Radioisotope Target Flash Sintering for Low-UAl2 Production
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Solution Overview
Problem
The existing 'picture-frame' process for manufacturing radioisotope targets using UAlx + Al mixtures is limited by high scrap rates due to prohibitive defects, requires lengthy holding times at moderate temperatures, and is inflexible to variations in uranium powder characteristics, affecting production times and costs.
Innovation Solution
A flash sintering method involving a rapid sintering process (SPS) under controlled pressure and temperature conditions to form UAl3 and/or UAl4, reducing UAl2 content, allowing for quicker and more adaptable target production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the picture-frame process is used to manufacture targets with UAlx + Al mixture, then the target can be produced with aluminum cladding and uranium-bearing core, but the production time is lengthy due to required holding times ranging from a few hours to twenty hours for temperature maintenance to transform UAl2 into UAl3 + UAl4
Solution Approach 1:
The invention changes the temperature parameter from moderate temperatures (440-550°C) to high temperature (above 600°C, preferably 650-750°C). This parameter change accelerates the transformation of UAl2 into UAl3 and UAl4, reducing the holding time from hours to minutes, thereby significantly improving productivity while reducing the duration of temperature maintenance
Solution Approach 2:
The invention introduces a periodic heating cycle with rapid heating rate (10-100°C per minute) followed by a short holding period. This periodic action with controlled heating and holding cycles achieves complete transformation of UAl2 phase much faster than continuous moderate temperature processing, reducing overall processing time while maintaining transformation completeness
2Productivity
If the picture-frame process is used with high volume fraction of uranium phase in UAlx + Al mixture, then the uranium charge is optimized for radioisotope production, but prohibitive defects such as porosity occur during rolling operations leading to high scrap rate
Solution Approach 1:
The invention changes the temperature parameter to above 600°C (preferably 650-750°C) which ensures complete transformation of UAl2 into UAl3 and UAl4 phases. This complete transformation eliminates the reactivity issues of UAl2 with aluminum matrix during rolling, allowing high volume fractions of uranium phase (up to 70-80% or more) to be processed without porosity defects, thereby optimizing uranium charge while maintaining reliability
Solution Approach 2:
The invention performs preliminary high-temperature treatment before rolling operations to completely transform UAl2 into UAl3 and UAl4. This preliminary action eliminates the harmful reactivity of UAl2 with aluminum matrix in advance, preventing porosity formation during subsequent rolling operations and reducing scrap rate while allowing optimized uranium loading
3Ease of manufacture
If the picture-frame process is used with UAl2 as starting uranium phase, then the target can be manufactured, but the process requires lengthy holding time to transform UAl2 into UAl3 + UAl4 and is inflexible to variations in uranium powder characteristics
Solution Approach 1:
The invention changes the temperature parameter to high temperature (above 600°C, preferably 650-750°C) which dramatically accelerates the transformation kinetics of UAl2 into UAl3 and UAl4. This parameter change reduces holding time from hours to minutes and makes the process insensitive to variations in uranium powder characteristics such as particle size, shape, and initial composition, thereby improving both ease of manufacture and process flexibility
Solution Approach 2:
The invention applies high temperature locally and rapidly to the powder mixture during the sintering process. This localized high-temperature treatment ensures complete transformation of UAl2 phase regardless of powder characteristics, while the short duration minimizes energy consumption. The process adapts to different powder characteristics without requiring adjustment of holding time, enhancing flexibility
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 method significantly reduces production time, minimizes UAl2 content, and optimizes uranium charge, enhancing production yield and flexibility to varying powder characteristics.
Implementation Method 1
a step (i) of flash sintering (SPS) of a powder P made of or comprising a uranium source and aluminium or an aluminium alloy to form said sintered compact
Implementation Method 2
Flash sintering, also known as electric current-assisted sintering (SPS), field-assisted sintering technique (FAST), or pulsed electric current sintering (PECS), is a sintering method that typically combines the effects of applying uniaxial pressure and a high-intensity, low-voltage pulsed current
Implementation Method 3
a step (i) of flash sintering (SPS) of a powder P made of or comprising a uranium source and aluminium or an aluminium alloy to form said sintered compact
Data Source
Figure 1~2
Figure 3a~4
Figure 5~6b
AI summary
The present invention relates to a method for preparing targets for the production of radioisotopes or nuclear fuels comprising a reactive sintering step.