Impacts de le récupération des eaux pluviales sur le régime hydrologique de petits bassins versants partiellement urbanisés

International audienceRainwater harvesting is a relevant and sustainable solution to reduce the pressure on conventional water resources. Rainwater harvesting techniques can as well provide stormwater management benefits through the reduction of runoff volumes. The impact of a wide implementation of these practices on the hydrological regimes of already disturbed catchments however remains unclear. The capture of significant fraction of runoff volume in urbanized areas to satisfy various uses, could in particular result in an over-extraction of water, exacerbating low streamflow issues. In this study, a method associating geodata processing and allotment-scale hydrological modeling is introduced to investigate the impact of rainwater harvesting on the hydrology of two semi-urban catchments, addressing both stormwater management benefits and low-flow effects. Results indicate that rainwater harvesting alone is unlikely to meet usual runoff-control objectives, but as well suggest that a systematic implementation of these practices on upstream catchments that already face low water flow issues might be detrimental to stream health.La récupération des eaux de pluie suscite aujourd'hui un intérêt croissant du fait des incertitudes sur la disponibilité future des ressources en eau. Celle-ci est par ailleurs fréquemment envisagée comme un moyen de limiter à la source les volumes de ruissellement générés niveau des surfaces revêtues, participant ainsi à la gestion des eaux pluviales urbaines. La perspective d'une mise en oeuvre de politiques incitatives de récupération des eaux pluviales impose cependant de s'interroger sur l'incidence de cette pratique sur le régime hydrologique de certains bassins versants. Dans les secteurs urbanisés, pour lesquels le potentiel de développement de la récupération des eaux pluviales est important, l'interception d'une fraction significative du ruissellement pour satisfaire divers usages pourrait en effet conduire à un déséquilibre hydrologique se traduisant par une aggravation des étiages. Une méthode associant modélisation hydrologique et exploitation de données géographiques est ici introduite pour construire différents scénarios de récupération des eaux pluviales et évaluer leur incidence de sur le régime hydrologique deux bassins-versants semi-urbains. L'analyse suggère ici que cette pratique n'est à elle seule pas suffisante pour satisfaire les objectifs usuels de gestion des eaux pluviales mais indique que sa systématisation sur des têtes de bassins versant présentant de faibles débits pourrait en revanche donner lieu à une aggravation des étiage

Mesures des écoulements d'air autours de gouttes de pluie

International audienc

Optical diagnostics development and coupling dedicated to heat, mass and aerosol transfers in a spray for severe accident safety analysis in nuclear power plant

Paper presented at the 6th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, South Africa, 30 June - 2 July, 2008.In order to study the interactions between a spray and an atmosphere representative of a severe accident in a Pressurized Water Reactor, in terms of pressure, temperature and composition (steam and aerosol), the French Institute for Radiological Protection and Nuclear Safety (IRSN) developed the TOSQAN facility. This paper presents the development and qualification of the global rainbow refractometry and Interferometric Laser Imaging for Droplets Sizing (ILIDS) that are respectively dedicated to measure the spray droplets temperature and size. In addition we present an extension of these two techniques in order to determine the aerosol concentration inside the droplet and the aerosol removal rate.vk201

Etude de l'atomisation de jet liquide par flash-boiling sous vide pour la sûreté d'ITER

International audienc

Experimental and numerical approaches of aerosols removal in spray for nuclear reactor containment application

Paper presented at the 6th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, South Africa, 30 June - 2 July, 2008.TOSQAN is an experimental program undertaken by the Institut de Radioprotection et de Sûreté Nucléaire (IRSN) in order to perform thermal hydraulic containment studies. The TOSQAN facility is a large enclosure devoted to simulate typical accidental thermal hydraulic flow conditions in nuclear Pressurized Water Reactor (PWR) containment. The TOSQAN facility, which is highly instrumented with non-intrusive optical diagnostics, is particularly adapted to nuclear safety CFD code validation. The present work is devoted to study the interaction of a water spray injection used as a mitigation means in order to reduce the gas pressure and temperature in the containment, to produce gases mixing and washout of fission products. In order to have a better understanding of heat and mass transfers between the spray droplets and the gas mixture, and to analyze mixing effects due to spray activation, we performed detailed characterization of the two-phase flow.vk201

R&D : Impact des particules incandescentes dans les réseaux de ventilation

Les particules métalliques incandescentes produites par les découpes à chaud sur les chantiers de démantèlement peuvent diminuer l’efficacité des filtrations et conduire à une perte d’intégrité du confinement, voire à un incendie. L’IRSN a engagé, en lien avec EDF-CIDEN, un programme de recherche pour étudier l’agression d’un filtre très haute efficacité par des particules incandescentes et, à terme, évaluer les dispositions prises par les exploitants en matière de confinement dynamique des opérations de maintenance, de démantèlement ou d’assainissement

Mesures des écoulements d'air autours de gouttes de pluie

International audienc

OECD International Standard Problem ISP-47 on containment thermal-hydraulics—Conclusions of the TOSQAN part

International audienceThe main objective of the ISP-47 is to assess the capabilities of Lumped-Parameter and ComputationalFluid Dynamics codes in the area of nuclear containment thermal-hydraulics. Three experimentalfacilities TOSQAN, MISTRA and ThAI were involved in this project. The present paper summarizes thespecifications, the results and the conclusions obtained for the TOSQAN open benchmark exercise.Wall condensation, steam injection in air or air/helium atmospheres, and buoyancy were addressedunder well-controlled initial conditions in the simple TOSQAN geometry. Detailed gas velocity and gasconcentration (air, steam and helium) fields were obtained for the first time in such an exercise.It is found that the model predictions fit with a generally good accuracy the experimental resultsobtained during condensation steady-state conditions, but the flow conditions in the transition regimeare not well reproduced by the calculations: some of the major transient phenomena are not alwayscorrectly modelled and if so, the transient evolutions or the levels of the concerned variables are not thesame in the calculations and in the experiment. Furthermore, two kinds of measurements were specificfor TOSQAN: boundary layer measurements and turbulence variables, which were addressed for the firsttime in such an exercise. It is concluded that more sophisticated modelling in CFD codes for the boundarylayers should be developed and that turbulence variables should be addressed more intensively in furtherexercises

Quantification de la fraction remise en suspension de simulant d'oxyde de plutonium dans un dispositif de dégradation thermique à petite échelle

International audienceAn IRSN programme, named FIGARO, focuses on glovebox fires with the aim of quantifying aerosol releases. This paper summarises the methodology developed in this project to quantify the aerosol resuspension through the measurement of the aerosol release fraction in a small-scale experimental facility of the IRSN (Saclay, France). The facility allows thermal degradations to study aerosol airborne resuspension by fire. The resuspension is characterized by the quantification of the aerosol release fraction from glovebox wall slabs. Investigations were carried out to identify surrogate and tracer particles. The contamination of the wall slabs was realised with a specific, qualified contaminating system