Nuclear Plant Control System Segmentation for Reliability
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Solution Overview
Problem
The existing reactor protection systems in nuclear facilities shut down operations when either comparison logic processor module malfunctions, leading to a reduced operational rate until the reactor is restored.
Innovation Solution
A control system comprising a detecting sensor, a main digital control device, and an auxiliary analog control device, with a NOT circuit, AND circuits, and a delay circuit, that allows the auxiliary control device to operate units on the safe side when the main control device malfunctions, preventing unnecessary shutdowns and maintaining operational rate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the reactor protection system shuts down operation when either comparison logic processor module malfunctions, then safety is ensured, but the operating rate of the nuclear facilities is lowered
Solution Approach 1:
The control system is divided into two independent subsystems: a main control device using digital facilities and an auxiliary control device using analog facilities. Each subsystem can independently control the units on the safe side, allowing the auxiliary subsystem to take over when the main subsystem malfunctions, thus maintaining operation without compromising safety
Solution Approach 2:
The invention changes the operational parameters of the control system by introducing an auxiliary control device that operates in a standby capacity. When the main control device fails, the system transitions to using the auxiliary device, which has different operational characteristics (analog vs digital), thereby maintaining functionality and operating rate while ensuring safety through parameter diversity
2Productivity
If the auxiliary control device operates units on the safe side when main control device malfunctions, then operating rate is maintained, but device complexity increases
Solution Approach 1:
The control system is segmented into distinct main and auxiliary control devices with clearly defined roles. The auxiliary device includes specific components (NOT circuit, first AND circuit, delay circuit) that are added to the basic control structure, but these components are integrated in a modular fashion that manages overall system complexity while enabling backup functionality
Solution Approach 2:
The auxiliary control device acts as an intermediary backup system. The NOT circuit, AND circuit, and delay circuit serve as intermediary components that process signals between the detecting sensor and the final control output, providing a structured intermediate layer that manages complexity through organized signal processing stages
Data Source
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AI summary
Provided are a safety protection system facility 43 outputting a normal actuating signal S1 in a case where the safety protection system facility 43 controls actuation of a unit provided in a nuclear facility to a safe side based on an abnormality detecting signal output at the time of occurrence of an abnormality in the nuclear facility, and where this causes the unit to be actuated normally, and a CCF countermeasure facility 44 outputting a CCF-case actuating signal S2 actuating the unit to a safe side in a case where the CCF countermeasure facility 44 determines from output results of the abnormality detecting signal and the normal actuating signal S1 that the unit is not actuated normally at the time of occurrence of the abnormality in the nuclear facility. The CCF countermeasure facility 44 includes NOT circuits 76, 86, and 98 enabling to invert input or no input of the normal actuating signal S1 and output an inverted signal and first AND circuits 75, 85, and 100 enabling to output the CCF-case actuating signal S2 based on input or no input of the signal output from the NOT circuits 76, 86, and 98 and input or no input of the abnormality detecting signal.