Fuel Rod Drying via Vacuum and Heated Gas Flow
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Solution Overview
Problem
Existing methods for drying fuel rods, particularly defective ones with hairline cracks and pinholes, are inefficient in reducing residual water content to a permissible level for dry storage, leading to potential water penetration and storage challenges.
Innovation Solution
A method involving a fuel rod quiver with a drying head connected to a vacuum device and a temperature-controlled medium, such as heated air, is used to evacuate water through hairline cracks and pinholes, ensuring effective drying by maintaining a temperature higher than storage conditions and utilizing a separate flow path to prevent re-moisture ingress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional evacuation methods are used to remove water from fuel rods, then some water is removed from the receiving space, but residual water content remains above permissible levels for dry storage
Solution Approach 1:
The patent applies parameter changes by heating the receiving space to elevated temperatures (e.g., 50°C to 150°C) to increase the evaporation rate of residual water from the fuel rod surfaces and cracks. This thermal parameter change transforms the drying process from passive evacuation to active thermal evaporation, significantly reducing residual water content to below 1 gram per fuel rod assembly
Solution Approach 2:
The patent implements preliminary action by performing a pre-drying phase where the receiving space is heated and evacuated multiple times before final sealing. This preliminary removal of bulk water through controlled heating and evacuation cycles prepares the fuel rod for the subsequent drying phase, ensuring that when the space is finally sealed, residual water content is already reduced to acceptable levels
2Temperature
If the fuel rod is stored in a spent fuel pool, then cooling is provided, but water penetrates through cracks and pinholes into the fuel
Solution Approach 1:
The patent converts the harmful effect of water penetration into a beneficial process by using the same cracks and pinholes that allow water ingress as pathways for water egress. During the drying process, heated gas flows through these same defects in reverse direction, carrying water vapor out of the fuel rod. The defects that caused the problem become the solution pathway for removal
Solution Approach 2:
The patent creates an inert drying atmosphere by filling the receiving space with heated nitrogen or other inert gases after evacuation. This inert environment prevents re-condensation of water vapor and eliminates oxygen that could promote corrosion. The inert gas flow through cracks and pinholes maintains a protective atmosphere throughout the fuel rod structure during storage
3Productivity
If a simple evacuation system is used, then device complexity is low, but water removal performance is insufficient
Solution Approach 1:
The patent implements multi-functionality by designing the receiving tube system to serve multiple purposes: it provides structural support for the fuel rod, creates a sealed evacuation chamber, serves as a heating chamber for thermal drying, and acts as a storage container for long-term dry storage. This universal design eliminates the need for separate drying chambers and storage containers, achieving high water removal performance without proportionally increasing device complexity
Solution Approach 2:
The patent uses heated gas (nitrogen or air) as an intermediary medium to transfer thermal energy to the fuel rod and carry water vapor away. Instead of direct contact heating or complex vacuum drying equipment, the gas mediator simplifies the system by combining heat transfer and mass removal functions in a single straightforward process
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 reliably reduces residual water content in fuel rods to less than 1 gram, ensuring safe dry storage by maintaining a controlled environment that prevents subsequent outgassing, suitable for both uranium dioxide and MOX fuels.
Implementation Method 1
Each receiving tube or each receiving space of a receiving tube is expediently evacuated in the drying section
Implementation Method 2
The temperature of the tempering medium is preferably set with a heating device... the temperature of the tempering medium is at least as high as the storage temperature of the fuel rod holder
Implementation Method 3
The temperature of the tempering medium is preferably set with a heating device... The tempering medium is expediently fed into the interior of the fuel rod holder on the cover side through the first tempering medium channel
Implementation Method 4
the flow path of the tempering medium through the interior of the fuel rod holder is formed separately from the receiving space of the receiving tube
Data Source
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AI summary
A method for drying a fuel rod held in a fuel rod canister, wherein at least one receiving tube, sealed at one end to prevent fluid leakage, is provided in an interior of the fuel rod canister. A fuel rod is inserted through an open end of the receiving tube into a receiving chamber of the receiving tube, wherein, in a drying step, the receiving chamber of the receiving tube is preferably evacuated using a vacuum device. The fuel rod canister and/or the interior of the fuel rod canister is tempered, preferably heated, with a tempering medium.