Abstract
Fusion energy is expected as a promising candidate for alternative next generation energy. For fusion reactor, the plasma facing components (PFCs) are the most critical components to achieve this goal. PFCs will suffer severe thermal shock due to repective cyclic high heat flux (HHF) loads. This paper investigates the effects of thermal shock and damage behavior of tungsten armored PFCs under steady, transient and combined thermal loads. The distribution of stress field is analyzed, and crack initiation is predicted using the extended finite element method (XFEM). The unique features of thermal-mechanical behavior of tungsten armored PFCs under simulated service condition are discussed. The dominant factor of the cracking of the tungsten armor is the brittleness of tungsten below ductile-to-brittle transition temperature (DBTT). Under the steady loads, the cracking position is apt to near the interface of tungsten armor and the interlayer, and the threshold of cracking is between 14 MW/m2 and 16 MW/m2. With 6 MW/m2 steady loads, applying 1 ms duration of transient load, the cracking threshold is between 0.2 GW/m2 to 0.4 GW/m2. The depth of cracking increases from 100 um to 500 um with the transient load increasing from 0.4 GW/m2 to 1.0 GW/m2. Researches are useful for the design and structural optimization of tungsten-armored PFCs, and the long-term stable operation of further reactor.
Highlights
Fusion energy is expected as a promising candidate for alternative generation energy
This paper investigates the effects of thermal shock and damage behavior of tungsten armored plasma facing components (PFCs) under steady, transient and combined thermal loads
As tungsten has many unique properties such as low sputtering erosion and tritium retention, high melting point and moderate thermal expansion[5], it has been choosing as the main divertor plasma facing materials (PFMs) in ITER and has been foreseen as the most suitable candidate for the first wall in demonstration fusion reactor (DEMO) or future fusion reactors[6,7,8]
Summary
The CuCrZr alloy has been chosen as the heat sink material because of its good irradiation resistance and high thermal conductivity, and its tube diameters are 12/15 mm (ID/OD). The ITER-relevant cooling condition is selected: coolant water for 10 m/s, 4.0 MPa at 100 °C and perfect thermal contacts at the interfaces were assumed[20]. Symmetric boundary conditions were applied based on simplification, and a pressure of 4.0 MPa was applied to the inner surface of cooling tube to simulate the pressure caused by cooling water. The boundary conditions were as follows: mechanical constraint in all directions at bottom face of W monoblock, the side surface of interlayer and tungsten armor is free; the thermal conduction between a heated tungsten armor and the neighbor armor is negligible; coolant temperature at 100 °C. It should be noted that all components are bonded to each other perfectly for simplifying the FE analysis
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