The isothermal corrosion behavior between 1000. °C and 1190. °C of Inconel 690 and 693 in an iron phosphate glass melt containing 26. wt.% of a simulated Hanford low activity nuclear waste (LAW) was investigated. At least three distinct corrosion processes were recognized for both alloys over different temperature ranges. Inconel 690 and 693 both display the best corrosion resistance at an intermediate temperature range (Inconel 690: 1050-1100. °C; Inconel 693: 1050-1165. °C), and more severe corrosion at both lower and higher temperatures. In general, Inconel 693 is less reactive over a wider temperature range than Inconel 690.