The present paper proposes a description of the Virtual Reality (VR) use within the System Engineering approaches. The VR is spread among different design context and for different purposes, especially during Validation and Verification phase (V&V). A case study is introduced, derived from the nuclear fusion project ITER. The scope of the work is to validate the maintainability of the Radial Neutron Camera (RNC) Ex-Port System. The RNC Ex-port system is a diagnostic tool for detection of un-collided neutrons and gain information about the plasma state. The context of this system needs precise and safe maintenance procedures due to the harsh and potentially dangerous environment. The VR method has been used for the validation of procedures. The CAD model has been adapted into the software Unity and needed scripts have been introduced. The substitution of a detector (the 4He scintillator) is taken into consideration, verifying the feasibility for one operator. The simulation led to validation of the operation with some corrections, confirming the VR as useful tool in supporting V&V phase.