A concurrent, generational garbage collector for a multithreaded implementation of ML

International audienceThis paper presents the design and implementation of a "quasi real-time" garbage collector for Concurrent Caml Light, an implementation of ML with threads. This two-generation system combines a fast, asynchronous copying collector on the young generation with a non-disruptive concurrent marking collector on the old generation. This design crucially relies on the ML compile-time distinction between mutable and immutable objects

The OCaml system release 5.0: Documentation and user's manual

This manual documents the release 5.0 of the OCaml system. It is organized as follows. Part I, "An introduction to OCaml", gives an overview of the language. Part II, "The OCaml language", is the reference description of the language. Part III, "The OCaml tools", documents the compilers, toplevel system, and programming utilities. Part IV, "The OCaml library", describes the modules provided in the standard library. Part V, “Indexes”, contains an index of all identifiers defined in the standard library, and an index of keywords

Variation in clutch size in relation to nest size in birds

Peer reviewe

Influence du retraitement physico-chimique du sel combustible sur le comportement du MSFR et sur le dimensionnement de son unité de retraitement

In order to face with the growing of the energy demand, the nuclear industry has to reach the fourth generation technology. Among those concept, molten salt reactor, and especially the fast neutron spectrum configuration, seems very promising: indeed breeding is achievable while the feedback coefficient are still negative. However, the reprocessing salt scheme is not totally set down yet. A lot of uncertainties remain on chemical properties of the salt. Thanks to numerical simulation we studied the behavior of the molten Salt Fast Reactor coupled to a nominal repossessing unit. We are now able to determine heat transfer and radiation in each elementary step of the unit and, by this way determine those that need special study for radioprotection. We also studied which elements are fundamental to extract for the reactor operation. Finally, we present a sensibility analysis of the chemical uncertainties to few relevant properties of the reactor behaviorL'industrie électronucléaire, pour faire face aux besoins énergétiques croissant, à besoin de développer une nouvelle génération de réacteur : la quatrième génération. Parmi les six candidats, on trouve les réacteurs à sels fondus, qui, en configuration rapide, semble avoir de très bonnes propriétés : la régénération est facilement accessible tout en gardant des coefficients de contre-réaction négatifs. Le procédé de retraitement du sel combustible n'est toutefois toujours pas établi de manière définitive. Beaucoup d'incertitude sur les paramètres physicochimiques des sels combustibles empêchent de définir de manière précise chaque étape du procédé. Grâce à la simulation numérique nous avons pu étudier le comportement du cœur du réacteur couplé à une unité de retraitement de référence. De cette manière nous avons pu quantifier les flux de chaleurs et les radiations pour identifier les étapes qui nécessiteront une attention particulière lors du dimensionnement. Nous avons aussi pu identifier les éléments pour lesquels une mauvaise extraction mettrait en péril le bon fonctionnement du réacteur. Enfin, toujours grâce à la simulation numérique, ce travail présente une analyse des sensibilités du procédé de retraitement sur un certain nombre de grandeurs physique représentative du cœur du MSFR

Modélisation des systèmes nucléaires électrogènes pour l'étude des futurs possibles de l'énergie nucléaire

L'évolution de la place du nucléaire au sein des systèmes de production électrique français, européen et mondial justifie un exercice de prospective basé sur de solides simulations de scénarios possibles pour le futur de l'énergie nucléaire. La difficulté de ces simulations provient de la modélisation du recyclage des matières. En effet la composition initiale pour chaque chargement de réacteur dépend des compositions des stocks de matières disponibles à recycler, qui sont inconnues à priori puisque ce sont des résultats de calculs. Le comportement sous irradiation de ces combustibles dépend également de la composition initiale. Un code de cycle performant, capable de simuler des scénarios mettant en oeuvre le recyclage des combustibles usés, doit alors intégrer ces spécificités pour espérer produire des résultats quantitatifs, et c'est ce qui a été fait dans le code CLASS développé au CNRS/IN2P3 depuis 2012

Development of a multi-zone fuel loading model for scenario studies involving ASTRID-like SFRs with the CLASS code

