Automatic Depressurization Blocking for Spurious Reactor Signals
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Solution Overview
Problem
The automatic depressurization system in pressurized water nuclear reactors can be actuated spurriously under normal conditions, leading to unnecessary flooding of the reactor containment and potential severe accidents, as it lacks a mechanism to differentiate between normal and accident scenarios.
Innovation Solution
A blocking device is integrated into the depressurization system that prevents automatic depressurization when the core makeup tanks are full, using sensors to monitor tank levels and only allow depressurization when the tanks are drained, ensuring that the system acts only during critical loss of coolant events.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the automatic depressurization system is activated under normal conditions, then the system can respond to perceived coolant loss, but it causes spurious actuation leading to unnecessary flooding and potential severe accidents
Solution Approach 1:
A blocking device is introduced as an intermediary component between the depressurization system and the control signal. This blocking device receives the depressurization signal and conditionally blocks it based on tank level sensors. When tanks are full, the blocking device prevents the signal from reaching the depressurization valves, thereby eliminating spurious actuation while maintaining the ability to respond to genuine accidents when tanks are drained.
2Adaptability or versatility
If the depressurization system operates without a blocking mechanism, then it can respond to all coolant loss events, but it cannot differentiate between normal operation and accident scenarios
Solution Approach 1:
The system incorporates feedback from tank level sensors to the blocking device. The sensors continuously monitor whether the core makeup tanks are full or drained and provide this information to the blocking device. This feedback mechanism enables the system to adapt its behavior: blocking depressurization when tanks are full (normal operation) and allowing depressurization when tanks are drained (accident scenario), thereby achieving both adaptability and reliability.
3Reliability
If a blocking device is added to prevent spurious actuation, then false alarms are reduced, but the device complexity increases
Solution Approach 1:
The blocking device operates autonomously based on signals from tank level sensors and the depressurization control system. It self-regulates the depressurization function by blocking or permitting operation according to tank conditions, without requiring external intervention or complex control logic. This self-service approach minimizes the added complexity while achieving the reliability improvement.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution reduces the frequency of spurious actuations of the automatic depressurization system, minimizing the risk of unnecessary flooding and associated costs, while ensuring the system remains fail-safe and operational during true accident scenarios.
Implementation Method 1
using sensors to monitor tank levels
Implementation Method 2
a depressurization system for automatically depressurizing the pressurized coolant circuit
Implementation Method 3
water is added to the coolant circuit by gravity flow from the in-containment refueling water supply tank
Data Source
AI summary
A blocking device for preventing the actuation of an automatic depressurization system in a pressurized nuclear reactor system due to spurious signals resulting from a software failure. The blocking signal is removed when the coolant level within the core makeup tanks drop below a predetermined level.