•A 3D/0D domain coupling tool was implemented and used to simulate the overall coolant circuit of the TRIGA MARK I IPRR1 openpool reactor.•The tool aim to reduce the computational cost in large ...thermal hydraulic systems.•Start-up, steady state and accidental scenarios were assessed in the TRIGA MARK I IPR-R1 reactor.•The model results provided valuable information from the reactor’s safety point of view.
The computational simulation of large-scale reactors is currently limited by the high computational cost. The system codes allow addressing these problems, although with the well-known loss of local information. The use of coupling domains to reduce the problems looks like a proper alternative to settle this issue. In the present paper, a multi-domain coupling 3-dimensional/0-dimensional method to solve the thermal hydraulics of the TRIGA Mark I IPR-R1 reactor was implemented into a Finite Volume suite. Despite of the broadly literature about coupling methods, even in the nuclear engineering community, most of them manage with different codes in a fully explicit way. In the other hand, the benefit of solve different domain approaches inside the same software is in the use of monolithic algorithms. The proposed method consists on using 3-dimensional full CFD to simulate the reactor pool and 0-dimensional modelling for the external cooling loop. This is made by implementing a set of ad hoc dynamics boundary conditions to model the momentum and energy balances along the pipeline. This strategy was used to perform long-time steady state simulations of the reactor at the design power of 100 kW as well as for the repowering up to 265 kW. The results demonstrated that the core is efficiently cooled at the higher power without need to increase the coolant mass flow rate of the external system. Moreover, two accidental events were simulated: the first case was the Station Black Out at full power of 265 kW. The results indicated that the loss of the external heat sink led to a slow pool heating, but the core remains being cooled by the natural circulation in the pool. In fact, the mass flow rate through the core is only reduced in 15% by the loss of the external loop circulation. Finally, a large-Loss of Coolant Accident for the operational power of 100 kW and keeping the pump running is performed. In this case, the pool is quickly empty if safety systems do not take action and the core is uncovered after 450 s completely losing the core cooling capacity.
Vanadium(IV or V) complexes with N,O- or O,O-ligands, i.e., VO{N(CH2CH2O)3}, CaV(HIDPA)2 (synthetic amavadine), CaV(HIDA)2, or Bu4N2V(HIDA)2 HIDPA, HIDA = basic form of 2,2‘-(hydroxyimino)dipropionic ...or -diacetic acid, respectively, VO(CF3SO3)2, BaVO(nta)(H2O)2 (nta = nitrilotriacetate), VO(ada)(H2O) (ada = N-2-acetamidoiminodiacetate), VO(Hheida)(H2O) (Hheida = 2-hydroxyethyliminodiacetate), VO(bicine) bicine = basic form of N,N-bis(2-hydroxyethyl)glycine, and VO(dipic)(OCH2CH3) (dipic = pyridine-2,6-dicarboxylate), are catalyst precursors for the efficient single-pot conversion of methane into acetic acid, in trifluoroacetic acid (TFA) under moderate conditions, using peroxodisulfate as oxidant. Effects on the yields and TONs of various factors are reported. TFA acts as a carbonylating agent and CO is an inhibitor for some systems, although for others there is an optimum CO pressure. The most effective catalysts (as amavadine) bear triethanolaminate or (hydroxyimino)dicarboxylates and lead, in a single batch, to CH3COOH yields > 50% (based on CH4) or remarkably high TONs up to 5.6 × 103. The catalyst can remain active upon multiple recycling of its solution. Carboxylation proceeds via free radical mechanisms (CH3 • can be trapped by CBrCl3), and theoretical calculations disclose a particularly favorable process involving the sequential formation of CH3 •, CH3CO•, and CH3COO• which, upon H-abstraction (from TFA or CH4), yields acetic acid. The CH3COO• radical is formed by oxygenation of CH3CO• by a peroxo-V complex via a V{η1-OOC(O)CH3} intermediate. Less favorable processes involve the oxidation of CH3CO• by the protonated (hydroperoxo) form of that peroxo-V complex or by peroxodisulfate. The calculations also indicate that (i) peroxodisulfate behaves as a source of sulfate radicals which are methane H-abstractors, as a peroxidative and oxidizing agent for vanadium, and as an oxidizing and coupling agent for CH3CO• and that (ii) TFA is involved in the formation of CH3COOH (by carbonylating CH3 •, acting as an H-source to CH3COO•, and enhancing on protonation the oxidizing power of a peroxo-VV complex) and of CF3COOCH3 (minor product in the absence of CO).
