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Benchmarking LWR Codes Capability to Model Radionuclide Deposition within SFR Containments: an Analysis of the Na ABCOVE Tests Nuclear Engineering and Design

pubblicazioni - Articolo

Benchmarking LWR Codes Capability to Model Radionuclide Deposition within SFR Containments: an Analysis of the Na ABCOVE Tests Nuclear Engineering and Design

Il presente lavoro è finalizzato a valutare la capacità degli attuali codici sviluppati per i reattori ad acqua leggera (LWR, Light Water Reactor), ASTEC, ECART e MELCOR nella modellazione del trasporto di aerosol all’interno di un contenimento di un reattore veloce a sodio (SFR, Sodium Fast Reactor) in condizioni BDBA.

Postulated BDBAs in SFRs might result in contaminated-coolant discharge at high temperature into the containment. A full scope safety analysis of this reactor type requires computation tools properly validated in all the related fields. Radionuclide transport, particularly within the containment, is one of those fields. This sets two major challenges: to have reliable codes available and to build up a sound data base. Development of SFR source term codes was abandoned in the 80’s and few data are available at present. The ABCOVE experimental programme conducted in the 80’s is still a reference in the field. The present paper is aimed at assessing the current capability of LWR codes to model aerosol transport within a SFR containment under BDBA conditions. Through a systematic application of the ASTEC, ECART and MELCOR codes to relevant ABCOVE tests, insights have been gained into drawbacks and capabilities of these computation tools. Hypotheses and approximations have been adopted so that differences in boundary conditions between LWR and SFR containments under BDBA can be accommodated to some extent. Two major outcomes result from this study: a reasonable approximation to the BDBA SFR scenario can be achieved with LWR codes whether suitable hypotheses are made and development and implementation of new models is mandatory to enhance predictability to the required level in safety analyses. Vaporization, nucleation and oxidation of Na and turbulent agglomeration of particles are some of those models. Additionally, the importance of a good morphological characterization of aerosol particles has been highlighted.

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