The alloy composed of zirconium has been used effectively for over 50 years in claddings of nuclear fuel, especially for PWR type reactors. However, to increase fuel enrichment with the aim of rising the burning and maintaining the safety of nuclear plants, is of great relevance the study of new materials that can replace safely and efficiently zircaloy cladding. Among several proposed material, silicon carbide (SiC) has a potential to replace zircaloy as fuel cladding material due to its high-temperature tolerance, chemical stability and a low absorption cross-section for thermal neutrons. In this paper, the goal is to expand the study with silicon carbide cladding, checking its behavior when submitted to an environment with burnable poison variations, the impact on multiplication factor and reactivity coefficients to both claddings: zircaloy and silicon carbide. The neutronic analysis was made using the SCALE 6.0 (Standardized Computer Analysis for Licensing Evaluation) code. This code system is widely accepted and used worldwide for safety analysis, and criticality of nuclear reactors has been utilized to model a typical fuel element of a PWR.