In-Reactor Tritium Release Behavior from Molten Lithium-Tin Alloy as a Liquid Metal Breeder

OVERVIEW

In-reactor tritium release experiments using the fast neutron source reactor "YAYOI" of the University of Tokyo were carried out in the temperature range of 673 to 873 K. The main chemical form (more than 99%) of released tritium was HT or T ₂ irrespective of the H ₂ concentration in He purge gas. The mass transfer coefficient increased with increasing hydrogen pressure in He purge gas up to 100 Pa at 873 K. The mass transfer coefficient for tritium from Li ₂₀Sn ₈₀ to pure hydrogen as the purge gas obeyed the following temperature dependence: K _D [m/s] = 2.82 10 ^-4exp(-27.2 [kJ/mol] / RT).

Keywords: Lithium, tin, molten alloy, tritium, mass transfer, liquid breeder

1 INTRODUCTION

Lithium-tin alloy with low vapor pressure, low viscosity, low density and high compatibility with structural materials has been proposed as the potential tritium breeding material for fusion reactor[1], especially for the free flow first wall.

In considering the material for tritium breeding, a detailed understanding of the chemical form of release, mass transfer, solubility and diffusivity of tritium and its isotopes in the material is crucial to determine the tritium inventory and tritium recovery method. No fundamental data of mass transfer, diffusivity of tritium in molten Li-Sn alloy is yet available, not even the results from the out of pile...