Trace Oxygen Leak Detection in Reactor Vessel Annulus
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Solution Overview
Problem
Detecting small sodium leaks in sodium-cooled fast reactors (SFRs) is challenging due to the difficulty in detecting leaks without requiring continuity detectors to be wetted by the leaking sodium, which can lead to hazardous conditions such as fires, explosions, and the spread of radioactive sodium.
Innovation Solution
A sodium leak detection system using an inert gas recirculation loop with a trace oxygen sensor and recirculator to detect sodium leaks in the reactor vessel-guard vessel annulus by monitoring oxygen concentration changes, combined with a radiation detector to confirm radioactivity levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If continuity type sodium leak detectors are placed in the bottom of the reactor vessel enclosure, then large leaks can be detected, but small leaks cannot be detected in a timely manner
Solution Approach 1:
The patent replaces the mechanical/physical contact-based continuity detector with an optical absorption-based detection system. The system uses a light source and photodetector to measure oxygen concentration changes in the annulus space, eliminating the need for physical contact with leaking sodium while achieving high sensitivity for small leaks.
Solution Approach 2:
The patent introduces oxygen as an intermediary substance in the annulus space. When sodium leaks, it reacts with the oxygen, causing a measurable decrease in oxygen concentration. This intermediary approach allows indirect detection of sodium leaks without direct contact between the detector and sodium.
2Reliability
If the enclosure surrounding the reactor vessel is a large volume, then it provides adequate containment, but typical instrumentation can only detect leakage in a limited area
Solution Approach 1:
The detection system divides the large annulus volume into multiple monitoring zones by strategically positioning light sources and photodetectors at different locations. This segmentation allows comprehensive coverage of the entire annulus space while maintaining the integrity of the large-volume containment structure.
Solution Approach 2:
The patent transitions from point-based detection (continuity detectors at specific locations) to volumetric detection by using light propagation through the entire annulus space. The optical path extends across the volume, enabling detection of leaks anywhere within the enclosed space rather than only at specific detector locations.
3Ease of operation
If sodium leaks are allowed to contact air or water for detection purposes, then leak location can be identified, but hazardous conditions such as fires, explosions, and corrosive reactions occur
Solution Approach 1:
The patent maintains an inert atmosphere (nitrogen or other inert gas) in the annulus space and introduces oxygen as a controlled trace component for detection purposes. This approach allows leak detection through oxygen consumption while preventing hazardous reactions by keeping the overall atmosphere inert, except for the controlled oxygen-sodium reaction that provides the detection signal.
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 system can detect small sodium leaks quickly and accurately, providing early warnings and enabling prompt remediation to prevent hazardous conditions, even for leaks as small as grams or milliliters, improving safety and containment.
Implementation Method 1
oxygen absorbs light at a wavelength of 760 nanometers
Implementation Method 2
sodium reacts exothermally with oxygen, which cause a fire hazard if leaking sodium is allowed to contact air
Implementation Method 3
sodium reacts exothermally with oxygen
Data Source
AI summary
A sodium leak detection system for a nuclear reactor vessel includes a recirculation loop having an inlet and an outlet in communication with the annular space between the nuclear reactor vessel and the guard vessel. The recirculation loop and the annulus are filled with an inert gas, such as argon. The inert gas is doped with a known trace quantity of oxygen, typically in the single-digit ppm range up to about 1%. A recirculator forces the inert gas and oxygen to mix and flow throughout the annulus. The recirculation loop further includes a trace oxygen sensor that determines the concentration of oxygen in the inert gas. Because sodium reacts with oxygen, the trace oxygen sensor is monitored for a reduction in the oxygen level, which indicates a sodium leak into the annulus.