Many scenario studies conducted by several countries consider the progressive deployment of low void effect Sodium-cooled Fast Reactor (SFR) [1]. Different options are investigated regarding the deployment time of this kind of Generation IV reactor, depending on the global nuclear energy development and the national energy mix strategies. In France, the SFR core design often used in this type of scenario is based on the 600 MWe ASTRID concept developed by the CEA and its industrial partners [2]. To reach a negative void coefficient, the core is divided in two radial parts: an inner and an outer core, which alternate different fertile and fissile zones.One challenge to simulate fuel cycle with fuel reprocessing is to consider the evolution of the materi-als to be recycled over time. Indeed, spent fuel compositions vary at each reprocessing as it de-pends of each fuel history (in which reactor it has been irradiated, burn-up achieved, cooling time…). Hence, to build a fresh fuel adapted to one reactor specificities, the CLASS (Core Library for Ad-vanced Scenario Simulation) software [3], a dynamic fuel cycle simulation code developed by CNRS in collaboration with IRSN, uses dedicated fuel loading models. In the case of this SFR, the aim is to keep the fuel heterogeneity of the core. To do that, the devel-opment of a new dedicated fresh fuel loading model taking into account the different fuel zones of the reactor was needed. This model is based on the reactor's neutron characteristics and it is usable for a wide variability of spent fuels to be recycled. In this way, for a given isotopic composition, the Pu contents of both the inner and the outer core are iteratively adjusted to reach a target power distri-bution in the core and a target multiplication factor (keff) at the beginning of cycle. An analysis of this SFR behavior during irradiation shows a relation between the power distribution and the ratio of Pu contents, between the inner and outer core. This relation is used by the model to calculate the initial Pu contents for a given isotopic composition assuring the target power distribu-tion. Then, to determine the keff associated to that specific fresh fuel composition, the model uses Artificial Neural Network (ANN) trained on a corresponding databank. This databank is composed of 1000 full core depletion Monte Carlo simulations generated with the VESTA code [4], in which MCNP is used as the transport solver. Each calculation differs from the other by the initial fresh fuel sam-pled in the parameter space of compositions covering many potential SFR fuel management strate-gies. This new model completes the implementation of a previous multi-zone fuel irradiation model devel-oped for this SFR [5]. Thanks to these two multi-zone models, the simulation of scenarios integrating multi-zone SFR with the code CLASS shows that the plutonium breeder, break-even or burner SFR property is highly dependent on its fresh fuel composition

Development of a multi-zone fuel loading model for scenario studies involving ASTRID-like SFRs with the CLASS code

Many scenario studies conducted by several countries consider the progressive deployment of low void effect Sodium-cooled Fast Reactor (SFR) [1]. Different options are investigated regarding the deployment time of this kind of Generation IV reactor, depending on the global nuclear energy development and the national energy mix strategies. In France, the SFR core design often used in this type of scenario is based on the 600 MWe ASTRID concept developed by the CEA and its industrial partners [2]. To reach a negative void coefficient, the core is divided in two radial parts: an inner and an outer core, which alternate different fertile and fissile zones.One challenge to simulate fuel cycle with fuel reprocessing is to consider the evolution of the materi-als to be recycled over time. Indeed, spent fuel compositions vary at each reprocessing as it de-pends of each fuel history (in which reactor it has been irradiated, burn-up achieved, cooling time…). Hence, to build a fresh fuel adapted to one reactor specificities, the CLASS (Core Library for Ad-vanced Scenario Simulation) software [3], a dynamic fuel cycle simulation code developed by CNRS in collaboration with IRSN, uses dedicated fuel loading models. In the case of this SFR, the aim is to keep the fuel heterogeneity of the core. To do that, the devel-opment of a new dedicated fresh fuel loading model taking into account the different fuel zones of the reactor was needed. This model is based on the reactor's neutron characteristics and it is usable for a wide variability of spent fuels to be recycled. In this way, for a given isotopic composition, the Pu contents of both the inner and the outer core are iteratively adjusted to reach a target power distri-bution in the core and a target multiplication factor (keff) at the beginning of cycle. An analysis of this SFR behavior during irradiation shows a relation between the power distribution and the ratio of Pu contents, between the inner and outer core. This relation is used by the model to calculate the initial Pu contents for a given isotopic composition assuring the target power distribu-tion. Then, to determine the keff associated to that specific fresh fuel composition, the model uses Artificial Neural Network (ANN) trained on a corresponding databank. This databank is composed of 1000 full core depletion Monte Carlo simulations generated with the VESTA code [4], in which MCNP is used as the transport solver. Each calculation differs from the other by the initial fresh fuel sam-pled in the parameter space of compositions covering many potential SFR fuel management strate-gies. This new model completes the implementation of a previous multi-zone fuel irradiation model devel-oped for this SFR [5]. Thanks to these two multi-zone models, the simulation of scenarios integrating multi-zone SFR with the code CLASS shows that the plutonium breeder, break-even or burner SFR property is highly dependent on its fresh fuel composition