Capitalisation des connaissances dans le cadre d'un transfert industriel

National audienceCet article présente le cas de l'utilisation d'une méthode de gestion des connaissances dans le cadre du transfert industriel d'un produit de la R&D. La démarche s'appuie sur la mise en contexte par modélisation de l'activité, l'identification des données par modélisation conceptuelle et le recueil de l'expertise par adaptation d'un formalisme de tâches. Cet article expose les réalisations qui ont jalonné l'action et les difficultés rencontrées. La principale de ces difficultés est due à la forte évolutivité du système, du contexte et de l'expertise associée. Cette évolutivité est due à la nécessaire poursuite de l'effort de R&D, en parallèle aux actions de transfert et d'industrialisation. Face à ce type de problématique, les méthodes de gestion des connaissances, qu'elles relèvent de la systémique, du génie logiciel ou du génie cognitif sont encore rares à intégrer les aspects ayant trait à l'évolution et au temps et ce thème constitue un axe d'étude prometteur. Cette expérience nous conduit aussi à replacer la problématique du transfert de connaissances au coeur des questions de management et d'organisation

Development and validation of agglomeration model for CFD simulations of aerosol dispersion during Fukushima fuel debris retrieval

International audienceThe general context of this article is related to demonstrate the feasibility of the use of the laser cutting technique for the fuel debris retrieval on the damaged reactors of Fukushima Dai-ichi. IRSN is involved in a project led by ONET, in collaboration with CEA, to bring relevant elements to analyze the risk occurred by the dispersion of aerosols emitted by the dismantling operations. During the laser cutting operations for retrieving the fuel debris in air condition, particles will be produced, inducing a potential risk of dispersion into the environment. Hence, evaluating the amount of aerosols able to deposit on the walls and those able to be released into the environment is one of the safety key issues in the dismantling actions of reactors of Fukushima Dai-ichi. For that, IRSN performed computational fluid dynamics (CFD) simulations of dispersion, agglomeration and deposition of particles whose size distribution was measured during laser cutting operations of inactive fuel simulants (Chagnot et al., 2018, Porcheron et al., 2018).These simulations were conducted with the ANSYS CFX CFD code into which a moment method called DQMOM and a deposition model previously developed by IRSN (Nerisson et al., 2011) were implemented. The first numerical results (Gelain et al., 2018) showed a quite good agreement with the experimental ones for a standard particle size distribution (lognormal with one mode), but some improvements are needed for less classical distributions such bimodal ones.The work presented here proposes an alternative method to the previous one allowing taking into account different kinds of particle size distribution in the CFD simulations of particle agglomeration. This method uses the real experimental distribution to calculate the distribution moments which are then directly implemented in the simulation instead of using a lognormal fit. The previous CFD simulations were calculated again by using this method and showed a better agreement with the experimental results issued from aerosol source term characterization for both absolute values and time evolutions

Development and validation of agglomeration model for CFD simulations of aerosol dispersion during Fukushima fuel debris retrieval

International audienceThe general context of this article is related to demonstrate the feasibility of the use of the laser cutting technique for the fuel debris retrieval on the damaged reactors of Fukushima Dai-ichi. IRSN is involved in a project led by ONET, in collaboration with CEA, to bring relevant elements to analyze the risk occurred by the dispersion of aerosols emitted by the dismantling operations. During the laser cutting operations for retrieving the fuel debris in air condition, particles will be produced, inducing a potential risk of dispersion into the environment. Hence, evaluating the amount of aerosols able to deposit on the walls and those able to be released into the environment is one of the safety key issues in the dismantling actions of reactors of Fukushima Dai-ichi. For that, IRSN performed computational fluid dynamics (CFD) simulations of dispersion, agglomeration and deposition of particles whose size distribution was measured during laser cutting operations of inactive fuel simulants (Chagnot et al., 2018, Porcheron et al., 2018).These simulations were conducted with the ANSYS CFX CFD code into which a moment method called DQMOM and a deposition model previously developed by IRSN (Nerisson et al., 2011) were implemented. The first numerical results (Gelain et al., 2018) showed a quite good agreement with the experimental ones for a standard particle size distribution (lognormal with one mode), but some improvements are needed for less classical distributions such bimodal ones.The work presented here proposes an alternative method to the previous one allowing taking into account different kinds of particle size distribution in the CFD simulations of particle agglomeration. This method uses the real experimental distribution to calculate the distribution moments which are then directly implemented in the simulation instead of using a lognormal fit. The previous CFD simulations were calculated again by using this method and showed a better agreement with the experimental results issued from aerosol source term characterization for both absolute values and time evolutions

