Understanding of runaway electrons is crucial for studying various physical phenomena such as disruptions of tokamak plasmas [1], lightning initiation in thunderstorm clouds [2] and solar flares via magnetic reconnection [3]. In a weakly ionized system with the low temperature, the primary generation mechanism of fast electrons is likely the Dreicer mechanism at the onset of their creation dynamics. Atomic interactions of fast electrons within this system are of crucial importance. Atomic interaction of fast electrons has been considered using the Fokker-Planck operator [4, 5]. However, the incident electrons with energy near the threshold energy lose most of their energy after inelastic collisions while other electrons don’t lose their energy due to the inelastic collisions. The use of ensemble average may blur the energy acceleration process. In this work, we will derive a particle-conservative Boltzmann operator to describe the hard inelastic collisions and implement a volume-averaged form of this operator in the gyro-averaged Fokker Planck solver. Subsequently, we will investigate how the hard and soft collision description of the inelastic collisions influences the electron acceleration. We will simulate the fast electron generation during the electron avalanche using the full kinetic simulation. This research was supported by National R&D Program through the National Research Foundation of Korea (NRF) funded by Ministry of Science and ICT (2021M3F7A1084419). [1] J.R. Martín-Solís et al 2017 Nucl. Fusion 57 066025 [2] A. V. Gurevich at al, Phys. Rev. 110, 185005 (2013) [3] H. Arnold at al, Phys. Rev. 126, 135101 (2021) [4] Boris N. Breizman et al 2019 Nucl. Fusion 59 083001 [5] L. Hesslow et al, Phys. Rev. 118, 255001 (2017)