Parametric study of the radiative load distribution on the EU-DEMO first wall due to SPI-mitigated disruptions

Plasma disruptions are rapid and dramatic off-normal operation events, lasting only a few milliseconds, which can damage the tokamak in-vessel structures. Shattered Pellet Injection (SPI) can be employed to mitigate these transients. This technique consists of injecting impurities to enhance the isotropic radiation emission, thus reducing the peak heat load onto the Plasma Facing Components (PFCs). In this work, we employ the CHERAB code to assess the radiative heat load on the EU-DEMO in-vessel structures following a disruption mitigated via SPI with 0.5 GJ of radiated energy. The effect of different penetration depths of shattered pellets varying in the range 0.2–3.5 m is parametrically studied. The computed peak radiative load in the case of deep deposition of the impurities ($\sim$ 5.6 $·$10² MW/m²) is around 18 times smaller than in the case of shallow penetration ($\sim$ 1.0 $·$10⁴ MW/m²). Instead, a figure for an intermediate penetration would be $\sim$1.5 $·$10³ MW/m².