the surgical specimen after CRT using multispectral fluorescence immunohistochemistry and compared the two groups.The immune profiles of 65 patients with rectal cancer were assessed; 30 were included in the recurrence group and 35 were included in the nonrecurrence group. CD3Vigorous CD3

As a part of round robin analysis to develop a finite element elastic-plastic seismic analysis procedure for nuclear safety class 1 components, a series of parametric analyses was carried out on the simulated pressurizer surge line system model to investigate sensitivity of the analysis results to finite element analysis variables. The analysis on the surge line system model considered dynamic effect due to the seismic load corresponding to PGA 0.6 g and elastic-plastic material behavior based on the Chaboche combined hardening model. From the parametric analysis results, it was found that strains such as accumulated equivalent plastic strain and equivalent plastic strain are more sensitive to the analysis variables than von Mises effect stress. The parametric analysis results also identified that finite element density and ovalization option in the elbow elements have more significant effect on the analysis results than the other variables.

In the previous studies, the energy-based damage model was developed by simulating cracked pipe fracture behaviour under seismic loading. The multi-axial fracture strain energy density, the parameter of energy-based damage model, was determined by standard tensile test data and monotonic cracked pipe test data. Very low cycle fatigue crack growth was simulated by applying the multi-axial fracture strain energy density under monotonic loading. When the previous energy-based damage model was applied to simulate cracked pipe fracture test under seismic loading, the simulated results were good agreement with experimental data under high load amplitude reverse cyclic loading and displacement controlled large scale cyclic loading. However, the conservative predicted results are shown in pipe test with low load amplitude and different load ratio. In this paper, the energy-based damage model was improved by incorporating the effect of load amplitude and load ratio on multi-axial fracture strain energy density. The cyclic multi-axial fracture strain energy density increased by depending on the load amplitude and load ratios. The improved damage model was applied by pipe fracture test under seismic loading with various load amplitudes and load ratios. The pipe tests were subjected by using circumferential through-wall crack (TWC) and surface crack (SC) pipe specimen. The seismic loading consisted of two load amplitudes and two load ratios. The simulated results were compared with experimental data and validated.

This paper proposes a simple method to predict the fracture toughness of hydrogen-embrittled material using a hydrogen-embrittlement constant. The effect of hydrogen-embrittlement on fracture strain can be quantified via hydrogen-embrittlement constant, and it can be obtained by simulating small punch test in hydrogen. The fracture toughness of hydrogen-embrittled material can be simply estimated by multiplying the constant on fracture toughness of the un-embrittled material. The result of estimation shows good agreement with the published experimental data.

In this study, Johnson-Cook fracture strain model considering the effect of stress triaxiality and strain rate is determined for austenitic stainless steel 304. Tensile test data of four different stress triaxiality and six different strain rate conditions are used to determine the parameters in the J-C fracture strain model. To see the effect of local variation of stress triaxiality and strain rate in the specimen, the J-C fracture models are determined in two different ways. The first case uses the initial stress triaxiality and nominal strain rate, and the second case uses the average value of local stress triaxiality and strain rate obtained from finite element analysis. The use of initial stress triaxiality gives conservative estimate of fracture strain at low stress triaxiality, and non-conservative estimate at high stress triaxiality. The use of nominal strain rate gives overall conservative estimate of fracture strain.

Spent nuclear fuels (SNFs) are stored in stainless steel canisters at Independent Spent Fuel Storage Installations (ISFSIs) typically near the seashore. During long-term storage of these canisters in the dry cask storage system (DCSS), chloride-induced stress corrosion cracking (CISCC) could occur due to the deliquescence of concentrated salt deposits on the canister surface. To evaluate such flaws on the accessible exterior metallic portions of containment systems while in service, the ASME Section XI Code Case N-860 provides inservice inspection requirements for aging management of canisters manufactured with welded austenitic stainless steels. It is noteworthy that CISCC crack growth rate (CGR) model in Code Case N-860 consists of the constitutive equations with temperatures (canister surface temperatures, storage site yearly mean temperature, and ambient temperature measured at overpack inlet) and is independent of stress intensity factor or other environmental factors. In this work, the mean temperature effect of the local storage site on the CGR is analyzed based on the CISCC CGR model in Code Case N-860. The specified mean temperature in the Code Case is calculated yearly however, the crack growth by CISCC can be evaluated differently if the mean temperature of storage site with a large annual range of temperature such as South Korea is applied. In that case, the monthly mean temperature is adjusted as the yearly mean temperature so the effect of averaging range for calculating the mean temperature is analyzed. Firstly, climate data of some candidate sites for the storage in South Korea are measured from Korea Meteorological Administration (KMA). The climate data of the Diablo Canyon Power Plant located in California (United States) is obtained from National Weather Service (NWS) for comparison. Yearly data from 2012 to 2020 are applied and the crack growth is estimated for sites of different annual ranges.

