CPS Based Liquid Metal Divertor Target for EU-DEMO
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ORIGINAL RESEARCH
CPS Based Liquid Metal Divertor Target for EU-DEMO S. Roccella1 • G. Dose2 • R. de Luca3 • M. Iafrati1 • A. Mancini1 • G. Mazzitelli1 Received: 3 June 2020 / Revised: 29 September 2020 / Accepted: 3 October 2020 Ó The Author(s) 2020
Abstract Power exhaust is a key mission in the roadmap to the realization of a future fusion reactor. Among the different solutions, the use of liquid metals as plasma facing materials are of interest due to their potential increased lifetime. Several liquid metal limiters have been successfully tested in the Frascati Tokamak Upgrade over the last 10 years. Liquid materials such as lithium and tin have been investigated using capillary porous systems (CPSs), and their impact on plasma performance has been explored. From such experience, a liquid metal divertor (LMD) concept design, CPS-based, is here proposed. Tin has been preferred as plasma facing material. The proposed LMD would operate, in low evaporative regime, with matching heat exhausting capabilities to those of the baseline ITER-like divertor. Continuous refilling of the CPS is guaranteed with a reservoir at the back of the unit, where the metal is kept liquid through a gas heating circuit. The study has been carried out using ANSYS and the thermal results will be shown. All the design choices are compatible with the current materials and the constraints adopted for the DEMO W divertor. Using such configuration, thermal loads up to 20 MW/m2 are exhausted while keeping the surface temperature below 1250 °C. The design foresees values of pressure, temperature and flow rate of the water coolant in the same range expected for the W DEMO divertor, thus facilitating the integration of such solution in the current cassette design. Technological and practical aspects are addressed, i.e. tin corrosion and CPS wettability. Possible solutions to prevent tin corrosion, and its compatibility with structural materials, will be outlined. Keywords DEMO Liquid metal divertor Plasma facing component Tin
Introduction The baseline strategy for the DEMO divertor plasma facing units (PFUs) consists in the W monoblock design, which foresees CuCrZr heat sink pipes joined to W monoblock armor through a soft Cu interlayer [1]. Lifetime of such components is affected by erosion, thermal fatigue, as well as damage due to a significant neutron flux. Many experiments [2] have confirmed liquid metals (LMs) as a promising candidate for plasma facing material. Their peculiar advantages are:
& S. Roccella [email protected] 1
Department of Fusion and Technology for Nuclear Safety and Security, ENEA, Frascati, Italy
2
Industrial Engineering Department, University di Rome ‘‘Tor Vergata’’, Via del Politecnico 1, 00133 Rome, Italy
3
DEIm Department, University of Tuscia, Via del Paradiso 47, 01100 Viterbo, Italy
1. Self-healing/renewability of the plasma facing surface. 2. Less sensitivity to the neutron damage. As a result, an increased lifetime with respect to a solid wall is e
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