Dispersion enhancement and damping by buoyancy driven flows in 2D networks of capillaries

The influence of a small relative density difference on the displacement of two miscible liquids is studied experimentally in transparent 2D networks of micro channels. Both stable displacements in which the denser fluid enters at the bottom of the cell and displaces the lighter one and unstable displacements in which the lighter fluid is injected at the bottom and displaces the denser one are realized. Except at the lowest mean flow velocity U, the average $C(x,t)$ of the relative concentration satisfies a convection-dispersion equation. The dispersion coefficient is studied as function of the relative magnitude of fluid velocity and of the velocity of buoyancy driven fluid motion. A model is suggested and its applicability to previous results obtained in 3D media is discussed

Real-time analysis of polymer flow under real processing conditions applied to microinjection molding

International audienc

Wave propagation simulation in the upper core of sodium-cooled fast reactors using a spectral-element method for heterogeneous media

ASTRID project, French sodium cooled nuclear reactor of 4th generation, is under development at the moment by Alternative Energies and Atomic Energy Commission (CEA). In this project, development of monitoring techniques for a nuclear reactor during operation are identified as a measure issue for enlarging the plant safety. Use of ultrasonic measurement techniques (e.g. thermometry, visualization of internal objects) are regarded as powerful inspection tools of sodium cooled fast reactors (SFR) including ASTRID due to opacity of liquid sodium. In side of a sodium cooling circuit, heterogeneity of medium occurs because of complex flow state especially in its operation and then the effects of this heterogeneity on an acoustic propagation is not negligible. Thus, it is necessary to carry out verification experiments for developments of component technologies, while such kind of experiments using liquid sodium may be relatively large-scale experiments. This is why numerical simulation methods are essential for preceding real experiments or filling up the limited number of experimental results. Though various numerical methods have been applied for a wave propagation in liquid sodium, we still do not have a method for verifying on three-dimensional heterogeneity. Moreover, in side of a reactor core being a complex acousto-elastic coupled region, it has also been difficult to simulate such problems with conventional methods. The objective of this study is to solve these 2 points by applying three-dimensional spectral element method. In this paper, our initial results on three-dimensional simulation study on heterogeneous medium (the first point) are shown. For heterogeneity of liquid sodium to be considered, four-dimensional temperature field (three spatial and one temporal dimension) calculated by computational fluid dynamics (CFD) with Large-Eddy Simulation was applied instead of using conventional method (i.e. Gaussian Random field). This three-dimensional numerical experiment yields that we could verify the effects of heterogeneity of propagation medium on waves in Liquid sodium

Overview of the system alone and system/CFD coupled calculations of the PHENIX Natural Circulation Test within the THINS project

International audienceThe PHENIX sodium cooled fast reactor started operation in 1973 and was shut down in 2009. Before decommissioning, an ultimate test program was designed and performed to provide valuable data for the development of future sodium cooled fast reactors, as the so-called Astrid prototype in France. Among these ultimate tests, a thermal-hydraulic Natural Convection Test (NCT) was set-up in June 2009. Starting from a reduced power state of 120 MWt, the NCT consists of a loss of the heat sink combined with a reactor scram and a primary pumps trip leading to stabilized natural circulation in the primary sodium system. The thermal-hydraulics innovative system project (THINS project), sponsored by the European Community in the frame of the 7th FP has selected this transient for validation of both stand-alone system code simulations and coupled simulations using system and CFD codes. Participants from three organizations (CEA, IRSN and KIT) have addressed this transient using different system codes (CATHARE, DYN2B and ATHLET) and CFD codes (TRIO-U and OPEN FOAM). The present paper depicts the different modeling approaches, methodologies and compares the numerical results with the available experimental data. Finally, the main lessons learned from the work performed within the THINS project on the PHENIX NCT with respect to code development and validation are summarized. © 2014 Elsevier B.V. All rights reserved

The PHENIX Final Tests

The 250 MWe (140 MWe since 1993) PHENIX sodium cooled fast reactor was shut down on March 6th, 2009. Before decommissioning, a final set of tests were performed during the May 2009 – January 2010 period covering core physics, fuel behaviour and thermalhydraulics areas. Detailed analysis of the tests results is ongoing. It will be used for the extension of the validation of ERANOS and DARWIN codes for core physics, TRIO_U and CATHARE for thermalhydraulics and GERMINAL for fuel behaviour. In addition, the program included two tests related to the comprehension of the four negative reactivity transients (AURN in French acronym) experienced during the reactor operation in ‘89 and ‘90 and not yet fully explained. This was also a great opportunity to involve young engineers in the different processes like the design of the tests, their carrying out, and the analysis of the results. The standard instrumentation of the reactor was completed by specifically designed devices

International benchmark on the natural convection test in Phenix reactor

The French Phenix sodium cooled fast reactor (SFR) started operation in 1973 and was stopped in 2009. Before the reactor was definitively shutdown, several final tests were planned and performed, including a natural convection test in the primary circuit. During this natural convection test, the heat rejection provided by the steam generators was disabled, followed several minutes later by reactor scram and coast-down of the primary pumps. The International Atomic Energy Agency (IAEA) launched a Coordinated Research Project (CRP) named "control rod withdrawal and sodium natural circulation tests performed during the Phenix end-of-life experiments". The overall purpose of the CRP was to improve the Member States' analytical capabilities in the field of SFR safety. An international benchmark on the natural convection test was organized with "blind" calculations in a first step, then "post-test" calculations and sensitivity studies compared with reactor measurements. Eight organizations from seven Member States took part in the benchmark: ANL (USA), CEA (France), IGCAR (India), IPPE (Russian Federation), IRSN (France), KAERI (Korea), PSI (Switzerland) and University of Fukui (Japan). Each organization performed computations and contributed to the analysis and global recommendations. This paper summarizes the findings of the CRP benchmark exercise associated with the Phenix natural convection test, including blind calculations, post-test calculations and comparisons with measured data. General comments and recommendations are pointed out to improve future simulations of natural convection in SFRs. © 2013 Elsevier B.V

Genetic Analysis of Avian Influenza Virus from Wild Birds and Mallards Reared for Shooting in Denmark

This paper reports complementary experimental and theoretical investigations focussed on the laser milling of theamorphous alloy Zr41.2Ti13.8Cu12.5Ni10Be22.5, also known as Vitreloy 1, in ambient air, using 220 ns pulses. Theconducted experiments showed that the formation of crystalline precipitates required a relatively large overlapbetween pulses when machining with a fluence of 6 J/cm2 and a pulse repetition frequency of 250 KHz. The loss ofthe fully amorphous nature of this material could also be achieved for a substantially smaller pulse overlap andfrequency. In this case, the lower thermal load associated with the reduction in the value of these parameters wasbalanced by increasing the delivered fluence by one order of magnitude, i.e. 70 J/cm2. Using theoretical temperatureprofiles associated with the considered laser milling operations, it was suggested that different crystallisationphenomena could be at play between both levels of fluence values utilised