The objective of this work is to analyze the behavior of a nondispersive solvent extraction plant in the uncertain space of concentration and flow rate of the feed stream. To carry out this task, a superstructure with a maximum number of 64 modules distributed in 8 parallel lines of 8 modules in series for both extraction and stripping subprocesses is developed. A flexibility analysis on the optimal design obtained with this superstructure is implemented using the equation-oriented flowsheeting package SPEEDUP (Aspen Technology, Inc). Further studies of the flexibility index for different overdesigns are done in order to obtain a deeper insight of the operability characteristics of the system. The results show that the optimal nondispersive solvent extraction processes for the case of removal and concentration of Cr(VI) with Aliquat 336 present low flexibility indices.