Sodium Corrosion of Westinghouse Liquid Metal Fast Breeder Reactor (LMFBR) Materials

Abstract

The Westinghouse sodium corrosion program on LMFBR materials has concentrated primarily on the combination of Type 316 stainless steel (cladding) and Type 304 stainless steel (I.H.X. tubing) for the primary system, and the combination of Type 304 stainless steel (I.H.X. tubing) and Incoloy 800 (steam generator tubing) for the secondary system. To date, eight loop runs have been completed on both types of systems which represent approximately 20,000 hours of operation at maximum temperatures ranging from 900°F to 1325°F. The loops used in this program are designed as system mock-ups of the Westinghouse Demonstration LMFBR. Parameters and ranges investigated during this program include temperature (900°F to 1325°F), temperature difference, ∆T, (200°F to 300°F), sodium oxide levels (< 10 ppm to ∿ m), velocity (3 fps to 20 fps), time (up to 10,000 hours), and material combinations. When the maximum temperature of the primary system (316 stainless steel — 304 stainless steel) is 1100°F, the oxide level is less than 10 ppm, the ∆T is 300°F, and the velocity is 7 fps, the corrosion rate at 2500 hours is approximately 0.09 mils per year; if the velocity is increased to 20 fps, the corrosion rate is approximately 0.11 mils per year, indicating that the velocity has only a slight effect on corrosion. However, if the velocity is held at 20 fps, and the maximum temperature is increased to 1325°F, the corrosion rate is increased roughly by one order of magnitude to approximately 1.2 mils per year. For a mock-up of the secondary system (304 stainless steel — Incoloy 800) with a maximum temperature of 1100°F, a ∆T of 300°F, an oxide level of less than 10 ppm, and velocity of 15 fps, the corrosion rate at 2500 hours is approximately 0.08 mils per year.