Design of Digital Safety Systems in NPP

1. Design of Digital Safety Systems in NPP Improvements regarding: System Requirements, Engineering, Argumentation for a Safety Case

2. Projects on W Atom Nuclear Automation • General • Modernizations of NPP • Claes • Design of a new Reactor Protection System • 2,5 years • Why Modernization? • Meet new reqirements • Advantages with the new technology

3. Reactor I&C Safety Systems RPS and acting upon events Logic for detecting Reactivity Isolation Cooling Functional Requirements • Reactor Protection System • Main Task • Supervise the plant during normal operation and automatically initiate safety functions.

4. RPS and acting upon events Logic for detecting The I&C System - Characteristics • I&C = Instrumentation and Control • Includes I/O, controllers, operator stations, etc... (Advant platform) • Based upon Industrial Products • New in the nuclear business for safety critical systems • Advantages with conventional technology • Useful reference for ABB • Safety Review • Customer uses results from the qualification and the design in their argumentation to the authorities (SKi) One part of the I&C system

5. RPS and acting upon events Logic for detecting Qualification of the Category A I&C • Category A FSE • Safety critical according to IEC 1226 • Designed according to IEC 880 • Qualification Issues (”Safety Case”) • Design Bases and Design Descriptions • Codes and Standards (Compliance) • Product Software Qualification (Static analyses) • Product Hardware Qualification • Analysis (FMEA, PSA, SIL) • V&V (Design Process) • QA/QC Category A I&C system

6. RPS and acting upon events Logic for detecting Design Issues for a Category A I&C System • Results from the Qualification • Restrictions, safety concepts • DinD&D (Defence in Depth and Diversity) • The classic design principle for safety systems • Single Fault Criterion • Redundancy • Experience – Process Knowledge • The I&C system must fit with the process interface

7. Conceptual Design • Non-Functional Requirements • Structure • Four functionally and physically separated divisions • Logic and voting in two levels • Category A logic separated from other logic • Testability and Maintainability • Performance • Behaviour upon errors • Separation according to the process (safety systems)

8. RPS and acting upon events Logic for detecting The Category A I&C Architecture • Category A Topology • Four redundancies,(divisions) • Physical and functional separation • Diversification (functionsand equipment)

9. Entire Network Topology

10. Input Approved Output Test Documentation Documentation Methodology Report Review Process Output Documentation Validation System Test System Validation Requirements Instruction Output Approved Output Documentation Documentation Review Process Review Process Approved Output Output Documentation Documentation Verification System Test System Design Verification Instructions Output Approved Output Documentation Documentation Review Process Review Process Approved Output Output Documentation Documentation Integration Test Detailed Design Integration Instructions Output Approved Output Documentation Documentation Review Process Review Process Approved Output Output Documentation Documentation Implementation The Design Process for Category A I&C • Life Cycle Model • Sequential

11. Research Areas ”Optimization of the Design Process” • Requirements • Interactions between product requirements and system requirements • Verification of requirements (testable, reviewable) • Traceability from plant level requirement to implemented application software • Category A Design Process • Distinguish the design process for category A

12. Research Areas cont. ”Optimization of the Design Process” • Qualification • Make the qualification more cost efficent. More focus on technology...

13. Seminal Papers • IEC 880 • European Commission Nuclear Science and Technology. Draft Report Revision 8. ”Licensing of safety critical software for NPP”, 1999. • IAEA-TECDOC-1066 ”Specification of Requirements...”, 1999. • Nancy G. Leveson ”System Safety and Computers”,1995.