Radioactive Waste Cask Sealing System with Axial Gaskets
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Solution Overview
Problem
Existing cylindrical casks for solid radioactive waste of medium activity face issues with complex and costly sealing systems, stagnation of liquids and particulate matter during decontamination, and compromised sealing efficiency under accidental events like shocks and fires.
Innovation Solution
A cask design featuring two coplanar axial gaskets and conical coupling surfaces for the primary sealing system, along with metal sealing rings and conical thread caps treated with solid lubricant for secondary sealing, simplifies assembly and enhances sealing efficiency while protecting against accidents and facilitating decontamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If combined axial and radial gaskets are used in the sealing system, then sealing efficiency is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The sealing system is divided into two separate axial gaskets positioned at different locations (first axial gasket at the interface between lid and body, second axial gasket at the interface between flange and body), each providing sealing for specific regions. This segmentation allows each gasket to be optimized for its specific function while maintaining overall sealing efficiency without the complexity of combined radial-axial configurations.
2Stability of the object's composition
If recesses are provided for lid closing screws, then structural stability is improved, but decontamination difficulty increases due to liquid stagnation
Solution Approach 1:
The recesses for lid closing screws are designed with curved, rounded contours rather than sharp corners or flat-bottomed geometries. This curvature prevents liquid stagnation by promoting drainage flow, while the recess depth and shape are optimized to maintain sufficient structural support for the screw heads, thus balancing decontamination ease with structural stability.
3Ease of operation
If the lid is recessed between the sides of the main body, then assembly flexibility is improved, but water stagnation risk increases during draining operations
Solution Approach 1:
The lid is designed to be completely removable from the main body, allowing it to be entirely extracted rather than merely recessed. This complete removal capability provides assembly flexibility while eliminating the creation of permanent recesses that would trap water. The lid can be fully detached and set aside, preventing any stagnation in the interface region between lid and body during draining operations.
4Reliability
If two coplanar axial gaskets are used in series, then sealing reliability is improved under all conditions, but manufacturing cost increases
Solution Approach 1:
Two axial gaskets are positioned in series at different interfaces (lid-body and flange-body) rather than stacking them at the same location. This merged configuration provides redundant sealing paths that enhance reliability under various conditions (normal operation, accidental events, thermal expansion) while avoiding the excessive material usage and manufacturing complexity of stacked gaskets, thus reducing overall manufacturing cost.
Data Source
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AI summary
A cask (1) for conditioning, storage and disposal of radioactive waste, in particular solid radioactive waste of medium activity, comprises: a main hollow body (2) extending along and about a longitudinal axis (A) and provided with an access opening (3); a lid (4) closing the opening (3) and is fixed to the body (2) by closing screws (5) which tighten respective flanges (11, 22) of the body (2) and the lid (4) against each other; and a primary sealing system (6) arranged between the body (2) and the lid (4) and comprising two gaskets (36) in series; the body (2) and the lid (4) are provided with respective conical coupling surfaces (15, 25) adjacent to the respective flanges (11, 22) and in contact with each other; the gaskets (36) in series of the primary sealing system (6) are axial gaskets acting parallel to the axis (A) between respective sealing surfaces (12, 23), parallel to one another and perpendicular to the axis (A), of the flanges (11, 22) of the body (2) and the lid (4).