3D-analysis of an ITER accident scenario

In this paper, a deterministic analysis of one of the ITER reference accident scenarios, the so-called ”Ex-Vessel Loss-of-Coolant Accident”, and of its consequences for system integrity is given. inflow rate data from a preceding MELCOR calculation, the evolution of the gas state in the ITER facility (vacuum vessel (VV), pressure suppression system (VVPSS), and drain tank (DT)) is calculated for the first 21,000 s of accident time with the GASFLOW code. Combining these results with new experimental data, for low initial pressures, on flame acceleration and transition to detonation, it is shown that a detonation in the VVPSS is possible, whereas the gas mixture in the VV and the DT never even reaches the flammability limit. To get an upper bound on the possible accident consequences, a detonation in the VVPSS was therefore postulated and simulated with the DET3D code. Using the resulting pressure loads for a structure–mechanical analysis of the end plate of the VVPSS with the ABAQUS code, it turned out that this end plate will almost fully change into the plastic state. Since this would violate the design rules of the ITER project, a further study of this accident scenario seems advisable.