We consider a cylinclrical crystal growing from the melt at a constant speed with a convex interface. Impurities from the melt segregate at the interface, and their approximate distribution in the solid is calculatecl in a dimensionless system with the following assumptions: a) the process occurs in the steady state; b) the impurities do not diffuse within the solid; c) the segregation at the interface is large. The determining parameter is the product of growth velocity and average curvature of the interface. When this parameter is large, the impurity concentration near the cylinder mantle is many orders of magnitude higher than near its axis. This gives rise to a radial refining process, which can be applied when diffusion in the liquid is low and convection has to be prevented. The problem is discussed for different shapes of the interface.