Corrosion studies of SS 316H and Alloy 617 in thermally purified molten NaF-KF-UF4-UF3 salts

Abstract

The study investigates salt chemistry and corrosion behavior of SS 316H and Alloy 617 in thermally purified molten NaF-KF-UF4-UF3 salts (UF4/UF3 initial ratio 12–14) at 800°C for 120, 72, and 32 h. UF4/UF3 ratio increases after corrosion tests. Cr species concentration in salts keeps increasing. Fe, Co, Ni, and Mo species increase first, then decrease. Cr/Mn oxides are formed along grain boundaries in SS 316H. Cr near the surface of Alloy 617 is completely depleted. A thin layer composed of Fe, Co, Ni, and Mo is observed on the Alloy 617 surface in 72-h and 32-h tests.