Fuel Assembly Coupling Structure for Foreign Matter Prevention

The harmful element (detachable nut) is extracted and replaced with a integrated locking mechanism. The lock key with locking protrusions engages with recesses in the guide tube, eliminating the separate nut component that could fall into the fuel while maintaining detachability of the upper nozzle.

The lock key acts as an intermediary mechanism between the upper nozzle and guide tube. It provides a secure connection through locking protrusions and recesses, replacing the direct nut-guide tube interaction and preventing foreign matter contamination while enabling controlled detachment.

Instead of having a gap between projecting and receiver portions, the design uses interlocking locking protrusions and recesses that engage positively. This inverted approach eliminates the gap and vertical play while maintaining detachability through the lock key mechanism.

The locking protrusions and recesses are pre-formed in precise positions to ensure proper alignment and engagement. This preliminary preparation of mating features eliminates the need for adjustment and prevents vertical play during operation.

The connection system is segmented into distinct components: the upper nozzle, lock key, and guide tube with locking features. This segmentation allows the connection to be as strong as welding through the interlocking mechanism, while enabling easy detachment by removing the lock key without permanent bonding.

The connection transitions from a static welded joint to a dynamic, controllable connection. The lock key can be inserted or removed to engage or disengage the locking protrusions, providing adjustable connectivity that maintains strength when engaged and allows detachment when needed.