Three-dimensional flow phenomena in a wire-wrapped 37-pin fuel bundle for SFR

AbstractThree-dimensional flow phenomena in a wire-wrapped 37-pin fuel assembly mock-up of a Japanese loop-type sodium-cooled fast reactor, Monju, were investigated with a numerical analysis using a general-purpose commercial computational fluid dynamics code, CFX. Complicated and vortical flow phenomena in the wire-wrapped 37-pin fuel assembly were captured by a Reynolds-averaged Navier–Stokes flow simulation using a shear stress transport turbulence model. The main purpose of the current study is to understand the three-dimensional complex flow phenomena in a wire-wrapped fuel assembly to support the license issue for the core design. Computational fluid dynamics results show good agreement with friction factor correlation models. The secondary flow in the corner and edge subchannels is much stronger than that in an interior subchannel. The axial velocity averaged in the corner and edge subchannels is higher than that averaged in the interior subchannels. Three-dimensional multiscale vortex structures start to be formed by an interaction between secondary flows around each wire-wrapped pin. Behavior of the large-scale vortex structures in the corner and edge subchannels is closely related to the relative position between the hexagonal duct wall and the helically wrapped wire spacer. The small-scale vortex is axially developed in the interior subchannels. Furthermore, a driving force on each wire spacer surface is closely related to the relative position between the hexagonal duct wall and the wire spacer

Interaction of edge waves with swell on a beach

Excitation of edge waves on a beach by incoming swell is considered on the basis of shallow-water model. Subharmonic resonance mechanism of interaction is analyzed by multi-scaled expansion asymptotic techniques. The generation of edge waves between wave breakers is found to have a dynamic threshold. It is defined by intensity and frequency of incoming swell, geometry of a shore zone. Nonlinear no stationary wave solutions for the envelope of interacting edge waves are described by generalized Sine-Gordon model. An infinite set of exact solutions are received by the Lamb method for the phase synchronism regime of wave’s interaction

Evaluation of a Sodium–Water Reaction Event Caused by Steam Generator Tubes Break in the Prototype Generation IV Sodium-cooled Fast Reactor

AbstractThe prototype generation IV sodium-cooled fast reactor (PGSFR) has been developed by the Korea Atomic Energy Research Institute. This reactor uses sodium as a reactor coolant to transfer the core heat energy to the turbine. Sodium has chemical characteristics that allow it to violently react with materials such as a water or steam. When a sodium–water reaction (SWR) occurs due to leakage or breakage of steam generator tubes, high-pressure waves and corrosive reaction products are produced, which threaten the structural integrity of the components of the intermediate heat-transfer system (IHTS) and the safety of the primary heat-transfer system (PHTS). In the PGSFR, SWR events are included in the design-basis event. This event should be analyzed from the viewpoint of the integrities of the IHTS and fuel rods. To evaluate the integrity of the IHTS based on the consequences of the SWR, the behaviors of the generated high-pressure waves are analyzed at the major positions of a failed IHTS loop using a sodium–water advanced analysis method-II code. The integrity of the fuel rods must be consistently maintained below the safety acceptance criteria to avoid the consequences of the SWR. The integrity of the PHTS is evaluated using the multidimensional analysis of reactor safety-liquid metal reactor code to model the whole plant

Mechanistic differences in RNA-dependent DNA polymerization and fidelity between murine leukemia virus and HIV-1 reverse transcriptases

We compared the mechanistic and kinetic properties of murine leukemia virus (MuLV) and human immunodeficiency virus type 1 (HIV-1) reverse transcriptases (RTs) during RNA-dependent DNA polymerization and mutation synthesis using pre-steady-state kinetic analysis. First, MuLV RT showed 6.5-121.6-fold lower binding affinity (Kd) to deoxynucleotide triphosphate (dNTP) substrates than HIV-1 RT, although the two RTs have similar incorporation rates (kpol). Second, compared with HIV-1 RT, MuLV RT showed dramatic reduction during multiple dNTP incorporations at low dNTP concentrations. Presumably, due to its low dNTP binding affinity, the dNTP binding step becomes rate-limiting in the multiple rounds of the dNTP incorporation by MuLV RT, especially at low dNTP concentrations. Third, similar fold differences between MuLV and HIV-1 RTs in the Kd and kpol values to correct and incorrect dNTPs were observed. This indicates that these two RT proteins have similar misinsertion fidelities. Fourth, these two RT proteins have different mechanistic capabilities regarding mismatch extension. MuLV RT has a 3.1-fold lower mismatch extension fidelity, compared with HIV-1 RT. Finally, MuLV RT has a 3.8-fold lower binding affinity to mismatched template/primer (T/P) substrate compared with HIV-1 RT. Our data suggest that the active site of MuLV RT has an intrinsically low dNTP binding affinity, compared with HIV-1 RT. In addition, instead of the misinsertion step, the mismatch extension step, which varies between MuLV and HIV-1 RTs, contributes to their fidelity differences. The implications of these kinetic differences between MuLV and HIV-1 RTs on viral cell type specificity and mutagenesis are discussed. © 2005 by The American Society for Biochemistry and Molecular Biology, Inc

