Bottom-Up Thermal Sleeve Replacement in Reactor Vessel Tubes
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Solution Overview
Problem
Existing methods for replacing thermal sleeves in nuclear reactor pressure vessel control rod drive mechanisms are inefficient and require complete removal of the reactor vessel closure head, leading to downtime and increased maintenance costs.
Innovation Solution
A method and device involving a first sleeve with a funnel on its lower end and a second sleeve acting as a retainer, which are intermeshed and secured in place using roll expansion, deformation, or welding, allowing for in-situ replacement without removing the reactor vessel closure head.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of repair
If the reactor vessel closure head is removed and placed on a head stand for sleeve replacement, then the thermal sleeve can be replaced, but reactor downtime increases and maintenance costs increase
Solution Approach 1:
The sleeve assembly is divided into two separate sleeves: a first sleeve that is inserted through the nozzle from the bottom, and a second sleeve that is inserted from the top. These two sleeves are then joined together inside the nozzle, allowing the replacement to be performed in situ without removing the closure head.
Solution Approach 2:
The first sleeve and second sleeve are nested within each other during insertion, with the first sleeve positioned inside the second sleeve. They are then joined together through rolling or welding to form a complete thermal sleeve assembly, enabling in-situ replacement.
2Ease of repair
If the reactor vessel closure head is removed for sleeve replacement, then the thermal sleeve can be accessed and replaced, but maintenance costs increase
Solution Approach 1:
The sleeve assembly is divided into two separate sleeves: a first sleeve that is inserted through the nozzle from the bottom, and a second sleeve that is inserted from the top. These two sleeves are then joined together inside the nozzle, allowing the replacement to be performed in situ without removing the closure head.
Solution Approach 2:
The replacement process requires no external support structures or disassembly of the closure head. The two sleeves are inserted and joined using tools that can operate through the existing nozzle openings, making the system self-sufficient and eliminating the need for expensive head stand equipment and extensive labor.
3Ease of operation
If a replacement sleeve is used with outer and inner flanges for bearing portion, then sleeve replacement is enabled without removing CRD, but the complexity of the replacement device increases
Solution Approach 1:
The sleeve assembly is divided into two separate sleeves: a first sleeve that is inserted through the nozzle from the bottom, and a second sleeve that is inserted from the top. These two sleeves are then joined together inside the nozzle, allowing the replacement to be performed in situ without removing the closure head.
Solution Approach 2:
Instead of inserting a single complex sleeve assembly from the top with flanges, the invention inserts a simple first sleeve from the bottom and a simple second sleeve from the top, then joins them together. This inverted approach simplifies the individual components while achieving the same functional result.
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
Enables efficient and cost-effective replacement of thermal sleeves without disrupting reactor operations, reducing maintenance downtime and costs by allowing in-situ installation and secure fixation within the control rod drive mechanism nozzle.
Implementation Method 1
locking the first sleeve and the second sleeve in position in a CRDM nozzle through intermeshing of the first and second sleeves with each other. After the intermeshing of the first and second sleeves, the first and second sleeves may be attached by means such as roll expansion, deformation, or welding.
Implementation Method 2
locking the first sleeve and the second sleeve in position in a CRDM nozzle through intermeshing of the first and second sleeves with each other. After the intermeshing of the first and second sleeves, the first and second sleeves may be attached by means such as roll expansion, deformation, or welding.
Data Source
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AI summary
A method for replacing a damaged sleeve (26) lining a tube (36) passing through a nuclear reactor pressure vessel (10) is provided. The damaged sleeve has an end including a radially enlarged end portion (48) configured for resting on a support section (44) of the tube for retaining the damaged sleeve in the tube. The method includes removing the damaged sleeve from the tube; providing a sleeve assembly (62) including a first sleeve (64) with a radially variable end configured for being deformed between a radially contracted configuration and a radially expanded configuration and a retainer (66) configured for being deformed between an installation configuration and a retention configuration; installing the sleeve assembly in the tube such that the radially variable end of the first sleeve is received by the support section, the radially variable end being in the radially contracted configuration during installation and being in the radially expanded configuration after the sleeve assembly is installed in the tube; and deforming the retainer from the installation configuration to the retention configuration to retain the radially variable end of the first sleeve in the radially expanded configuration.