Lightweight Broad-Energy Neutron Remmeter with Segmented Moderators
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Solution Overview
Problem
Conventional neutron remmeters are too heavy due to large moderators, sacrificing dose-equivalent accuracy for smaller, lighter designs, which are inadequate for broad energy range neutron dosimetry.
Innovation Solution
A remmeter using two different-sized hydrogenous moderators with integrated spectroscopic fast and thermal neutron detectors for accurate dosimetry across a wide energy range, employing spectral dosimetry and minimizing signal-processing electronics for a lightweight form factor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a large moderator is used in conventional remmeters, then dose-equivalent accuracy is improved, but the device weight increases to over 5 kg
Solution Approach 1:
The invention divides the single large moderator into two separate smaller moderators with different dimensions. The first moderator has dimensions optimized for detecting neutrons in one energy range, while the second moderator has dimensions optimized for a different energy range. This segmentation allows the system to maintain broad energy coverage and dosimetric accuracy without requiring a single large heavy moderator, thereby reducing overall device weight while preserving measurement precision across the full energy spectrum.
Solution Approach 2:
Each moderator is designed with specific local dimensions and geometries tailored to its intended detection function. The first moderator has particular size characteristics optimized for certain neutron energies, while the second moderator has different size characteristics optimized for other energies. This local optimization of moderator properties allows the lightweight design to achieve accurate dosimetry across broad energy ranges without compromising measurement precision.
2Ease of operation
If a smaller moderator is used to reduce weight, then ease of operation is improved, but dose-equivalent accuracy deteriorates
Solution Approach 1:
The system segments the neutron detection function across two smaller moderators instead of using one large moderator. Each smaller moderator maintains portability and ease of operation, while their combined response across different energy ranges restores the dose-equivalent accuracy that would otherwise be lost with a single small moderator.
Solution Approach 2:
The two-modernator system provides multi-functional capability, where the first moderator handles neutron detection in one energy range and the second moderator handles detection in another energy range. This universal approach allows the lightweight device to maintain accurate dosimetry across the full broad energy spectrum, effectively making the small moderators as accurate as a large moderator would be.
3Device complexity
If a single moderator design is used, then device complexity is reduced, but adaptability to different neutron energy ranges deteriorates
Solution Approach 1:
The invention segments the neutron energy detection into two distinct moderator configurations, each optimized for specific energy ranges. This segmentation enhances adaptability to different neutron energy fields, allowing the system to accurately measure neutrons across a broad spectrum from thermal to fast energies, whereas a single moderator design would be limited in its energy range coverage.
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
Achieves accurate neutron dosimetry from thermal to >15 MeV with reduced weight, improving dose calculation accuracy and sensitivity, and enabling both low and high dose rate detection.
Implementation Method 1
The physics of neutron moderation is such that dose-equivalent accuracy is sacrificed
Implementation Method 2
with a thermal neutron detector in the center
Implementation Method 3
hydrogenous spectroscopic fast neutron detector with neutron/gamma discrimination capability
Data Source
AI summary
A remmeter includes two or more different-sized hydrogenous moderators, each incorporating a hydrogenous spectroscopic fast neutron detector and a thermal neutron detector to provide more accurate neutron dosimetry across a wide range of neutron energies (thermal neutrons to >15 MeV) in a form factor that is lighter than conventional remmeters. The remmeter utilizes the principle of spectral dosimetry, where the energy or energy distribution of the incident neutrons is first measured and then this energy information (along with the measured fluence) is used to establish the dosimetric quantity using the various fluence-to-dose conversion curves (e.g. H*(10) (ICRP(1997)), NCRP-38(1971)). Using the method of spectral dosimetry, the large variation in response in these curves as a function of neutron energy (especially over the region 1 keV to 1 MeV) is largely mitigated through the use of the energy and fluence information, and the appropriate fluence-to-dose conversion curve to calculate the dose.