Collapsible Trunnion Design for Spent Nuclear Fuel Cask Handling
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Solution Overview
Problem
Conventional trunnion designs for handling hazardous materials like spent nuclear fuel face issues such as frozen threaded joints, inability to handle without trunnions, and restricted location, which are unsatisfactory for withstanding free fall events and maintaining containment integrity.
Innovation Solution
A collapsible trunnion design featuring a two-part structure where the second component is axially slidable relative to the first component, allowing it to retract into the container body upon impact, preventing penetration and enabling safe handling and storage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the trunnion projects out from the cask to provide engagement shoulder for lift yoke, then the cask can be handled and lifted, but the trunnion projection interferes with the crushing action of impact limiter during free fall event
Solution Approach 1:
The trunnion is designed with dynamic functionality to change its state between protruded and retracted positions. During normal operation, the trunnion protrudes to enable lift yoke engagement. During impact events, the trunnion can be forced into the cask body to retract, eliminating the harmful projection effect while maintaining handling capability during normal use.
Solution Approach 2:
The impact limiter is designed to preemptively force the trunnion into the cask body before impact occurs. The impact limiter acts as a preliminary protective mechanism that repositions the trunnion to a safe state, preventing trunnion penetration during the subsequent impact event.
2Reliability
If the trunnion is threaded into the cask flange for removal, then the trunnion can be eliminated during storage, but the threaded joint freezes under bending moment making removal problematic
Solution Approach 1:
The trunnion assembly is segmented into multiple components: the cask body, the trunnion itself, and the impact limiter. This segmentation allows the trunnion to be permanently attached to the cask body while the impact limiter provides the removable element that can be independently positioned or replaced without affecting the trunnion's structural connection.
3Ease of operation
If the trunnion is permanently attached to the cask, then the cask can always be handled, but the trunnion cannot be removed to eliminate penetration threat during storage
Solution Approach 1:
The system transitions from a static trunnion design to a dynamic one where the trunnion's effective position changes based on operational state. The permanent attachment ensures continuous handling capability, while the dynamic retraction mechanism eliminates penetration risk during storage by forcing the trunnion into the cask body during impact events.
4Object-affected harmful factors
If the trunnion projection is minimized by locating it in the cask neck, then the impact interference is reduced, but the handling capability is compromised
Solution Approach 1:
The impact limiter performs a preliminary action by forcing the trunnion into the cask body before the actual impact event occurs. This preliminary repositioning reduces the trunnion's projection to minimize interference with the impact limiter's crushing action, while the trunnion returns to its protruded state for normal handling operations.
Data Source
AI summary
A container for storing and/or transporting spent nuclear fuel. The container includes a body that defines an internal cavity that holds the spent nuclear fuel and an outer surface. The outer surface has holes formed therein into which trunnions are positioned. The container can be lifted by a lift yoke by coupling the lift yoke to the trunnions. The trunnions may include first and second components such that the first component is slidable in its axial direction relative to the second component when a force that exceeds a threshold acts on the second component. Thus, the second component may be slidable between a protruded state in which a portion of the second component protrudes from the outer surface of the body and a retracted state in which the second component does not protrude from the outer surface of the body.