A detection system is described for monitoring on-line radioactive process solutions by solid scintillation counting. The system consists of a flow cell with perspex windows coated with the plastic scintillator MeltilexTM. The cell is confined in a chamber welded to a La Calhène container. Thus the detection device is easily attached to, detached from and transported between glove boxes, and the electronic parts and the multiplers can be kept outside the box containment. Using outside coated windows, the detector responds to radiation, using inside coated windows, and particles can be detected. Selective measurements can be carried out by installing a chromatographic column in the detector loop. The detection limits of the cell for Am amount to 4·10–9 g Am/ml for outside coated windows and 10–9 g Am/ml for inside coated windows. windows and 10–9 g Am/ml for inside coated windows.