A novel simulation code that enables us to analyze the interaction of the runaway electron generation and avalanches with dynamic changes of the confining magnetic fields due to MHD instabilities has been developed. Using the developed simulation code, it has been shown that (1) the perturbed electric field associated with the MHD instability causes the burst generation of runaway electron generation because of the exponential sensitivity of the primary generation to the electric field; (2) the MHD instability causes the flattening of beam current profile, which results in the increase of the net runaway electron generation through the modification to internal inductance of beam plasmas. Additionally, the runaway beam equilibrium code, the VDE code, the impurity code, and the orbit following code have been developed. These individual codes build up a basis for performing the integrated simulation studies for rapid shutdown scenarios of ITER as the next step of the research.