Récupération du corium des réacteurs de Fukushima Dai-ichi : efficacité d'épuration des aérosols produits lors de la découpe au laser sous eau de simulants de corium

International audienc

Fukushima Daiichi fuel debris simulant materials for the development of cutting and collection technologies

International audienceCutting fuel debris (solidified corium) is an important issue for the decommissioning of Fukushima Daiichi Nuclear Power Station. The main reasons for developing and using fuel debris simulants are presented. The relative merits of the various types of materials (stainless steel, zirconium, sintered alumina-zirconia, cast fused zirconia, metal+zirconia, melted inactive simulants, prototypic fuel debris simulant, irradiated fuel debris simulant) that can be used to simulate fuel debris cutting have been assessed against criteria relevant for the cutting technique itself (hardness, melting temperature, elastic modulus, toughness, heterogeneity) as well as relevant to (radioactive) aerosol and combustible gas generation. It appears that simplified simulants can be used for the development of fuel debris cutting techniques but have some limitations in terms of representativity so that melted inactive fuel debris simulant must be used to assess the cutting performance. Concerning combustible gas generation, zirconium plates will provide an upper bound in term of underwater generation of hydrogen. Finally, for aerosol and dust generation, it appears that non-radioactive simulant cannot correctly represent the aerosol formation during cutting. Prototypic fuel debris simulant, using depleted uranium and natural isotopic composition for the fission product elements are the best available option for determination of cutting secondary outlet

Implementation and validation of an aerosol collection model by a spray in a CFD code – Application to the scavenging of aerosols emitted during laser cutting operations of fuel debris for the dismantling of the damaged reactors of Fukushima Dai-ichi

International audienceThe general context of this article is related to the dismantling of the damaged reactors of Fukushima Dai-ichi and more specifically to the use of the laser cutting technique for the fuel debris retrieval on the damaged reactors. IRSN is involved in a project led by ONET, in collaboration with CEA, to bring relevant elements to analyze the risk involved by the dispersion of aerosols emitted by the dismantling operations. During the laser cutting operations for retrieving the fuel debris in air condition, particles will be produced, inducing a potential risk of dispersion into the environment. Hence, their collection, to prevent their release into the environment, is one of the safety key issues in the dismantling actions of Fukushima Dai-ichi reactors. For that, IRSN performed CFD simulations of aerosol scavenging by a spray, to evaluate the capability of collection by this technique.These simulations, conducted with the ANSYS CFX code, use an eulerian method for the continuous phase and a lagrangian method for the spray for which a collection model detailed by Plumecocq [1] or Marchand [2] was implemented. Aerosols are modelled by the way of a DQMOM population balance implemented by Gelain et al [3] (already used for recent simulations in the same context) and enriched with a deposition model developed by Nerisson et al [4].In a first time, CFD simulations are performed with the geometry of the TOSQAN vessel, comparatively to experimental results presented in a companion paper. This first step allows to validate the implementation of the collection model and to study the sensitivity to the aerosol size.In a second time, the CFD simulations are conducted with the geometry of the pedestal of Fukushima Dai-ichi reactors, to be more representative of a realistic case. In this configuration, sensitivity studies are described, highlighting the influence of a multispray and of thermal-hydraulic conditions (temperature) on aerosol scavenging

Development and validation of an agglomeration model for CFD simulations of aerosol dispersion in the frame of Fukushima fuel debris retrieval

