Design and Testing of Advanced Liquid Metal Targets for DEMO Divertor: The OLMAT Project
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ORIGINAL RESEARCH
Design and Testing of Advanced Liquid Metal Targets for DEMO Divertor: The OLMAT Project D. Alegre1
•
E. Oyarzabal1 • D. Tafalla1 • M. Liniers1 • A. Soleto1 • F. L. Tabare´s1
Accepted: 7 September 2020 Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract In a future fusion reactor like DEMOnstration reactor (DEMO) one of the main concerns is the handling of the power exhaust from the plasma, especially at the divertor. The expected power loads cannot easily be handled by traditional armor solutions based on solid materials like tungsten, especially when the effect of intense neutron bombardment is also considered. Interest in armor concepts based on liquid metals has been subsequently on the rise, as they prove to be more resilient against high, fast power loads and neutron bombardment. However, engineering solutions for those concepts are very complex, and need to be tested. For this purpose, Optimization of Liquid Metal Advanced Targets project (OLMAT) has been envisaged. The project will use the Neutral Beam Injection of the TJ-II stellarator to irradiate liquid metal targets with power densities (neutrals plus occasionally ions) relevant to DEMO steady state operation, in the range of 20 MW/m2. OLMAT design will allow a series of experiments that other divertor simulator devices cannot easily perform: in-situ measurements of hydrogen retention, redeposition, vapor shielding, material fatigue, dust and precipitates effects, etc. Moreover, a high-power fiber laser will be used to simulate Edge Localized Modes in a small area, or to simulate the strike point power deposition profile. Keywords Liquid metals Divertor simulator Vapor shielding Redeposition DEMO CPS
Introduction Materials resilience is one the main causes of the delay in the achievement of an economically viable nuclear fusion reactor based on magnetic confinement. This is especially true for the inner shielding at the divertor area against the plasma exhaust (i.e. strike points): the target plates. Peak power densities up to 20 MW/m2 may arise during normal operation [1]. Moreover, off-normal transient events like Edge Localized Modes (ELMs), disruptions and VDEs (Vertical Displacement Events), if not mitigated, may lead to fast (1 ms) power loads ranging from a few GW/m2 (ELMs) to tens GW/m2 (disruptions and VDEs), see [1] and references therein. When the critical damage caused by intense neutron bombardment is also considered, the resilience of traditional shielding based on solid materials like & D. Alegre [email protected] 1
tungsten, or even advanced materials like tungsten fibers, is seriously compromised [1, 2]. Opposed to this, liquid metals (LM) offer conceptual advantages such as the lack of permanent damage and the possibility of in-situ replacement, among others [3, 4]. LM-based armors are underdeveloped compared to solid-based armors [3, 4] and important physics and engineering problems need to be overcome. The physics challeng
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