Assessment of corrosion phenomena in liquid lithium at T < 873 K. A Li(d,n) neutron source as case study

Abstract The corrosion induced by alkali metals in steels has been the subject of long decades of intense studies under both nuclear fission and fusion research programs. Li or its eutectic Pb-17Li is the liquid metal coolant choice for fusion blankets due to the tritium breeder capability of Li. Non-metal impurities enhance corrosion, but only N becomes potentially a problem given its high solubility in liquid Li and the depletion of Cr through ternary nitrides Li-Cr-N. The low solubility of C and O allow its cold trapping to values Li 9 CrN 5 . Fortunately, the mass transport phenomena of Cr within the ΔT = 350 K in the loop is limited due to the poor solubility of Cr in liquid Li (0.21 wppm at 873 K). In turn, at 523 K Li the activity of N to form the ternary compound is negligible. However, the high solubility of Ni in Li (2144 wppm at 873 K), suggests the presence of mass transport phenomena of Ni from the stainless steel piping; unfortunately, the physicochemical kinetics are not fully understood. Lifus 6, in operation in Brasimone (ENEA) since the end 2015, will close in a definitive manner remaining open questions.