Reactor Water-Level Measurement via Thermal Conduction
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Solution Overview
Problem
Existing reactor water-level measurement systems fail to accurately measure water levels when the water level is low or during extreme conditions, such as fuel melting or core damage, leading to potential system failure and inability to operate normally.
Innovation Solution
A reactor water-level measurement system comprising a core bottom water-level measuring device with a heating element, heat insulating element, and temperature difference measuring element that evaluates the water level based on temperature differences between insulated and non-insulated portions, allowing for continuous measurement from the reactor core to the pressure vessel bottom, even under abnormal conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a sensor is installed in the reactor core to measure water level, then measurement precision is improved, but reliability deteriorates because the sensor may be damaged by extreme conditions such as fuel melting or core damage
Solution Approach 1:
The patent extracts the water level measurement function from the reactor core environment and relocates it to the bottom of the reactor pressure vessel. The core bottom water level meter measures water level from a position outside the core, eliminating exposure to extreme conditions while maintaining measurement capability through thermal conduction principles
Solution Approach 2:
The patent introduces a thermal conduction intermediary mechanism where the heating element and temperature sensing element measure water level indirectly through temperature differences in the surrounding medium, rather than directly exposing sensors to the core environment. This intermediary thermal field allows measurement without direct contact with extreme conditions
2Length of stationary object
If the water level in the reactor falls extremely low, then the measurement range is extended to cover lower levels, but the sensor is heated by fuel and fails to operate normally
Solution Approach 1:
The patent changes the measurement dimension from within the reactor core (vertical measurement through core height) to the bottom of the pressure vessel (horizontal measurement across the base). This dimensional shift allows coverage of the entire water level range from core to bottom without exposing the sensor to fuel heating conditions
3Measurement precision
If a monitoring apparatus is designed for water-level evaluation when cooling water is located in the reactor core, then measurement precision is improved for normal conditions, but it cannot monitor water level when the water level is lower than the reactor core
Solution Approach 1:
The patent creates a universal water level measurement system that functions across all water level conditions - from normal operating levels down to the pressure vessel bottom. The core bottom water level meter provides multi-functional capability to measure both normal and extreme low water levels using the same thermal conduction principle
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
Enables reliable and continuous measurement of reactor water levels regardless of conditions, reducing the risk of system failure and providing accurate data even during extreme situations like fuel melting or core damage.
Implementation Method 1
a heating element, a heat insulating element installed by surrounding part of the heating element in a height direction of the heating element, and a temperature difference measuring element that measures a temperature difference between an insulated portion of the heating element surrounded by the heat insulating element and a non-insulated portion not surrounded by the heat insulating element
Data Source
AI summary
It is provided with a reactor water-level measurement system being possible to measure water-level in a reactor core regardless of a state in the reactor core. The reactor water-level measurement system includes a core bottom water-level measuring device that includes a heating element, a heat insulating element installed by surrounding part of the heating element in a height direction of the heating element, and a temperature difference measuring element that measures a temperature difference between an insulated portion of the heating element surrounded by the heat insulating element and a non-insulated portion not surrounded by the heat insulating element, a water-level evaluation device that evaluates a water level of a reactor based on the temperature difference, wherein the core bottom water-level measuring device measures at least a water level from a lower end of a reactor core contained in a reactor pressure vessel to a bottom of the reactor pressure vessel.