International audienceThe general context of this article is related to demonstrate the feasibility of using laser cutting technique for the retrieval of the fuel debris of the Fukushima Daiichi damaged reactors. IRSN is involved in a project led by ONET Technologies, in collaboration with CEA, to bring relevant elements to analyse the risk occurred by the dispersion of aerosols emitted by the dismantling operations. During the laser cutting operations dedicated to retrieve the fuel debris in air condition, particles will be produced, inducing a potential risk of dispersion into the environment. Hence, evaluating the fate of these particles in terms of wall deposition and release into the environment is one of the safety key issues for these dismantling operations. In this objective, IRSN performed CFD simulations of dispersion, agglomeration and deposition of particles representative of inactive fuel debris simulants [1][2][3][4].The first numerical results [5] showed a quite good agreement with the experimental ones but also the need to use more realistic and complex particle size distributions (PSD) than the one used in these first simulations (lognormal distribution). Hence, the work presented here proposes an alternative method to better initialize the agglomeration calculation, in order to take account for different kinds of particle size distribution in the CFD simulations and to better evaluate the fate of aerosols produced by the debris cutting in the damaged reactors of Fukushima-Daiichi pedestal

Implementation and validation of an aerosol collection model by a spray in a CFD code – Application to the scavenging of aerosols emitted during laser cutting operations of fuel debris for the dismantling of the damaged reactors of Fukushima Dai-ichi

International audienceThe general context of this article is related to the dismantling of the damaged reactors of Fukushima Dai-ichi and more specifically to the use of the laser cutting technique for the fuel debris retrieval on the damaged reactors. IRSN is involved in a project led by ONET, in collaboration with CEA, to bring relevant elements to analyze the risk involved by the dispersion of aerosols emitted by the dismantling operations. During the laser cutting operations for retrieving the fuel debris in air condition, particles will be produced, inducing a potential risk of dispersion into the environment. Hence, their collection, to prevent their release into the environment, is one of the safety key issues in the dismantling actions of Fukushima Dai-ichi reactors. For that, IRSN performed CFD simulations of aerosol scavenging by a spray, to evaluate the capability of collection by this technique.These simulations, conducted with the ANSYS CFX code, use an eulerian method for the continuous phase and a lagrangian method for the spray for which a collection model detailed by Plumecocq [1] or Marchand [2] was implemented. Aerosols are modelled by the way of a DQMOM population balance implemented by Gelain et al [3] (already used for recent simulations in the same context) and enriched with a deposition model developed by Nerisson et al [4].In a first time, CFD simulations are performed with the geometry of the TOSQAN vessel, comparatively to experimental results presented in a companion paper. This first step allows to validate the implementation of the collection model and to study the sensitivity to the aerosol size.In a second time, the CFD simulations are conducted with the geometry of the pedestal of Fukushima Dai-ichi reactors, to be more representative of a realistic case. In this configuration, sensitivity studies are described, highlighting the influence of a multispray and of thermal-hydraulic conditions (temperature) on aerosol scavenging

Development and validation of an agglomeration model for CFD simulations of aerosol dispersion in the frame of Fukushima fuel debris retrieval

This article is devoted to demonstrate the feasibility of laser cutting technique for the fuel debris retrieval into the Fukushima Daiichi damaged reactors. IRSN is involved in a project led by ONET Technologies, in collaboration with CEA, to evaluate the risk occurred by the dispersion of aerosols emitted by the dismantling operations [4]. During the laser cutting operations of fuel debris in air condition, particles will be produced, inducing a potential risk of dispersion into the environment. Hence, evaluating the fate of these particles after their emission is one of the safety key issues for these dismantling operations. In this objective, IRSN performed CFD simulations of dispersion of particles representative of inactive fuel debris simulants (1)(2)(3)(4). The first numerical results (5) showed a quite good agreement but some improvements were needed to take into account complex particle size distributions (PSD). Consequently, this article proposes an alternative method to better initialize the agglomeration calculation, in order to take account for different kinds of particle size distribution in the CFD simulations and to better evaluate the fate of aerosols produced by the debris cutting in the damaged reactors of Fukushima-Daiichi pedestal