Neutron Source Segmentation for Antimony Melting
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Solution Overview
Problem
Current neutron source designs for subcritical reactors face issues with antimony melting during manufacture and operation, leading to stratification of the antimony-beryllium composition and efficiency degradation, posing challenges for reliable and safe reactor start-up.
Innovation Solution
A neutron source design featuring a durable steel enclosure with a niobium-based alloy ampule for antimony and separate beryllium cavities, surrounded by a beryllium powder bed, and additional safety barriers, ensuring leak-tightness and heat transfer with helium filling, and sealed with argon arc welding for enhanced reliability and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If antimony and beryllium are housed together in a single enclosure, then the device complexity is reduced, but antimony melting occurs during manufacture and operation causing stratification and source efficiency degradation
Solution Approach 1:
The patent divides the enclosure into separate compartments: an inner ampule containing antimony and an outer enclosure containing beryllium. This segmentation prevents direct contact between antimony and beryllium, eliminating the stratification problem while maintaining structural integrity and source efficiency throughout operation.
2Use of energy by moving object
If neutron source materials are placed directly in contact with coolant, then heat transfer is improved, but safety barriers are reduced and reliability decreases
Solution Approach 1:
The patent implements a nested structure where the inner ampule containing antimony is placed within the outer enclosure containing beryllium, which in turn is surrounded by coolant channels. This nested arrangement provides multiple safety barriers while maintaining efficient heat transfer from the neutron source materials through the layered structure to the coolant.
3Ease of manufacture
If the ampule enclosure is made reactive with antimony for ease of manufacture, then manufacturing is simplified, but material compatibility and operational reliability are compromised
Solution Approach 1:
The patent employs an intermediary material (niobium-based alloy) for the inner ampule enclosure that is chemically compatible with antimony. This intermediary material prevents direct reaction between the antimony and the outer enclosure materials, ensuring material compatibility and operational reliability while remaining manufacturable through standard nuclear-grade fabrication processes.
4Device complexity
If beryllium is housed in direct contact with structural materials, then device complexity is reduced, but chemical reactions may occur degrading source performance
Solution Approach 1:
The patent segments the beryllium into a separate outer enclosure compartment, isolating it from direct contact with reactive structural materials. This segmentation prevents unwanted chemical reactions that could degrade source performance, while the enclosed structure maintains structural integration and mechanical strength of the overall neutron source assembly.
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 design provides a reliable and durable neutron source that maintains controlled reactor start-up throughout the reactor's service life, preventing antimony melting and ensuring consistent neutron flux, thus enhancing reactor safety and operational longevity.
Implementation Method 1
The central ampule enclosure is made of a material which does not react with the antimony during filling and operation, for example, a niobium-based alloy. The central enclosure of the ampule is leak tight.
Implementation Method 2
The neutron source enclosure inner cavity is filled with helium to ensure heat transfer.
Implementation Method 3
The beryllium powder bed porosity is 45 %, with particle size from 60 to 200 micron.
Implementation Method 4
The neutron source enclosure is sealed with two shanks: upper and lower ones. It is sealed by argon arc welding.
Implementation Method 5
The gas collector is pressed against the ampule through washers with a spring.
Data Source
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AI summary
The invention relates to nuclear engineering and is designed for controlled reactor start-up by rising the reactor to the working power level after normal and abnormal shutdowns. The invention solves the problem of improving the reliability of the operational neutron source by creating additional safety barriers between the coolant and the source active part materials. The operational neutron source is designed as a steel enclosure inside of which there is an ampule containing active elements: antimony and beryllium with separate antimony and beryllium cavities positioned coaxially. The antimony is contained in the central enclosure made of a niobium-based alloy which does not react with the antimony during filling and operation. A beryllium powder bed is located between the antimony enclosure and the ampule enclosure. The ampule enclosure is made of martensite-ferrite steel poorly reacting with beryllium. An upper gas collector is located above the ampule, which serves as a compensation volume collecting gaseous fission products. At the bottom, the ampule is supported by a reflector and a bottom gas collector. The gas collectors, reflector and washers are made of martensite-ferrite grade steel. 12 dependent claims, 2 figures.