Steam Generator Tube Plate Disassembly With Primary-Side TIG Heating
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Solution Overview
Problem
During the decommissioning of nuclear power facilities, existing methods for disassembling steam generators are inefficient in preventing the spread of radioactive contaminants when removing multiple heat transfer tubes, requiring a more effective approach to ensure safe and efficient disassembly.
Innovation Solution
A method involving cutting the end surfaces of heat transfer tubes and the tube plate to create a disassembly target, using a TIG heating head to release the fixation between the tubes and the plate by heating from the primary region side and moving the head along the longitudinal direction, and then pulling out the tubes from the secondary region side to minimize contamination and facilitate smooth removal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If heating is performed from the secondary region side to release fixation, then the heat transfer tube can be pulled out, but contaminants may spread to the surroundings
Solution Approach 1:
The heating direction is inverted from the conventional secondary region side to the primary region side. By inserting the heating device from the primary region side and moving it in the direction from primary to secondary region, the heat transfer tube expands and contracts in a controlled manner that prevents contaminant spread while enabling successful removal of the tube from the tube plate.
2Productivity
If all heat transfer tubes are removed during decommissioning, then complete disassembly is achieved, but the risk of contaminant spread increases
Solution Approach 1:
The method establishes proper heating procedures and contamination control measures before beginning the removal of all heat transfer tubes. By pre-positioning heating devices on the primary region side and establishing the correct heating sequence, the system enables complete disassembly while maintaining contamination control throughout the entire decommissioning process.
3Productivity
If heating is performed efficiently to release fixation quickly, then workability improves, but contamination control may be compromised
Solution Approach 1:
The heating is applied locally and sequentially from the primary region side toward the secondary region side. This localized heating approach allows efficient release of fixation at each position while maintaining contamination control, as the heating process is confined to a specific region at any given time rather than affecting the entire heat transfer tube simultaneously.
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 method efficiently reduces the spread of contaminants and allows for stable and smooth separation of heat transfer tubes from the tube plate, enhancing the disassembly process while preventing damage to the tubes.
Implementation Method 1
releasing fixation between the part of the heat transfer tube and the tube plate by inserting a TIG heating head into the part of the heat transfer tube fixed to the tube plate to heat the heat transfer tube
Data Source
AI summary
A method of disassembling a steam generator including a body portion, a water chamber, a tube plate and a plurality of heat transfer tubes, the method includes: a step of obtaining a disassembly target including the tube plate and a part of the heat transfer tubes; a step of specifying the heat transfer tube fixed to the tube plate; a step of releasing fixation between the part of the heat transfer tube and the tube plate; and a step of pulling out the part of the heat transfer tube from the through-hole, in the step of releasing the fixation, the TIG heating head is inserted from the primary region side, and in the step of releasing the fixation, the TIG heating head is moved to a plurality of streaks only in a direction from the primary region side to the secondary region side.