Tritium release behavior from neutron-irradiated FLiNaK mixed with Ti powder

Abstract

• FLiNaK mixed with Ti powder was irradiated by mainly thermal neutrons. • Amounts of TF, T2 and T2O released from the FLiNaK by heating were investigated. • Chemical form ratio of released tritium was approximately TF:T2:T2O = 5:70:25. • Approximately 70% of tritium was released as T2O from the FLiNaK exposed to air. • Ti powder mixed to the FLiNaK contributed to the suppression of tritium release. FLiNaK is used as a simulant of FLiBe and FLiNaBe which are promising candidates of liquid blanket material in fusion reactors. In this study, to obtain useful knowledge for tritium release behavior from molten salts such as FLiBe and FLiNaBe, tritium release experiments were carried out for neutron-irradiated FLiNaK containing Ti powder. The solid-state samples were irradiated by mainly thermal neutrons at Kyoto University Research Reactor, and tritium release behavior as TF and T 2 by heating in Ar gas flow was observed and additionally total amount of released T 2 O was obtained. Most of the tritium generated inside the FLiNaK was released to the gas phase even when the FLiNaK was in a solid state at a temperature below its melting point. From the molten FLiNaK unintentionally exposed to air, approximately 70% of tritium was released as tritiated water vapor. The amount of TF released from the molten FLiNaK was considerably less than that of T 2 . This result is consistent with the tendency of tritium release from neutron-irradiated FLiNaBe in our previous study. The ratio of chemical form was approximately TF:T 2 :T 2 O = 5:70:25. It was experimentally confirmed that the Ti powder added to the salt contributes to the suppression of tritium release from the molten salt.