Cables are important components in nuclear reactors, which are used to power and control the various equipments of the reactor systems. The presence of combustible, plastic materials in large quantity pose a significant fire risk to nuclear reactors and the safety of reactor systems could be jeopardized by the loss of functionality of cables due to the damage caused by fire. In this connection, CFD based 3D models have been developed for the horizontal and vertical cable tray fire configurations (which are commonly used arrangements in nuclear power plants) using FDS code and analyzed their resultant thermal transients in enclosed cells. Simulations have been carried out for benchmark horizontal cable tray fire (3 trays in 120 m³ cell) and vertical cable tray fire (1 tray in 27 m³ cell) of two cable materials (PVC & XLPE). The combustion of PVC and XLPE have been represented using appropriate chemical equations with products like CO and soot yield along with experimental heat release rate data. The model predictions for transient gas temperature variation along the height, oxygen concentration and location of hot layer with time are fairly in line with experimental results for both the configuration cable tray fire scenarios. This validated model is used in the influence approach CTF safety analysis of SFR.