Vapor Corrosion Response of Low Carbon Steel Exposed to Simulated High Level Radioactive Waste

Liquid-Air Interface Corrosion of A537 Steel in High Level Liquid Radioactive Waste Simulant in a Sealed Container

“…It has been reported that mild steels may be subjected to corrosion at the liquid-air interface (LAI) in high-level liquid radioactive waste, [1][2][3][4][5][6] although severe leaks due to this issue have not been reported yet. 6 The liquid radioactive waste is mainly alkaline, consisting of NaNO 2 , concentrated NaNO 3 and sometimes a relatively small amount of chloride.…”

“…1,[6][7][8][9][10][11] Nitrite has been reported to inhibit corrosion of alloys, [12][13][14][15][16] while nitrate was regarded as either a corrosion inhibitor [17][18][19][20][21][22] or an aggressive species. 6,[23][24][25] Several hypotheses of LAI corrosion in this environment have been proposed, which include increase of aggressive chloride concentration due to evaporation, 2,26 ohmic potential drop due to crevice-like meniscus geometry, 6,27 and depletion of OH − due to CO 2 from air. 2,3,5,26,28 Firstly, LAI corrosion in liquid nuclear waste environment has been ascribed to the formation of a chloride concentration cell, and the chloride concentration at the meniscus would increase due to evaporation.…”

“…6,[23][24][25] Several hypotheses of LAI corrosion in this environment have been proposed, which include increase of aggressive chloride concentration due to evaporation, 2,26 ohmic potential drop due to crevice-like meniscus geometry, 6,27 and depletion of OH − due to CO 2 from air. 2,3,5,26,28 Firstly, LAI corrosion in liquid nuclear waste environment has been ascribed to the formation of a chloride concentration cell, and the chloride concentration at the meniscus would increase due to evaporation. 2,26 However, it is a fact that the concentration of inhibiting nitrite may also increase during evaporation, similarly forming a nitrite concentration cell, while this is not further considered in these studies.…”

“…2,3,5,26,28 Firstly, LAI corrosion in liquid nuclear waste environment has been ascribed to the formation of a chloride concentration cell, and the chloride concentration at the meniscus would increase due to evaporation. 2,26 However, it is a fact that the concentration of inhibiting nitrite may also increase during evaporation, similarly forming a nitrite concentration cell, while this is not further considered in these studies. On the other hand, the local electrochemical reduction of nitrite may lead to a local decrease of nitrite concentration, and its replenishment may be prevented due to the meniscus geometry resulting in pitting corrosion.…”

“…Thirdly, the dissolution of CO 2 from air will firstly decrease the pH of the meniscus, leading to the loss of passivity. 2,3,5,26,28 However, due to the limitation of the size of commercially available micro pH meter, the change of pH at the top of the meniscus cannot be characterized. 6 z E-mail: w.xu@qdio.ac.cn; ytli@qdio.ac.cn It is also worth mentioning the difference between waterline corrosion and LAI corrosion.…”