Cases of core coolant flow blockage transient have been simulated and analysed for the TRIGA IPR-R1 research reactor using the RELAP5-MOD3.3 code. The transients are related to partial and to total ...obstruction of the core coolant channels. The reactor behaviour after the loss of flow was analysed as well as the changes in the coolant and fuel temperatures. The behaviour of the thermal hydraulic parameters from the transient simulations was analysed. For a partial blockage, it was observed that the reactor reaches a new steady state operation with new values for the thermal hydraulic parameters. The total core blockage brings the reactor to an abnormal operation causing increase in core temperature.
Little is known about
Salmonella
biofilm assembly, making the prevention of the disease a challenge in the poultry production chain. The objective of the present study was then to evaluate biofilm ...formation from different serotypes of
Salmonella
spp. in both polystyrene plates and eggshells.
Salmonella
Gallinarum and
S
. Minnesota were both classified as producers of biofilms of moderate intensity. Interestingly,
S
. Gallinarum produces biofilm even though being a serotype without flagellum and not having the
lux
gene in its genome, suggesting that there might be other important structures and genes associated with biofilm formation. Regarding Enteritidis, Typhimurium, Typhimurium variant, and Heidelberg serotypes, despite having high counts, BFI (Biofilm Formation Index) showed low biofilm production, probably due to the scarcity of extracellular matrix produced by such strains. A turkey eggshell model was then used for
S
. Enteritidis and
S
. Heidelberg biofilm formation. The results from the microbial count and scanning electron microscopy showed that
Salmonella
serotypes were also able to generate biofilm in eggshells, suggesting the presence of biofilms in poultry producing farms, a main concern for the poultry production industry.
•Hi-Nicalon type S alloy was used as fuel cladding of a PWR fuel.•A simplified thermal-hydraulic model was modeled for the two clad materials.•The neutronic analysis used the average temperature ...obtained from the thermal model.•Burnable poison rods and temperature feedback on the multiplication were analyzed.
In this paper, the SiC reinforced with Hi-Nicalon type S fibers (SiC HNS) was used as fuel cladding, and its behavior from the neutronic viewpoint was compared with the Zircaloy. To evaluate the average temperature of the fuel, cladding, and moderator used in the neutronic studies, a simplified thermal-hydraulic simulation of the core was performed using the RELAP5 code for the two cladding materials. Then, after that, a standard PWR fuel element was simulated, considering normal conditions of operation at Beginning Of Life (BOL) and full power, and using the average temperatures coming from the RELAP5 code calculation. The effects of burnable poison rods and temperature feedback on the core neutron multiplication factor have been evaluated changing the clad material at criticality steady state condition. Finally, the fuel element is analyzed during burnup. The neutronic analysis was made using the SCALE 6.0 (Standardized Computer Analysis for Licensing Evaluation) code.
Oxides of group 5–7 metals are convenient and efficient catalysts for the single-pot carboxylation of gaseous (methane, ethane, propane) and liquid alkanes to carboxylic acids, as well as for the ...aqueous peroxidative hydroxylation/oxygenation of liquid alkanes to alcohols and ketones. The reactions occur under mild conditions, and the carboxylations proceed with unprecedented remarkably high turnover numbers. The diagonal metals commonly provide the most active oxide catalysts in the order V > Re > Mo.
This study proposed to determine global microRNA (miRNA) expression and miRNA-regulated pathways in Intestinal Neuronal Dysplasia type B (IND-B). Fifty patients (0-15 years old) with IND-B were ...included in the study. Peripheral blood samples were collected from all 50 patients and from 10 healthy asymptomatic children (controls). Rectal biopsies were collected from 29/50 patients; biopsy tissues were needle microdissected to isolate the different intestinal layers, for molecular analysis. Global miRNA expression was determined using TaqMan arrays. Correlation analysis between miRNA expression in plasma and biopsy samples as well as among tissues derived from the distinct intestinal layers was performed. Computational approaches were used for miRNA target prediction/identification of miRNA-regulated genes and enriched pathways biologically relevant to IND-B pathogenesis. miRNAs were statistically significantly deregulated (FC ≥ 2 and p ≤ 0.05) in submucosal and muscular layers: over-expressed (miR-146a and miR-146b) and under-expressed (miR-99a, miR-100, miR-130a, miR-133b, miR-145, miR-365, miR-374-5p, miR-451). Notably, let-7a-5p was highly over-expressed in patient plasma compared to healthy controls (FC = 17.4). In addition, miR-451 was significantly under-expressed in both plasma and all biopsy tissues from the same patients. Enriched pathways (p < 0.01) were axon guidance, nerve growth factor signalling, NCAM signalling for neurite out-growth, neuronal system and apoptosis. miRNA expression is deregulated in the submucosa and muscular layers of the rectum and detected in plasma from patients with IND-B. Biologically enriched pathways regulated by the identified miRNAs may play a role in IND-B disease pathogenesis, due to the activity related to the neurons of the enteric nervous system.
