Closure Head Mounting Fixture for Protected Reactor Head Lifting
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Solution Overview
Problem
The challenge of safely and efficiently moving and manipulating a heavy closure head of a nuclear reactor pressure vessel during manufacturing operations, particularly to prevent damage to control rod guide tubes and ensure correct lifting operations, is not adequately addressed by existing technologies.
Innovation Solution
A fixture system comprising a support ring with upstanding projections and an underframe for mounting and lifting the closure head, featuring distinct fastening points for precise lifting and protection, along with optional additional fixtures for varied manufacturing needs, including a detachable second fixture and an invertible third fixture for inverted operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the closure head is moved between manufacturing operations, then productivity is improved, but the risk of damage to control rod guide tubes increases
Solution Approach 1:
The fixture is designed with pre-positioned support elements and alignment features that are prepared in advance. The closure head is mounted on the fixture before movement, ensuring proper positioning and protection of guide tubes prior to transportation between operations.
Solution Approach 2:
The fixture acts as an intermediary device between the closure head and the ground/transportation system. It provides a stable interface that protects the closure head during movement, preventing direct contact that could cause damage to vulnerable components like control rod guide tubes.
2Ease of operation
If lifting gear is attached to the closure head for lifting operations, then ease of operation is improved, but the risk of incorrect lifting and damage increases
Solution Approach 1:
The fixture provides specifically designed lifting attachment points with distinct local characteristics (e.g., different geometries, positions, or configurations). These localized features ensure that lifting gear can only be correctly attached to appropriate points, preventing incorrect lifting operations while maintaining ease of operation.
Solution Approach 2:
The fixture's lifting attachment points are designed to be self-identifying and self-regulating. The geometry and configuration of the attachment points automatically guide correct lifting gear placement and prevent incorrect attachment, making the system self-checking without requiring additional active control mechanisms.
3Manufacturing precision
If the closure head is supported during manufacturing operations, then manufacturing precision is improved, but the complexity of the support system increases
Solution Approach 1:
The fixture is divided into modular segments or components that can be independently positioned and adjusted. This segmentation allows the support system to provide precise positioning for the closure head while keeping each individual component relatively simple, avoiding the need for a single complex monolithic structure.
Data Source
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AI summary
A fixture is provided for mounting a closure head of a nuclear reactor pressure vessel during manufacture of the closure head. The closure head has a central section for penetration therethrough by control rod guide tubes and a peripheral section containing a circumferential row of through holes corresponding to positions of bolt holes by which, in use, the closure head is bolted to the reactor pressure vessel. The fixture has a support ring providing a circumferential row of upstanding projections which are matingly engageable through respective holes of the circumferential row of holes of the peripheral section of the closure head to mount the closure head on the support ring. The fixture further has an underframe for holding the support ring and closure head mounted thereon off the ground.