Core Barrel Manufacturing Precision via Segmented Welding
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Solution Overview
Problem
Conventional core barrel manufacturing methods in pressurized water reactors face challenges in maintaining the accuracy of the placement surface and fuel alignment pin holes due to the proximity of weld lines, which can lead to stress corrosion cracking and deformation, affecting the positional accuracy of the fuel assembly.
Innovation Solution
A method involving the welding of a short ring to the lower core support plate, followed by machining and dimensional stabilization heat treatment, allows for the formation of the placement surface and fuel alignment pin holes with improved accuracy, and subsequent welding of the main body barrel with weld lines positioned away from the support plate to prevent deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the lower core support plate is welded to the lower barrel first, then the structural integrity is ensured, but the placement surface accuracy deteriorates due to welding deformation
Solution Approach 1:
The core barrel is divided into multiple segments (upper barrel, middle barrel, lower barrel) that are manufactured separately and then assembled. This segmentation allows each component to be manufactured with high precision independently, and the final welding occurs during assembly rather than during the manufacturing of critical surfaces, thus preserving placement surface accuracy while ensuring structural integrity.
Solution Approach 2:
The lower core support plate is preliminarily manufactured with high-precision placement surface through machining before any welding operations. By completing all precision machining operations on the placement surface before welding the lower barrel, the critical surface is protected from welding-induced deformation, and subsequent welding does not affect the already-established precision geometry.
2Ease of manufacture
If welding is performed close to the placement surface, then the manufacturing process is simplified, but the placement surface accuracy deteriorates due to thermal influence
Solution Approach 1:
The critical placement surface is extracted as a separate functional element that requires protection from welding thermal influence. The lower core support plate is designed so that the placement surface is positioned at a sufficient distance from the welding zone between the lower barrel and the support plate, effectively separating the precision surface from the thermal process zone and eliminating welding-induced deformation on the placement surface.
Solution Approach 2:
All precision machining operations on the placement surface are performed as preliminary actions before any welding operations take place. This sequencing ensures that the placement surface achieves its final high-precision dimensions and surface quality before being exposed to any thermal processes, thereby preventing welding heat from affecting the critical geometric accuracy of the placement surface.
3Reliability
If a forged core barrel is used, then weld lines facing the fuel assembly are reduced, but the manufacturing cost increases
Solution Approach 1:
The core barrel is segmented into multiple components (upper barrel, middle barrel, lower barrel, lower core support plate) that are manufactured separately using cost-effective processes and then assembled through welding. This segmentation allows the use of economical manufacturing methods for each component while positioning weld lines away from the fuel assembly area, achieving both cost efficiency and reliability by eliminating the need for expensive full-forging processes.
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 approach enhances the shape and positional accuracy of the fuel assembly placement surface, reducing the risk of deformation and stress-related issues, while also offering a cost-effective manufacturing process compared to forging.
Implementation Method 1
welding one end part of a short ring to a lower core support plate; welding a main body barrel to the other end part of the short ring
Implementation Method 2
dimensional stabilization heat treatment
Data Source
AI summary
A method for manufacturing a core barrel according to the embodiment includes: welding one end part of a short ring to a lower core support plate; and machining the lower core support plate to which the short ring is welded. The machining of the lower core support plate includes forming a placement surface on which the fuel assembly is to be placed; and forming a fuel alignment pin hole, in which a fuel alignment pin for positioning the fuel assembly is to be inserted. After the machining of the lower core support plate, a main body barrel is welded to the other end part of the short ring, where the main body barrel covers the reactor core including the fuel assembly to be placed on the placement surface.