Tokamak First Wall Repair Under Vacuum by Refractory Metal Deposition
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Solution Overview
Problem
Tokamak plasma vessels face significant downtime due to the need to repressurize and degas the chamber for regular maintenance and repair of divertor and first wall surfaces, which are prone to high heat and wear, requiring frequent replacement or repair.
Innovation Solution
In-situ refractory metal deposition techniques such as additive manufacturing, physical vapour deposition, thermal spray, arc ion plating, diode laser cladding, and chemical vapour deposition are used to repair the divertor and first wall surfaces within the tokamak plasma vessel while maintaining a pressure below 25 mbar, allowing for temporary suspension of plasma operations and immediate reuse of the chamber.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the divertor and first wall surfaces are made from refractory metals to withstand high heat and wear, then the resistance to erosion and heat tolerance is improved, but the frequency of replacement and repair increases due to inevitable wear
Solution Approach 1:
The patent applies the discarding and recovering principle by collecting worn refractory metal particles from the divertor and first wall surfaces and re-depositing them onto these surfaces during maintenance periods. This recovery process extends the service life of the components by restoring the eroded metal layers, thereby reducing the frequency of replacement while maintaining the heat and erosion resistance properties.
2Reliability
If the plasma vessel is shut down for regular maintenance and repair of divertor and first wall surfaces, then the reliability and performance of plasma components are maintained, but significant downtime occurs due to repressurization and degassing requirements
Solution Approach 1:
The patent implements continuity of useful action by enabling maintenance and repair operations to be performed while the plasma vessel maintains vacuum conditions. The in-situ refractory metal deposition system allows repair activities to continue without interrupting the vacuum state, eliminating the time-consuming cycles of repressurization and degassing. This enables uninterrupted maintenance operations that significantly reduce overall downtime while maintaining component reliability.
Solution Approach 2:
The patent introduces an intermediary deposition system that operates within the vacuum environment of the plasma vessel. This intermediary system delivers refractory metal materials directly to the divertor and first wall surfaces through vacuum-compatible delivery mechanisms, enabling repair operations without breaking the vacuum seal. The intermediary system acts as a bridge between the maintenance requirements and the vacuum operational constraints.
3Ease of manufacture
If conventional repair methods requiring chamber repressurization are used, then the repair process can be performed with standard equipment, but the chamber must be returned to vacuum through lengthy de-gassing processes
Solution Approach 1:
The patent applies the inert atmosphere principle by creating and maintaining a vacuum environment throughout the repair process. The in-situ deposition system is designed to operate exclusively in vacuum conditions, using vacuum-compatible material delivery and deposition mechanisms. This eliminates the need to break vacuum for material introduction or process execution, allowing repairs to proceed in the inert vacuum environment without subsequent de-gassing requirements.
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 reduces downtime by enabling in-vacuum repair of the tokamak components without the need for repressurization, allowing for quicker resumption of plasma operations and minimizing the impact of wear and heat damage on the divertor and first wall surfaces.
Implementation Method 1
The refractory metal is deposited onto the divertor or first wall surface within the plasma vessel via a deposition process which is one of: additive manufacturing; physical vapour deposition; thermal spray; arc ion plating; diode laser cladding; and chemical vapour deposition.
Implementation Method 2
The refractory metal is deposited onto the divertor or first wall surface within the plasma vessel via a deposition process which is one of: additive manufacturing; physical vapour deposition; thermal spray; arc ion plating; diode laser cladding; and chemical vapour deposition.
Implementation Method 3
The refractory metal is deposited onto the divertor or first wall surface within the plasma vessel via a deposition process which is one of: additive manufacturing; physical vapour deposition; thermal spray; arc ion plating; diode laser cladding; and chemical vapour deposition.
Implementation Method 4
The refractory metal is deposited onto the divertor or first wall surface within the plasma vessel via a deposition process which is one of: additive manufacturing; physical vapour deposition; thermal spray; arc ion plating; diode laser cladding; and chemical vapour deposition.
Data Source
AI summary
A method of repairing a divertor or first wall surface in a tokamak plasma vessel. The divertor or first wall surface comprises a refractory metal having a melting point of at least 2000° C. A pressure of less than 25 mbar is maintained within the plasma vessel following the end of operation of the plasma vessel. The refractory metal is deposited onto the divertor or first wall surface within the plasma vessel via a deposition process which is one of: additive manufacturing; physical vapour deposition; thermal spray; arc ion plating; diode laser cladding; and chemical vapour deposition.