Downcomer Coolant Level and Flow Velocity Measurement
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Accurate measurement of fluid level and flow velocity in the downcomer of a natural recirculation boiling water reactor is challenging due to the complexities of a two-phase steam-water mixture, where existing methods lack precision and reliability, especially in volatile environments.
Innovation Solution
A probe system combining electrical conductivity (EC) probes, thermal conductivity (TC) probes, and time-domain reflectometry (TDR) probes is used to measure the conductivity, resistivity, and reflection time of electromagnetic pulses within the downcomer, providing a synergistic approach to determine coolant level and flow velocity, minimizing the need for differential pressure systems and enhancing accuracy in multi-phase environments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single probe type (EC or TDR) is used to measure fluid level, then the measurement method is simple, but the measurement precision deteriorates in two-phase steam-water environments with foam layers
Solution Approach 1:
The patent combines EC probes and TDR probes into a single integrated probe system. The EC probe measures electrical conductivity to detect foam and steam-water mixture conditions, while the TDR probe measures dielectric properties to determine fluid level. By merging these complementary measurement techniques, the system achieves accurate level measurement in two-phase environments where single probe types fail.
Solution Approach 2:
The probe system functions as a composite measurement apparatus, integrating probes with different operating principles (electrical conductivity and time-domain reflectometry). Each probe type compensates for the limitations of the other, creating a robust measurement system that handles foam layers and two-phase mixtures effectively.
2Device complexity
If conventional measurement methods are used in two-phase environments, then the device complexity is low, but the reliability of measurement deteriorates due to foam and steam-water mixture interference
Solution Approach 1:
The system continuously monitors both electrical conductivity and dielectric properties, using feedback from multiple measurement channels to compensate for environmental variations. The controller processes signals from both EC and TDR probes to distinguish between foam, steam, and liquid water, maintaining reliable measurements despite two-phase flow conditions.
Solution Approach 2:
The probe system acts as an intermediary measurement apparatus that indirectly detects fluid level by measuring electrical properties of the medium. Rather than directly observing the liquid surface, the system uses electrical conductivity and dielectric constant measurements to infer level, bypassing the interference caused by foam and steam-water mixtures.
3Measurement precision
If differential pressure systems are used for measurement, then the measurement coverage is adequate, but the device complexity and cost increase
Solution Approach 1:
The patent replaces mechanical differential pressure measurement systems with electrical field-based EC and TDR probes. Instead of using pressure sensors and mechanical components to infer level, the system uses electromagnetic field interactions with the fluid to directly measure level and flow characteristics, reducing mechanical complexity while maintaining measurement capability.
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
The combined probe system achieves precise and reliable measurements of coolant level and flow velocity, improving operational efficiency and reducing complexity and cost by leveraging the strengths of each probe type to compensate for environmental variations and interference, such as foam layers between steam and water layers.
Implementation Method 1
In one example, a constant voltage (AC) is imposed across a gap between two electrodes. The magnitude of the resulting current is determined by the ability of the medium to conduct the current, where admittance is the reciprocal of impedance.
Implementation Method 2
When these impulses hits the surface of the medium to be measured, an impedance mismatch (due to the different dielectric constants of the two phases) causes part of the impulse energy to be reflected back up the probe to the circuitry (due to the mismatch of the dielectric property) which then calculates the fluid level from the time duration between the impulse sent and the impulse reflected
Implementation Method 3
an impedance mismatch (due to the different dielectric constants of the two phases) causes part of the impulse energy to be reflected
Implementation Method 4
a combination of electrical conductivity (EC) probes, thermal conductivity (TC) probes and one or more time-domain reflectometry (TDR) probes
Data Source
AI summary
A boiling water reactor includes a reactor pressure vessel having a feedwater inlet for the introduction of recycled steam condensate and/or makeup coolant into the vessel, and a steam outlet for the discharge of produced steam for appropriate work. A fuel core is located within a lower area of the pressure vessel. The fuel core is surrounded by a core shroud spaced inward from the wall of the pressure vessel to provide an annular downcomer forming a coolant flow path between the vessel wall and the core shroud. A probe system that includes a combination of conductivity/resistivity probes and/or one or more time-domain reflectometer (TDR) probes is at least partially located within the downcomer. The probe system measures the coolant level and flow velocity within the downcomer.