Suspended Basket Upper Internals for Compact Reactors
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Solution Overview
Problem
Compact nuclear reactor designs face challenges with the complexity, volume, and weight of upper internals, which complicate reactor refueling and maintenance due to the need for external control rod drive mechanisms and guide frames, and introduce undesirable vessel penetrations that increase the risk of coolant loss during abnormal events.
Innovation Solution
A suspended basket system using adjustable length threaded tie rods and turnbuckle connections supports upper internals, allowing for internal control rod drive mechanisms and guide frames to be lifted as a unit during refueling, reducing complexity and vessel penetrations while maintaining structural integrity and alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If external control rod drive mechanisms and guide frames are used, then the upper internals can be properly supported and controlled, but the complexity and volume of the reactor vessel increases
Solution Approach 1:
The patent combines the control rod drive mechanisms and guide frames into a single integrated upper internals assembly that functions as one unified structure. This merging reduces the overall complexity by eliminating separate support systems while maintaining all necessary control functions within the basket structure.
Solution Approach 2:
The control rod drive mechanisms are nested within the guide frames, which are themselves part of the basket structure. This nesting arrangement allows multiple functional components to be housed within each other, reducing the external volume and complexity while preserving all control functions.
2Reliability
If external control rod drive mechanisms are used, then control functions are maintained, but vessel penetrations increase the risk of coolant loss
Solution Approach 1:
The patent extracts the control rod drive mechanisms from their traditional external position and relocates them entirely within the reactor vessel as part of the upper internals basket. This extraction from the external environment eliminates the need for penetrations through the vessel wall, thereby eliminating the pathway for coolant loss while maintaining full control functionality.
3Reliability
If complex upper internals are used, then control and guidance functions are achieved, but refueling and maintenance time increases
Solution Approach 1:
The patent segments the upper internals into a modular basket structure that can be removed as a single unit during refueling operations. This segmentation allows the entire assembly containing all control and guidance functions to be extracted together, significantly reducing refueling time compared to disassembling individual components.
Solution Approach 2:
The basket structure incorporates adjustable tie rod connections that allow for dynamic assembly and disassembly during maintenance operations. This dynamic feature enables quick configuration changes and rapid removal of the entire upper internals assembly, reducing both assembly time and refueling time while maintaining structural integrity.
4Strength
If traditional guide frames with tie rods are used, then structural support is provided, but alignment precision during assembly becomes difficult
Solution Approach 1:
The tie rod connections incorporate threaded adjustability that allows for dynamic alignment corrections during assembly. This dynamic adjustment capability enables precise alignment of the basket components while maintaining the structural strength provided by the tie rod framework.
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 reactor refueling by allowing the upper internals to be removed as a self-contained unit, reducing maintenance time and complexity, and minimizes the risk of coolant loss by eliminating the need for external penetrations, enhancing the safety and efficiency of compact reactor operations.
Implementation Method 1
rotating the tie rod coupling portion adjusts the position of the tie rod respective to the plate
Data Source
AI summary
A suspended basket includes a plurality of plates, tie rods, and adjustable length threaded tie rod couplings connecting threaded ends of the tie rods with threaded features of the plates. Control rod drive mechanisms (CRDMs) with CRDM motors are mounted in the suspended basket, which is suspended in a pressure vessel above a nuclear reactor core to control insertion of control rods into the reactor core. In one embodiment each adjustable length threaded tie rod coupling is a turnbuckle coupling that includes a sleeve threaded onto the threaded end of the tie rod and onto the threaded feature of the plate, and the sleeve is rotatable to adjust the position of the tie rod respective to the plate. Guide frames may be mounted in the suspended basket between the CRDMs and the nuclear reactor core to guide portions of the control rods withdrawn from the nuclear reactor core.