Modeling of the MARA 10 mock-up simulating a core disruptive accident

In the case of a Hypothetical Core Disruptive Accident in a Liquid Metal Fast Breeder Reactor, it is assumed that the core of the nuclear reactor has melted partially and that the chemical interaction between molten fuel and liquid sodium has created a high-pressure gas bubble in the core. The violent expansion of this bubble is similar to an explosion: it loads and deforms the reactor vessel and the internal structures, thus endangering the safety of the nuclear plant. The MARA 10 experimental test simulates a Hypothetical Core Disruptive Accident (HCDA) in a 1/30-scale mock-up schematising simply the reactor block of a Fast Breeder Reactor: the external vessel, the roof as well as the main internal structures of the reactor are represented. In the mock-up, the liquid sodium cooling the reactor core is replaced by water and the argon blanket laying below the reactor roof is simulated by an air blanket. The test is fired using an explosive charge. This paper presents the numerical model used in the simulation of the MARA 10 test with the fast dynamics core EUROPLEXUS. A specific HCDA constitutive law has been implemented in this code to simulate this kind of explosion. The external structures are represented by shells. Coupled fluid-structure computations are carried out. (author)