Corrosion behavior of Alloy 690 and Alloy 693 in simulated nuclear high level waste medium

Investigation of passive films formed on the surface of alloy 690 in borate buffer solution

“…Nickel based alloy 690 was candidate materials for the storage of high level waste generated from reprocessing of spent nuclear fuel [1]. Moreover, the alloy 690 also was currently as an alternative to traditional austenitic stainless steel due to its high strength, lower nickel concentration and excellent corrosion resistance [2].…”

Enhancement of corrosion resistance of nickel based superalloys by laser surface melting

“…31,32 The solidification occurred epitaxially from the boundary between the treated region and the untreated matrix. The presence of Ti and Cr rich precipitates was observed in the microstructure of the as received specimens, 25,26 while for the solution annealed specimen, a homogenised microstructure with traces of precipitates was observed. 27 These precipitates were found to be completely absent with laser surface melting, as shown in the microstructure (Fig.…”

“…The improvement in E pit could be attributed to the refined microstructure after laser treatment. It can be seen that the precipitates, which were present in the as received condition, 25,26 were not found in the laser melted specimens. This is due to the dissolution of precipitates, owing to the high energy density of the laser beam.…”

“…27 The optical and SEM images of the as received specimens showed Ti and Cr rich precipitates, 25,26 while a homogenised microstructure with some traces of precipitates was noticed for the solution annealed specimens. 25,27 For the LSM specimens, the micrographs showed homogeneous cellular microstructures with all precipitates dissolved in the solid solution matrix.…”

Corrosion in Nuclear Waste Containers

“…In addition, the possibility of localized corrosion should be considered. However, the pitting potential measured for nickel-based alloys 690 (Ni-30Cr-9Fe) and 693 (Ni-30Cr-4Fe-2Nb-3Al) in simulated high level waste conditions is high and only a few pits have been observed [34]. A simulation of the corrosion of Alloy 22 in the high level waste storage conditions indicates that crevice corrosion is more likely than stress corrosion cracking, and that stress corrosion cracking is feasible, but unlikely at temperatures above 100°C [35].…”