Experimental setup and pre-experiment issues for multi-component hydrogen isotopes permeation through metals, in non-steady-state

• Published in: Fusion engineering and design 2020-08, Vol.157, p.111677, Article 111677
• Main Authors: Bidica, Nicolae, Sofilca, Nicolae, Popescu, Gheorghe, Monea, Bogdan, Moraru, Carmen
• Format: Article
• Language: English
• Subjects: Deuterium; experimental; Fusion reactors; Hydrogen; Hydrogen isotopes; Hydrogen permeation; isotope; Isotopes; Measurement methods; multi-component; Nuclear fuels; Penetration; permeation; Steady state models; Tritium
• ISSN: 0920-3796; 1873-7196
• DOI: 10.1016/j.fusengdes.2020.111677

•The synergistic isotope effect in hydrogen isotopes permeation through metals is important in the assessment of tritium permeation through the structural materials of the fusion reactors.•More precise methods and carefully designed experimental techniques are required to emphasize experimentally the mutual influence in multi-isotope permeation.•A new experimental setup, measuring methods and procedures are presented in this paper; the technique of purging of both membrane faces is implemented, but also a new (sequential) version of the gas accumulation method combined with isotopic composition measurement and continuous flow evacuation under vacuum. The permeation of hydrogen isotopes (especially tritium) through the structural materials of the fusion reactors is an important issue. The isotope effects have to be taken into account in the permeation assessments because both deuterium and tritium are fuel constituents. However, there still are some controversies regarding the mutual influence among isotope species in the multi-isotope permeation; some authors state that the lighter isotope reduces the permeation flux of the heavier one, while others state the contrary. In a previous work, using a non-steady-state model for multi-isotope hydrogen permeation in surface-limited regime, it was shown that the presence of hydrogen leads to an increase in the permeation of deuterium. In order to highlight experimentally the small differences between single- and multi-isotope permeation, carefully designed experimental techniques are required. A review of the most important techniques is presented in this paper, outlining their advantages and drawbacks that were considered in the design of the experimental setup also presented here in detail. Three measuring methods of the permeation rates were implemented within; one of them is a new (sequential) version of the gas accumulation method. The measuring methods are also described in the paper, along with operating procedures.