Granular Support for Hazardous Waste Canisters in Drillholes
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Solution Overview
Problem
The safe and secure long-term storage of hazardous waste, particularly nuclear waste, poses challenges due to the need for reliable containment and retrieval methods, as conventional techniques face issues with weight support and diffusion barriers in subterranean formations.
Innovation Solution
A hazardous waste repository is designed with a drillhole extending from the surface into a subterranean formation, using a granular material like sand to support canisters and a pre-perforated casing without cement, positioned within an impermeable layer to isolate waste from mobile water and provide a long-term leakage barrier.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional waste storage methods using tunnels or boreholes are used, then storage location identification is simplified, but weight support and containment reliability deteriorate
Solution Approach 1:
A granular material is introduced as an intermediary substance between the canisters and the drillhole casing/formation. This granular material provides both weight support for the canisters and containment functionality, eliminating the need for separate structural support elements and improving overall reliability while maintaining ease of operation.
Solution Approach 2:
The system uses a composite configuration combining the granular material with the pre-perforated casing and the subterranean formation. This composite structure integrates multiple functions (weight support, containment, diffusion barrier) into a unified system that is more reliable than conventional single-function approaches.
2Reliability
If cement is used in the annulus between casing and formation, then containment is improved, but retrievability and environmental soundness deteriorate
Solution Approach 1:
The cement is extracted/removed from the annulus between the casing and the formation. Instead of using cement for containment, the system relies on the granular material and the pre-perforated casing design, which allows for retrievability while maintaining containment through alternative means.
Solution Approach 2:
The pre-perforated casing serves as a disposable or easily replaceable component that provides containment through its perforated structure and interaction with the granular material, rather than relying on permanent cement bonds. This approach prioritizes retrievability and environmental soundness over permanent fixation.
3Reliability
If granular material is installed in the drillhole, then weight support is improved, but device complexity increases
Solution Approach 1:
The granular material is installed in a manner that allows it to self-organize and provide weight support automatically. The material naturally packs and distributes loads without requiring complex mechanical support structures, thereby improving weight support reliability while minimizing the increase in device complexity.
Solution Approach 2:
The granular material's porous nature allows it to provide weight support through particle-to-particle contact and friction, rather than requiring a solid, complex support structure. This approach achieves reliable weight support with minimal structural complexity.
4Ease of operation
If pre-perforated casing is used without cement, then retrievability is improved, but containment reliability may worsen
Solution Approach 1:
The granular material serves as an intermediary that bridges the gap between the pre-perforated casing and the formation, providing containment functionality without requiring cement. The granular material fills the annulus and works with the perforated casing to create a containable barrier, maintaining reliability while preserving retrievability.
Solution Approach 2:
The pre-perforated casing provides containment through localized perforations that allow controlled interaction with the granular material and formation, rather than requiring complete cement encasement. This local quality approach maintains retrievability while providing sufficient containment reliability through the strategic placement of perforations.
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 configuration ensures secure, retrievable storage of hazardous waste by distributing weight evenly and preventing diffusion through the use of a granular material and impermeable layers, offering a cost-effective and environmentally sound solution for long-term containment.
Implementation Method 1
a granular material installed in a volume of the drillhole between a casing and the plurality of canisters and between adjacent canisters of the plurality of canisters, the granular material configured to support at least a portion of a weight of each of the plurality of canisters
Data Source
AI summary
A hazardous waste repository includes a drillhole formed from a terranean surface into a subterranean formation. The drillhole includes an entry at the terranean surface and an access portion that extends from the entry toward a storage portion within the subterranean formation. The hazardous waste repository further includes a plurality of hazardous waste canisters emplaced within the storage portion of the drillhole, each of the hazardous waste canisters enclosing hazardous waste; and a granular material installed in a volume of the drillhole between a casing and the plurality of canisters and between adjacent canisters of the plurality of canisters. The granular material is configured to support at least a portion of a weight of each of the plurality of canisters.