Modelling of x-ray radioscopy for phase topology estimationduring corium sodium interaction

Shifali Singh (1) , Nathalie Cassiaut-Louis (1) , Christophe Journeau (1) , Magali Zabiego (1)

1 CEA-DES (ex-DEN) - CEA-Direction des Energies (ex-Direction de l'Energie Nucléaire)

In case of a severe accident scenario in a Sodium cooled Fast Reactor (SFR) such as the ASTRID demonstrator, the fuel might melt and interact with the coolant i.e. liquid sodium. Thismolten Fuel Coolant Interaction (FCI) can generate an energetic vapor explosion that can jeopardize the reactor structures. The yield of the vapor explosion is strongly dependent on the local distribution of the fragmented melt with respect to the local vapour fractions. The medium is composed of three phases, i.e. corium, liquid sodium and vapor sodium. Thus, a study of the three phase distribution within the system is a key to understand the extent of the explosion.PLINIUS-2, the future large mass experimental platform of CEA Cadarache will be dedicated to conduct experiments to understand the behavior of prototypic corium in case of severe accidents.In order to study these interactions, a high energy X-ray imaging system is being developed. This system consists of a 15 MeV Linear accelerator producing high energy X-rays withsignificantly high flux, which are attenuated as it passes through the highly dense test section. The transmitted radiation forms a visual spectrum on the scintillator screen Gadox coupled to theCMOS camera. Using this system to study the interaction between corium and sodium is particularly challenging due to the small corium particulates of size of the order of less than 1 mm. The qualification of the foreseen radioscopy system on the visualization of such an interaction requires development of physical phantoms.This paper presents the preliminary simulations of expected images of corium fragments in sodium, vapor bubbles and vapour film around the fragments. The simulations are carried out usinga CEA Cadarache in-house tool MODHERATO, which produces radiographic images in satisfactory agreement with the real time imaging. The simulation of particles is based on the knowledgeof interaction phenomenology gained from past experiments and on the statistical analysis of the size of corium particles formed.The models which, according to MODHERATO results, qualify to be detected and resolved, help manufacturing physical phantoms to conduct the experiments.

Mots clés: PLINIUS2; Radioscopie X; Interaction corium sodium; FCI

Domaines: Physique Nucléaire Expérimentale [nucl-ex]; Physique Nucléaire Théorique [nucl-th]

Shifali Singh, Nathalie Cassiaut-Louis, Christophe Journeau, Magali Zabiego. Modelling of x-ray radioscopy for phase topology estimationduring corium sodium interaction. 26th International Conference on Nuclear Engineering (ICONE - 26), Jul 2018, Londres, United Kingdom. ⟨cea-02339326⟩