Passive Cooling Jacket for Nuclear Fuel Casks
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Solution Overview
Problem
Current casks used for transporting and storing spent nuclear fuel face challenges in efficiently dissipating heat, particularly when natural convection is insufficient due to high heat loads or ambient temperatures, and require auxiliary cooling systems that are independent of active power sources and minimize radiation exposure for personnel.
Innovation Solution
A cooling system comprising a cylindrical cooling jacket mounted around the cask, filled with a sublimating medium like dry ice that absorbs heat through endothermic sublimation and vents carbon dioxide, providing an efficient external heat sink that operates independently of ambient temperature changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If thick walls are used for radiation shielding in casks, then radiation shielding effectiveness is improved, but heat dissipation capability deteriorates
Solution Approach 1:
The cask structure is segmented into distinct functional layers: an inner canister for fuel storage, a intermediate cooling layer with water-filled channels, and an outer shielded overpack. This segmentation allows each layer to perform its specific function optimally without interfering with others.
Solution Approach 2:
A water-filled cooling jacket is introduced as an intermediary layer between the fuel canister and the outer radiation shield. This intermediary serves dual purposes: it actively removes heat from the fuel assemblies through forced circulation while the outer shield handles radiation protection, thus resolving the conflict between thermal and radiation management.
2Device complexity
If natural convection cooling is used, then device complexity is reduced, but cooling effectiveness deteriorates under high heat loads
Solution Approach 1:
A forced convection cooling system using water circulation is implemented. Pumps and flow distribution manifolds are installed within the cask to actively circulate cooling water through channels in the canister walls, ensuring reliable heat removal even under high heat loads and ambient temperatures without requiring complex external cooling infrastructure.
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 system effectively maintains cask temperatures within safe limits by providing a reliable, passive cooling mechanism that reduces the need for personnel proximity and minimizes radiation exposure, suitable for both transport and storage applications.
Implementation Method 1
a sublimating cooling medium which exists as a solid at normal atmospheric pressure is used which changes phase directly to a gaseous phase by absorbing heat generated by the cask
Implementation Method 2
a sublimating cooling medium which exists as a solid at normal atmospheric pressure is used which changes phase directly to a gaseous phase by absorbing heat generated by the cask
Implementation Method 3
The spent nuclear fuel (SNF) in the fuel assemblies within the canister is still highly radioactive and produces considerable heat which must be dissipated
Data Source
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AI summary
A system for externally cooling a cask containing heat-emitting spent nuclear fuel includes the cask comprising a radiation shielding body defining an internal cavity configured to hold a canister containing the spent nuclear fuel. A continuously annular cooling jacket extends circumferentially around an external surface of the cask body. The cooling jacket may have a double shell construction including an internal cavity for a cooling medium which provides an external heat sink for absorbing heat radiated from the external wall surface of the cask generated by the spent nuclear fuel. The heat emitted by the spent nuclear fuel is absorbed by the cooling medium in the cooling jacket, thereby in turn cooling the cask. In one embodiment, the cooling medium may be dry ice which undergoes sublimation by absorbing the heat to change from solid to gaseous phase directly. The jacket may be formed of multiple segments.