Schistosoma mansoni is the primary causative agent of schistosomiasis, which affects 200 million individuals in 74 countries. We generated 163,000 expressed-sequence tags (ESTs) from normalized cDNA ...libraries from six selected developmental stages of the parasite, resulting in 31,000 assembled sequences and 92% sampling of an estimated 14,000 gene complement. By analyzing automated Gene Ontology assignments, we provide a detailed view of important S. mansoni biological systems, including characterization of metazoa-specific and eukarya-conserved genes. Phylogenetic analysis suggests an early divergence from other metazoa. The data set provides insights into the molecular mechanisms of tissue organization, development, signaling, sexual dimorphism, host interactions and immune evasion and identifies novel proteins to be investigated as vaccine candidates and potential drug targets.
•Behavior of Accident Tolerant Fuels (ATF) have been studied in a Pressurized Water Reactor.•Zircaloy 4, SiC HNS and FeCrAl (KANTHAL) claddings materials were considered in the analysis.•Steady state ...and transient situations were evaluated using the RELAP5 code.•UO2 fuel has been replaced by U3Si2 to verify the thermal behavior of the reactor.
Nuclear Fission Technology (NFT) is constantly developing to seek an increasingly safer operation and, consequently, increase the public acceptance of nuclear energy generation. Therefore, the development of new types of nuclear fuels and the search for different materials for cladding fuel rods has been the subject of research mainly to provide better efficiency in to carry energy in nuclear reactors and also to reduce possible damages in accident situations. In this way, this work aimed to compare the thermal response and behavior of Zircaloy 4, SiC reinforced with Hi-Nicalon type S (HNS) and FeCrAl alloy when they were considered as fuel cladding at steady state and transient conditions during operation of a PWR (Pressurized Water Reactor). Two thermal hydraulic models using the RELAP5 MOD3.3 and RELAP5-3D v. 4.3.4 codes and the reference data from the document Final Safety Analysis Report of Angra 2 PWR were used to perform the investigations. The work was developed in two steps. In the first one, the results of the Angra 2 nodalization in steady state conditions were compared with the Angra 2 reference data, obtaining good agreement. In the second step, the thermal response, when the cladding materials were changed, was evaluated in steady state and transient situations. The transients LOFA (Loss of Flow Accident), LBLOCA (Large Break - Loss of Coolant Accident), and coolant channel blockage were simulated in extreme conditions. The results have shown that substituting Zircalloy 4 alloy by FeCrAl or ceramic cladding SiC HNS presented a similar and better thermal response. Moreover, in another simulation, UO2 fuel has been replaced by U3Si2. The results showed lower temperatures at the fuel center in the rods with U3Si2 than those using UO2 as nuclear fuel, demonstrating the advantages of using U3Si2 fuel concerning the radial heat transfer in the rod.
•The feasibility of replacing Zircaloy-4 with FeCrAl-based alloys (C06M, C35M, C36M, Kanthal APMT) was evaluated.•Physical–chemical, thermal, and neutronic properties were considered.•The Kanthal ...APMT alloy presented the worst performance, and the C35M alloy showed more advantageous characteristics.•Considering the neutronic behavior, the Kanthal APMT alloy, with more Cr percentile, presents the lowest keff.•Axial and radial power distribution did not change significantly after the cladding replacement.
Discussing and researching issues related to their safety is essential to guarantee the continuity of fission systems in generating energy for existing and new electrical matrices. Commercial fission reactors currently in operation have undergone a series of redesigns. One aspect much discussed in recent years is related to research about new fuels and cladding materials. Therefore, in this work, the feasibility of replacing Zircaloy-4 with FeCrAl-based alloys (C06M, C35M, C36M, Kanthal APMT) was evaluated considering these materials' physical–chemical, thermal, and neutronic properties. Moreover, thermal–hydraulic and neutronic simulations have been presented to compare the cladding behavior in a PWR core in steady state and transient operation conditions. The results showed, in a general way, that the analyzed alloys have equivalent properties from a physical–chemical and thermal point of view. Despite the similarity, the Kanthal APMT alloy presented the worst performance, and the C35M alloy showed more advantageous characteristics. Considering the similarities in the composition of the C06M, C35M, and C36M alloys, which have the same elements in their constitution, the alloy with the best thermal performance has the lowest aluminum content. Considering the neutronic behavior, the Kanthal APMT alloy, with more Cr percentile, presents the lowest neutron effective multiplication factor, keff. Axial and radial power distribution did not change significantly after the cladding replacement. Nevertheless, modifications must be made to keep the criticality during the fuel cycle burnup for all FeCrAl alloys.
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