International Doctoral College in Fusion Science and Engineering
 Thesis catalogue
High sensitivity measurements of hydrogen isotope retention in liquid metals of interest for PFCs in a Fusion Reactor.
PhD Code: 2016-DC-12:
Mobility
  • Host institute 1: FP4-Universidad Carlos III de Madrid (Home University) - AM01-Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas (Home Institution)
  • Host institute 2: AM07-Aix- Marseille Université (Host University) - FP8-Institut de Recherche sur la Fusion par confinement magnétique, Saint-Paul-lez-Durance, France (Host Institution)
Research fields:
  • F4. Plasma-wall interaction and material research
Promotor(s):
  • Prof. José Ramon Martin Solis (promotor)
  • Prof. Jean Marc Layet (co-promotor)
  • Dr. Francisco Tabares (mentor)
  • Dr. Christian Grisolia (mentor)
Contact Person and email: Francisco Tabares - tabares@ciemat.es

Subject description
Background: The present problems found in the selection of suitable materials for the high flux components of a Fusion Reactor call for the development of alternative solutions. Compared to solid-state materials, as it is the case of the ITER choice of tungsten, liquid metals offer unique properties, including the lack of permanent surface damage and the capability of full in situ regeneration. At present, liquid tin, lithium and Sn-Li alloys are the best-characterized materials for Fusion applications. Two major concerns, however, remain with respect to their use in a realistic Reactor scenario: Tritium retention and excessive vapor pressure. These are particularly serious for the case of lithium, the best studied liquid metal for Fusion. In the case of tin, a concern about plasma contamination by this high Z element exists, while the use of a SnLi alloy could offer the combined good characteristics of both elements. Little is known however about the actual performance of this alloy in a hot plasma. The level of fuel retention a material should have for its validation as a potential PFC is very low, and a total limit of 700g of tritium has been established by Nuclear safety regulations for the whole life of the divertor. Although it is already known that either tin or lithium at T>500ºC show a very small level of retention when exposed to a Fusion plasma, technical problems make it very difficult to assess hydrogen isotope retention level below 1% in liquid metals. The high sensitivity of tritium detection techniques appears as a powerful tool in solving thus problem, as it has been shown in the analysis of DT experiments at JET and TFTR in the past. However, due to constrains in handling tritium at the laboratory level, such measurements are challenging.

Expected outcomes

Objective: The presently existing facilities at CIEMAT for H retention studies in liquid metals will be used for Hydrogen and Deuterium uptake in lithium, tin and their alloys. Both, TDS and Laser Induced desorption studies will be undertaken at different temperatures at the lab. Extensive use of Capillary Porous Systems with different parameters and materials will also be used to reproduce the operational conditions in a Reactor. These studies will determine the minimum retention level that can be quantified by using non radioactive isotopes. In a second phase, two different kind of loading techniques will be used in the tritium lab at CEA: Microwave plasma implantation and gas exposure. Full thermal desorption for Li samples, and chemical solution of the metal for the Sn and Sn-LI alloys, respectively, will be used together with scintillation T detection. MW Plasma characterization by means of optical and probe diagnostics will provide the evaluation of tritium fluxes to the samples when required. Time line and mobility scheme (research need to be performed for at least six month in two different countries): A two year stay in Ciemat followed by 1 year stay at CEA is foreseen for this project.

 

 

Original document: 2016-DC-12



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