In order to strengthen the nuclear design calculation capacity in Turkey, CNUREAS (Cekmece Nuclear Reactor System) was developed to provide easy usage of neutronic and thermal hydraulic nuclear codes included in the CNUREAS package. It was tested and used for research reactors and PWR type power reactors. Modifications were performed to add hexagonal geometry support taking into account VVER type reactors employing hexagonal fuel assemblies that will be built in Turkey. "VVER-1000 MOX Core Computational Benchmark" was used to test new features of the CNUREAS. The maximum deviation in effective multiplication factor results of CNUREAS was 0.7% with deterministic codes and 1.5% with Monte Carlo codes. It was concluded that CNUREAS can be used for neutronic calculations of VVER type power reactors with appropriate cross section libraries and deterministic and Monte Carlo techniques give comparable results when both provided with appropriate cross section libraries. (C) 2015 Elsevier Ltd. All rights reserved.