[en] Reactor Monitoring System is one of very important part of Reactor Instrumentation and Control system. Current monitoring system is using analog system whereby all circuits are discrete circuit and all displays and indicators are not digitalized. The proposed new system will use using a Commercial Off-The-Shelf, state of the art, Supervisory Control and Data Acquisition system such as Programmable Logic Controller as well as Computer System. The implementations of Programmable Logic Controller are used for Data Acquisition System and as a sub-system for Computer System where all the activities involved are stored for operation record and report as well as use for research purposes. Programmable Logic Controller receives galvanised or optically isolated signal from Reactor Protection System. Programmable Logic Controller also receives signal from other parameters as a digital and analog input related to reactor system. (author)