Underground Nuclear Fuel Storage Modules
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Solution Overview
Problem
Current spent nuclear fuel and radioactive waste storage systems face challenges in efficiently managing decay heat and radiation containment, particularly in reducing site boundary radiation doses and minimizing storage area requirements.
Innovation Solution
A below-ground storage system utilizing vertically stacked canisters within underground modules, which employs natural convection for passive heat removal and soil shielding to contain radiation, thereby reducing radiation exposure and site requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If spent nuclear fuel is stored in above-ground dry storage casks at generating plants, then radiation containment and decay heat management are maintained, but storage area requirements and site boundary radiation doses increase
Solution Approach 1:
The patent transitions from horizontal above-ground storage to vertical below-ground storage. Multiple canisters are stacked vertically in underground modules, utilizing the third dimension (depth) to increase storage density. This dimensional change allows more fuel to be stored in a smaller surface footprint while the surrounding soil provides natural radiation shielding, thereby reducing site boundary radiation doses.
Solution Approach 2:
The patent introduces underground modules as intermediary structures between the canisters and the surface environment. These modules provide structural containment and position the canisters within the earth, which acts as an intermediary shielding material to attenuate radiation before it reaches the surface, thus reducing site boundary radiation exposure.
2Adaptability or versatility
If consolidated interim storage facilities are established to centralize waste from multiple plants, then control over dispersed waste stockpiles is improved, but transportation requirements and facility complexity increase
Solution Approach 1:
The patent divides the consolidated storage facility into multiple standardized underground modules, each capable of independently storing a specific number of canisters (e.g., 10 canisters per module). This segmentation allows the facility to be scaled by adding or removing modules as needed, providing flexibility in managing waste from different plants while maintaining a relatively simple, repeatable design for each module.
Solution Approach 2:
The underground modules are designed as universal, multi-functional units that can store various types of spent fuel and radioactive waste canisters. Each module serves multiple purposes: structural containment, radiation shielding, heat dissipation through natural convection, and secure storage. This universality simplifies facility design and operation while providing adaptable capacity for consolidated waste management.
3Use of energy by moving object
If passive heat removal systems are used in underground storage modules, then energy consumption is reduced, but heat removal efficiency may be limited
Solution Approach 1:
The patent employs passive heat removal systems that utilize natural convection currents within the underground modules. The system is self-service in that it automatically dissipates decay heat without requiring external energy input. Air enters through lower openings, rises as it is heated by the canisters, and exits through upper openings, creating a continuous natural circulation pattern that effectively removes heat while consuming zero energy.
Solution Approach 2:
The heat removal system utilizes pneumatic principles through natural convection of air. The temperature-driven density differences in the air create continuous flow patterns that transport heat from the canisters to the surrounding environment. This pneumatic approach provides effective passive cooling without mechanical components or energy consumption.
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 achieves vanishingly low site boundary radiation doses and efficient decay heat management, allowing for a significant reduction in storage area needs while maintaining safety during catastrophic events.
Implementation Method 1
the system takes advantage of the surrounding soil or subgrade to provide shielding, physical protection
Implementation Method 2
The canister storage system is further configured to provide passive heat removal from the canisters via natural convection during storage in the modules
Data Source
AI summary
An underground ventilated system for storing nuclear waste materials. The system includes a storage module having an outer shell defining an internal cavity and an inner shell. A majority of the height of the outer shell may be disposed below grade. The outer shell may include a hermetically sealed bottom. First and second canisters are positioned in lower and upper portions within the cavity respectively in vertically stacked relationship. A centering and spacing ring assembly is interspersed between the first and second canisters to transfer the weight of the upper second canister to the lower first canister. The assembly may include centering lugs which laterally restrain the first and second canisters in case of a seismic event. A natural convection driven ventilated air system cools the canisters to remove residual decay heat to the atmosphere. In one non-limiting embodiment, the shells are made of steel.