Abstract:

Background: Tritium, as a by-product in the core of Thorium-based Molten Salt Reactors (TMSRs), easily diffuses through the structure materials at high temperatures and into the atmosphere. Purpose: To reduce the damage of tritium to the environment, it is necessary to research the permeation behaviors of tritium in the candidate structural materials of TMSRs. Methods: In this study, Hastelloy alloy C230, Hastelloy alloy C276, Hastelloy alloy N and GH3535, the candidate structural materials of TMSRs, were used. With the method of gas driven permeation, hydrogen and deuterium were used to simulate the permeation process of tritium and their permeabilities in these materials were examined at the temperature range of 400?700 oC. Results: The fluxes of hydrogen and deuterium were proportional to the square root of the gas pressure. Their permeabilities were a little different in these alloys and increased with experimental temperature. The relationship between the permeability and the reciprocal of the temperature was suit for Arrhenius formula. Conclusion: The permeabilities of hydrogen isotopes in GH3535 and Hastelloy alloy N are very close, which is in the same magnitude with that in Hastelloy alloy C230 and Hastelloy alloy C276. At the experimental temperatures, the ratios of the permeability between hydrogen and deuterium in these materials are all close to 1.4, which is consistent with the classical diffusion theory. According to the theory, pre-exponential factors for tritium permeation in these materials are 1.1×10?7?1.6×10?7 mol?m?1?s?1?Pa?1/2 and activation energy is 59?62 kJ?mol?1.

Key words: Hydrogen isotope, Molten Salt Reactor (MSR), Structural material, Permeability