[en] In the framework of the French Act of 28 June 2006 about nuclear materials and waste management, a GEN IV and actinides incineration demonstration prototype is to be commissioned in the 2020 decade. In this objective a prototype called ASTRID (Advanced Sodium Technological Reactor for Industrial Demonstration) is proposed to demonstrate the progress made in SFR technology at an industrial scale by qualifying innovative options, some of which still remain open in the areas requiring improvements, especially safety and operability. More specifically, we aim for a level of safety that is at least equivalent to that of the EPR (third generation), with improvements made in SFR-specific fields. The integration of safety issues in the early phase of the design of ASTRID is necessarily expected. For this purpose, CEA and its partners AREVA and EDF have planned to perform a level-1 PSA to support and orientate the preliminary design of ASTRID reactor. This paper presents the PSA approach and current studies for the assessment of safety systems and the future work to be done for the 2012-2014 period. The preliminary preparation of PSA studies is presented: objectives and scope of the early design phase PSA, definition of core damage states, selection and grouping of initiating events, assessment of safety functions and related systems. Work under progress is also presented: modelling of event trees, construction of fault trees of safety systems, transient calculations of accident sequences with the CATHARE2 code and reliability data assessment. Main objectives of a level-1 PSA performed at conceptual design stage are an early assessment of the safety architecture of the reactor and findings about the most effective areas for improvement, but also the identification of dominant accident sequences and comparison with alternative designs. After the elaboration of a simplified level-1 PSA model for nominal state and main internal initiators, various design alternatives will be evaluated from the viewpoint of PSA in order to support the design choices of the ASTRID reactor. (authors)

[en] The main objective assigned to the Work Package 4 (WP4) of the 'ASAMPSA2' project (EC 7. FPRD) consist in the verification of the potential compliance of L2PSA guidelines based on PWR/BWR reactors (which are specific tasks of WP2 and WP3) with Generation IV representative concepts. Therefore, in order to exhibit potential discrepancies between LWRs and new reactor types, the following work was based on the up-to-date designs of: - The European Fast Reactor (EFR) which will be considered as prototypical of a pool-type Sodium-cooled Fast Reactor (SFR); - The ELSY design for the Lead-cooled Fast Reactor (LFR) technology; - The ANTARES project which could be representative of a Very-High Temperature Reactor (VHTR); - The CEA 2400 MWth Gas-cooled Fast Reactor (GFR). (authors)

[en] The European project ASAMPSA2 (Advanced Safety Assessment Methodology: level 2 PSA) of the 7. Framework Program aims at writing practical guidelines for conducting PSA level 2 studies on Light Water Reactors (PWR and BWR). The project includes also a supplemental task dealing with GEN IV reactors. Two main objectives are assigned to this task: 1) the verification of the potential compliance of L2PSA guidelines based on PWR/BWR reactors with Generation IV concepts; 2) a brief survey of the modelling needs to describe the new features of GEN IV reactor concepts in terms of performing a level 2 PSA. Taking into account the ASAMPSA2 partners knowledge, the project has focused on four concepts: SFR, LFR, GFR and VHTR. For each of those concepts, a conceptual design was selected as reference: the European Fast Reactor (EFR) for sodium cooled fast reactors, the ELSY project for lead cooled fast reactor, the CEA GFR2400 project and the ANTARES project for VHTR. As a first stage, relevant data for each concept have been collected when available. These included: 1) basic general parameters and design characteristics relevant for safety studies with a specific attention given to passive devices; 2) information about former PSA2 studies on such concepts; 3) expert reviews about accident phenomenology knowledge (like PIRT); 4) list of computational tools developed or used for accident progression studies with, if possible, some basic information about the tools (availability, level of development, validation, documentation). In a second stage, the collected data were used to evaluate the compliance of the LWR guideline chapters with GEN IV concepts. The LWR guidelines may be divided into two main sections: chapters dealing with a specific phenomenon induced by core degradation and chapters dealing with general PSA methodology (like interface between PSA1 and PSA2, human risk assessment, system modelling and the role of expert opinion). The overall conclusion is that methodology is not very much affected by the reactor type contrary to what is related to the accident phenomena. (authors)

