TOWARDS MODEL-BASED SPECIFICATION AND SAFETY ASSURANCE OF NUCLEAR IC SYSTEMS – APPLICABILITY OF SYSML AND AADL

摘要

Complexity of modern control and safety systems challenge the usual linear document-basedpresentation of system design. This complicates the work of designers, assessors and regulatorscomprehending the system, whose understanding often depends on building a mental model of thesystem and thus assessing its suitability. More rigorous and structured way to represent the system,than the linear documents-based, is model-based approach. Based on a literature review, SysML andAADL were identified as suitable candidates. They were tried in an exploratory case studymodelling APR1400 reactor protection system, based on its linear description from a real applicant’sdesign control document. Effort was also taken to extract safety assurance information (forindependence) from the documentation and organize it into a structured safety argument. Researchserves also to discuss the strengths and weaknesses of model-based specification and assessmentcompared to document-based approaches.Modelling of the system based on design document and extracting safety assuranceinformation was challenging. Results, based on the modelling experiences and literature review,argue that the studied architecture languages offer benefits over the use of natural language in clarity,ambiguity and traceability. However, using these architecture description languages requireextensive modelling expertise and effort to allow a smooth modelling process and understanding. Inaddition, multidisciplinary insight into the system at both the conceptual level as well as hardwareand software level is required. We also identified support of classical safety analysis methods withinSysML and AADL.