In this paper, a strain-based failure assessment is performed on a canister made of stainless steel when a spent nuclear fuel dry storage system goes through a drop accident, to investigate the effects of strain rate on strain-based failure assessment results. The KORAD-21 multi-purpose dry storage container system developed for interim storage and transportation at the Korea Radioactive Waste Agency (KORAD) is considered. A finite element (FE) analysis is performed on a 1m puncture drop of the KORAD-21 model. Based on the FE results, the canister under a 1m puncture drop is evaluated by two different criteria: (1) strain-based acceptance criteria suggested in ASME Boiler and Pressure Vessels Code Section III, Appendix FF, “Strain-based acceptance criteria for energy-limited events” and (2) the Johnson-Cook fracture strain model based on experimental data. The difference between the two criteria is that the Johnson-Cook fracture strain model expresses the true fracture strain as a function of stress triaxiality and strain rate, whereas the formula in App. FF establishes strain limit (combination of uniform strain and true fracture strain) as a function of stress triaxiality only. In this study, the safety margins of Appendix FF are analyzed by comparing the failure assessment results for canister drop simulation with those applying the Johnson-Cook fracture strain model.

The Korean rockfish, Sebastes schlegeli, is most commonly farmed in sea cages along the coast of Korea; however, detailed information on intestinal microbiota regarding this fish is not readily available. In this study, comparison of the seasonal changes of microbial communities in the intestine between farmed and wild through the amplicon sequencing approach was conducted. The composition of major species in the intestine of this fish was very simple compared to that of other marine fish species, with members affiliated with the family Vibrionaceae hyper-dominating and comprising on average 97.6% of microbiota. However, the composition at the genus or species level and the pattern of seasonal changes of diversity indices showed significant differences between farmed and wild fish. In the farmed fish, Photobacterium phophoreum was most dominant throughout the year, accounting for 58.8% of the total. Aliivibrio fisherii and/or Aliivibrio finisterrensis also were dominant in the fall to winter but substituted by Photobacterium damselae during spring to summer. In the wild fish, on the other hand, opportunistic pathogens in the genera Aliivibrio or Vibrio were dominant in most of the samples. The analysis of shared species between gut microbiome, feed microbiota, and seawater microbiota indicated that the intestinal microbial diversity of farmed fish was affected more by microbiota of seawater than that of feed in spring and winter seasons. Additionally, the proportion of potential pathogenic Vibrio spp. in the gut showed a negative correlation with plasma glucose levels of the host. This study and following studies will be helpful in understanding the interaction between microbiome hosts and the development of techniques to enhance production of healthy Korean rockfish.

This paper suggests a fracture simulation method for SFR metallic fuel pin under accident condition. Two major failure mechanisms - creep damage and eutectic penetration - are implemented in the suggested method. To simulate damaged element, stress-reduction concept to reduce stiffness of the damaged element is applied. Using the proposed method, the failure size of cladding can be predicted in addition to the failure time and failure site. To verify the suggested method, Whole-pin furnace (WPF) test and TREAT-M test conducted at Argonne National Laboratory (ANL) are simulated. In all cases, predicted results and experimental results are overall in good agreement. Based on the simulation result, the effect of eutectic-penetration depth representing failure behavior on failure size is studied.

This paper presents numerical estimation of burst pressures of axial cracked U-bend tubes, considering the U-bending process analysis. The validity of the FE simulations is confirmed by comparing with published experimental data. From parametric analyses, it is shown that existing EPRI burst pressure estimation equations for straight tubes can be conservatively used to estimate burst pressures of the U-bend tubes. This is due to the increase in yield strength during the U-bending process. The degree of conservatism would decrease with increasing the bend radius and with increasing the crack depth.

