Nuclear Pump Captive Member for Broken Stud Retention
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Solution Overview
Problem
In nuclear reactor primary pumps, the breakage of the connecting member can lead to the nut and stud becoming a migrating body in the primary circuit, potentially damaging other equipment, especially in the reactor core.
Innovation Solution
A captive member is interposed between the drive shaft and the hub, chosen to prevent passage through the orifice in the event of connecting member breakage, ensuring the pump wheel remains linked to the drive shaft and preventing the support member and second end of the connecting member from entering the primary circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a simple connecting member (stud and nut) is used to connect the pump wheel to the drive shaft, then the device complexity is reduced and ease of manufacture is improved, but the reliability deteriorates because the broken parts can become migrating bodies in the primary circuit
Solution Approach 1:
A locking element is introduced as an intermediary component between the connecting element and the hub. This locking element captures the broken end of the connecting element and the support element, preventing them from becoming migrating bodies while maintaining a relatively simple overall structure
Solution Approach 2:
The locking element is designed in advance to counteract the potential harmful effect of connecting element breakage. By providing a capturing structure before breakage can occur, the system prevents the formation of migrating bodies without requiring complex redundant connection systems
2Reliability
If the locking element is designed to completely prevent passage through the orifice, then the reliability is improved by preventing migrating bodies, but the device complexity increases due to the additional component and its integration requirements
Solution Approach 1:
The locking element is designed to surround and capture the connecting element and support element within its structure. The broken end of the connecting element and the support element are nested within the locking element's internal features, creating a compact assembly that prevents migration without requiring separate containment structures
Solution Approach 2:
The locking element uses its axial dimension to prevent radial passage through the orifice. By creating an axial barrier with the locking element's geometry, the system blocks the path of potential migrating bodies without interfering with the radial flow path through the pump wheel hub
Data Source
Figure 1
Figure 2
AI summary
The pump (1) comprises: a drive shaft (3); a pump impeller (5) comprising a hub (31) having an orifice (39); a connection (33) of the pump impeller (5) to the shaft (3), comprising a connecting member (41) having a second end part (45) in the orifice (39), the connection (33) also comprising a support member (47) connected to the second end part (45) of the connecting member (41) and bearing against a face of the hub (31) that is remote from the drive shaft (3), the connection (33) comprising a plurality of ancillary connecting members (59), each of which secures the pump impeller (5) to the drive shaft (3). The pump (1) also comprises an anti-loss member (60) that is connected to the connecting member (41) and is interposed between the drive shaft (3) and the hub (31), having a shape chosen so as not to be able to pass through the orifice (39) in the event of the connecting member (41) breaking.