PWR Top Nozzle Deflector for Fuel Assembly Loading
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Solution Overview
Problem
In Soviet-designed pressurized water nuclear reactors, the non-removable top nozzles cause interference issues during fuel assembly loading, leading to extended refueling outage times and increased costs due to solid contact between bottom nozzles of newly loaded assemblies and those already in the core.
Innovation Solution
A top nozzle design featuring a plate portion with peripheral deflector portions extending inwardly at an acute angle, which deflects the bottom nozzle during loading, preventing undesirable engagement and allowing smooth assembly without prolonging the refueling process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the top nozzle is designed with a solid, fixed structure to provide structural support and positioning, then the structural strength and positioning accuracy are improved, but the bottom nozzle of a newly loaded fuel assembly makes solid contact with the top nozzle of an already loaded assembly, causing interference and extending refueling outage time
Solution Approach 1:
The top nozzle is segmented into multiple functional portions: a plate portion for structural support, a hub portion for positioning, support portions connecting them, and deflector portions extending from the peripheral portion. This segmentation allows the deflector portions to specifically address the interference issue while other portions maintain their structural functions.
Solution Approach 2:
The deflector portions act as intermediary elements between the bottom nozzle of the newly loaded assembly and the top nozzle of the already loaded assembly. These deflector portions deflect the bottom nozzle away from solid contact, serving as a mediator that prevents harmful interference while allowing the loading process to continue without extension.
2Manufacturing precision
If the top nozzle is designed with a fixed, non-removable structure to maintain positioning accuracy, then the positioning accuracy of the control rod cluster assembly is improved, but the bottom nozzle engages solidly with the top nozzle during loading, causing interference
Solution Approach 1:
Different portions of the top nozzle have different local qualities and functions. The plate portion and hub portion maintain fixed, precise positioning for structural integrity and positioning accuracy. The deflector portions, however, have a different local quality - they are designed to deflect and redirect the bottom nozzle during loading, improving ease of operation without compromising the overall positioning accuracy.
3Adaptability or versatility
If the top nozzle is designed to provide structural support and positioning functions, then the structural support and positioning are improved, but the solid contact between bottom and top nozzles causes extended outage time and increased costs
Solution Approach 1:
The top nozzle is designed with multi-functionality: the plate portion provides structural support, the hub portion provides positioning, the support portions connect these functions, and the deflector portions prevent interference during loading. This universal design allows a single component to address multiple issues - structural integrity, positioning accuracy, and loading ease - thereby reducing outage time without sacrificing any single function.
Data Source
AI summary
The present invention provides a top nozzle for use with PWR nuclear reactors and power plants, and in particular, VVER nuclear reactors. The top nozzle includes a plate portion having a peripheral portion; a hub portion spaced from the plate portion; a plurality of support portions extending from the plate portion to the hub portion; and at least one deflector portion extending inwardly from the peripheral portion at an acute angle with respect to the plate portion.