Tritium Removal Process Using Membrane Diffusion and Thermal Columns
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Solution Overview
Problem
Current large-scale tritium recovery processes from water, particularly in nuclear reactors, face challenges such as the use of hazardous liquid cryogens, complex and costly cryogenic distillation methods, and the inability to scale thermal diffusion for high throughput, leading to inefficiencies and safety concerns.
Innovation Solution
A process combining membrane diffusion for initial tritium stripping and enrichment with thermal diffusion for final enrichment, eliminating the need for liquid cryogens and enabling modular, scalable, and safer operation with reduced hydrogen inventory.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If cryogenic distillation is used for large-scale tritium separation, then high tritium throughput is achieved, but the process requires hazardous liquid cryogens and complex vacuum insulated vessels
Solution Approach 1:
The invention changes the temperature parameter from cryogenic conditions to ambient or elevated temperatures by using a reactive metal bed that chemically binds tritium. This eliminates the need for liquid nitrogen and vacuum insulated vessels while maintaining high throughput capability through continuous flow processing
Solution Approach 2:
The invention replaces the mechanical cryogenic distillation system with a chemical reaction-based system using reactive metal beds. The chemical binding mechanism substitutes for the physical phase separation process, eliminating the need for cryogenic equipment and associated hazards
2Manufacturing precision
If cryogenic distillation is used for tritium separation, then high separation efficiency is achieved, but the process requires large liquid hydrogen inventory and complex plant infrastructure
Solution Approach 1:
The invention divides the separation process into multiple discrete reactive metal bed stages arranged in series. Each stage performs a portion of the separation, and the beds can be individually operated, maintained, or replaced. This modular segmentation achieves high separation efficiency while simplifying overall plant complexity compared to a monolithic cryogenic distillation column
Solution Approach 2:
The reactive metal beds can be replaced when depleted or contaminated, serving as consumable components. This approach simplifies the overall plant design by eliminating the need for complex, permanent cryogenic infrastructure, vacuum systems, and insulation vessels, while maintaining high separation efficiency through multiple replaceable stages
3Ease of operation
If thermal diffusion is used for hydrogen isotope separation, then simple operation is achieved, but the process cannot be scaled to large throughput
Solution Approach 1:
The invention segments the separation function across multiple reactive metal bed stages that can be operated in series. Each stage operates independently with simple flow-through operation, and the cumulative effect of multiple stages achieves both high throughput and high separation efficiency, overcoming the throughput limitation of single-stage thermal diffusion
Solution Approach 2:
The invention implements continuous flow through the reactive metal bed stages, eliminating batch operations and downtime associated with thermal diffusion column cycling. Hydrogen gas continuously flows through the sequence of beds, maintaining constant separation action and achieving large throughput while preserving operational simplicity
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
This approach simplifies and economizes tritium recovery, reducing hazards and operational complexity while achieving high tritium concentrations of 99% or higher in a continuous process, suitable for large-scale applications without the need for batch operations or liquid nitrogen adsorption.
Implementation Method 1
a Pd/Ag membrane cascade has been proposed as an alternative technology to cryogenic distillation
Implementation Method 2
Thermal diffusion columns have been used to separate hydrogen isotopes on a small scale since the 1950's
Implementation Method 3
a catalytic exchange reaction such as DTO + D2 ⇆ D2O + DT
Implementation Method 4
direct electrolysis of water, i.e., DTO → DT + 1⁄2 O2
Data Source
Figure 1
AI summary
A diffusion based process for tritium removal from water by tritium transfer from water to an elemental hydrogen stream, followed by a membrane diffusion cascade for tritium stripping and enrichment, and final tritium enrichment by one or more thermal diffusion columns. The combination of process steps takes advantage of membrane diffusion's large throughput capability at low tritium concentration with the simplicity of thermal diffusion for small throughput final tritium enrichment. The membrane diffusion stages use supported or unsupported microporous or hydrogen permeable metal membranes (such as Pd/Ag alloy). The diffusion process is compatible with any front-end process to transfer tritium from tritiated water to elemental hydrogen. The process may be designed and operated at low pressure, with small gas inventory, and no inherent overpressure hazard.