The French 600 MWe Advanced Sodium Technological Reactor for Industrial Demonstration (ASTRID) project reached in 2015 the end of its conceptual design phase. The core design studies are being conducted by the CEA with support from AREVA NP and EDF. Innovative design choices for the core have been made to comply with the GEN IV reactor objectives, marking a breakthrough with the former Phénix and SuperPhénix Sodium Fast Reactors. One of the biggest challenges of the last five years was to propose a consistent design for the reflectors and neutron shielding sub-assemblies surrounding the fuel core in order to fulfill ASTRID requirements of minimising the secondary sodium activity level. Heavy iterative studies on both core and sub-assemblies were necessary to propose and evaluate different solutions following a strict value analysis process considering neutron shielding performances, life duration, maturity levels, washing and manufacturing capability, and qualification needs. Evaluated options were reflectors sub-assemblies made of steel or MgO rods, and radial neutron shielding sub-assemblies made of B 4 C or borated steel, with different configurations in the design and in the core layout. This paper presents the iterative engineering studies, conducted by CEA and performed by AREVA NP, concerning the radial shielding sub-assemblies for ASTRID core, from the selection of possible solutions to a final consistent conceptual design.

The French 600 MWe Advanced Sodium Technological Reactor for Industrial Demonstration (ASTRID) project has reached the end of its Conceptual Design phase. The core design studies are being conducted by the CEA with support from AREVA and EDF. Innovative design choices for the core have been made to comply with the GEN IV reactor objectives, marking a break with the former Phénix and SuperPhénix Sodium Fast Reactors. The main objective to improve safety compared with current GEN II or III reactors led to a core design that demonstrates intrinsically safe behaviour. A negative sodium void worth is achieved thanks to a new fuel subassembly design including (U,Pu)O 2 and UO 2 axially heterogeneous fuel pins, a large cladding/small spacer wire bundle, a sodium plenum above the fuel pins, and upper neutron shielding with both enriched and natural boron carbide (B 4 C) which also maintain a low secondary sodium activity level. As these Na-bonded B 4 C pins can lead to the retention of unacceptable amounts of sodium, the whole upper neutron shielding has been made removable on-line through the sub-assembly head just before the washing operations. Finite elements calculations have been performed to increase the stiffness of the stamped spacer pads in order to analyse its effect on the core mechanical behaviour during hypothetical radial core flowering and compaction events. More generally, all design choices for ASTRID have been made with the permanent objective of minimising the sub-assembly height to decrease the overall costs of the boiler reactor and the fuel cycle. This paper describes the fuel sub-assembly design for the ASTRID CFV v4 core at the end of the Conceptual Design phase (AVP2). Focus is placed on innovations and specificities in the design compared with former French SFRs.

Résumé. Nous décrivons les premiers diagnostics X développés actuellement pour le LMJ. Ceux-ci sont principalement dédiés à la qualification de l'installation (mesure de tache focale, contrôle du pointage et de l'équilibrage des faisceaux), mais également au diagnostic de la cavité, du transfert radiatif (mesure de rendement de conversion X), au diagnostic de l'hydrodynamique (expériences de radiographie d'instabilités hydrodynamiques) et à l'imagerie de microballons DT. Ce premier lot de diagnostics comprend deux systèmes de multi imagerie X bidimensionnelle associés à un tube obturateur et un système d'imagerie monodimensionnelle avec une caméra à balayage de fente. Ces trois systèmes d'imagerie X appelés « imageurs X » mesurent le rayonnement dans le domaine [500 eV-15 keV]. Un diagnostic de spectrométrie X large bande fonctionnant dans le domaine [30 eV-20 keV] est également développé. Le design des diagnostics prend en compte les problématiques de vulnérabilité aux produits de tirs, de durcissement aux X-durs, gammas et neutrons, de contamination au tritium. Les contraintes liées à l'exploitation sont également considérées puisque l'intervention humaine au sein des diagnostics doit être limitée au cours d'une campagne d'expériences. Les concepts retenus pour ces diagnostics sont présentés, de même que la caractérisation d'une première maquette de microscope de multi imagerie X.

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