A numerical analysis technique that incorporates Voronkovs model were examined and used to estimate the distribution of defects during crystal growth. By comparisons of the distribution of the density of LSTD and the position of R-OSF in non-nitrogen-doped (non-N-doped) and nitrogen-doped (N-doped) silicon crystals, it is found that the results of the numerical analyses agree with practically evaluated data. The observations suggest that the R-OSF nucleus is a VO2 complex that is formed by bonds between oxygen atoms and residual vacancies consumed during the formation of void defects. This suggests that Voronkovs model can be used to accurately predict the generation and growth of defects in silicon crystals. This numerical analysis technique was also found to be an effective method of estimating the distribution of defects in silicon crystals during crystal growth.