Problems in Survivors of Biliary Atresia -5 or More Year After surgery-

Hepatic porto-enterostomy or Kasai's original Roux-en Y portojejunostomy was done on 56 patients during the 1980-1985 period. Seventeen patients or 30 per cent had survived more than 5 years at the end of 1990, and are presently being followed up. Average survival age is 7.5 years after surgery. No survivor has clinical or laboratory jaundice. Esophageal varices were demonstrated in 8 patients (47%), and 4 had bleeding episodes. Five patients or 29 per cent had more than one episode of hospitalization for cholangitis. Growth was above 75 per centile in height in 53 per cent. Nine patients(53%) have normal liver function, showed neither varix and nor ascites. Good prognostic factors for 5 year survival were an operative age of 60 days or less, mild fibrosis of the liver, and a big fibrotic mass at the porta hepatis at the time of surgery

Defecation Patterns after Posterior SagittaI Anorectoplasty with an Objective Scoring System

Imperforate anus, the common name representing a wider spectrum of anorectal malformations in newborns is one of the major congenital lesions in pediatric surgery. Since the establishment of pediatric surgery in Seoul National University (1978), more than 500 cases of anorectal anomalies had been treated up to 1990. To evaluate the quality of life after corrective treatment, defecation patterns were studied using clinical Kelly scores in 90 patients with high type ano-rectal anomalies repaired during the 1978-1985 period. These 90 patients were treated by two surgical repair methods (26 Rehbein, 64 Pena). Not only the continence scores but also other aspects of social adaptation as well as an index of quality of life were compared with a control group. Although precise anatomical repair under direct view (Pena) will give a better defecation pattern compared to the blind type of abdomino-perineal repair, their long term adaptation is not significantly superior. This study showed that the function is not always the net result of anatomic repair. Thus, the importance of the initial corrective operation is again emphasized

Neonatal Surgical Emergencies At Seoul National University Hospital: Comparison Between the Pre- and Post-Children's Hospital Period

Results of management of the neonatal surgical emergencies were analyzed and compared between 460 infants treated during the 1979-85 period (prechildrens hospital) and 471 infants treated during the 1986-92 period (post-childrens hospital). No statistical difference was noted in patients population, and average mortality rate in the pediatric surgical department which has already been functioning as an independent unit since 1978. Other surgical departments have experienced 2-3 fold increases in number of patients. Patient's age at admissionl delay in transfer} was not significantly improved. However, significant improvement in survival was noted in patients who required respiratory support such as gastroschisis, and esophageal atresia with tracheo-esophageal atresia. Changes in the general management plan are discussed

Falciform Ligament Abscess after Omphalitis: Report of a Case

A falciform ligament abscess is a rare type of intra-abdominal abscess. A 2-yr-old male, who had omphalitis two months previously, presented with a fever and right upper quadrant abdominal pain. The ultrasound and CT scan showed an abdominal wall abscess located anterior to the liver, which was refractory to conservative management with percutaneous draninage and antibiotics. On the third recurrence, surgical exploration was performed and revealed an abscess arising from the falciform ligament; the falciform ligament was excised. A follow up ultrasound confirmed complete resolution of the abscess with no further recurrence

Macrophage tropism of HIV-1 depends on efficient cellular dNTP utilization by reverse transcriptase

Retroviruses utilize cellular dNTPs to perform proviral DNA synthesis in infected host cells. Unlike oncoretroviruses, which replicate in dividing cells, lentiviruses, such as human immunodeficiency virus type 1 (HIV-1) and simian immunodeficiency virus, are capable of efficiently replicating in non-dividing cells (terminally differentiated macrophages) as well as dividing cells (i.e. activated CD4+ T cells). In general, non-dividing cells are likely to have low cellular dNTP content compared with dividing cells. Here, by employing a novel assay for cellular dNTP content, we determined the dNTP concentrations in two HIV-1 target cells, macrophages and activated CD4+ T cells. We found that human macrophages contained 130-250-fold lower dNTP concentrations than activated human CD4+ T cells. Biochemical analysis revealed that, unlike oncoretroviral reverse transcriptases (RTs), lentiviral RTs efficiently synthesize DNA even in the presence of the low dNTP concentrations equivalent to those found in macrophages. In keeping with this observation, HIV-1 vectors containing mutant HIV-1 RTs, which kinetically mimic oncoretroviral RTs, failed to transduce human macrophages despite retaining normal infectivity for activated CD4+ T cells and other dividing cells. These results suggest that the ability of HIV-1 to infect macrophages, which is essential to establishing the early pathogenesis of HIV-1 infection, depends, at least in part, on enzymatic adaptation of HIV-1 RT to efficiently catalyze DNA synthesis in limited cellular dNTP substrate environments

Regression of Advanced Gastric MALT Lymphoma after the Eradication of Helicobacter pylori

A 66-year-old female presented with a 1-month history of dyspepsia. An initial upper gastrointestinal endoscopy with biopsy revealed a low-grade mucosa-associated lymphoid tissue (MALT) lymphoma. A rapid urease test was positive for Helicobacter pylori. Endoscopic ultrasound (EUS) and computed tomography (CT) revealed a 30×15-mm lymph node (LN) in the subcarinal area. Histopathologic and phenotypic analyses of the biopsy specimens obtained by EUS-guided fine-needle aspiration revealed a MALT lymphoma, and the patient was diagnosed with a stage 4E gastric MALT lymphoma. One year after H. pylori eradication, the lesion had disappeared, as demonstrated by endoscopy with biopsy, CT, fusion whole-body positron emission tomography, and EUS. Here, we describe a patient with gastric MALT lymphoma that metastasized to the mediastinal LN and regressed following H. pylori eradication