Subsea Gamma Scanning with Linear Detector Arrays
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current gamma radiation scanning technologies for structures, particularly in subsea applications, face challenges such as slow data acquisition, unsuitability for high-pressure deep-sea environments, and limitations in detector technology for low count rates and high-energy gamma sources, as well as inadequate source container safety for subsea locations.
Innovation Solution
A method and apparatus using a linear array of detectors parallel to the axis of rotation, combined with a point source, to rapidly scan significant axial lengths of structures, and a secondary arcuate array for radially resolved data, along with improved pixelated detector arrays and Type B certified source containers for safe subsea operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a large number of detectors are used closely spaced in an arc to obtain high resolution data, then measurement precision is improved, but scanning speed deteriorates
Solution Approach 1:
The detector array is divided into multiple independent linear arrays that can be selectively activated. Instead of using all detectors simultaneously for high-resolution scanning, the system segments the detection task across multiple linear arrays, allowing faster scanning while maintaining sufficient resolution through coordinated data collection from multiple segments.
Solution Approach 2:
The system uses a partial action approach by employing fewer detectors than would be required for maximum resolution at each position. Multiple linear arrays are used sequentially or in combination, collecting sufficient data through multiple passes rather than requiring all detectors to capture complete information in a single rotation, thereby increasing scanning speed.
2Reliability
If the apparatus is designed to withstand high pressure for deep-sea operation, then reliability is improved, but device complexity increases
Solution Approach 1:
The detector arrays and source containers utilize pressure-compensated designs with thin-walled pressure vessels that maintain internal pressure differentials. The scintillator crystals and photodetectors are housed in pressure-equilibrated environments, allowing the apparatus to function reliably at depth without requiring complex heavy-pressure containment structures.
Solution Approach 2:
The system incorporates pressure-resistant sealing and protection mechanisms in advance, with Type B certified source containers and pressure-compensated detector housings that are pre-engineered to withstand deep-sea pressures. This beforehand cushioning approach ensures reliability without adding operational complexity during deployment.
3Measurement precision
If pixelated detectors with photodiodes are used for x-ray scanning, then linearity is improved, but sensitivity to low count rates deteriorates
Solution Approach 1:
The system changes the detection parameter from photodiode current integration to photon counting. By using photomultiplier tubes that convert scintillation light into electrical pulses and counting individual photon events, the system achieves high sensitivity for low count rates from gamma sources while maintaining linearity through pulse height analysis and energy windowing techniques.
Solution Approach 2:
The system replaces the x-ray photodiode detector mechanism with a gamma-ray optimized scintillator-photomultiplier system. This substitution changes the fundamental detection mechanism to one that is inherently more sensitive to the lower flux levels characteristic of gamma radiation, while maintaining measurement linearity through electronic pulse processing.
4Reliability
If Type B certified source containers are used for safe transport, then safety is improved, but compactness for subsea deployment deteriorates
Solution Approach 1:
The Type B certified source container is nested within the subsea deployment apparatus, with the container integrated into the overall instrument housing. The source container is positioned within the pressure vessel structure, and the shielding is optimized to provide Type B certification while minimizing the external dimensions of the deployed apparatus for compact subsea operation.
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 efficient and rapid scanning of lengthy structures with sufficient quality for defect identification, improved sensitivity and accuracy in detecting density variations, and safe handling of gamma sources in deep-sea conditions.
Implementation Method 1
Gamma rays entering the scintillation crystal interact with the scintillating material to produce photons in the visible and/or ultraviolet region
Implementation Method 2
These scintillation photons are detected using a photodetector, for example a photomultiplier tube, which outputs an electrical pulse providing information about the number and energy of the incident gamma photons
Implementation Method 3
Counting the number of gamma photons transmitted from the source to the detectors, through the structure being scanned, enables differences in the density of different parts of the structure to be detected
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
A subsea apparatus (1, 101, 201) and method for scanning a subsea structure (6, 106, 207) to detect differences in density between different parts of the subsea structure (6, 106, 207) is described. A source (2, 102, 204) of gamma radiation and a plurality of detectors (3a - 3g, 103a- 103h) arranged to detect gamma radiation emitted by the source are provided. The subsea structure (6, 106, 207) is positioned between the source (2, 102, 204) and the detectors (3a - 3g, 103a-103h) and the detectors (3a - 3g, 103a-103h) and the source (2, 102, 204) rotated in a fixed relationship to each other about an axis of rotation (5) located between the detectors(3a - 3g, 103a-103h) and the source (2, 102, 204). The plurality of detectors (3a - 3g, 103a-103h) are arranged in a linear array (4, 104, 205), the linear array (4, 104, 205) being substantially parallel to the axis of rotation (5). A pixelated detector array (420, 440) and a source container (501) are also disclosed.