1.Introduction The injection of large amounts of high-Z impurities by Massive Gas Injection (MGI) or Shattered Pellet Injection (SPI) constitutes the most promising candidate for the mitigation of runaway electrons (RE) during disruptions in large devices like ITER [1,2]. In this paper, the dissipation and decay of the RE current by injection of high-Z impurities during tokamak disruptions is analyzed using a simplified approach, based on the kinetic treatment of Ref. [3], which includes the effect of the collisions with the plasma particles and the impurity ions, the synchrotron radiation losses associated with the pitch angle scattering of the REs when colliding with the impurity atoms as well as the bremsstrahlung radiation. The model allows to get simple estimates of the RE current duration, the RE distribution function and energy during the dissipation phase. A comparison of the effects associated with the different runaway loss mechanisms (collisions, synchrotron and bremsstrahlung radiation) will be also presented.
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