Abstract: A mathematical model for a square cascade with locally enlarged flow in the depleted part of the cascade was established, which is used for separating multicomponent mixtures. The cascade under consideration consists of two square parts of different width and has four external flows: the feed, waste, the product flows and an additional intermediate product flow. The equations of the cascade with the additional product flow was solved by a computation method for steady state based on the quasi-linearization of cascade governing equations. Meanwhile, the concentration distribution of W-184 in WF₆ was calculated based on the cascade model and demonstrated that, compared with a conventional square cascade, the cascade with locally enlarged flow enabled the concetration of an intermediate component to be considerably increased with the same total flow.