We present a model of the plasma boundary region that has been developed to study the flow of impurities generated at the target plates in the pumped divertor configuration planned for JET. The model is one dimensional, parallel to the magnetic field, in the flow equations but treats in two dimensions the neutral species. All the ionisation stages of an impurity can be treated separately or, alternatively, an average charge impurity species can be considered. The validity of this approximation is assessed. Results are presented, showing that impurities can be retained near the target plates by a forced flow of plasma generated by re circulating, across the separatrix from the main plasma into the scrape-off layer, a fraction of the flow reaching the target plates.