Nuclear Reactor Nozzle Repair via Plug Compression
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Solution Overview
Problem
The existing nozzle repair methods for nuclear reactor vessels are complex and costly, leading to increased repair costs due to the precision required in forming buttered-grooving portions and buttered-welding, which complicates the repair process.
Innovation Solution
A nozzle repair method involving the removal of the connection portion with respect to the in-core instrumentation cylinder, forming a plug attachment portion, applying a pressing load to the semi-spherical portion, and welding the plug to the plug attachment portion, which simplifies the repair process and reduces costs by eliminating the need for heat treatment and minimizing welding material usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the buttered-grooving portion is formed on the inner surface of the vessel and the plug is inserted and buttered welded, then the new nozzle can be attached with high precision, but the repair process becomes complex and repair cost increases
Solution Approach 1:
The method applies a pressing load to the semi-spherical portion before welding the plug, pre-compressing the joint area. This preliminary action ensures that when the plug is welded and shrinks due to cooling, it maintains intimate contact with the groove-welding portion without forming gaps, thereby achieving high precision attachment without requiring complex buttered-grooving processes
Solution Approach 2:
The method changes the physical state and mechanical parameters of the semi-spherical portion by applying a pressing load that deforms it elastically. This parameter change allows the plug to be pressed tightly against the groove-welding portion during welding, ensuring precise fit and eliminating the need for complex preliminary grooving operations
2Device complexity
If the groove-welding portion is removed and the plug is welded to the semi-spherical portion without pressing load, then the repair process is simplified, but gaps may form between the plug and the semi-spherical portion due to thermal contraction
Solution Approach 1:
The pressing load is applied to the semi-spherical portion before welding the plug, pre-compressing the joint area. This preliminary action ensures that when the plug is welded and shrinks due to cooling, it maintains intimate contact with the groove-welding portion without forming gaps, thereby achieving high precision attachment without requiring complex buttered-grooving processes
Solution Approach 2:
The pressing load counteracts the anticipated thermal contraction of the plug during welding. By applying this preliminary opposing force, the method prevents the formation of gaps that would otherwise occur due to cooling shrinkage, ensuring precise fit without complex procedures
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method improves workability and reduces repair costs by allowing for easy plug fixation without gaps, ensuring high precision and stress corrosion cracking resistance, and simplifying the welding operation, thus enhancing the overall repair efficiency.
Implementation Method 1
applying a pressing load to the semi-spherical portion by attaching a plug to the plug attachment portion
Implementation Method 2
welding and fixing the plug attached to the plug attachment portion
Data Source
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AI summary
A nozzle repair method and a nuclear reactor vessel include: removing a trepanning portion (208) as a connection portion with respect to an in-core instrumentation cylinder (204) in a groove-welding portion (206); removing the in-core instrumentation cylinder (204) from a lower end plate (66); forming a plug attachment opening (211) by removing the groove-welding portion (206); applying a pressing load to the lower end plate (66) by attaching a plug (212) to the plug attachment opening (211); and welding and fixing the plug (212) attached to the plug attachment opening (211). Accordingly, since a repair is easily performed, it is possible to improve the workability and to decrease a repair cost.