BWR Shroud Replacement Using Removable Fasteners
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Solution Overview
Problem
Boiling water nuclear reactors (BWRs) face challenges with shroud cracking over time, making replacement difficult due to welding, which complicates maintenance and operation.
Innovation Solution
A method involving forming cuts in the shroud to detach and remove damaged sections, allowing for the installation of a replacement shroud system using removable fastening devices, facilitating easier and less labor-intensive replacement compared to traditional welding methods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If traditional welding methods are used to assemble and replace shrouds, then structural strength and integrity are improved, but ease of repair and replacement time deteriorate significantly
Solution Approach 1:
The shroud is divided into multiple modular segments that can be independently removed and replaced. Each segment is connected through detachable coupling mechanisms rather than permanent welds, allowing individual segments to be exchanged without replacing the entire shroud structure. This segmentation enables maintenance crews to quickly replace only the damaged portions while preserving intact segments.
Solution Approach 2:
The shroud transitions from a static welded structure to a dynamic assembly with movable and detachable components. The coupling mechanisms allow for quick disassembly and reassembly, transforming the shroud from a permanent fixture into a maintainable component system that can be rapidly reconfigured during maintenance operations.
2Reliability
If welding is used to permanently attach shroud components, then reliability of the shroud structure is improved, but loss of time for maintenance operations increases
Solution Approach 1:
Replacement shroud segments are pre-assembled and pre-inspected outside the reactor vessel before being needed for installation. This preliminary preparation ensures that replacement components are ready immediately when maintenance is required, eliminating the need for on-site assembly and inspection during time-critical maintenance windows.
Solution Approach 2:
Traditional welding processes are replaced with mechanical coupling systems that use bolts, clamps, or interlocking mechanisms instead of thermal welding. This substitution eliminates the time-consuming welding operations while maintaining structural integrity through proven mechanical fastening methods that can be quickly installed and removed.
3Reliability
If the entire shroud is replaced as a single unit, then reliability is improved by ensuring no damaged components remain, but device complexity and cost increase
Solution Approach 1:
The shroud is segmented into standardized modular units with uniform coupling interfaces. This segmentation allows the shroud to be reconfigured by assembling different combinations of segments, enabling partial replacements that maintain overall integrity while reducing the complexity and cost of full-unit replacements.
Data Source
AI summary
An improved method of replacing at least a portion of a shroud apparatus of a BWR includes forming a cut in the shroud and removing at least a portion of the shroud apparatus that is adjacent the cut from a remaining portion of the shroud apparatus. The method also includes positioning a replacement shroud system adjacent the remaining portion of the original shroud apparatus and connecting a plurality of removable fastening devices between the new replacement shroud system and the remaining portion of the original shroud apparatus. The replacement shroud system thus can, in the future, be readily replaced by detaching the removable fastening devices, removing the replacement shroud system, and installing a new replacement shroud system with less effort than was required in cutting through the original shroud and replacing it with the replacement shroud system. An improved replacement shroud system is also disclosed.