Bacteria in the Desulfovibrionaceae family, which contribute to S element turnover as sulfate-reducing bacteria (SRB) and disproportionation of partially oxidized sulfoxy anions, have been extensively investigated since the importance of the sulfur cycle emerged. Novel species belonging to this taxon are frequently reported, because they exist in various environments and are easy to culture using established methods. Due to the rapid expansion of the taxon, correction and reclassification have been conducted. The development of high-throughput sequencing facilitated rapid expansion of genome sequence database. Genome-based criteria, based on these databases, proved to be potential classification standard by overcoming the limitations of 16S rRNA-based phylogeny. Although standards methods for taxogenomics are being established, the addition of a novel genus requires extensive calculations with taxa, including many species, such as Desulfovibrionaceae. Thus, the genome-based criteria for classification of Desulfovibrionaceae were established and validated in this study. The average amino-acid identity (AAI) cut-off value, 63.43 ± 0.01, was calculated to be an appropriate criterion for genus delineation of the family Desulfovibrionaceae. By applying the AAI cut-off value, 88 genomes of the Desulfovibrionaceae were divided into 27 genera, which follows the core gene phylogeny results. In this process, two novel genera (Alkalidesulfovibrio and Salidesulfovibrio) and one former invalid genus (“Psychrodesulfovibrio”) were officially proposed. Further, by applying the 95–96% average nucleotide identity (ANI) standard and the 70% digital DNA–DNA hybridization standard values for species delineation of strains that were classified as the same species, five strains have the potential to be newly classified. After verifying that the classification was appropriately performed through relative synonymous codon usage analysis, common characteristics were listed by group. In addition, by detecting metal resistance related genes via in silico analysis, it was confirmed that most strains display metal tolerance.

A novel bacterium, designated SCR006T, was isolated from tidal flat sediment from Suncheon Bay, Republic of Korea. Cells of strain SCR006T were strictly anaerobic, motile cocci, Gram-reaction-negative, and catalase- and oxidase-negative. Growth was observed at 4–41 °C (optimum, 34–37 °C), at pH 6.5–10.0 (optimum, pH 7.0–7.5) and in presence of 0–8 % NaCl (optimum, 0–2 %). Fermentation products of peptone–yeast–glucose medium were acetate and ethanol. Results of phylogenetic analyses based on 16S rRNA gene sequences indicated that strain SCR006T had high sequence similarity to Proteiniclasticum ruminis D3RC-2T (97.9 %), followed by Youngiibacter multivorans DSM 6139T (95.9 %) and Youngiibacter fragilis 232.1T (95.0 %). The average nucleotide identity value between strain SCR006T and P. ruminis DSM 24773T was 72.7 %, which strongly supported that strain SCR006T reresents a novel species within the genus Proteiniclasticum . The major cellular fatty acids are iso-C15 : 0 (27.2 %) and anteiso-C15 : 0 (16.9 %). The polar lipids were diphosphatidylglycerol, phosphatidylglycerol, two unidentified phospholipids, an unidentified aminolipid and five unidentified lipids. The genomic size was 3.2 Mb with genomic DNA G+C content of 45.6 mol%. The results of 16S rRNA-based and genome-based phylogenetic tree analyses indicated that SCR006T should be assigned to the genus Proteiniclasticum . Strain SCR006T could be distinguished from P. ruminis D3RC-2T by its growth conditions, cell morphology and genomic characteristics. Based on the phenotypic, phylogenetic, genomic and chemotaxonomic features, strain SCR006T represents a novel species, for which the name Proteiniclasticum aestuarii sp. nov. is proposed, with the type strain SCR006T (=KCTC 25245T= JCM 34531T)

This paper proposes an elastic-plastic-based decoupling criterion that can be applied to the seismic analysis of large-scale complex piping systems in nuclear power plants under beyond design basis earthquakes. First, the existing elastic-based decoupling criteria for seismic analyses were critically reviewed. Next, the effect of plasticity on the decoupling criteria was investigated by considering the equivalent damping and stiffness reduction. Finally, the decoupling criterion considering plasticity was developed based on the changes resulting from existing decoupling criteria. The validity of the proposed decoupling criterion was confirmed through its application to an analysis of a real piping system.

In this study, a method which would improve reliability of coated vertical type micro-probe under Joule heating is described. The method is to decouple the mechanical and electrical characteristics of a probe. That is, the method is to coat a metal with good electrical characteristics on a core metal with a good mechanical characteristics by electroplating. For various configurations of cross-sectional area of probe, FE analysis are performed, and a fabricated vertical micro-probe is tested to improve the accuracy of FE analysis. By increasing the coating thickness of a metal (gold, Au) with good electrical characteristics by electroplating while keeping a total cross-sectional area of a probe constant, the maximum temperature of probe continues to decrease as the cross-sectional area of core metal (nickel, Ni) with the good mechanical characteristics is reduced. A simple formula to predict the maximum temperature of probe depending on the coating thickness based on the results of FE analysis is proposed. The formula describe that the maximum temperature of the probe by Joule heating is a function of the ratio of the conductivity of the coating metal to the core metal and the ratio of the cross-sectional area of the coating metal to the total cross-sectional area of the probe.

