In-Core Instrument Thimble Handling with Retractable Coiled Cabling
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Solution Overview
Problem
In nuclear reactor systems, particularly in small modular reactors, the existing methods for accessing and removing in-core instrumentation from the core for refueling are cumbersome and prone to damage due to the compact design and lack of space, requiring multiple steps and potential exposure to radiation for plant workers, especially when top-mounted instrumentation is used.
Innovation Solution
The design modifies the in-core instrument thimble assemblies to have a retractable upper section with coiled signal cabling, allowing simultaneous withdrawal of all thimble assemblies without disassembling electrical connectors underwater, and incorporates a telescoping guide tube to facilitate safe removal, reducing the number of steps and radiation exposure during refueling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If traditional bottom-mounted in-core instrumentation is used, then instrumentation can be easily removed through the bottom penetration, but leakage occurs at the bottom penetration which presents significant repair problems
Solution Approach 1:
The patent inverts the traditional bottom-mounted instrumentation approach by implementing top-mounted instrumentation that accesses the core from above through the reactor head, eliminating the bottom penetration leakage problem while maintaining instrumentation functionality
2Object-affected harmful factors
If fixed in-core instrumentation enters through the top of the vessel, then leakage at penetrations is avoided, but the instrumentation must be withdrawn through complex upper internal structures during refueling
Solution Approach 1:
The patent segments the in-core instrument thimble assembly into multiple sections with telescoping guide tubes that can be independently manipulated, allowing the instrumentation to be withdrawn from the complex upper internal structure in a controlled manner without requiring complete disassembly of the structure
Solution Approach 2:
The patent introduces telescoping guide tubes as intermediary structures that facilitate the withdrawal of instrumentation from the upper internal structure, providing a guided path that simplifies the removal process while maintaining structural integrity
3Adaptability or versatility
If in-core instrumentation is retracted before refueling in small modular reactors, then access to the core is enabled, but the compact design and lack of space make the procedure cumbersome and prone to damage
Solution Approach 1:
The patent implements dynamic, movable guide tubes that can extend and retract along with the instrumentation, adapting to the compact space constraints of small modular reactors while providing adequate clearance and protection during the withdrawal operation
Solution Approach 2:
The patent employs nested telescoping guide tubes where inner tubes slide within outer tubes, allowing compact storage when not in use and providing extended guidance and protection during instrumentation withdrawal, effectively utilizing the limited space in small modular reactors
4Reliability
If multiple steps are required to remove instrumentation with traditional methods, then electrical connectors can be protected, but the critical path time and labor required for refueling increase
Solution Approach 1:
The patent performs preliminary actions by pre-configuring the telescoping guide tubes and maintaining electrical connectivity before instrumentation withdrawal begins, allowing the entire removal process to be completed in a single operation without intermediate disconnection steps
5Productivity
If workers are exposed to radiation during instrumentation removal, then refueling can be performed, but the radiation exposure increases health risks
Solution Approach 1:
The patent enables the instrumentation withdrawal to be completed in a single rapid operation by maintaining electrical connectivity and using telescoping guide tubes, minimizing the time workers are exposed to radiation during the refueling process
Data Source
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AI summary
A reactor in-core instrument handling system in which the signal leads are routed from the instrument sensors through an outer sheath through the upper reactor internals and out of and around the sheath in a substantially tightly wound spiral before exiting the reactor vessel.