PLC based DESFAS in nuclear power plant

The trend toward digitalization in safety systems from the conventional analog type is growing to form completely digitalized instrumentation and control (I&C) systems in nuclear power plants (NPP's). Digital Engineered Safety Features Actuation System (DESFAS) was developed as one of the safety systems to keep in step with such a trend. The DESFAS is to generate safety signals for actuating pumps and valves to protect the effluence of radioactive materials in case of rupturing the primary pressure boundary. The application of the programmable logic controller (PLC) in DESFAS requires faultless hardware and software. DESFAS was designed and developed in two trains and programmed in two languages to meet such requirements in dealing with redundancy and diversity. In addition, the evaluation and simulation of programmed function logic was accomplished for software verification and validation.