Variable Circumference Lock Insert for Nuclear Fuel Top Nozzle
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Solution Overview
Problem
The existing fastening structure of the top nozzle and lock insert in nuclear fuel assemblies makes it difficult to disassemble and reassemble, particularly due to the hydraulic uplift force and thermal expansion, which complicates maintenance and remote operation.
Innovation Solution
A system with a lock insert featuring a variable circumference insertion part and latching members that can be easily inserted and separated from the guide hole, along with a separation part to lift the top nozzle, simplifying the disassembly and reassembly process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the top nozzle insert and lock tube are firmly coupled to the flow channel plate using a conventional fastening structure, then the mechanical stability is improved, but the disassembly and reassembly become difficult and time-consuming
Solution Approach 1:
The lock insert employs a circumferential expansion mechanism that transitions from a compressed state during insertion to an expanded locked state. The insertion part expands circumferentially to engage with the guide hole, creating a dynamic fastening system that is easy to insert but difficult to remove without deliberate action.
Solution Approach 2:
The fastening structure is divided into separate functional components: the lock insert with insertion part, the guide hole with latching features, and the separation part. This segmentation allows the coupling and decoupling functions to be independently controlled, enabling easy disassembly when needed while maintaining firm coupling during operation.
2Reliability
If the top nozzle is firmly fixed to prevent movement during reactor operation, then the structural stability is improved, but the remote handling and maintenance operations become more complex
Solution Approach 1:
The separation part is introduced as a dedicated extraction tool that removes the lock insert from the guide hole. This separates the firm coupling function (performed by the lock insert) from the release function (performed by the separation part), simplifying remote handling operations while maintaining structural stability during operation.
3Reliability
If multiple components are used to ensure secure coupling, then the coupling reliability is improved, but the number of parts increases making maintenance more difficult
Solution Approach 1:
The lock insert combines multiple functions into a single component: it provides the insertion mechanism, the expansion for securing, and the engagement with latching features. This merging reduces the number of separate parts while maintaining coupling reliability through the integrated multi-functional design.
4Manufacturing precision
If the insertion part has a fixed circumference, then the manufacturing precision is improved, but the ease of insertion and separation is reduced
Solution Approach 1:
The insertion part transitions from a fixed dimension during manufacturing to a variable dimension during operation. The ability to expand and contract circumferentially enables easy insertion and separation while maintaining precise manufacturing specifications for the locked position.
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 solution simplifies the disassembly and reassembly of the top nozzle, reduces the number of parts, and enhances handleability, making remote maintenance and repair easier while preventing parts from breaking during coupling and disassembly.
Implementation Method 1
a circumference of the insertion part being variable in size, thereby being capable of being inserted into the guide hole
Implementation Method 2
a first latching member brought into contact with a latching step; and a second latching member brought into contact with a latching groove
Data Source
AI summary
Disclosed is a system for separating and coupling a top nozzle of a nuclear fuel assembly. There is provided a lock insert configured to support the top nozzle of the nuclear fuel assembly by being coupled to a guide hole provided in a flow channel plate of the top nozzle, the lock insert including: a body in a hollow shape; and an insertion part provided on a top portion of the body and inserted into the guide hole, wherein a circumference of the insertion part is variable in size, thereby being capable of being inserted into the guide hole. Accordingly, disassembly and reassembly of the top nozzle of the nuclear fuel assembly and the lock insert are simplified, thereby simplifying and reducing the number of processes involved therein. Accordingly, the system is effective for maintenance and repair of the nuclear fuel assembly.