Dual Head Sludge Lance for Nuclear Steam Generator Tube Cleaning
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Solution Overview
Problem
Existing methods for removing sludge deposits from the tube sheets of steam generators, particularly nuclear steam generators, are inadequate as they struggle to effectively clean the central row of tubes due to the limitations of single-head sludge lances that cannot bypass the central rod, leading to incomplete removal and potential radioactive leaks.
Innovation Solution
A dual-head sludge lance system that can extend beyond the central stay rod in the tube bundle, allowing for simultaneous and complete cleaning of both the hot and cold leg sides of the steam generator tube bundle by using a moveable lance with dual heads and a monorail support system to traverse the central tube lane.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single-head sludge lance is used, then the device complexity is reduced, but the cleaning completeness deteriorates because it cannot bypass the central rod to clean the central row of tubes
Solution Approach 1:
The single-head sludge lance is divided into two separate heads (first sludge lance head and second sludge lance head) that can operate independently. Each head is positioned to clean a specific side of the central rod, allowing complete coverage of all tubes including the central row that was previously inaccessible.
Solution Approach 2:
The lance structure transitions from a single-point cleaning approach to a multi-point distributed cleaning approach by extending heads on opposite sides of the central rod. This spatial dimensionality change allows the lance to bypass the central rod obstruction and access the previously unreachable central row of tubes.
2Device complexity
If a single-head sludge lance is used, then the device complexity is reduced, but the lancing time increases because it cannot clean both hot and cold legs simultaneously
Solution Approach 1:
Two cleaning heads are merged into a single lance assembly, allowing simultaneous cleaning of both the hot leg and cold leg sides of the tube bundle. This combination maintains operational efficiency while achieving complete coverage of all surfaces including those previously inaccessible from a single position.
Solution Approach 2:
The dual-head configuration enables continuous cleaning action across the entire tube bundle surface by eliminating the need to reposition the lance between cleaning different sections. Both heads operate concurrently to maintain uninterrupted cleaning throughput.
3Productivity
If sludge accumulates on the tube sheet, then the sludge removal efficiency is reduced, but the tube wall thinning increases due to concentration of corrosive agents
Solution Approach 1:
The cleaning system applies localized high-velocity water jets specifically targeted at sludge accumulation zones on the tube sheet surface. The dual-head configuration ensures that both the hot leg side and cold leg side receive focused cleaning attention, preventing corrosive agent concentration at tube walls by completely removing sludge deposits.
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
The dual-head sludge lance system enables 100% sludge removal from the tube sheet surface, reducing lancing time by 50% and ensuring the central row of tubes is cleaned, thereby preventing radioactive leaks and maintaining the integrity of the steam generator.
Implementation Method 1
sludge lancing the hot leg side and the cold leg side of the tube bundle
Data Source
AI summary
A moveable sludge lance said moveable sludge lance having duel lance heads passed through handholes in the side of a nuclear steam generator and into a central tube lane having a central stay rod which cleans with high pressure fluid through the row 1 tubes in the tube lane, where the distance between the dual lance heads is wide enough to allow the dual lance heads to extend beyond the central stay rod.