A nuclear power plant (NPP) is a complex engineering system. In Prototype Fast Breeder Reactor (PFBR) which is a NPP, identification of any abnormality or transient should be notified to the operator in the control room to avoid accidents. During any such abnormality, the operator plays a major role in bringing back the plant to a safe mode of operation, when the safety features incorporated in the plant fails to act automatically. The proper decision making ability of the operator can avoid any catastrophe in the plant. There are many techniques used for the operator assistance in taking a legitimate decision. Fuzzy logic is one such technique which guides the operator in identifying the occurrence of any transient with a quicker response time and minimum information overloading. This paper discusses about the implementation of fuzzy logic based transient identification system for operator guidance. A comparative study has been made using plant parameters like reactor inlet temperature and deaerator level as fuzzy input variables to two different systems. Observations based on the stability and the response time on these two parameters shows the effectiveness of the developed system for operator guidance.