Interpretation with the Europlexus code of the MARA8 experiment simulating a hypothetical Core Disruptive Accident

Marie-France Robbe (1) , Michel Lepareux (1) , Yves Cariou (2)

1 DYN - Laboratoire d'études de DYNamique
2 FRAMATOME-ANP

In the case of a Hypothetical Core Disruptive Accident (HCDA) in a Liquid Metal Fast Breeder Reactor, the interaction between the fuel and the liquid sodium leads to the formation of a bubble of gas at high pressure in the core of the reactor. The violent expansion of this bubble loads and deforms the vessel and the internal structures. The MARA8 mock-up is a small-scale experiment representing a simplified reactor. A Hypothetical Core Disruptive Accident is simulated in the mock-up. The mock-up includes a flexible vessel with a flexible roof. The vessel is filled with water, topped with an air blanket. The test is fired using an explosive charge. The mock-up is well-instrumented in order to be able to compare the experimental results with numerical computations. Up to now, several numerical simulations have been carried out with different computer codes. To conclude the study, the last model has been improved and a complete analysis of the accident has been performed. This paper presents a numerical simulation of the MARA8 experiment with the fast-dynamics code EUROPLEXUS and the comparison of the numerical results with the experimental ones. The explosion is simulated using a specific sodium-argon-bubble constitutive law describing the three-component mixture. Coupled fluid-structure computations are carried out to simulate the internal fluid and the external structures modeled by shells. The computation shows the propagation of a shock wave from the explosive zone towards the external structures. Water vaporizes in the middle of the mock-up and the air layer, initially located below the roof, is crashed in the top corner of the mock-up. The vessel base and the roof move away and two bulges appear in the lateral wall of the vessel. The comparison of the results computed by EUROPLEXUS with the experimental results and previous numerical results carried out with the codes SIRIUS, CASTEM-PLEXUS and EUROPLEXUS shows that the current results are in good agreement with the experiment but some discrepancies are still present.

Mots clés: explosion; safety; Fast Breeder Reactor

Domaines: Mécanique des structures [physics.class-ph]; Mécanique des fluides [physics.class-ph]; Modélisation et simulation

Marie-France Robbe, Michel Lepareux, Yves Cariou. Interpretation with the Europlexus code of the MARA8 experiment simulating a hypothetical Core Disruptive Accident. 2nd Student Conference of the American Nuclear Society, American Nuclear Society, Apr 2002, Penn State University, United States. ⟨cea-03081905⟩