[en] ASTRID, the Advanced Sodium Technological Reactor for Industrial Demonstration, is a GEN-IV technological demonstrator to be commissioned near the end of the 2020 decade to demonstrate the progress made in Sodium Fast Reactor technology on an industrial scale by qualifying innovative options, especially relative to safety and operability. A level-1 probabilistic safety assessment (PSA) is being performed by CEA and its partners, AREVA NP and EDF, at the conceptual design stage of ASTRID. Selected accident sequences starting from the nominal state are analysed through the fault trees/event trees methodology. The modelling milestones as well as transient calculations performed with the CATHARE2 code are presented. At this stage, the PSA model aims at providing probabilistic insights to assess design choices and to highlight the weaknesses of the design under safety considerations. A reference configuration of the safety systems is first evaluated to identify dominant accident sequences. Sensitivity studies are performed for various design alternatives to define the optimal safety systems configurations to minimize the core damage frequency. (authors)

[en] The objective of this coordinated action was to develop best practice guidelines for the performance and application of Level 2 PSA with a view to achieve harmonisation at EU level and to allow a meaningful and practical uncertainty evaluation in a Level 2 PSA. Specific relationships with communities in charge of nuclear reactor safety (utilities, safety authorities, vendors, and research or services companies) have been established in order to define the current needs in terms of guidelines for Level 2 PSA development and application. An international workshop was organised in Hamburg, with the support of VATTENFALL, in November 2008. The Level 2 PSA experts from ASAMPSA2 project partners have proposed some guidelines for the development and application of L2PSA based on their experience, open literature, and on information available from international cooperation (EC Severe Accident network of Excellence - SARNET, IAEA standards, OECD-NEA publications and workshop). There are a large number of technical issues addressed in the guideline which are not all covered with the same level of detail in the first version of the guideline. This version was submitted for external review in November 2010 by severe accident and PSA experts (especially from SARNET and OECD-NEA members). The feedback of the external review will be dis cussed during an international open works hop planned for March 2011 and all outcomes will be taken into consideration in the final version of this guideline (June 2011). The guideline includes 3 volumes: - Volume 1 - General considerations on L2PSA. - Volume 2 - Technical recommendations for Gen II and III reactors. - Volume 3 - Specific considerations for future reactors (Gen IV). The recommendations formulated in the guideline should not be considered as 'mandatory' but should help Level 2 PSA developers to achieve high quality studies with limited time and resources. It may also help Level 2 PSA reviewers by positioning one specific study in comparison with some state-of-the art information. (authors)

[en] The objective of this coordinated action was to develop best practice guidelines for the performance of Level 2 PSA methodologies with a view of harmonisation at EU level and to allow meaningful and practical uncertainty evaluations in a Level 2 PSA. Specific relationships with community in charge of nuclear reactor safety (utilities, safety authorities, vendors, and research or services companies) have been established in order to define the current needs in terms of guidelines for level 2 PSA development and applications. An international workshop was organised in Hamburg, with the support of VATTENFALL, in November 2008. The level 2 PSA experts from the ASAMPSA2 project partners have proposed some guidelines for the development and application of L2PSA based on their experience and on information available from international cooperation (EC Severe Accident network of Excellence - SARNET, IAEA standards, OECD-NEA publications and workshop) or open literature. The number of technical issues addressed in the guideline is very large and all are not covered with the same relevancy in the first version of the guideline. This version is submitted for external review in November 2010 by severe accident experts and PSA, especially, from SARNET and OECD-NEA members. The feedback of the external review will be dis cussed during an international open works hop planned in March 2011 and all outcomes will be taken into consideration in the final version of this guideline (June 2011). The guideline includes 3 volumes: - Volume 1 - General considerations on L2PSA. - Volume 2 - Technical recommendations for Gen II and III reactors. - Volume 3 - Specific considerations for future reactor (Gen IV). The recommendations formulated in the guideline should not be considered as 'mandatory' but should help the L2PSA developers to achieve high quality studies with limited time and resources. It may also help the L2PSA reviewers by positioning one specific study in comparison with some state-of-the art information. (authors)