An anaerobic, rod-shaped, mesophilic, chemolithoautotrophic, sulfate-reducing bacterial strain IOR2T was isolated from a newly found deep-sea hydrothermal vent (OVF, Onnuri Vent Field) area in the central Indian Ocean ridge (11°24'88″ S 66°25'42″ E, 2021 m water depth). The 16S rRNA gene sequence analysis revealed that the strain IOR2T was most closely related to Desulfovibrio senegalensis BLaC1T (96.7%). However, it showed low similarity with the members of the family Desulfovibrionaceae, such as Desulfovibrio tunisiensis RB22T (94.0%), D. brasiliensis LVform1T (93.9%), D. halophilus DSM 5663T (93.7%), and Pseudodesulfovibrio aespoeensis Aspo-2T (93.2%). The strain IOR2T could grow at 23-42°C (optimum 37°C), pH 5.0-8.0 (optimum pH 7.0) and with 0.5-6.5% (optimum 3.0%) NaCl. The strain could use lactate, pyruvate, H2, and glycerol as electron donors and sulfate, thiosulfate, and sulfite as electron acceptors. The major fatty acids of the strain IOR2T were iso-C15:0, iso-C17:0, ante-iso-C15:0, and summed feature 9 (C16:0 methyl/iso-C17:1ω9c). Both the strains IOR2T and BLaC1T could grow with CO2 and H2 as the sole sources of carbon and energy, respectively. Genomic evidence for the Wood-Ljungdahl pathway in both the strains reflects chemolithoautotrophic growth. The DNA G + C content of the strain IOR2T and BLaC1T was 58.1-60.5 mol%. Based on the results of the phylogenetic and physiologic studies, Paradesulfovibrio onnuriensis gen. nov., sp. nov. with the type strain IOR2T (= KCTC 15845T = MCCC 1K04559T) was proposed to be a member of the family Desulfovibrionaceae. We have also proposed the reclassification of D. senegalensis as Paradesulfovibrio senegalensis comb. nov.

Little is known about the community structure and metabolic potential of microbial communities in hydrothermal fields in the Central Indian Ridge (CIR). In this study, a metagenomic sequencing approach was conducted to explore the microbial diversity in three sediment samples collected during the 2019 expedition from two recently discovered hydrothermal vent fields; Invent E and Onnuri Vent Field (OVF). Analysis of unassembled metagenomic reads using the Metagenomic analysis server (MG-RAST) revealed that microbial communities of the two sampling sites were very similar, showing the dominance of Bacteria over Archaea. Proteobacteria, Firmicutes, Bacteroidetes, as well as Euryarchaeota were dominant in all samples. Functional annotation based on KEGG categories shows that the microbial populations in these vent fields possess metabolic capabilities for aerobic respiration, carbon fixation through the Calvin–Bassham–Benson (CBB) cycle, the reverse tricarboxylic acid (rTCA) cycle, and reductive acetyl-CoA pathway as well as sulfur and nitrogen metabolisms. Comparative metagenome analysis with different datasets obtained from different ocean ridges showed that microbial communities at low activity or hydrothermally influenced area differ from highly active hydrothermal communities. This study provides insights into the genetic diversity and functional capability of the microbial communities of slow to intermediate spreading hydrothermal systems.

To predict fracture behavior for ductile materials, some ductile fracture simulation methods different from classical approaches have been investigated based on appropriate models of ductile fracture. For the future use of the methods to overcome restrictions of classical approaches, the applicability to the actual components is of concern. In this study, two benchmark problems on the fracture tests supposing actual components were provided to investigate the prediction ability of simulation methods containing parameter decisions. One was the circumferentially through-wall and surface cracked pipes subjected to monotonic bending, and the other was the circumferentially through-wall cracked pipes subjected to cyclic bending. Participants predicted the ductile crack propagation behavior by their own approaches, including finite element method (FEM) employed Gurson–Tvergaard–Needleman (GTN) yielding function with void ratio criterion, are FEM employed GTN yielding function, FEM with fracture strain or energy criterion modified by stress triaxiality, extended FEM with J or ΔJ criterion, FEM with stress triaxiality and plastic strain based ductile crack propagation using FEM, and elastic-plastic peridynamics. Both the deformation and the crack propagation behaviors for monotonic bending were well reproduced, while few participants reproduced those for cyclic bending. To reproduce pipe deformation and fracture behaviors, most of the groups needed parameters that were determined to reproduce pipe deformation and fracture behaviors in benchmark problems themselves and it is still difficult to reproduce them by using parameters only from basic materials tests.