Reaction of Inconel 690 and 693 in Iron Phosphate Melts: Alternative Glasses for Waste Vitrification

Day, Delbert E. Kim, Cheol-Woon

University of Missouri-Rolla, Rolla, MO

关键词: Corrosion;    Iron Phosphate Glass;    Electrode;    Electrodes;    Low Activity Waste;   

DOI  :  10.2172/877121
RP-ID  :  NONE
RP-ID  :  FG02-04ER63831
RP-ID  :  877121

美国|英语

来源: UNT Digital Library

【 摘 要 】

The corrosion resistance of candidate materials used for the electrodes (Inconel 690 & 693) and the melt contact refractory (Monofrax K-3) in a Joule Heated Melter (JHM) has been investigated at the University of Missouri-Rolla (UMR) during the period from June 1, 2004 to August 31, 2005. This work was supported by the U.S. Department of Energy (DOE) Office of Biological and Environmental Research (DE-FG02-04ER63831). The unusual properties and characteristics of iron phosphate glasses, as viewed from the standpoint of alternative glasses for vitrifying nuclear and hazardous wastes which contain components that make them poorly suited for vitrification in borosilicate glass, were recently discovered at UMR. The expanding national and international interest in iron phosphate glasses for waste vitrification stems from their rapid melting and chemical homogenization which results in higher furnace output, their high waste loading that varies from 32 wt% up to 75 wt% for the Hanford LAW and HLW, respectively, and the outstanding chemical durability of the iron phosphate wasteforms which meets all present DOE requirements (PCT and VHT). The higher waste loading in iron phosphate glasses, compared to the baseline borosilicate glass, can reduce the time and cost of vitrification considerably since a much smaller mass of glass will be produced, for example, about 43% less glass when the LAW at Hanford is vitrified in an iron phosphate glass according to PNNL estimates. In view of the promising performance of iron phosphate glasses, information is needed for how to best melt these glasses on the scale needed for practical use. Melting iron phosphate glasses in a JHM is considered the preferred method at this time because its design could be nearly identical to the JHM now used to melt borosilicate glasses at the Defense Waste Processing Facility (DWPF), Westinghouse Savannah River Co. Therefore, it is important to have information for the corrosion of candidate electrode and refractory materials in iron phosphate melts in a JHM. During the period from June 1, 2004 to August 31, 2005, the corrosion resistance of coupons of Inconel 690 & 693 metals and Monofrax K-3 refractory, partially submerged in several iron phosphate melts at 950-1200C, has been investigated to determine whether iron phosphate glasses could be melted in a JHM equipped with such electrodes and refractory in the same manner as now being used to melt borosilicate glass. These representative iron phosphate melts, which contained 30 wt% Hanford LAW and 40 wt% Idaho SBW simulants, did not corrode the Inconel 690 to any greater extent than what has been reported for Inconel 690 in the borosilicate melt in the JHM at DWPF. Inconel 693 appeared to be an even better candidate for use in iron phosphate melts since its corrosion rate (1.8 to 25.4 ?m/day) was only about one half that (5.4 to 45.4 ?m/day) of Inconel 690. The dynamic corrosion measured for the candidate refractory, Monofrax K-3, by iron phosphate melts is quite encouraging since the measured corrosion (0.011 to 0.132 mm/day at 9.2 rpm) is less than the corrosion (0.137 mm/day) that has been reported in the JHM used to melt borosilicate glass at DWPF. During the period covered by this final report, the results of the research on iron phosphate glasses have been described in seven technical papers and have been presented at one national meeting. In addition to the principal investigator, one research professor and one undergraduate research aide were supported by this project.