Micro-Pocket Fission Detector for In-Core Neutron Flux Monitoring
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Solution Overview
Problem
Current neutron detectors are not suitable for high-radiation and high-heat environments within nuclear reactor cores, as they either burn up quickly or become unreliable due to high neutron flux and gamma-ray exposure, and existing solutions for in-core measurements are either large, fragile, or lack accuracy for real-time flux monitoring.
Innovation Solution
Development of a miniaturized micro-pocket fission detector (MPFD) with a loose-stacked design and non-sealed gas chamber, using radiation-hard materials and neutron-reactive coatings, which allows for extended operation in high radiation fields and provides accurate real-time neutron flux measurements without significant perturbation of the neutron flux.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional neutron detectors are used in high-radiation and high-heat environments within nuclear reactor cores, then neutron flux detection is achieved, but detector lifetime is significantly reduced due to burnup from high neutron flux and gamma-ray exposure
Solution Approach 1:
The detector is segmented into multiple functional layers including a substrate, neutron-reactive coating, and protective overcoat. This segmentation allows each layer to perform its specific function optimally while protecting the sensitive detection components from radiation damage and chemical degradation, thereby extending detector lifetime in high-radiation environments
Solution Approach 2:
The detector employs composite material construction with a substrate made from radiation-hard material, a neutron-reactive coating layer, and a protective overcoat. This composite structure combines the radiation resistance of the substrate material with the neutron detection capability of the coating and the environmental protection of the overcoat, enabling sustained operation in harsh reactor core conditions
2Volume of moving object
If miniaturized detectors are deployed for in-core measurements, then flux perturbation is reduced and spatial resolution is improved, but detector fragility increases making them unsuitable for harsh reactor environments
Solution Approach 1:
The detector utilizes a thin-film protective overcoat that provides environmental protection while maintaining the miniaturized form factor. This thin film structure protects the sensitive internal components from chemical degradation and physical damage without significantly increasing the detector volume, thus preserving spatial resolution while improving robustness
Solution Approach 2:
The miniaturized detector employs composite material construction with radiation-hard substrate material and protective coatings, enabling the small detector to withstand harsh reactor core conditions including high radiation, temperature, and chemical exposure, thereby improving reliability without sacrificing size benefits
3Reliability
If sealed gas chamber designs are used in traditional fission detectors, then gas containment is maintained, but dead time increases reducing real-time monitoring capability
Solution Approach 1:
The detector employs a dynamic gas flow system where process gas continuously flows through the detection chamber rather than being statically contained. This dynamic approach allows fresh gas to constantly replace saturated gas, maintaining detection sensitivity and reducing dead time while enabling real-time monitoring capability in high-flux environments
4Measurement precision
If traditional fission chamber designs are used, then neutron detection capability is achieved, but significant perturbation of the neutron flux occurs affecting reactor operation
Solution Approach 1:
The detector is segmented into multiple thin layers including substrate, neutron-reactive coating, and protective overcoat. This segmentation reduces the total material density and volume interacting with neutrons compared to traditional bulk fission chambers, thereby minimizing neutron flux perturbation while maintaining detection capability through the distributed neutron-reactive coating
Solution Approach 2:
The invention transitions from traditional three-dimensional bulk fission chamber geometry to a planar, multi-layered structure. This dimensional change reduces the detector's cross-sectional area and material volume in the neutron flux path, minimizing flux perturbation while maintaining effective neutron detection through the extended surface area of the neutron-reactive coating
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 MPFD offers improved detector lifetime, reduced dead time, and enhanced accuracy for real-time neutron flux monitoring within nuclear reactors, enabling precise power and thermal profiling and facilitating more accurate burnup calculations and fuel management.
Implementation Method 1
neutrons are converted into charged particle reaction products in the conversion material (4) which then ionize the gas (5) in the cavity (33)
Implementation Method 2
charged particle reaction products in the conversion material (4) which then ionize the gas (5) in the cavity (33) between the electrodes (3)
Data Source
AI summary
A radiation detector to monitor the neutron flux of a nuclear reactor or other high-radiation environment, that can withstand the high temperatures and radiation fields of such environment, is provided. A small dielectric substrate with a low neutron-activation cross section is provided. The substrate is coated with a neutron conversion material, such as uranium oxide or thorium oxide. One or more substrates form a micro-sized detection cavity that is filled with a detection gas. A voltage is provided across anode and cathode wires in the detection cavity. A neutron absorbed in the conversion material may release reaction products into the gas, causing ionization of the gas which then produces a current or voltage signal. The small detector volume minimizes energy deposition into the detection gas by competing particles such as gamma rays, fast electrons, and beta particles, and therefore minimizes false counts while retaining large signals from neutron interactions.