Multiphysics analysis of heat pipe cooled microreactor core with adjusted heat sink temperature for thermal stress reduction using OpenFOAM coupled with neutronics and heat pipe code

Heat-pipe-cooled microreactors (HPRs) have advantages such as a compact design, easy transportation, and improved system reliability and stability. The core of an HPR consists of fuel rods and heat pipes in a monolith, which is a solid block structure containing many holes for the fuel rods and heat pipes. When designing the core of an HPR, high thermal stress and reactivity feedback owing to thermal expansion are important considerations. Therefore, a high-fidelity multiphysics analysis tool is required for accurately analyzing an HPR core. When performing a multiphysics analysis, it is necessary to couple the heat pipe thermal analysis code, thermal-structural analysis code, and neutronics code. To develop a multiphysics analysis tool, OpenFOAM, an open source Computational Fluid Dynamics (CFD) tool, and ANLHTP, a heat pipe thermal analysis code, were coupled. In this process, the structural analysis solver of OpenFOAM was verified, and its limitations were improved. To confirm the proper working of the code, the mini-core problem was analyzed using the OpenFOAM-ANLHTP coupled code. Next, to consider the reactivity feedback, coupling with PRAGMA, a GPU-based continuous-energy-Monte Carlo neutronics code was performed, and the multiphysics analysis capability of the OpenFOAM-ANLHTP-PRAGMA coupled code was confirmed through an analysis of the MegaPower reactor core. To reduce the temperature distribution within the monolith, the temperature distribution of the heat pipe sink was adjusted, and the reduced thermal stress of an HPR core was observed

Experimental study on the measurement of effective themal conductivity for VHTR fuel block geometry

Papers presented to the 11th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, South Africa, 20-23 July 2015.Effective thermal conductivity models which can be used to analyze the heat transfer phenomena of a prismatic fuel block were evaluated by the experiments. In the accident condition of VHTR when forced convection is lost, the heat flows in radial direction through the hexagonal fuel blocks that contain the large number of coolant holes and fuel compacts. Due to the complex geometry of fuel block and radiation heat transfer, the detail computation of heat transfer on the fuel block needs excessive computation resources. Therefore, the detail computation isn't appropriate for the lumped parameter code and a system code such as GAMMA+ adopts effective thermal conductivity model. Despite the complexity in heat transfer modes, the accurate analysis on the heat transfer in fuel block is necessary since it is directly relevant to the integrity of nuclear fuel embedded in fuel block. To satisfy the accurate analysis of complex heat transfer modes with limited computing sources, the credible effective thermal conductivity (ETC) models in which the effects of all of heat transfer modes are lumped is necessary. In this study, various ETC models were evaluated with the experiment result. Experiments for measuring the ETC values of the VHTR fuel block geometry were conducted with IG-11 graphite block. And four probable models compared to the experiment result showed good agreement with them, and thus they could be a candidate ETC model for VHTR fuel block.This research was supported by the National Nuclear R&D Program through the National Research Foundation of Korea(NRF) funded by MSIP; Ministry of Science ICT & Future Planning (No. NRF-2014M2A8A2074314)am201

Hemophagocytic Syndrome in a Patient with Acute Tubulointerstitial Nephritis Secondary to Hepatitis A Virus Infection

Hepatitis A virus (HAV) infection is generally a self-limited disease, but the infection in adults can be serious, to be often complicated by acute kidney injury (AKI) and rarely by virus-associated hemophagocytic syndrome (VAHS). Our patient, a 48-yr-old man, was diagnosed with HAV infection complicated by dialysis-dependent AKI. His kidney biopsy showed acute tubulointerstitial nephritis with massive infiltration of activated macrophages and T cells, and he progressively demonstrated features of VAHS. With hemodialysis and steroid treatment, he was successfully recovered

Implication of Genetic Variants Near TCF7L2, SLC30A8, HHEX, CDKAL1, CDKN2A/B, IGF2BP2, and FTO in Type 2 Diabetes and Obesity in 6,719 Asians

OBJECTIVE— Recent genome-wide association studies have identified six novel genes for type 2 diabetes and obesity and confirmed TCF7L2 as the major type 2 diabetes gene to date in Europeans. However, the implications of these genes in Asians are unclear

Effects of the route of erythropoietin administration on hemoglobin variability and cardiovascular events in hemodialysis patients

Introduction Despite of the routine use of erythropoietin in hemodialysis patients to correct anemia, its administration route’s effects on hemoglobin variability and cardiovascular events remain elusive. Herein, we determined different erythropoietin administration routes’ effects on hemoglobin variability in hemodialysis patients and the associated factors of hemoglobin variability and cardiovascular events. Methods This is a post hoc analysis of a prospective, controlled, randomized, unblinded study with 78 Korean hemodialysis patients receiving intravenous (n = 40) or subcutaneous (n = 38) erythropoietin therapy. We evaluated hemoglobin variability by calculating the frequency of hemoglobin measurements outside the target range during all visits. The high-frequency group was defined by those with hemoglobin variability over the median value (25%) while the low-frequency group was defined by those with hemoglobin variability of <25%. Results In this analysis, 37 patients (51.1%) were male, and the mean age was 50.6 ± 12.5 years. The frequency of the value being outside the target hemoglobin range was higher in the subcutaneous group compared to the intravenous group (p = 0.03). The low-frequency group required significantly lower erythropoietin doses compared to the high-frequency group. In the adjusted Cox analysis, the parameter high group was a significant independent risk factor for cardiovascular events (p = 0.03). Conclusion The risk out of the target hemoglobin range increased with subcutaneous administration compared with intravenous erythropoietin administration in hemodialysis patients. An increased frequency of the value being outside the target hemoglobin range was also associated with an increased risk of cardiovascular events

The paradoxical effect of aldosterone on cardiovascular outcome in maintenance hemodialysis patients

Background Patients with end-stage kidney disease face increased risk of cardiovascular events, and left ventricular diastolic dysfunction (LVDD) contributes to the high occurrence of cardiovascular mortality (CM). Although a high serum aldosterone (sALD) level is involved in the development of cardiovascular complications in the general population, this association is unclear in patients undergoing hemodialysis. We aimed to determine the impact of sALD on LVDD and CM among hemodialysis patients (HDPs). Methods We performed a prospective cohort study of maintenance HDPs without cardiovascular disease. The patients were divided into two groups according to the median level of sALD. All patients underwent baseline echocardiography to evaluate diastolic dysfunction (E/e' ratio > 15). The LVDD and CM rates were compared between the high and low aldosterone groups. Results We enrolled a total of 60 adult patients (mean age, 57.9 ± 12.1 years; males, 30.0%). The low aldosterone group had an increased left ventricular diastolic dimension compared with the high aldosterone group (52.2 ± 8.4 mm vs. 50.3 ± 5.2 mm, respectively; p = 0.03). Low log-aldosterone (odds ratio [OR], 0.40; 95% confidence interval [CI], 0.19–0.86) and large left atrial dimension (OR, 1.31; 95% CI, 1.11–1.54) were independent risk factors for LVDD at baseline. In addition, Cox regression analysis demonstrated that low sALD was an independent predictor of CM in HDPs (hazard ratio, 0.46; 95% CI, 0.25–0.85; p = 0.01) during follow-up. Conclusion Low sALD was not only associated with LVDD but was also an independent predictor of CM among HDPs regardless of their interdialytic weight gain