Corrosion Phenomenon of Stainless Steel in Boiling Nitric Acid Solution Using Large-Scale Mock-Up of Reduced Pressurized Evaporator

Abstract

To evaluate the component life in a spent nuclear fuel reprocessing plant, a large-scale mock-up test apparatus of a reduced pressurized thermosiphon evaporator was constructed, and the corrosion mechanism of a heat transfer tube made of ultralow carbon type 304 stainless steel in boiling nitric acid solution was studied. The corrosion tests were conducted for about 36,000 h, and changes in the corrosion amount and rate in the test duration were discussed. The relationships between the amount of corrosion and tube surface temperature and heat flux were investigated, and the corrosion propagation mechanism considering intergranular penetration was studied based on the observations of morphologies of corrosion surfaces and the measurements of intergranular penetration depths. After a long duration, the increases in the corrosion amount and rate saturated when intergranular penetration and grain dropping occurred by turns. This result means that a linear estimation can be applied to the life prediction for corrosion. Three portions of the tube were observed, and the amounts of corrosion were different among the three portions, but no difference in the morphology of intergranular corrosion existed. The amount of corrosion was affected by both tube surface temperature and heat flux. A large amount of corrosion could be observed in both the boiling starting portion and the top, where high tube surface temperature and heat flux were observed.

Tooling

“…4.36, right) is labeled by a pronounced intergranular corrosion, as already described by Wendler et al [Wen12]. In accordance to [Uen08], the removal is assumed to comprise intergranular penetration and grain dropping occurring by turns. In contrast, the laser-induced chemical removal using acidic aqueous solution, e.g.…”

Intergranular corrosion in evolving media: Experiment and modeling by cellular automata

“…From the experimental point of view, different techniques are used to characterize IGC. In addition to qualitative observations of the surface, optical or scanning electron microscopy can be performed on the cross section of the sample to geometrically characterize the intergranular grooves in 2D [15,[24][25][26][27][28][29][30][31][32][33]. A promising 3D characterization approach has also been attempted by µ-Xray-tomography [34].…”