Massive material injection (MMI), in particular shattered pellet injection (SPI) will be used in the ITER disruption mitigation system to prevent disruption-related damage. Recent JOREK modelling has identified the key role of plasmoid drifts in material assimilation, MHD activities and radiation properties in pure deuterium (D2) SPI experiments on JET, which could impair the effectiveness of D2 SPI on runaway electron avoidance [^1]. These \\(\boldsymbol{E}\times\boldsymbol{B}\\) plasmoid drifts originate from the charge separation induced by the \\(\nabla B\\) drifts, where \\(\boldsymbol{E}\\) and \\(\boldsymbol{B}\\) refer to the electric and magnetic field, respectively. Two main mechanisms can counteract the charge separation and thus plasmoid drifts based on theory [^2]: the propagation of shear Alfvén waves (SAWs) from both ends of the plasmoid (“SAW braking”) and the generation of 3D external currents that connect the top and bottom of the plasmoid (“Pégourié braking”). To clarify the fundamental processes and compare with existing theory, we have performed studies with JOREK using a single massive gas injection source. The simulations show a good qualitative agreement with the theory, for example the early saturation of drift velocity due to the SAW braking for sources with small amplitude, stronger Pégourié braking for sources with larger toroidal extent, etc. We also identity the key role of the size of the \\(\boldsymbol{E}\times\boldsymbol{B}\\) flow region on plasmoid drifts considering 3D toroidal geometry and propose an effective pressure to be used when comparing with existing theory. We will discuss all these aspects in the proposed talk. [^1]: M. Kong et al., Nucl. Fusion 64 (2024) 066004 [^2]: B. Pégourié et al., Nucl. Fusion 47 (2006) 44