ITER enhanced heat flux first wall technology

ITER enhanced heat flux first wall shields extra-high thermal flux from its burning plasma and limit the plasma boundary. With a surface heat load up to 4.7 MW/m², it uses a profiled surface of Be tiles mounting on the hypovaportron (HVT) cooling structure that composes of Cu Cr Zr alloy and stainless steel. Heat load are being transferred to 4 MPa and 2 m/s cooling water through these well-bonded materials. It is able to withstand the pulse operation of ITER for 15000 cycles. Hot iso-static pressing (HIP) and explosion bonding technologies have been successfully developed to make reliable Be/Cu Cr Zr and Cu Cr Zr/316L (N) joints, respectively. The tensile strength and microstructure of the copper alloy was well controlled by optimizing heat treatment and thermal process. The residual stress of the post-HIP ed Be/Cu Cr Zr joints was reduced significantly by improving the interface layers. The thermal fatigue life of the HVT cooling channel was greatly extended with an innovative design. Full-scale FW finger pairs and a semi-prototype were made, the pairs successfully withstood thermal fatigue test at 4.7 MW/m² for 7500 cycles and 5.9 MW/m² for 1500 cycles. The enhanced heat flux technology was thus successfully qualified according to ITER requirements. (authors)