Validation of 3D neutronic-thermalhydraulic coupled codes RELAP5/PARCSv2.7 and TRACEv5.0P3/PARCSv3.0 against a PWR control rod drop transient

[EN] In nuclear safety field, neutronic and thermalhydraulic codes performance is an important issue. New capabilities implementation, as well as models and tools improvements are a significant part of the community effort in looking for better Nuclear Power Plants (NPP) designs. A procedure to analyze the PWR response to local deviations on neutronic or thermalhydraulic parameters is being developed. This procedure includes the simulation of Incore and Excore neutron flux detectors signals. A control rod drop real plant transient is used to validate the used codes and their new capabilities. Cross-section data are obtained by means of the SIMTAB methodology. Detailed thermalhydraulic models were developed: RELAP5 and TRACE models simulate three different azimuthal zones. Besides, TRACE model is performed with a fully 3D core, thus, the cross-flow can be obtained. A cartesian vessel represents the fuel assemblies and a cylindrical vessel the bypass and downcomer. Simulated detectors signals are obtained and compared with the real data collected during a control rod drop trial at a PWR NPP and also with data obtained with SIMULATE-3K code.The authors would like to acknowledge the economic support provided by Centrales Nucleares Almaraz-Trillo (CNAT) and IBERDROLA Ingeniería y Construcción (Iberinco) for the realization of this work, and express their great appreciation to Arturo López, Juan Antonio Bermejo and Alberto Ortego for their valuable collaboration and their willingness to develop this work. This work has also been supported by the Spanish Ministerio de Economía y Competitividad, through the projects NUC-MULTPHYS (ENE2012-34585) and VALIUN-3D (ENE2011-22823), and the Generalitat Valenciana (GVA), through the project PROMETEO II/2014/008.Garcia-Fenoll, M.; Mesado Melia, C.; Barrachina, T.; Miró Herrero, R.; Verdú Martín, GJ.; Bermejo, JA.; López, A.... (2017). Validation of 3D neutronic-thermalhydraulic coupled codes RELAP5/PARCSv2.7 and TRACEv5.0P3/PARCSv3.0 against a PWR control rod drop transient. Journal of Nuclear Science and Technology. 54(8):908-919. https://doi.org/10.1080/00223131.2017.1329035S90891954

Free abdominal fluid without obvious solid organ injury upon CT imaging: an actual problem or simply over-diagnosing?

Whereas a non-operative approach for hemodynamically stable patients with free intraabdominal fluid in the presence of solid organ injury is generally accepted, the presence of free fluid in the abdomen without evidence of solid organ injury not only presents a challenge for the treating emergency physician but also for the surgeon in charge. Despite recent advances in imaging modalities, with multi-detector computed tomography (CT) (with or without contrast agent) usually the imaging method of choice, diagnosis and interpretation of the results remains difficult. While some studies conclude that CT is highly accurate and relatively specific at diagnosing mesenteric and hollow viscus injury, others studies deem CT to be unreliable. These differences may in part be due to the experience and the interpretation of the radiologist and/or the treating physician or surgeon

SARS-CoV-2 Infection Is at Herd Immunity in the Majority Segment of the Population of Qatar.

BACKGROUND: Qatar experienced a severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) epidemic that disproportionately affected the craft and manual worker (CMW) population, who comprise 60% of the total population. This study aimed to assess ever and/or current infection prevalence in this population. METHODS: A cross-sectional population-based survey was conducted during July 26 to September 09, 2020, to assess both anti-SARS-CoV-2 positivity through serological testing and current infection positivity through polymerase chain reaction (PCR) testing. Associations with antibody and PCR positivity were identified through regression analyses. RESULTS: The study included 2641 participants, 69.3% of whom were <40 years of age. Anti-SARS-CoV-2 positivity was 55.3% (95% CI, 53.3%-57.3%) and was significantly associated with nationality, geographic location, educational attainment, occupation, and previous infection diagnosis. PCR positivity was 11.3% (95% CI, 9.9%-12.8%) and was significantly associated with nationality, geographic location, occupation, contact with an infected person, and reporting 2 or more symptoms. Infection positivity (antibody and/or PCR positive) was 60.6% (95% CI, 58.6%-62.5%). The proportion of antibody-positive CMWs who had a prior SARS-CoV-2 diagnosis was 9.3% (95% CI, 7.9%-11.0%). Only seven infections were ever severe, and only 1 was ever critical-an infection severity rate of 0.5% (95% CI, 0.2%-1.0%). CONCLUSIONS: Six in every 10 CMWs in Qatar have been infected, suggestive of reaching the herd immunity threshold. Infection severity was low, with only 1 in every 200 infections progressing to be severe or critical. Only 1 in every 10 infections had been previously diagnosed, which is suggestive of mostly asymptomatic or mild infections

Novel Extraction Method for Source and Drain Series Resistances in Silicon Nanowire Metal-Oxide-Semiconductor Field-Effect-Transistors Based on Radio-Frequency Analysis

In this work, we present a novel analytical method based on radio-frequency (RF) analysis for the accurate and reliable extraction of source and drain (S/D) series resistances in silicon nanowire (SNW) metal-oxide-semiconductor field-effect transistors (MOSFETs). The proposed method provides decomposed RF model equations for the gate-bias-independent off-state and gate-bias-dependent on-state components from both Y-and Z-parameters. The validity of our extraction method for S/D series resistances in SNW MOSFETs has been carefully tested in comparison with that of a previously reported method as well as with the physical three-dimensional (3D) device simulation. The schematically modeled Y-and Z-parameters have demonstrated excellent agreement with the numerical 3D device simulation results for various SNW MOSFET structures up to the 100 GHz frequency regime.close0