FPGA Control System for Nuclear Plant Protection
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Solution Overview
Problem
Software-based microprocessor systems in safety-critical control systems, such as nuclear plant reactor protection systems, are prone to common-mode failures due to inherent operational issues, making them unreliable for high-reliability applications.
Innovation Solution
A hardware-based control system architecture utilizing Field Programmable Gate Arrays (FPGAs) with advanced logic circuits, digital bus communications, and redundant components to eliminate software common-mode failures and enhance reliability and integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If software-based microprocessor systems are used for control, then operational flexibility and programmability are improved, but reliability deteriorates due to common-mode failures
Solution Approach 1:
The system is divided into multiple independent redundant channels (at least two) that operate separately. Each channel processes inputs and generates outputs independently, preventing a single fault from affecting the entire system. This segmentation eliminates common-mode failures while maintaining operational flexibility through programmable logic in each channel.
Solution Approach 2:
Redundant copies of the control system are created with identical hardware architecture and logic implementation. Each copy independently performs the same control functions, and their outputs are compared through voting logic. This copying approach ensures that if one copy fails, the redundant copy continues to operate, maintaining system reliability.
2Reliability
If redundant software-microprocessor systems are implemented, then fault tolerance is improved, but common-mode failures still occur due to shared fault conditions
Solution Approach 1:
The control system is segmented into physically separate redundant channels with independent hardware paths from inputs to outputs. Each channel has its own microprocessor, memory, and I/O interfaces, eliminating shared fault paths. This physical segmentation prevents common-mode failures while maintaining fault tolerance through redundancy.
Solution Approach 2:
A voting logic intermediary is introduced between the redundant channels and the final output. The voting logic compares outputs from multiple redundant channels and selects the correct output based on majority voting or other decision rules. This intermediary prevents faulty outputs from propagating while allowing the system to tolerate individual channel failures.
3Reliability
If multiple redundant channels are used, then reliability is improved, but system complexity increases
Solution Approach 1:
Each redundant channel is designed with universal, identical hardware architecture and logic implementation. The same microprocessor, memory configuration, and I/O interfaces are used in each channel, allowing for standardized manufacturing and simplifying maintenance. This universality reduces complexity by eliminating the need for custom designs while maintaining reliability through redundancy.
Solution Approach 2:
Instead of designing complex unique systems, simple redundant copies of the same hardware architecture are created. Each copy contains identical logic implemented in programmable devices, making the system easier to analyze, test, and maintain. The copying approach trades increased quantity for reduced individual complexity.
Data Source
AI summary
The Advanced Logic System (ALS) is a complete control system architecture, based on a hardware platform rather than a software-based microprocessor system. It is significantly different from other PLC-type control system architectures, by implementing a FPGA in the central control unit. Standard FPGA logic circuits are used rather than a software-based microprocessor which eliminate problems with software based microprocessor systems, such as software common-mode failures. It provides a highly reliable system suitable for safety critical control systems, including nuclear plant protection systems. The system samples process inputs, provides for digital bus communications, applies a control logic function, and provides for controlled outputs. The architecture incorporates advanced features such as diagnostics, testability, and redundancy on multiple levels. It additionally provides significant improvements in failure detection, isolation, and mitigation for the highest level of integrity and reliability.