Remote TDR Liquid Level Measurement in Reactors
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Solution Overview
Problem
Conventional methods for measuring liquid levels in hostile environments, such as boiling water reactors, are not suitable for remote operation due to the need for electronics in close proximity, which is unsafe in high-radiation and high-temperature conditions.
Innovation Solution
A system using time-domain reflectometry (TDR) with a probe extending into the reactor pressure vessel, a pulsing unit remotely located up to 1000 feet away, and a digitizer to receive reflected pulses, allowing for safe and accurate liquid level measurement by calculating the time difference between initial and air/liquid interface reflections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional TDR systems use electronics in close proximity to the probe for measurement, then measurement precision is maintained, but the system cannot operate in hostile environments with high radiation and high temperatures
Solution Approach 1:
The system divides the measurement function into two separate segments: a probe that can be placed in the hostile environment (reactor vessel) and electronics that remain in safe locations. The probe contains only passive TDR elements (transmission line and reflector) while the active electronics (pulse generator and signal processor) are located remotely, connected via long cables. This segmentation allows the measurement function to be separated from the hazardous zone.
Solution Approach 2:
Long transmission cables act as intermediaries, connecting the probe in the hostile environment with the electronics in safe locations. These cables transmit both the excitation pulses and the reflected signals over distances up to 1000 feet, enabling remote operation without compromising measurement capability. The intermediary cable system bridges the gap between the dangerous measurement zone and the safe electronics zone.
2Reliability
If the pulsing unit is located remotely up to 1000 feet away from the probe, then safety in hostile environments is improved, but signal transmission accuracy may deteriorate
Solution Approach 1:
The system merges the transmission line and reflector into an integrated probe assembly that is inserted as a single unit into the reactor vessel. This unified probe structure minimizes connection points and potential sources of error, ensuring that the TDR measurement path remains intact and accurate despite the long distance to the electronics.
Solution Approach 2:
The system replaces complex mechanical signal conditioning equipment with a purely electrical TDR measurement approach. By using voltage pulses and electrical reflections along transmission lines, the system eliminates the need for mechanical sensors or contact-based measurement devices that would be susceptible to environmental degradation over long distances.
3Adaptability or versatility
If conventional methods require electronics near the measurement site, then ease of operation is maintained, but adaptability to remote hostile environments is limited
Solution Approach 1:
The TDR probe assembly is designed as a universal measurement tool that can be inserted into various reactor vessel configurations and measurement locations. The standardized probe design with configurable reflector positions allows the same basic apparatus to measure different parameters (liquid level, fuel assembly position, etc.) in different locations, enhancing versatility without requiring complex localized electronics at each measurement point.
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 safe and accurate liquid level measurement in boiling water reactors, even in hostile environments, by using TDR technology to determine the liquid level and temperature, overcoming the limitations of conventional methods that require close proximity to the measurement site.
Implementation Method 1
time-domain reflectometry (TDR) to characterize and locate faults in metallic cables
Implementation Method 2
A first impedance mismatch is received from the probe/air interface in a form of a positive reflected pulse, and a second impedance mismatch is received from the air/water interface in a form of a negative reflected pulse
Implementation Method 3
A time between the positive reflected pulse and the negative reflected pulse is calculated, and the time is converted to a distance
Data Source
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AI summary
A system for measuring a level of a liquid may include a receptacle, a probe, a pulsing unit, and a digitizer. The receptacle has a top and a bottom and is configured to contain the liquid. The probe may extend into the receptacle through the bottom. The pulsing unit is configured to transmit a pulse to the probe. The digitizer is configured to receive at least a first reflected pulse and a second reflected pulse from the probe. The time between the first reflected pulse and the second reflected pulse may be calculated and converted to a distance that is indicative of the level of the liquid in the receptacle.