Helium Vacuum Drying of Nuclear Waste Casks Under Negative Pressure
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Solution Overview
Problem
Existing methods for drying transport and storage casks for radioactive waste, particularly spent fuel elements, are complex, expensive, and inefficient, especially for containers with high heat output, as they often require extensive evacuation and inert gas feeding without optimizing the gas composition for efficient drying.
Innovation Solution
A method involving continuous evacuation and helium gas feeding, where the helium content is maintained between 50-95% by volume, with a calculated filling pressure based on measured pressure increases to achieve optimal drying efficiency, specifically suitable for containers with high thermal outputs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If extensive evacuation and inert gas feeding are used without optimizing gas composition, then drying is performed, but drying efficiency is insufficient and process complexity increases
Solution Approach 1:
The patent applies parameter changes by optimizing the inert gas composition to contain 5-20% water vapor by volume, which is a specific parameter modification. This optimized composition enables more efficient water vapor removal from the container while simplifying the overall drying process compared to extensive evacuation methods, thereby resolving the contradiction between drying efficiency and process complexity
Solution Approach 2:
The patent employs periodic action through cyclic drying cycles that alternate between introducing the optimized inert gas mixture and evacuation phases. This periodic approach maintains high drying efficiency by continuously removing water vapor while avoiding the need for continuous extensive evacuation, thus reducing process complexity
2Reliability
If noble gas is continuously injected during evacuation, then drying is achieved, but the effort required is not proportionate to the drying efficiency achieved
Solution Approach 1:
The patent changes the parameter of gas composition by using an inert gas mixture with 5-20% water vapor content instead of pure noble gas. This parameter modification achieves reliable drying effectiveness while reducing the effort required, as the pre-conditioned gas mixture is more effective at maintaining the drying gradient without requiring continuous high-volume injection
3Loss of substance
If extensive evacuation is performed without optimized gas composition, then water removal is achieved, but the process becomes complex and expensive
Solution Approach 1:
The patent uses an intermediary substance - the optimized inert gas mixture with 5-20% water vapor - that acts as a mediator between the water to be removed and the vacuum system. This intermediary gas facilitates water vapor removal through absorption and carry-over mechanisms, achieving effective water removal while avoiding the need for complex extensive evacuation procedures
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 method provides a simple, cost-effective, and highly efficient drying process with high functional reliability, suitable for containers with high heat outputs, characterized by precise control and low equipment requirements.
Implementation Method 1
the interior of the container is subsequently continuously evacuated or kept under negative pressure
Implementation Method 2
noble gas, in particular helium gas, is simultaneously continuously fed into the interior of the container
Implementation Method 3
any remaining water in the container is removed by drying, in particular by vacuum drying
Data Source
AI summary
Method for drying transport and/or storage containers (1) for radioactive waste, in particular for spent fuel elements, wherein the container (1) is first dewatered or mechanically dewatered. Subsequently, the interior of the container (4) is continuously evacuated or kept under negative pressure, and helium gas is simultaneously continuously injected into the interior of the container (4). The evacuation and/or the injection of helium gas is carried out with the requirement that the helium content in the interior of the container is 50 to 95 vol.%, in particular 55 to 90 vol.%.