Backup Safety Logic for Common-Cause Failure Isolation
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Solution Overview
Problem
Existing CCF countermeasure facilities in nuclear power plants, composed of analog circuits like switches and relays, require multiple signal input and output devices, leading to increased scale and complexity as the number of detectors and safety-system components grows.
Innovation Solution
A safety protection system backup device that uses digital signal processing and separate communication protocols for the safety protection device and the CCF device, allowing sharing of input and output devices and preventing the need for additional devices specific to the CCF device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If analog facilities including switches and relays are used for CCF countermeasure, then the CCF device can be designed with relaxed design grade, but the number of signal input devices and signal output devices increases with the number of detectors and safety-system components
Solution Approach 1:
The patent merges the CCF device with the safety protection device by sharing common input devices (detectors), communication control circuits, and output devices (safety-system local components). This integration allows the CCF device to utilize existing hardware resources rather than requiring separate dedicated components for each detector and output, thereby reducing the overall number of devices while maintaining independent safety functionality.
Solution Approach 2:
The patent implements multi-functionality where a single input device can serve both the safety protection device and the CCF device simultaneously. The communication control circuits are designed to handle multiple functions: normal safety protection operations and CCF countermeasure operations. This universal design allows the same hardware infrastructure to support both safety functions without requiring additional dedicated components.
2Reliability
If separate input and output devices are provided for CCF device, then electric fault isolation is achieved, but the scale of the CCF device increases according to the number of inputs and outputs
Solution Approach 1:
The patent introduces communication control circuits as intermediary components that enable fault isolation between the CCF device and safety protection device without requiring separate physical input and output devices. These communication control circuits act as mediators that can interrupt or isolate signals when electric faults are detected, while still allowing the CCF device to share hardware resources with the safety protection device for normal operations.
Data Source
AI summary
This safety protection system backup device detects a state of a plant, and then, if an abnormality is found, issues an instruction to a safety-system local component according to an output of a first safety protection logic in a safety protection device and, if a common cause failure is found in the safety protection device, issues an instruction to the safety-system local component according to an output of a second safety protection logic in a CCF device. The first safety protection logic and the second safety protection logic are configured to execute digital signal processings based on logical configurations different from each other, whereby an input device and an output device can be shared by the safety protection device.