REPUBLIC OF KOREA

Abstract: Software qualification includes such activities as a software Verification and Validation (V&V), a software safety analysis, a software configuration management and a software quality assurance for the safety-critical applications in Nuclear Power Plant (NPP). This paper presents the software qualification of a safety grade Programmable Logic Controller (PLC) which is applied to a Reactor Protection System prototype. The software V&V is characterized by defining the inputs, tasks, and outputs for all the software life cycle phases defined in the software V&V plan, and the V&V techniques such as a checklist-based review and the Fagan Inspection, a traceability analysis, a formal verification, and a software test are applied to improve the software quality. The software safety analysis process, which employs the HAZard OPerability (HAZOP) methodology, has been developed and applied to improve the software safety. All the software documents and source codes are managed as software configuration items throughout the software life cycle under the control of a software quality assurance plan and procedure. Automated software tools and a 3rd part review also support the activities for the software qualification. Our experience shows that the software qualification is very efficient for systematically qualifying the safety-critical software of a PLC to be embedded in the safety-critical systems of a NPP, and they can be easily extended to other safety-critical applications such as in the railways, military, medicine, etc. Key-Words: Nuclear software qualification, software verification and validation, Software safety analysis