Power Exhaust Concepts and Divertor Designs for Japanese and European DEMO Fusion Reactors

Concepts of the power exhaust and divertor design have been developed, with a high priority in the pre-conceptual design phase of the Japan-Europe Broader Approach DEMO Design Activity. A common critical issue is the large power exhaust and its fraction in the main plasma and divertor by the radiative cooling. Different exhaust concepts in the main plasma and divertor have been developed for JA and EU DEMOs. JA proposed a conventional closed divertor geometry to challenge large Psep/Rp handling of 30-35 MWm-1 in order to maintain the radiation fraction in the main plasma at the ITER-level (fradmain = Pradmain/Pheat ~0.4) and higher plasma performance. EU challenged both increasing fradmain to ~0.65 and handling the ITER-level Psep/Rp in the open divertor geometry. Power exhaust simulations have been performed by SONIC (JA) and SOLPS5.1 (EU) with corresponding Psep = 250-300 MW and 150-200 MW, respectively. Both results showed that large divertor radiation fraction (Praddiv/Psep 0.8) was required to reduce both peak qtarget ( 10MWm-2) and Te,idiv. In addition, the JA divertor performance with EU-reference Psep of 150MW showed benefit of the closed geometry to reduce the peak qtarget and Te,idiv near the separatrix, and to produce the partial detachment. Integrated designs of the water cooled divertor target, cassette and coolant pipe routing have been developed in both EU and JA, based on the tungsten (W) monoblock concept with Cu-alloy pipe. For year-long operation, DEMO-specific risks such as radiation embrittlement of Cu-interlayers and Cu-alloy cooling pipe were recognized, and both foresee higher water temperature (130-200 °C) compared to that for ITER. At the same time, several improved technologies of high heat flux components have been developed in EU, and different heat sink design, i.e. Cu-alloy cooling pipes for targets and RAFM steel ones for the baffle, dome and cassette, was proposed in JA. The two approaches provide important case-studies of the DEMO divertor, and will significantly contribute to both DEMO designs

Plasma Exhaust and Divertor Designs in Japan and Europe Broader Approach, DEMO Design Activity

Concepts of the power exhaust and divertor design have been developed, with a high priority in the pre-conceptual design phase of the Japan-Europe Broader Approach DEMO Design Activity (BA DDA). A common critical issue is the large power exhaust in the main plasma and divertor by the radiative cooling. (i) Different exhaust concepts in the main plasma and divertor have been developed for JA and EU DEMOs, and both divertor operations were systematically simulated and compared. (ii) Integrated designs of the heat removal components and cassette structures also have been developed. (iii) Both divertor designs are adequate to handle the peak heat loads on the target (qtarget) of 10 MW/m2 level under neutron irradiation condition.28th IAEA Fusion Energy Conferenc

Plasma Exhaust and Divertor Designs in Japan and Europe Broader Approach, DEMO Design Activity

Concepts of the power exhaust and divertor design have been developed, with a high priority in the pre-conceptual design phase of the Japan-Europe Broader Approach DEMO Design Activity (BA DDA). A common critical issue is the large power exhaust in the main plasma and divertor by the radiative cooling. (i) Different exhaust concepts in the main plasma and divertor have been developed for JA and EU DEMOs, and both divertor operations were systematically simulated and compared. (ii) Integrated designs of the heat removal components and cassette structures also have been developed. (iii) Both divertor designs are adequate to handle the peak heat loads on the target (qtarget) of 10 MW/m2 level under neutron irradiation condition.28th IAEA Fusion Energy Conferenc

Plasma Exhaust and Divertor Designs in Japan and Europe Broader Approach, DEMO Design Activity

Concepts of the power exhaust and divertor design have been developed, with a high priority in the pre-conceptual design phase of the Japan-Europe Broader Approach DEMO Design Activity (BA DDA). A common critical issue is the large power exhaust in the main plasma and divertor by the radiative cooling. (i) Different exhaust concepts in the main plasma and divertor have been developed for JA and EU DEMOs, and both divertor operations were systematically simulated and compared. (ii) Integrated designs of the heat removal components and cassette structures also have been developed. (iii) Both divertor designs are adequate to handle the peak heat loads on the target (qtarget) of 10 MW/m2 level under neutron irradiation condition